Biology Revision Sheet

8/2/2019 Biology Revision Sheet

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Biology Revision Sheet:

Chapter 1:

Living organisms are classified into 5 major groups called kingdoms:

Animalia (eukaryotic), Plantea (eukaryotic), Fungi (eukaryotic), Protista - unicelullar (eukaryotic), Prokaryotic Bacteria -

unicellular and lack the nucleus( Two domains: Eubacteria and Archaebacteria)

Order of classification: Kingdom, Phylum, Class, Order, Family, Genus, Species.All living things have certain characteristics. Living things are called organisms.

1) Movement - causes an organism to change its position or place. Plants move their leaves and stems towards the sun-

light to get as much light as possible.

2) Respiration - involves chemical reactions that release energy in cells

3) Sensitivity - being able to detect and respond to stimuli (changes in the environment surrounding an organism). Ani-

mals have sensory cells and sense organs for detecting light, sound,...

4) Growth - permanent increase in size and mass, involves making more complex chemicals such as proteins.

5) Reproduction - produce offsprings or results in the formation of new individuals. Asexual reproduction is one parent

giving rise to offsprings that are often identical to each other and to the parent. Sexual reproduction involves two parents

produce gametes which fuse to rise an offspring. The offspring shows variation (differences).

6) Excretion - the removal of waste chemicals made in the cells during metabolism e.g they exhale CO2 (from respira-tion) and they urinate (ejection of urine).

7) Nutrition - involves the use of food for energy, growth and repair. Nutrients are compound that may be large (e.g car-

bohydrates) or simple (e.g mineral ions)

The genus is a group of species that are closely related, but do not interbreed with each other.

A species is a group of individuals that look alike. They live in the same habitat and breed together to give offspring

which are fertile.

The binomial system: The binomial system was first deisgned by Carl Linnaeus, is the "two-named" system. It is the

genus and the specie name (trivial) of an animal or we can say the generic name and the specific name. Example: Suri-

cata suricatta (meerkat), human (homosapiens)

Invertebrates: animals that do not have a veterbral column or backbone

Phyla of invertebrates:

Nematodes/roundworms: a group of worms that have thread like bodies that taper at mouth and anus. They have no

heads and no legs. Bodies are not made up of segments. Tiny. Live in soil and water. Some species are parasites means

they live inside another animal as the host.

Annelids: worms that have soft bodies made up of segments. Have paddle-like extensions for moving. Have chaetae or

bristles for making contact with mud and soils. When they burrow through soil, they have pointed front end for moving

and make mucus as lubricant. Most species live in the sea and some live soil and freshwater.

Molluscs: have soft bodies that are not segmented. Have muscular foot for burrowing or movement. Many species have

1 or 2 shells for protection (e.g snail) - they can retreat inside the shell if a predator is close by or avoid excessive water

loss. Octopus does not have shell.\

Arthropod: The largest phylum in the animal kingdom. An arthropod is an invertebrateanimal having an exoskeleton

(external skeleton), a segmented body, and jointed appendages(external body part that protrudes from an organism's

body).

Arthropod classes:

Crustaceans: body divided into a cephalothorax (head-thorax) and abdomen. Many have chalky exoskeleton that pro-

vides a very effective protection against predators. Have 2 pairs of antennae and compound eyes. Have 5-20 legs.

Breath using gills. Nearly all live in water. Examples: crab, woodlice.
http://en.wikipedia.org/wiki/Invertebratehttp://en.wikipedia.org/wiki/Animalhttp://en.wikipedia.org/wiki/Animalhttp://en.wikipedia.org/wiki/Exoskeletonhttp://en.wikipedia.org/wiki/Appendagehttp://en.wikipedia.org/wiki/Appendagehttp://en.wikipedia.org/wiki/Organismhttp://en.wikipedia.org/wiki/Organismhttp://en.wikipedia.org/wiki/Animalhttp://en.wikipedia.org/wiki/Exoskeletonhttp://en.wikipedia.org/wiki/Appendagehttp://en.wikipedia.org/wiki/Organismhttp://en.wikipedia.org/wiki/Invertebrate


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Myriapods: centipedes and millipedes. Have long segmented bodies and not divided into separate regions. Centipedes:

1 pair of legs each segment, fast-moving carnivores, have powerful jaws to paralyse their preys. Millipedes: 2 pairs of

legs each segment, slow-moving herbivore, they feed in leaf litter.

Insects: the largest arthropod group. Bodies divided into three parts: head, thorax, and abdomen. 3 pairs of legs on the

thorax and many species have 2 pairs of wings. Have 1 pair of antennae on the head. Compound eyes made of tiny indi-vidual components. Breath through holes inside the thorax and abdomen called spiracles. They colonize most habitats,

but very few species live in the sea. Success on land: covered with waterproof cuticle to prevent water loss, they can fly.

Example: butterfly, cockroach.

Arachnids: bodies divided into 2 parts: cephalothorax and abdomen. Have 4 pairs of legs and no wings. No antennae.

Have several pairs of simple eyes. They paralyse their prey with poison fangs. Spiders - weave silken webs with their

spinnerets. Example: scorpion.

Vertebrates: animals that have the veterbral column or backbone. All vertebrates have an internal skeleton made of ei-

ther bone or cartilage.

Phylum chordata:Chordates areanimalswhich are either vertebrates or one of several closely related invertebrates.

Vertebrate Classes:

Fish: live in water permanently, but some species can survive out of water such as mud skipper. Fish are streamlined

and have fins for swimming and for balance. Have eyes and a lateral line for detecting pressure changes in water. They

breathe dissolved oxygen from the water using their gills. Skin is covered with scales. Example: tuna. Other vertebrates

have ears for detecting sound and four limbs.

Amphibians: have smooth, moist skin. Most live on land but return to water to breed. Fertilisation is external since ga-

metes are released into the water. Development is external - eggs hatched into offsprings that have gills for breathing. On

land, adult amphibians breathe using lungs, in water they breath through their skin. Examples: salamander, frog.

Reptiles: have dry and scaly skin to cut down water loss. They can live in dry regions since they dont have to return to

water to breed. Fertilisation is internal, but developmennt is external as they lay eggs with leathery and water proof shell.

They have lungs to breathe air. Example: Snake, crocodile.

Birds: have feathers and front limbs (wings). Most are able to fly, except for penguins and ostriches. Have no teeth. Fer-

tilisation is internal and development is external (female lays eggs protected by shells). They are homeothermic (warm-

blooded)-able to regulate temperature and keep it constant. Example: hawk, eagle.

Mammals: have hair or fur. Both fertilisation and development are internal. Female mammals suckle their young on milk

from mammary glands. All mammals even aquatic mammals use lungs for breathing. Mammals are homeothermic -

maintain constant internal temperature. Example: dolphin.

Microorganisms:

Many species of bacteria and fungi break down dead and decaying material. These are called decomposers.

Microbes that cause disease are called pathogens.

Bacteria: simple cell structure, shape: spherical or rod-shaped, exist in short chains of cells, size: a few micrometers,

seen by light and electron microscopes, cells are surrounded by cell walls, some species have cells surrounded by slime

capsule, no nucleus - just a loop of DNA within the cytoplasm; additional loops of DNA are called plasmids, dont have

chloroplast or mitochondria, have flagella for moving through fluids, they are found everywhere, in good condition: may

divide every 20 minutes, large group of bacteria is called colony, they secrete enzymes to breakdown simple molecule

like sugar, can survive in harsh condition, produce spores within their cells - spores germinate and divide again.
http://en.wikipedia.org/wiki/Animalhttp://en.wikipedia.org/wiki/Animalhttp://en.wikipedia.org/wiki/Animalhttp://en.wikipedia.org/wiki/Vertebratehttp://en.wikipedia.org/wiki/Invertebratehttp://en.wikipedia.org/wiki/Animalhttp://en.wikipedia.org/wiki/Vertebratehttp://en.wikipedia.org/wiki/Invertebrate


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Fungi: seen under light microscope, most are multicellular but yeast is unicellular, have nucleus, cell wall is made out of

chitin, have no chlorophyll, main fungus body is called mycelium - consists of branching network called hyphae which re-

lease enzymes to digest food on the outside, food is absorbed by hyphae, reproduce by making spore, they feed on de-

caying matters (saprotrophs), some are parasites.

Virus: extremely small, seen under electron microscope, they are not cells, made up of genetic material (DNA or RNA),

surrounded by protein coat, they are parasites - enter other organisms as the host to multiply - take over the host cellsand make new viruses, they reproduce quickly, do not respond to antibiotics, constantly changing into new strains.

Flowering plants: multicellular, green since many cells contain chloroplasts. Have transport systems consisting of tiny

tubes : xylem vessels (carry water and mineral salts), ad phloem tubes (transport dissolved food).

Features of flowers:

Stamens (male): anther, supported by filament, contains pollen cell

Carpels/Pistil (female): stigma, style, ovary - contains sex cells (ovule)

Petals: brightly coloured, attract insects for pollination

Sepals: below the main petals, protect flower in the side bud

Shoot: part of the plant above the ground

Stem: bearing leaves, buds and flowers, support the structure of the shoot, spaces the leaves to receive enough light

and air, holds flowers in position for pollination.

Apical bud: part where stem grows new leaves.

Root: part of the plant below the ground, dont contain chlorophyll therefore white, absorbs water and mineral ions from

the soil.

Dicotyledons: broad leaves with network of branching veins, stamens are in multiples of four or five in each flower, have

two cotyledons (seed leaves) in a seed. Example: magnolia

Monocotyledons: long narrow leaves with parallel veins, leaves with variety of shape, parts of the flowers are in multipleof three, have one cotyledons. Example: grasses, cereal.

Dichotomous keys are used to identify living things. Dichotomous means diving into two.

Chapter 2:

Cells are the small building blocks that make up all living organisms.

Feature Plant cell Animal cell

cellulose cell wall present absent

shape permanent shape determined by

the cell wall (can be box-like, cylin-

drical, or spherical

shapes very since there is no

cell wall

chloroplasts present in some cells absent

vacuole large vacuole containing cell sap small vacuoles and do not have

cell sap; some animal cells

dont have vacuoles

nucleus present (often at the side of the

cell - close to the cell wall)

present (found anywhere within

the cell)

Function of cell structures


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Cell structure Functions

cell membrane forms barrier between the cell and its

surrounding

keep contents of cell inside

allow simple substances to enter and

leave, e.g oxygen, CO2 and H2Ocontrol the movement of other sub-

stances into and out of cell, e.g glu-

cose

has tiny holes that allow small mole-

cules to pass through but not large

one (partially permeable)

nucleus controls all activities inside the cell

and how cells develop

cytoplasm place where chemical reaction takes

place e.g respiration and making pro-

teins for the cell

chloroplast photosynthesis

store starch

cell wall stops cell from bursting when they fill

with water

allows water and dissolved sub-

stances to pass through freely (fully

permeable)

sap vacuole full of water to maintain shape and

firmness of cell

stores salts and sugars

Different types of cells:

1) Ciliated epithelial cell (trachea and the oviduct of the female) - it has cilia on the surface to move mucus that trap dirts

out of the lungs; back & forth movement of the cilia creates current in the fluid next to the surface of the cell. In the

oviduct, cilia move the egg from the ovary to the uterus

2) Muscle cell - be able to change and help to move.

3) Nerve cell (neurones) - long cells to carry message around the body quickly

4) Root hair cell - have long extensions to provide more surface area to absorb water and minerals ions from the soil

more quickly. Thin cell wall - easy to pass through.

5) Xylem vessels: cylindrical and empty, arranged into columns like pipes. Cell walls are thickened with bands or spiral

of cellulose and a water proof called lignin, allow water and ions to move from the root to the rest of the plant, support

stem and leaves.

6) Palisade cell - large surface area and contain many chloroplasts to absorb sunlight and CO2 for photosynthesis,

make up the upper layer of the mesophyll

7) Red blood cell: have protein haemoglobin that carries oxygen, flatten disc shaped - provides large surface area - effi-

cient for the absorption of oxygen.

8) Muscles cells: make up fibre that is able to shorten and contract. Some muscles are attached to the skeleton (when

they contract, they move bones at joints); muscles cells also found in gut and heart.

Size of cells and specimens:


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Actual size: image size/magnification (mm)

Levels of organisation:

Organelles to cells (the building blocks) to tissues (a group of similar cells work together to carry out a shared

function) to organs (group of different tissues that work together to perform specific function) to systems(group

of different organs with related functions that work together) to organisms (made up of different organ systems).

Example of tissue:Muscle is a tissue capable of contracting and relaxing to create movement.

Example of organs:

Heart: made up of different tissues, e.g cardiac muscle, nervous tissue, fibrous tissue and blood that work together to

pump blood around the body.

Organ system Organs Job

Circulatory System heart, blood vessels, & blood transport nutrients,CO2, O2 and

others around the body

Digestive System gullet, stomach, pancreas, liver and in-testines

breakdown food and absorb nutri-ents

Excretory System kidneys, ureter, bladder & urethra filter out waste, toxin, and excess

water

Endocrine System glands secrete hormones

Lymphatic/Immune System lymph node, white blood cells destroy invading microbes and

viruses in the body

Muscular System skeletal and smooth muscles provide movement

Nervous System brain, spinal cord, nerves carry messages around the body

Respiratory System nose, trachea, lungs gas exchange

Reproductive System Female: ovaries, oviducts, uterus &

vagina

Male: testes, sperm ducts, prostate

gland and penis.

produce offsprings

Skeletal System bones, cartilage, tendons, & ligaments provide support for the body, protect

delicate organs

Plant tissues and organs:

Mesophyll: tissue that carries out photosynthesis in leaves

Palisade cells: make up the upper layer of the mesophyll,closely packed and full of chloroplasts for absorbing light.

Palisade mesophyll tissue is made up of palisade cells.

Plants organs: leaf, roots and stems.

Flowers and fruits are modified leaves.

See diagram on page 23.

Chapter 3:

DIFFUSION:

Diffusion: the net movement of molecules from a region of high concentration to a region of lower concentration down a

concentration gradient.

Concentration gradient: the difference in concentration of a substance in two places


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Molecules carry on diffusing until they are spread out evenly. When there is no longer a difference in concentrations, dif-

fusion has stopped.

A concentrated solution has a large mass of solute dissolved in a given volume of the solvent

A dilute solution has a small mass of solute dissolved in a given volume of solvent.

Cells gain some of the substances they need by diffusion from their surroundings. They also lose some of their waste

substances to their surroundings by diffusion. These substances have to cross cell membranes that are partially perme-

able as they allow the small molecules to go across them (cell membranes are thin).Passive moment: the movement of molecules by diffusion across cell membranes, but cells do not need to use energy

to move the molecules.

Factors affect the efficiency of diffusion:

1) the distance molecules have to travel

2) the concentration gradient - cells use the substances that diffuse in as quickly as possible, so they keep a low con-centration inside the cytoplasm. The molecules from the outside keep diffusing since the cell is maintaining a steep con-

centration gradient.

3) the surface area - some cells have folded cell membrane to give a large surface area to allow many molecules tocross by diffusion.

4) the temperature - molecules move faster and collide more often as the temperature increases. Diffusion is faster atwarmer temperatures.

5) The size of molecule - small molecules diffuse faster than large ones.

Gas versus Liquid: diffusion through air is many times faster than through water.

Animals and plants exchange the gases oxygen and CO2 with their surroundings at gas exchange surfaces.

Mammal:

Alveoli inside the lungs is where gaseous exchange takes place.

Gaseous exchange is where oxygen diffuses into the blood and carbon dioxide diffuses out of the blood.

Alveoli have a large surface area and one cell thick wall, it will be easier more gas to be diffused. Oxygen gets diffused

into blood vessel and dissolved in the blood plasma. Breathing constantly refreshes air in the alveoli and blood constantly removes oxygen and brings carbon dioxide, so

the concentration gradient are always steep.

There are many alveoli to give a large surface area for gas exchange.

Plant:

Gas exchange occurs inside the leaves

The spongy mesophyll cells provide large surface area for gaseous exchange and there are air spaces between the cells

so each cell exchanges gases with this air.

Cells exchange gases with the air in the space between the plant and the cells.

Water as a solvent:

Solute + solvent = solutionA solute can be solid, liquid or gas because all of them can dissolve in the solvents. Substances that dissolve in a sol-

vent is described as soluble.

About 75% of cytoplasm is water. Water is the main component of transport fluids like blood, xylem sap and phloem sap

in plants.

Everything transported in plants and animals has to dissolve in water and most chemical reactions occur in cells happen

in water.

OSMOSIS:

Osmosis is a special kind of diffusion involving water molecules. It occurs when 2 solutions are separated by a partially

permeable membrane. It is a diffusion of water from a dilute solution into a more concentrated solution.

Dilute solution: many water molecules but less solute molecules --> high water potentialConcentrated solution: less water molecules (low concentration of water) but many solute molecules --> low water po-

tential


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Water molecules pass through the tiny holes of the cell membrane, but the solute molecules are too big to pass through.

Water potential: the tendency for water molecules to move by diffusion. It is influenced by how much water is available

and other factors such as the pressure exerted on the water in plant cells by the cell wall. The water molecules diffuses

down the water potential gradient

Example of partially permeable membrane: visking tubing (dialysis tubing)

Osmosis in plant cells and animal cells:

1)Plant cells:

When plant cells are placed in water, water moves into the cell sap inside the vacuole (a solution of salts and sugars) be-

cause there is a water concentration gradient. As water enters, it makes the cell swell up. The water pushes against the

cell wall; the strong cell wall stops the cell from bursting. The cell is turgid. Turgid cells give the plant support. They keep

the stems of many plants upright. When plant cells lose water, they are no longer firm and turgid; plant stems and leaves

wilt.

When plant cells are placed into a concentrated sugar or salt solution, water passes out of the cell by osmosis. The sap

vacuole starts to shrink. These cells are no longer firm, and become flaccid. As more water leaves the cells the cyto-

plasm starts to move away from the cell wall. This is plasmolysis.

2) Animal cells:

a) animal cells placed in distilled water --> water passes into the cells by osmosis; since there is no cell wall, the cells

swell too much that they burst

b) animals cells placed in a concentrated solution of salt --> the cells shrink as the water passes out of the cells by os-

mosis.

ACTIVE TRANSPORT:

Cells take up molecules and ions and keep them in high concentration.

Active Transport: the movement of molecules or ions in or out of a cell through the cell membrane from a region of low-

er concentration to a region of higher concentration (against the concentration gradient) using energy released from res-

piration.

The cell membrane contains carrier protein. These carrier proteins span their cell membrane and provide means by

which ions and molecules can enter or leave a cell by active transport. First the molecules or ions combine with the carri-

er protein. Energy from respiration enables the carrier protein to change its change to carry the molecules or ions inside

the membrane. The carrier protein then reverts to its original shape.

Root hair cells and epithelial cells (lining villi in the small intestine) are adapted for active transport by having many carrier

proteins in their cell membranes and a high rate of respiration to provide energy.

Active transport relies upon respiration to take up ions or molecules against a concentration gradient. Any factor that af-

fects the rate of respiration will also affect the rate of active transport, such as a lack of oxygen would reduce respiration

rate or an increase in temperature in temperature would increase the respiration rate. The presence of poisons such as

cyanide would stop respiration and there wont be active transport.

Chapter 4:

A catalyst speeds up a chemical reaction and remains unchanged at the end of the reaction. Enzymes are proteins, pro-

duced by organisms that speed up chemical reactions. They are known as biological catalyst.

There are many different types of enzymes as each one catalyses a different reaction. Some enzymes work inside the

cells and some work outside the cells.

Three types of enzymes reaction:

1) Breaking large molecules into small ones: large foods are broken down into small ones so that they can be ab-sorbed and then used.


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2) Building up large molecules from small ones: small molecules such as glucose are joined together to make largemolecules. These enzymes work inside cells to speed up the formation of storage molecules such as starch, and struc-

tural molecules such as cellulose for cell wall in plants.

3) Converting one small molecule into another: Most chemical reactions that occur inside cells involve small changesto molecules, such as adding or removing atoms or group of atoms.

Properties of enzymes:

1) They are all proteins

2) Each enzyme catalyses one reaction

3) They can be used again and again

4) They are influenced by temperature

5) They are influenced by pH

Protein molecules of enzymes can be folded into many different shapes and each enzyme has a shape that makes it suit-

able for catalysing one reaction. Protein is influenced by the conditions of their surroundings, and this makes them to

change shape. Enzymes stop acting as catalyst when they change shape.

Enzymes work on substances called substrate.

The reaction takes place on a surface called active site of the enzyme. The shape of an enzymes active site is main-

tained by bonds between different parts of the molecule.

Only a substrate molecule has a shape that fits into the active site will take part in the reaction. Other substrates have

the wrong shape will not be involved in the reaction.

A small amount enzymes needed to catalyse a reaction because it can be used over and over again and they also can

catalyse a large quantity of substrate.

After the products leave the active site, more substrates enter in and the enzymes keep on working until all the sub-

strates are used up.

Factors affecting enzyme action:

The rate of the reaction that enzyme catalyses can be shown by measuring how much product is formed or how much

substrate is used over a period of time.

Effects of temperature on enzymes:

The temperature at which the maximum rate of reaction occurs is called the optimum temperature. This is the best tem-

perature for the enzyme. For example: 20C (fungal and plant enzymes), 37C (human enzymes), 90C (bacterial enzymes

in industry).

Increasing the temperature of an enzyme-controlled reaction will increase the rate. Enzyme and substrate molecules gain

more kinetic energy so they move around more quickly and there are more chances of them colliding, the substrate fits

into the active site and reaction takes place.

At higher temperature, the bonds holding the enzyme molecule together start to break down. This changes the shape of

the active site, therefore the substrate can no longer fit in. The enzyme has been denatured and it can no longer catalyse

the reaction.

Effects of pH on enzymes:

Enzymes work best at its optimum pH.

The shape of the active site changes in respond a change in pH. The bonds that hold the enzyme molecules together are

broken by a change in pH. When the rate of reaction is zero, the shape of the active site has changed and substrates

cannot fit in. At these values of pH, the enzymes are denatured.

Enzymes in Industry:Enzymes are very important in the industry and some processes use enzymes as catalysts because enzymes work at

lower temperature than other catalysts so reducing the cost of fuels.


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1) Making beer:

Germinate barley seeds in warm and moist environment.

Enzymes in the seeds become active and convert stored starch into the sugar maltose (this sugar is used by yeast in the

fermentation process to produce alcohol in beer)

Starch is stored in the seeds as a source of energy for respiration. Some other seeds like sunflower seeds contain oil as

their energy storage. The enzyme lipase is produced inside these seeds to break down the oils when they germinate.These seeds can be harvested for their oils so they wont be germinated.

2) Extracting juices:

Pectinases are enzymes that break down pectins, which are molecules that act like glue in plant cell walls. Pectinases

are used to extract fruit juices and to soften vegetables.

3) Industrial fermentation:

Industrial processes use microorganisms to produce a useful products. The organisms involved might respire with or

without oxygen.

Industrial fermenters are large tanks that can hold 500,000 dm cube of fermenting mixture. Conditions inside are carefully

controlled.

Production of antibiotic penicillin:

Stainless steel fermentation vessel contains the required nutrients such as sugars and ammonium salts. Some of the fun-

gus Penicillium is added. Sugars provide energy for respiration and ammonium salts are used by the fungus to make pro-

teins and ribonucleic acids (DNA and RNA). After a few days the fungus start to produce penicillin.

A stirrer keeps the microorganisms suspended so they always have access to nutrients and oxygen and maintains the

temperature throughout the process.

An air supply provides oxygen for aerobic respiration for the fungus (In brewing, no oxygen is supplied)

A water-cooled jacket removes the heat produced by fermentation to give a constant temperature of 24C.

The probes maintain the temperature and make sure the pH is constant at 6.5 by adding alkali if necessary.

After fermentation is complete, the mixture is drained and filtered. Penicillin is extracted as a salt like material.

4) Biological washing powders:

Enzymes that are released outside tend to break down complex substrate, such as carbohydrate.

Bacteria (bacillus) and fungi (aspergillus) are grown in fermenters to produce enzymes for biological washing powders.

Enzymes released by the microbes that are extracted from the material in the fermenter by filtration.

Biological washing powder may contain several different enzymes:

Proteases - break down proteins stains

Lipases - break down fat in oily stains

Amylases - break down starch stains

Cellulases - break down cellulose fibre to glucose on the outside of cotton fabric to remove dirt.

These enzymes are modified to withstand high temperature and alkaline condition. Enzymes break down stains and the

products of the reaction dissolve in water and then be removed.

The newest biological washing powder work at lower temperature than non-biological washing powder to save energy.

Enzymes are broken down into harmless products (they do not harm the environment) after they have been used.

Plants:

Green plants use light energy to convert raw materials from their surroundings into simple sugars. This process

is called photosynthesis.

Photosynthesis:

Carbon dioxide + water + light -> glucose + oxygen

CO2 + H2O C6H12O6 + O2

Balanced equation: 6CO2 + 6H2O -> C6H12O6 + 6O2


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Photosynthesis converts light energy into chemical bond energy in simple sugars. This provides energy for the plant

and also for other organisms that feed on plants directly or indirectly .

Photosynthesis is not a simple reaction, there are many chemical reaction take place in the chloroplasts (in leaf cells)

to produce simple sugar and oxygen. Each reaction is catalyzed by one enzyme.

Too much sugars produced --> dissolved in cell sap in the vacuole of plant cells --> water moves in by osmosis and

causes the cell to swell so much that they would need to make thicker cell wall --> prevention: glucose molecules are

linked to form starch which are insoluble.Testing a leaf for starch:

1) Put the leaf in boiling water to destroy its membrane, making it easier to extract chlorophyll

2) Turn of the bunsen burner

3) Put the leaf in a test tube of ethanol; chlorophyll will dissolve in the ethanol

4) Put the test tube in a beaker of hot water for a while

5) Was the leaf in cold water to remove the ethanol and rehydrate the leaf (the leaf becomes soft and easy to spread out)

6) Put some drops of iodine on the leaf surface

7) Postive: blue/black; negative: red/brown

The requirements for photosynthesis:

Light: provide energy for the process

Chlorophyll: green pigment that absorbs energy from light; in the chloroplast of the leaf

Carbon dioxide: diffuses into the leaves from the air, then diffuses into the chloroplast in the mesophyll cells.

Water: absorbed by the plants root from the soil

Water and CO2 are raw materials

Investigations demonstrate that chlorophyll, carbon dioxide and light are needed for photosynthesis. We cannot test water

because plants need water for many other reasons and most of the plant is water --> hardly to take water away. If there is

photosynthesis, there are starch inside the plants. To make the investigation valid:

1) Make sure the leaves have no starch at the start (left in the dark for at least 48 hours) - destarching

2) The plant is then given all the things it needs except for the substance that we are testing

Chlorophyll test:

1) Take a de-starched, variegated plant; variegated means some parts of the leaves are white because there is no chloro-

phyll there.

2) Place the plant in sunlight

3) Take one leaf

4) Test the leaf for starch

5) Green parts have blue/black colour; white part - no photosynthesis --> negative result

Carbon dioxide test:

1) Take a de-starched plant

2) Enclose the plant in a bag with soda lime for absorbing carbon dioxide

3) Leave the plant in the light for some hours

4) Test a leaf for starch

5) The leaf should show a negative result

6) A control experiment is set up without the soda lime to show that it was the absence of CO2 that the plant did not pho-

tosynthesize and not keeping the plant inside the plastic bag.

Light test:

1) Take a de-starched plant

2) Cover a apart of the leaf with aluminium foil to prevent light getting through

3) Leave the plant in the light for some hours

4) Test the leaf for starch

5) Covered part: negative result; uncovered part: blue black (positive)

Products of photosynthesis:


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Simple sugars:

1) Converted into starch to be stored for energy in the leaves for future use, e.g at night

2) Stored in seeds as oils for energy

3) Converted into sucrose and transported to other parts of the plant in the phloem

4) Used as energy to transport minerals from roots to the plant.

5) Used to make other organic substances such as cellulose to build cell wall.

6) Combined with nitrates from the soil to make amino acids, which are built up to form proteins (needed for growthand cell repair and for making enzymes and hormones)

7) Required for respiration in the leaf.

Oxygen is a by-product (a secondary or unintended product produced from a process). Plants may use oxygen for res-

piration or oxygen can be diffused into the atmosphere to be used by other organisms.

Plants provides raw materials for industry (e.g timber and cotton) food and medicine (e.g digitalis - heart drug); pro-

vides habitats for animals and microorganisms; photosynthesis helps to keep constant concentration of carbon dioxide

and oxygen in the atmosphere (without green plants - concentration of CO2 increases and concentration of oxygen de-

creases) Plants as food:

Fruits (apple), leaves (bokchoy), stems (celery), flowers (cauliflower), roots (carrot), beans (green beans), cereals (rice),

nuts (peanuts).

Oxygen produced in photosynthesis:

1)Take a pondweed put it in a funnel

2)Turn a test tube upside down to cover the smallest open end of the funnel

3)Put the set up in a beaker of water

4) A lamp provides light energy

5)CO2 is dissolved in water (add sodium hydrogen carbonate powder in water to provide CO2)

6)Place the funnel upon the plasticine gives gaps to allow CO2 dissolved in water to reach the pondweed

7)Collect the number of bubbles of gas every minute

8) Test the gas for oxygen with a glowing splint

Rate of photosynthesis:

We can determine how fast or slow photosynthesis occurs by measuring the amount of oxygen produced in a certain

time. This can be done by counting bubbles or measuring the volume of oxygen produced. The rate of photosynthesis

can also be measured by measuring the amount starch produced by measuring the change in dry mass in a given time.

Faster photosynthesis --> plants grow bigger --> more food is made --> increase yield of crops.

Light intensity, carbon dioxide concentration, water supply and temperature affect the rate of photosynthesis.

Limiting factor: something present in the environment in such short supply that it restricts life processes. Limiting factors

of photosynthesis are light intensity, temperature and carbon dioxide concentration.

The only way to increase the rate is to increase the limiting factor. There is only one factor can limit the rate any anytime

as it depends on the one that has the shortest supply.

Water is not a limiting factor because there is enough water in the plants. However, in dry condition, plants reduce their

water loss by closing their stomata --> carbon dioxide cannot diffuse in --> slows down the rate of photosynthesis.

Light intensity (determines energy available)

Photosynthesis increases when light gets brighter but only up to certain point because other factors such as carbon diox-

ide concentration or temperature are restricting the rate.

Light intensity experiment:

1)A beaker filled with water


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2)Attach a small piece of pondweed to a paper clip to stop it floating on the water surface in the beaker

3)Put the lamp at a certain distance and measure the distance

4)Count the number of bubbles every 5 minutes. Repeat several times and calculate the average

5)Repeat this procedure with the lamp placed at different distances from the plant

6) The number of bubbles should decrease as the distance between the lamp and the plant increases because thepondweed is receiving much less energy, therefore the rate of photosyntheses decreases.

Many plants spread their leaves wide to receive as much light as possible.

Strong light can damage the chloroplasts.

Shade plants: plants that are adapted to grow in areas such as under forest tree where they have dim light.

Temperature (influences the activity of enzymes in the chloroplast)

Chemical reactions catalysed by enzymes increase with temperature. Increase in temperature increases the rate of pho-

tosynthesis until it reaches the maximum rate. The maximum rate occurs at the enzymes optimum temperature. The rate

of photosynthesis decreases at higher temperature because the enzyme are denatured. Tropic plants have higher opti-

mum temperature than those in colder regions.

Carbon dioxide concentration:

The higher the CO2 concentration, the faster the rate of photosynthesis and the greater the crop yield. It is not possible to

control the carbon dioxide concentration outdoor because the air usually contains 0.04% carbon dioxide.

CO2 experiment:

1)A beaker filled with water

2)Add sodium hydrogencarbonate to give more CO2 which dissolve in water.

3)Attach a small piece of pondweed to a paper clip to stop it floating on the water surface in the beaker

4)Put the lamp at a certain distance and measure the distance

5) Light intensity and temperature must be kept constant6)Count the number of bubbles every 5 minutes.

7)The plant produces more bubbles as the CO2 concentration increases. The rate of photosynthesis should in-crease up to a point and then becomes constant because another factor becomes limiting.

Glasshouse production:

Crops are grown in glasshouse so that the growers have the opportunity to control the factors that limit the rate of photo-

synthesis. Growers always try to improve the yield of their crops by giving them the best conditions for photosynthesis to

take place. This allow the plant to:

1)grow earlier in the year

2)grow in places where they would not normally grow wellTemperature: sunlight heats up the inside of the glasshouse, the glass stops the heat from escaping, electric heaters are

used in cold weather, ventilator flaps are opened to cool the glass house on hot days.

Light: glass lets in sunlight, artificial lighting is used when the light intensity is too low,.

Carbon dioxide: growers can pump more carbon dioxide into the glasshouse, they can burn butane or natural gas to give

CO2 and heat to raise the temperature inside the glasshouse during cold weather.

Water: have automatic watering systems using sprinklers and humidifiers which ensure planets always get enough water.

These are all controlled by computer --> few staffs needed: there are sensors to detect changes in CO2 concentration,

humidity, light intensity, and temperature. Computers control sensors, heating, ventilation, lighting and shading.

Leaves:The leaf structure:

Leaf has an ideal shape for photosynthesis. Leaves have:


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1)a large surface area to absorb light rays

2)a thin shape so that gases can diffuse in and out easily

3)many chloroplasts for absorbing light

4)veins to support the leaf surface, carry water and mineral ions to the leaf cells and take sucrose and amino acidsto other parts of the plant.

Structure Description Function

Upper cuti-

cle

this is not a tissue but a

waxy layer covering the out-

side of the leaf

reduces water loss

Upper epi-

dermis

one layer of cells, no chloro-

plasts, transparent

secrete waxy cuticle to prevent water loss, prevents gas exchange, al-

lows light to pass, barrier against infection

Palisade

mesophylllayer

long cells lined up close to-

gether with short side fac-ing top (fence-like), has

many chloroplasts,

photosynthesis

Spongy

mesophyll

layer

irregular shaped cells with

air spaces between, has

fewer chloroplasts than the

palisade layer because it re-

ceives less light

air spaces: allow rapid diffusion of oxygen and carbon dioxide; less

friction and wider space

photosynthesis

Lower epi-

dermis

no thick cuticle, closely fit-

ting cells, has many tiny

holes called stomata(sur-

rounded by guard cells)

stomata open and close to allow gas exchange and reduce water loss,

secretes cuticle, barrier against infection

Stomata are small pores (holes) that allow gases to diffuse in and out of the leaf. Stomata are usually present in the low-

er epidermis, but some plants like water lily has them in the upper epidermis.

Opening and closing of stomata:

Stomata are opened and closed by guard cells

Day: water moves into the guard cells by osmosis, the guard cells bend and so the stomata opens, CO2 diffuses in for

photosynthesis, oxygen made in photosynthesis diffuses out, water vapour diffuses out

Night: water passes out of the guard cells by osmosis and they straighten and move closer together so closing the stoma-ta pores. Stomata closes in hot and dry weather to prevent the plants from wilting.

Looking at stomata:

1)Paint a small square (1x1cm) of nail varnish on the underside of the leaf

2)When the nail varnish dries, peel it off

3)Put it on a slide with drop of water and cover slip

4)Observe the stomata using high power of the microscope.

Mineral requirements:

Plants need mineral salts or plant nutrients. Nutrients are absorbed by the root from the soil in small quantities as ions byactive transport.

Lack nutrients --> presence of deficiency symptoms


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Nutrients Function

Nitrate ions make amino acids which are then

built up to proteins for growth.

Deficiency symptom: poor growth

Magnesium ions used to make chlorophyll

Deficiency symptom: chlorophyll

looks yellow (chlorosis)

Phosphate ions used to make compounds such as

DNA and for respiration

Deficiency symptom: poor root

growth, younger leaves turn purple

rather than green.

Fertilisers:Farmers add fertilises if there is not enough nutrients in the soil.

NPK fertilisers contain:

1)Nitrogen (in the form of nitrate ions) for growth of leaves and stems

2)Phosphorus (in the form of phosphate ions) for healthy root

3)Potassium (in the form of potassium ions) for healthy leaves and flowers.The proportion for each nutrient is written in the ration N:P:K

Natural fertilisers and artificial fertilisers:

Chemical/ artificial fertilisers: used in huge quantities, easy to store and add to the land, release nutrients quickly, short

lasting, there is a definite amount of nutrient in the fertilisers, growers have to be careful of how much fertiliser is usedand when.

When it rains, fertilisers run off into rivers and streams:

1) Provide nutrients for algae

2) Algae grows fast in the lake, use up lots of oxygen and block sunlight

2) Aquatic plants die - provides food for microbes

3) More oxygen is used up - fish die

Natural fertilisers: farmyard manure and composts --> add humus to soil --> improves structure of the soil, releases nutri-

ents slowly and over a long period of time, the mass of each nutrient in the fertiliser is not known.

Plant transport:

Most organisms need a transport system.

Organisms with small bodies only rely on diffusion alone to gain oxygen and remove carbon dioxide. Transport systems

in large organisms like vertebrates and flowering plants move fluids through tubes so that all the fluid moves in the same

direction within each tube. This transport is called mass flow.

Vertebrates have a circulatory system. Flowering plants have two separate transport systems: xylem and phloem.

Xylem and phloem are tissues composed of cells that are specialised for transport. These tissues are found roots, stem,

and leaves.


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Transport tissues Structure Function

Xylem Pipes - like

Contains xylem vessels

Walls are thickened with cellulose

and lignin --> waterproof and strong

to hold the stem uprightInside the vascular bundle --> help to

support the stem

Made of dead and empty cells (no cy-

toplasm and organelles) --> no ob-

struction to the flow of water and min-

eral ions

Transport water and mineral ions

One direction: root through stem to

leaves

Phloem Sieve plate contain holes that allow

sucrose and amino acids to pass

from one cell to the next.

Made up of living tissues that have

some cytoplasm.

Transport sucrose, amino acids, and

hormones throughout the plant.

Transported in 2 directions:downwards: leaves to root

upwards: leaves to flowers, fruits, and

buds; storage organs to new stems

and leaves.

Sucrose is made for transporting energy. It is made in the leaves with the sugars from photosynthesis and sugars from

starch in storage organ, such as swollen roots and stem.

Hormones control cell division for growth of the stem, roots, leaves, flowers, and fruits.

Structure of the root:

The tip is called the root cap --> protects the root tip as it grows (cells divide) through the soil

Phloem: transport sucrose and amino acids from the leaves which are used to make new cells at the root tip

Xylem: transports water and ions up the root

Cortex: stores some food as starch

Root hairs: the extended cells of the epidermis (on the outside of the root); absorbs water and mineral ions

Structure of the stem:

Vascular bundle: made up of phloem, xylem and cambium

Cambium: cells make new xylem and phloem as the plant grows

Epidermis:a single layer of cells on the outside of the stem which protects the stem and reduces water loss

Phloem: transports sucrose and amino acid to the root and up to the flowers and fruits

Xylem: transport water and mineral ions up to the leaves.

Water uptake:

Roots: anchor the plant in the soil and take up mineral ions

Soil water is a dilute solution of various solutes.

Root hairs have thin, permeable cell walls and provide a large surface area for absorbing water.

The cell sap in the root hair cells is a more concentrated solution (contains mineral ions, sugars, and other solutes). The

cell membrane is partially permeable so water diffuses from the soil into the root hair cells by osmosis down the water po-

tential gradient.

Water passes across the cortex to the xylem in the centre of the root (most water move in the space between cell walls,

but some also move from cell to cell) down the water potential gradient.


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Water then moves up the xylem through the stem to the leaves and finally enters the spongy mesophyll cells.

Much of the water enters the cell wall, evaporates to form water vapour and then diffuses through the stomata

into the atmosphere.

Transpiration is the evaporation of water from the leaves and the loss of water vapour to the atmosphere. Water

vapour diffuses when the stomata open. Water is pulled up the xylem in the stem from the roots to the leaves by

transpiration pull. As water is used up for photosynthesis or lost from the leaves, more water is sucked up fromthe root.

The mass flow of water relies on 2 properties of water:

1)Cohesion: the water molecules attract together or stick together

2)Adhesion: the water molecules stick to the side of other surface, in this case it is the internal surface ofthe xylem vessel.

There is a continuous flow of water from the roots to the leaves. The movement of water up the xylem through

the stem is called transpiration stream.

Transpiration:

In the spongy mesophyll layer, the air spaces are lined by mesophyll cells which have damp cell walls. Water

evaporates from this huge internal surface so the air spaces become saturated with water vapour.

There is more water vapour in the air spaces than in the outside air, so water vapour diffuses out through the

stomata into the atmosphere. The volumes of water lost by transpiration is slightly less than the volume of water

taken because some of the water is used for photosynthesis and keeping the plant cells turgid.

Wilting:

More transpiration takes place at day the stomata tend open during the day and closed at night. The stomata

close at night to reduce the volume of water lost by transpiration. They may also close in hot, dry conditions dur-

ing the day as water loss in transpiration is not replaced by the water from the soil. When the plants do not get

enough water, they start to wilt. The plant cells become flaccid and then soft, so they cannot give the plant sup-

port; as a result, stem is not upright and the leaves droop.

Wilting may not be a bad thing. The leaves move downwards and they dont get much contact from the sunlight.

When the temperature decreases, they absorb more water to pay back for the water lost by transpiration.

Environmental factors affecting transpiration:

1)Light: as the light intensity increases, the stomata opens wider. The rate of transpiration also increasesto the maximum point.

2)Humidity: in a humid condition, there is no water potential gradient between the air and in the leaves.The water vapour is not diffused and so there is less transpiration.

3)Warmth: warm condition increases the rate of transpiration. The stomata opens and so water vapour dif-fuses out. Increasing temperature increase the rate.

4)Windy condition: water molecules are blown away by the wind, so the air becomes less saturated. Thereis a steep concentration gradient so more water vapour diffuse out.


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Measuring transpiration: We use the potometer to measure the rate of water uptake. The potometer is sub-

merged in water. The distance moved of the air bubble in the capillary tube measures the rate of transpiration.

Adaptations of plants to different environments:

All plants have to balance water uptake with water loss. Very high rates of transpiration can kill a plant if it can-

not absorb enough water to prevent long-term wilting.

Xerophytes: plants that are able to survive in hot, dry regions where water is scarce, for example, cacti.

Cacti reduce water loss and conserve in a number of ways:

Leaves reduced to spines --> reduce surface area so not so much water evaporated

Have thick, waxy cuticle to cover the leafs surface --> reduce transpiration

Have swollen stem containing water-storage tissue

Have a shallow, spreading root system to absorb water quickly

Have round, compact shape --> reduces surface area --> not much water can be lost

Have shiny surface which reflects heat and light

Stomata close during the day to reduce water loss; stomata open at night to absorb CO2 which they store for

use in photosynthesis during the day.

Hydrophytes: plants that grow submerged in water.

Benefits:

1)Buoyed up by water --> no need for water transport --> save energy because they dont need to producexylem tissue

2)Roots, if present, are for anchorage; there are no root hairs to absorb water and mineral ions.

3)Have no cuticles on leaves and stem because there is no need to conserve water.

Problems: CO2 and oxygen diffuses through water much more slowly because they are not very soluble in wa-

ter, therefore the rate oh photosynthesis may slow down. To solve this, hydrophytes have extensive system of airspaces in their stems and leaves so that gases can diffuse through quickly. The air spaces give buoyancy to the

plants so that they have closer contact with the sunlight.

Mesophytes: plants that do not experience extreme water supply and do not have extreme adaptations like xero-

phytes to reduce water loss. Most garden plants are mesophytes: colourful, scented flowers --> provide an at-

tractive environment.

Translocation:

Food is made in the leaves by photosynthesis. Soluble products include sucrose, amino acids, and fatty acids.

These are carried in the phloem to other parts of the plant. This movement is called translocation. The transportof food takes place from the region of production to the region of storage or the region where respiration and

growth take place. Simple sugars produced by photosynthesis are converted into sucrose. Sucrose:


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1)broken down by enzymes to give simple sugars for respiration

2) changed to starch for storage in the root cortex and in seeds

3) used to make cellulose for cell wall at the tip of the root and the shoot

4) stored in some fruits to make them sweet

Translocation of systemic pesticides:

1)Farmers use pesticides to control pests and diseases that spoil crops and reduce yields.

2) Contact pesticides kill the pests that are sprayed onto, but the spray may not reach to those pests thathide under the leaves

3) Systemic pesticides are sprayed on the crop plants that absorb them. The pesticides are translocated toall parts of the plant in the phloem. The pests would ingest the pesticide when they feed on the plants.This would kill them.

Transpiration and translocation:

1)Source: the part of the plant where the substance starts its journey, e.g the leaves

2) Sink: the part of the plant where the substance ends its journey, e.g region growth (root and shoot tips),region of storage (root cortex and seeds), and respiring plant tissues.

3)The movement of water in the xylem vessel is passive, since it relies upon the evaporation of watervapour from the leaves producing the tension in the xylem. Transpiration involves dead tissues. Transpi-

ration is greatest on hot, dry, and windy days.

4)Translocation is an active process in the phloem. Movement in the phloem requires active transport ofthe sucrose at the source. Water enters the phloem to build up a pressure that forces the phloem sap to

travel to the sinks. Translocation is most active on warm and sunny days when the amount of sugar pro-

duced is big.

Chapter 5:

Living organisms need useful substances called nutrients. Nutrients are compound that can be complex (like carbohy-

drate, proteins and vitamins) or simple (like mineral ions). Animals get nutrients from plants and nutrients that animals re-

quire are present in their diet.

There are 7 different nutrients needed for a balance diet of human: carbohydrate, proteins, fats,vitamins, minerals, fibre,

water.

Carbohydrates:

Made up of carbon, hydrogen and oxygen.

Include sugars and starches

Glucose: simple sugar, made in photosynthesis, used in respiration, transported in blood, consists of six carbon atoms

arranged into a ring.


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Complex sugar: made up of simple sugar joined together by chemical bond, e.g sucrose (the sugar that you add to food

and drinks), maltose (used by yeast in fermentation to produce alcohol in beer), and lactose (milk sugar). All these sugars

are sweet and soluble and provide energy in a ready-to-use form.

Complex carbohydrate: made up of many simple sugars molecules joined together by chemical bonds. Plants stores

starch - polymer (macromolecule composed of repeating structural units) of glucose - as an energy store. Glycogen (ani-

mal starch) is another complex carbohydrate made from glucose by animals as a store of energy. Glycogen is stored in

the liver and muscle. Starch and glycogen are insoluble and do not taste sweet.

Proteins: complex molecules made up of carbon, hydrogen, oxygen, nitrogen and sulphur; proteins are long chain mole-

cules made up of smaller molecules called amino acids. After formation, they can be folded into different shapes or ar-

ranged into long fibre.

There are about 20 different types of amino acids. The sequence of the different amino acids determines the type of pro-

tein that is formed. Amino acids are joined together by the chemical bond called the peptide bond. Each kind of protein

must have all 20 different types of amino acids to become a complete proteins.

Haemoglobin, enzymes, antibodies and some hormones (e.g insulin) are soluble proteins. They dissolve in water cyto-

plasm or in the blood. Keratin is an insoluble protein used to make fibre and is found in hair and skin.

Fats:

Oils" is usually used to refer to fats that are liquids at normal room temperature, while "fats" is usually used to refer to

fats that are solids at normal room temperature. "Lipids" is used to refer to both liquid and solid fats.

Made up of carbon, hydrogen, and oxygen.

Each fat molecule is made up of 1 molecule of glycerol and three fatty acids.

Different types of fatty acids form different fats with different properties.

Fats are used for energy storage and thermal insulation (cut down heat loss) in the body.

Chemical tests for nutrients:

Make an extract from the material that you are testing; it involves grinding up the extract with some water with

pestle and mortar or putting it into a blender. The chemical is put into the solution in the extract.

Starch test:

Half fill the test tube with the extract

Add 2-3 drops of iodine solution

Iodine looks yellow or light brown, so a positive result shows a blue-black colour and a negative result remains

yellow or light brown.

Reducing sugars test:

Put a known volume of the extract in the test tube

Place a beaker on a heat-proof mat

Half fill the beaker with boiling water from the kettle

Add Benedict solution into the test tube and place it in the beaker

Benedicts solution is bright blue


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changes: green --> yellow --> orange

Green means the extract contains a small amount of reducing sugars; deep orange colour means the extract

contains a lot of reducing sugars; blue colour means the extract does not contain reducing sugars.

Reducing sugar is any sugar that has an aldehyde group or is capable of forming one in solution through iso-

merization (the process of one molecule transforms into another molecules but still has the same compositionthat is arranged into a different structure. The aldehyde group allows the sugar to act as a reducing agent. The

sugar that give a positive result reduces the copper ions in the Benedicts solution when the mixture is heated.

The type of reaction occurs is a reduction reaction. Reducing sugars are simple sugars such as glucose, lac-

tose and maltose. Sucrose is not a reducing sugar and gives a negative result because sucrose contains 2 sug-

ars (fructose and glucose) that are joined by the glycosidic bond which prevents the glucose to isomerize to

aldehyde.

Protein test:

Half fill the test tube with the extract

Add 5-6 drops of biuret solution ( a mixture of copper sulfate solution and sodium hydroxide solution - corrosive)

Biuret solution is blue

A positive result shows a colour of purple, violet or lilac; negative result remains blue.

Fats test:

Fats do not dissolve in water but they will dissolve in ethanol. A solution of fat in ethanol added to water gives a

cloudy white emulsion

Chop up a small a mount of the material you wish to test for fats

Put the extract in test tube and add ethanol to cover it

Put the stopper over the open end of the test tube and shake up the contents.

Half fill the test tube with distilled water

Shake one more

Positive result: cloudy white emulsion or milky colour emulsion, negative result: no cloudy white emulsion.

Sources of nutrients:

Carbohydrates - They are needed for instant energy that is easily respired; simple sugars are absorbed almost immedi-

ately by the stomach to give immediate source of energy (from respiration)

Rice, pasta, and breads are good sources.

Proteins - Needed to make new cells for growth and repair damaged cells; our bodies digest proteins into amino acids

and we use them to make our own proteins such as enzymes. Our bodies need to have all 20 different types of amino

acids to make proteins. Cell membranes and cytoplasm contains a great amount of proteins. Proteins can also be

respired to provide energy.Meat, fish, and milk are good sources.


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Fats - Provides a long term energy store and provide insulation; fats are stored under the skin and around the heart and

kidneys, it releases twice the amount of energy that carbohydrate or proteins release. When we are short of energy, our

bodies use fats. Fats give buoyancy to marine animals such as whales thick layer of blubber.

Meat, dairy product and nuts are good sources.

Vitamins/Minerals - Needed to stay healthy; only need small and regular amount of minerals and vitamins

lack of vitamins or mineral result in some deficiency disease.

Found in many foods, especially vegetable and fruit.

Vitamins/

Minerals

Foods Needed for Disease

A butter, carrot keep cells in respi-

ratory system

healthy

Cells in respiratory

system infection,

night blindness

B wholemeal bread,

liver

Involved in many

chemical reaction in

the body

Beri-beri

C oranges, lemons,

other citrus fruits

tissue repair, resis-

tance to disease

Scurvy (bleeding

gums)

D butter, fish oil, milk strengthens bones

and teeth

Rickets (soft bones,

legs bow outwards)

iron liver, meat, eggs used in formation of

haemoglobin in red

blood cells for trans-

porting oxygen

tiredness, lack of en-

ergy (anaemia)

calcium milk, fish, green

vegetables

strengthens bones

and teeth

weak, brittle bones

and teeth (rickets),

weak muscle and

cramps

Water - make up 2/3 of our body mass, needed for chemical reaction that take place in solution, waste chemicals are

passed out in urine, and water in sweats cool our bodies down, intake of water each day must be equal the loss of water

in urine, faeces, sweat and breath.

Fibre/Roughage - made up of cellulose from plant cell walls, cannot be digested, adds bulk to food, does not provide en-

ergy, helps the movement of food in the alimentary canal by peristalsis so preventing constipation, absorbs poisonous

wastes from bacteria in the gut, lowers concentration of cholesterol in blood, reduces the risk of heart disease and bowel

(intestine) cancer.

Found in fresh vegetables, cereals, and wholemeal bread.

Use of microorganisms in industry:

Biotechnology: branch of industry in which microorganisms or their products are used. Bacteria are used to pro-

duce yoghurt and a fungus is used to make mycoprotein (a form of single cell protein which is manufactured into

meat substitute).

Microbes grow and reproduce very quickly in suitable condition. In many of the food productions processes, mi-

crobes are fed on waste materials of other industries because this helps to reduce the costs.

Yoghurt:


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1) Milk is pasteurized to kill disease-causing bacteria

2) The milk is thickened with skim milk powder

3) Set the temperature at 40C (ideal for growth of the bacteria), add bacteria

4) Bacteria respire anaerobically (without oxygen) and use lactose as their source of energy

5) The bacteria produce lactic acid, which lowers the pH of the milk and causes the milk to coagulate (becomes

semi-solid)

6) Cool the yoghurt and then mix the yoghurt with fruit to create different types of yoghurt with different flavours

7) Some yoghurts are treated to kill all bacteria, while others contain live culture. These bacteria are naturally

found in our gut that help our digestion.

Yoghurt production is an example of batch culture. Fermentation takes place in stainless steel tanks and after

the yoghurt is removed, all the equipments are cleaned before starting a new batch.

Mycoprotein:

Microbes are very good at producing proteins.

1) Mycoprotein is a material produced by a fungus Fusarium.

2) Mycoprotein is made by continuous culture - the nutrients are continually added ad the products are continu-

ally removed. The fermenter works continually without having to be emptied or sterilised.

3) The fungus is supplies with glucose and oxygen as their energy source; mineral salts and ammonia (source

of nitrogen) are added for the fungus to make amino acids. The fermetner is kept at 30C.

4) Fungal hyphae give a meat-like texture and flavourings are added so that it can be into a variety of products.

5) Mycoprotein: high in protein, low in fat,

Food additives:

Benefits of food additives: preserve food --> e.g ethanoic (acetic acic) in vinegar of pickled food acts as a

preservative --> the low pH prevents microbes growing on food (which causes its decays --> tastes and flavours

ruined)

Sugars and salts are 2 traditional preservative.

Food additives can also colour and add flavour to food. Some are natural substances and some are artificial

substances.

Colourings: used to make food more attractive to customers.

Preservatives and anti-oxidants: protect food from being decomposed by bacteria and fungi or oxidised by oxy-

gen in the air. For example, fats in food are oxidised to acid make the food become rancid.

Flavourings: smell of strawberry: a complex mixture of 280 different compounds, flavour enhancers like salt areused to increase the taste sensation; monosodium glutamate (MSG) is used to enhance the original flavour of

the food.


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Emulsifiers and stabilisers: enable fats and oil to mix with water.

International numberings system for food additives:

Additives number Use of additives

100 -181 colouring (tartrazine is 102)

200 - 290 preservatives (ethanoic acid is 260)

296 - 385 anti-oxidants and acids (ascorbic acid - vita-

min C is 300)

400 - 495 emulsifiers and stabilisers

500 - 585 anti-caking agents and mineral salts

620 - 640 flavour enhancers (MSG is 621)

900 - 1520 others, e.g sweeteners and wax glazes on

fruit

Disadvantages of food additives:

1) Tartrazine (artificial substances): causes asthma attack and hyperactivity in children, banned in Norway

2) Butylated hydroxyanisole (320): causes cancer, banned in Japan, McDonald stopped using it in 1986

3) Saccharin (artificial sweetener - 954): banned in USA in 1977, but then some further research in 2000 had

not shown any hazards to human health.

Animal Nutrition:

A balanced diet:

Humans need to eat a balanced diet. This really means some of every food group but not too much or too little of a par-

ticular one. A balanced diet provides an adequate amount of nutrients to ensure good health and growth.

Nutrient functions:

1)To provide energy: role of carbohydrate and fats. Proteins are used to provide energy when they are in excess of

requirements for growth, development, repair and replacement.

2)To allow growth and repair of body cells and tissues. Proteins provide amino acids for cells to make their own pro-teins.

3)To regulate the bodys metabolism - require all nutrients.

Basal metabolic rate (BMR): the energy required for the body functions. This varies from person to person.

Diet depends on age, sex and activity.

You exercise: uses up energy, increased protein requirements when muscles start to develop bigger --> need extra pro-

tein in the diet (for sporty people in general)


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You are growing: have higher BMR, need more protein for developing and making new cells.

You are ill: lower metabolic rate --> need more nutrients such as carbohydrate and fats to produce energy and more pro-

teins for white blood cells to make antibodies to fight against disease.

You are pregnant: need extra nutrients when pregnant and breast-feeding.

You are old: lower BMR, lower protein needs, need to have a balanced diet to stay healthy

Women have a relative higher fat content in their bodies than men. Fat is stored in fat tissue, e.g under the skin. Fat tis-

sues have lower metabolic rate than muscle, so women have lower energy requirement for men.

Fats:

1)Two main types of fats: saturated fats (solid at rtp; from animals), unsaturated fats (liquid at rtp; from fish andplants)

2)Saturated fat increases the level of LDL (low density lipoprotein - bad cholesterol); it is not heart-healthy (arterialdisease)

3)Unsaturated fat decreases the level of LDL and increases the level of HDL (high density lipoprotein - good choles-terol). There 2 types of unsaturated fat: mono-saturated fat (have little effect on blood cholesterol) and poly-unsat-

urated fat (reduce cholesterol concentration in the blood --> reduce the risk of heart disease)

4)Cholesterol is chemical made in the liver and found in the blood. The quantity of cholesterol depends upon ourdiet and our genes that determine our metabolism. High concentration of cholesterol in the blood leads to the nar-

rowing of the arteries which then induces high blood pressure and heart disease.

5) High fat diet increases the risk of producing more cholesterol and having a high concentration in the blood.

6) Cholesterol is carried in the blood by molecules called lipoprotein (a compound contains both lipid and protein).The lipid is bound to hydrophyllic protein so that it can move through water because fats are hydrophobic.

7) There are 5 types of lipoproteins: chylomicrons, VLDL, IDL, LDL, and HDL.

8) LDL carries cholesterol from the liver to cells; if there is too much of LDL --> harmful buildup of LDL inside thecells

9) HDL takes cholesterol away from the cells and back to the liver. In the liver the HDL is broken down or expelledfrom the body as waste.

Function of cholesterol:

It builds and maintains cell membranes (outer layer)

It is essential for determining which molecules can pass into the cell and which cannot (cell membrane permeabili-

ty)

It is involved in the production of sex hormones (androgens and estrogens)

It aids in the production of bile

It converts sunshine to vitamin D

Balancing energy needs:

If you eat more food than you need, you body store the extra as fat.

Energy intake: the energy you get in a day from you food such as protein, carbohydrate, fats.

Energy output: the energy your body uses in a day.

If energy intake is greater than energy output, then fat is stored in the body and body mass increases --> become over-

weight and obese.

People with lower BMR are more likely to get overweight or obese than those who have higher BMR. It is likely that their

diet consist of a lot of fatty foods or refined food with a lot of added sugars.


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Obesity:

Causes:

1)High intake of fatty food and refined food containing a lot of added sugar

2)Too little exercise

3) Emotional stress which leads to comfort eating

Obese people tend to have health problems such as heart disease, high blood pressure, diabetes caused high bloodsugar and arthritis (worn joints)

Lose some weight:

1)Eat less high-energy food (lower the energy intake)

2) More exercise (increase the energy output)

3) Have a balanced diet

4) A gradual increase in exerciseDefinition:

1)Being 20% above the recommended weight for his or her height

2)Having a body mass index (BMI) greater than 30

BMI = body mass (in kg)/ height squared (in metres) --> for adults (different interpretations are made to children)

1)< 20 : underweight

2) 20 < x < 24: acceptable

3) 25 < x < 30: overweight

4) 30 < : obese

5) 40 < : severely obese

Constipation:

Roughage or fibre is indigestible and adds bulk to our food --> the food becomes harder --> stimulate the mus-

cles of the gut wall to contract effectively to squeeze the food along and keep the food moving down the alimen-

tary canal.

If the movement of food is slow (due to soft foods) --> constipation --> difficult to defecate (discharge faeces

from the body)

Fruit and vegetables contains a lot of roughage.

Malnutrition: diets are not balance due to either to little energy or too much energy, shortage of nutrients or far

too much of that nutrients. Constipation is a form of malnutrition because the diet lacks fibre.

Starvation:

Digestive System:

We ingest our food into the mouth, our teeth grind up (mastication) the food into small pieces and our tongues mix the

food up with saliva. (physical digestion)

Saliva is formed in the salivary glands and it contains the enzyme amylase, which breaks down starch.

The food travels along the oesophagus. The epiglottis covers the way to the trachea so that the food wont go into the

wrong way.

The food then enters to the stomach. There are goblet cells along the way to secrete mucus to make food slide easier.

The stomach has a very strong muscular wall so that it can break up the food with hydrochloric acid and protease

pepsin. Hydrochloric acid kills all the bacteria in the food.

In the small intestine, there are pancreatic juice from the pancreas and bile from the liver. The pancreatic juice contains

protease trypsin, amylase, and lipase. Amylase breaks down starch to glucose, protease breaks down proteins into


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amino acids and lipase breaks down fats to fatty acids and glycerol. Bile helps to digest fats into small fat droplets - emul-

sification. (chemical digestion)

Soluble food molucule will be absorbed into the bloodstream and there are villi on the wall that are only one cell thick to

absorb food easily. They also have large surface area so that the food can be absorbed more quickly.

Food that cannot be absorbed go along the large intestine, where water is reabsorbed. They are stored in the rectum

and egested through the anus as faeces.

Peristalsis is involved throughout the alimentary canal.

Key terms:

Ingestion: taking food into the digestive system

Digestion: breaking food down into molecules small enough to be absorbed into the bloodstream.

Absorption : taking molecules into the bloodstream. This happens almost entirely in the small intestine (ileum)

Assimilation: using food molecules to build new molecules in our bodies. I.e. the food molecule physically becomes part

of our body.

Egestion: Removing unwanted food from the digestive system ). This is not excretion, because the unwanted food has

never, technically, been inside the body.

Peristalsis: the contraction of muscle in the intestine wall behind a bolus of food (ball of food). This pushes the bolus

through the intestine.

Adaptation of the small intestine in absorbing digested substances:

Feature Function

It is very long, about 5 m in an

adult

This gives plenty of time for digestion to be

completed, and for digested food to be ab-

sorbed as it passes through

It has villi. Each villus is cov-

ered with cells which have

even smaller projections on

them, called microvilli

This give the small intestine a very large in-

ner surface area. The larger the surface

area, the faster the food can be absorbed.

Villi contain blood capillaries Digested food passes into the blood, to

then taken to the liver and then around the

body.

Villi contain lacteals Fats are absorbed into the lacteals

Villi have walls only one cell

thick

The digested food can cross the wall to

reach the blood capillaries and lacteals

easily and quickly.

Teeth:

Human teeth are specialized for eating both plant and

animal food. Viewed simply, humans are carnivores in the front

of the mouth and herbivores in the back (see figure 48.6). The


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four front teeth in the upper and lower jaws are sharp, chisel shaped

incisors used for biting. On each side of the incisors

are sharp, pointed teeth called cuspids (sometimes referred to

as canine teeth), which are used for tearing food. Behind the

canines are two premolars and three molars, all with flattened,

ridged surfaces for grinding and crushing food.

Transport in humans:

Circulatory System:

Artery - away from the heart; Vein - in the heart; Capillaries - connect arteries and veins

This is a transport system which collects and delivers materials around the body. It contains arteries, veins, and capil-

laries, and the heart which pumps the blood around the body.

Inside the blood vessels, there are many red blood cells carrying oxygen around the body and they contain

haemoglobin which binds to oxygen to make oxyhaemoglobin (red). RBC- no nucleus - more haemoglobin

The blood moves through the capillaries and some of the plasma leaks out and form tissue fluid. Oxygen diffuses out

of the red blood cells, through the plasma and tissue fluid and into the body cells and joins with glucose for respiration.

Respiration produces carbon dioxide and water and releases energy. Carbon dioxide diffuse into the plasma. The

blood is now deoxygenated and carried by veins to the heart.

The blood enters the vena cava (the biggest vein in our body), to the right atrium, to the right ventricle and finally goes

out of the heart through the pulmonary artery which leads to the lungs. The oxygenated blood from the lungs travels back

to the heart entering from the pulmonary vein into the left atrium, to the left ventricles and to the Aorta (the biggest artery

and also the main blood vessel in our bodies).

It will then go to the rest of the body cells for respiration. This is also called double circulation and it will repeat over andover again ALL the time.

Note: In each part of the heart, there are valves to prevent the blood going backward.

Substance From To

Oxygen Lungs Cells

Nutrients Small Intestine Cells

CO2 Cells CO2

Lactic Acid (Anaero-

bic)

Muscle cells Liver

Documents

Biology Revision Sheet