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IGCSE Biology Notes
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Contents
The Variety of Life . Taxonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Binomial Naming System . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kingdoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Animal Kingdom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Protoista . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Charaeristics of Lⅳing Things . . . . . . . . . . . . . . . . . . . . . . . . . . . Branching Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Couplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cells, Diffusion & Osmosis . Specialised Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cell Aⅳities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Enzymes . Properties of Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . How Enzymes Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Uses for Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Immobilisng Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Nutrition & Balanced Diets . Food Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sugar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Starch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Protein (Biuret test) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Alcohol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Digestion & Absorption . Teeth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tooth Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Duodenum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Small Intestine (Ileum) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lⅳer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Large Intestine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Nutrition in Plants . Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Leaf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chloroplasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stomata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transport in Animals . The Circulatory System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Arteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Veins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Composition of the Blood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blood Cloing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tissue Fluid Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. The Lymphatic System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Immune System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Transplants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transport in Plants . Osmosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Transpiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Faors Affeing Transpiration . . . . . . . . . . . . . . . . . . . . . . . . . . . Xerophytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Movement of Photosynthetic Produs . . . . . . . . . . . . . . . . . . . . . . . . Systemic Pesticides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Respiration & Gaseous Exchange . Aerobic Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anaerobic Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Yeast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calorimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Lungs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Increase in Breathing Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cigaree Smoke . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Excretion & Homeostasis . Excretion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Homeostasis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Pancreas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reproduction . Asexual Reproduion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Baeria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Funghi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
List of Figures A baerium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A pical plant cell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A pical animal cell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The process of osmosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A plant cell reaing to different pes of turgor pressure. . . . . . . . . . . . . . The aion of an enzyme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The alimentary canal (digestⅳe system). . . . . . . . . . . . . . . . . . . . . . . A cross-seion of a human tooth. . . . . . . . . . . . . . . . . . . . . . . . . . A single human ⅵllus om the small intestine. . . . . . . . . . . . . . . . . . . A pical leaf. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A chloroplast. On each membrane are many molecules of chlorophyll. . . . . . . A single stoma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diagram of a human heart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Human blood vessels. The lumen in the artery is much smaller than the lumen in
the vein, as the blood is at a much higher pressure. . . . . . . . . . . . . . . . . Red blood cells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Antigens on a cell. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A lymphocyte. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A lymphocyte indentiing a baerium. . . . . . . . . . . . . . . . . . . . . . . A root hair cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Water vapour build-up around a stoma. . . . . . . . . . . . . . . . . . . . . . . A simple calorimeter – used to measure the energy value of a respiratory substrate. The lungs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Some alveoli. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The aion of breathing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part of the lining of the respiratory passages. . . . . . . . . . . . . . . . . . . . The excretory system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Urea produion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Suure of an amino acid. R can stand for anything. The NH part of
the molecule (ammonia) is toⅺc, and is converted into urea. Deamination is theremoval of the niogen-containing part of the amino acid. . . . . . . . . . . . .
How urine is produced – there are two processes: ula-filation, and seleⅳereabsorption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
An indⅳidual glomerulus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Kidney failure – if one or both kidneys fail then dialysis is used or a ansplant
performed to keep urea and solute concenation in the blood constant. . . . . . . Kidney ansplant may be necessary as Rhenal dialysis is inconvenient for the patient
and costly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A summary of how body and blood temperature are maintained. . . . . . . . . .
The Variety of Life. Taxonomy
This is the scientific name for puing things into groups – classification and naming.This largest group is called a ‘kingdom’.The system was deⅵsed in the th Century by Carl Linnaeus.— Kingdom
— Phylum ..increasing similari— Class
— Order— Family
— Genus— Species
. The Binomial Naming System
All organisms have two Latin (a unⅳersal language) names – Genus and Species. The Genus iswrien with a capital leer. When handwriting, both words are underlined. When ping, they areput in italics. For example:Homo Sapiens (Handwrien)
Felix cattus (Typed)
. Kingdoms
• Animalia
• Plantae
• Baeria (monera, prokaryote)
• Fungi
• Protoista
Animal Kingdom
There are Phyla. Among them are:
• Chordates (vertebrates) (in order of evolution:)
– Fish
– Amphibians– Reptiles– Birds– Mammals
• Arthropods
– Inses* Grasshoppers, buerflies, beetles, ants etc.* , described world species* Three body regions: head, thorax, abdomen* Sⅸ legs aached to the thorax (which has segments)* Adults with one or two pairs of wings aached to the thorax (some have none)* Tow antennae* Lateral compound eyes
– Arachnids* Spiders, scorpions, ticks, moites, etc.* , described world species* Two body regions: cephalothorax, abdomen* Eight legs* No antennae* Mouth parts are chelicerae (modified appendages) which in spiders are fangs
– Crustaceans* Technically a subphylum* Classes include crabs, shrimps, lobsters, barnacles, isopods etc.* , described world speies* Two body regions* Two pairs of antennae* or more pairs of legs* Primarily aquatic, few terrestrial
– Myriapods* Chilopods
· Centipedes· , described world species· well-defined head· first pair of legs modified for envenomation· flaened top to boom· one pair of legs persegment
· one pair of antennae* Diplopods
· Millipedes· , described world species· Two pairs of legs per segments, first four segments have pair of legs· one pair of antennae· well-defined head· usually cylindrical
• Nematodes
– Roundworms– Can be microscopic, or up to m in length– Can be ee lⅳing or parasitic– No circulatory or respiratory system– Suure is a “tube within a tube”– No chaetae– Use sexual reporoduion
• Molluscs
– So bodied– No segmentation– Single muscular foot– Hard external shell (calcium carbonate) or internal shell– Most have rasping tongue (radula)– Filter feeders – mussels– Carnⅳorous – oopi– Marine organisms with shells (except barnacles and crustaceans)– Terrestrial – snails & slugs
• Annelids
– Segmented worms (e.g. earthworm)– Leeches– Sexual and asexual reporoduion (depending on species)– Vascular and nervous system– No legs but may have chaetae (stiff hairs) to aid movement– may have obⅵous head
Protoctista
• Single-celled – Eukaryotes – Protista¹
– Protozoa & Protophyta
• Multicelled
– Seaweed* Kelp* Algae
– Slime molds– Amoeba– Ciliates– Diatoms– Paramecia– Forams– etc.
. Characteristics of Living Things
M ovement
R espiration
S ensitⅳi
G rowth
R eproduion
E xcretion
N uition
. Branching Keys
A key is a means of identiing an unfamiliar organism om a seleion. Indⅳidual organisms arefound by following a series of paired, numbered options, or a chart which offers no more than twochoices at each stage. A key either wrien in couplets, or as a chart:
¹They have a proper nucleus as opposed to Baeria. Eukaryots are aquatic/plant-like organisms that don’t fit in theAnimal/Plant/Baeria kingdoms.
Couplets
. Hairy skin — .Non-hairy skin — go to .
. External pips — .No external pips — go to .
. Near spherical shape — go to .Other shape — .
. Smooth surface — .Indented surface — go to .
. Suure made up of sub-units — .Suure made up of single unit — .
Key
Foop: Woop: Moop:
..Does it have three antennae?
.Does it have three eyes?
.Is it round?
.It’s a Moop.
.
.It’s a Foop.
.
.
.It’s a Woop.
.
.
.It does not eⅺst.
.
Cells, Diffusion & Osmosis
. Specialised Cells
All cells are designed to do a particular job in an organism. This is called .Examples of specialised cells are shown below.
Pili
Plasmid
Ribosomes
Cytoplasm
Plasma membrane
Cell wall
Capsule
Nucleoid (circular DNA)
Bacterial Flagellum
Source: http://en.wikipedia.org/wiki/File:Average_prokaryote_cell-_en.svg
Figure : A baerium.
Plant cells Animal CellsAlways have cell wall made of cellulose and hence a definite shape No cell wall, hence no difinite shape
Usually have large, permanent vacuole Any vacuoles are small and temporarySome have chloroplasts Never have chloroplasts
Up to mm long Usually less than .mm long.Examples:palisade cells cheek lining cells
phloem sieve tube elements muscle fibresroot hair cell red blood cells
Table : Differences between plant and animal cells.
Golgi body
(Golgi apparatus)
Golgi vesicles
Cytoplasm
Peroxisome
Mitochondrion
(mitochondria)
VacuoleTonoplast
thylakoid membrane
Starch grain
Cell wall
Plasma membrane
Plasmodesmata
Filamentous
cytoskeletonSmall membranous
vesicles
Smooth
endoplasmic
reticulum
Ribosomes
Nuclear pore
Vacuole
Chloroplast
Nucleus
Nuclear envelope
NucleolusRough
endoplasmic
reticulum
Source: http://en.wikipedia.org/wiki/File:Plant_cell_structure_svg.svg (Public Domain)
Organelle FunctionNucleus Conols the cell’s aⅳities, contains DNACytoplasm Where metabolic reaions take place
Cell membrane Partially permeable, conols the eny/eⅺt of substancesMitochondria Where aerobic respiration takes place
Cell wall (plants only) Fully permeable, prevents cell om burstingPermanent vacuole Storage area, contains cell sap
Chloroplast (plants only) Where photosynthesis takes placeFigure : A pical plant cell.
Sperm cell designed to fertilise eggsA sperm cell is very small and has a lile tail which proⅵdes movement so it can swim and findan egg to fertilise.Its head contains enzymes (in the vacuole) which allow it do digest its way through an eggmembrane so the two nuclei can join.It contain half the number of chromosomes in the nucleus – these caryy genetic informationom the father, which will be passed on to the offspring.
Smooth endoplasmic reticulum
Rough endoplasmic reticulum
Plasma membrane
Mitochondrion
Peroxisome
Cytoskeleton
Free Ribosomes
Ribosomes
Nucleus
Nucleal poreNucleal envelope
ChromatinNucleolus
Golgi vesicles
(golgi apparatus) Lysosome
Centrioles
Cytoplasm
Secretory vesicle
Source: http://en.wikipedia.org/wiki/File:Animal_cell_structure_en.svg (Public Domain)
Organelle FunctionNucleus Conols cell aⅳities, contains DNACytoplasm Where metabolic reaions take place
Cell membrane Partially permeable, conols eny/eⅺt of substancesMitochondia Site of aerobic respiration
Figure : A pical animal cell.
Ovum (egg) cell designed to be fertilisedAn ovum is large and bulky because no aⅳe ovement is needed – it just sits and waits for thesperm to find it.It contains yolk (in the cytoplasm) which proⅵdes a large food store needed for the developingyoung organism once it’s fertilised.It contains half the number of chromosomes, which carry genetic information om the mother– this will be passed on to the offspring.
Palisade cell for photosynthesis
A palisade cell is tall with a large surface area. It’s found on the top side of a leaf – ideal for goodabsorpion of carbon dioⅺde and light – both are needed for photosyntheses.They’re packed with chloroplasts, which contain the green pigment chlorophyll, which is neededfor photosynthesis.
Ciliated cell to stop lung damageCiliated cells line all the air passages in the lungs. Mucus is sticky and so aps dust and baeria.The cilia wa and sweep up the mucus to the back of the throat where it is swallowed. Thebaeria are then killed by the acid in the stomach.
Root hair cell for absorbtionThe long hair cell increases the surface area of the root, which helps absorption of water andminerals.It has a very thin cell wall, which makes it easier for minerals to pass across into the root itself.
Red blood cells (erythrocytes) for ansportThey do not contain a nucleus, so there is more room for the protein molecule to carry oxygen.Their biconcave shape gⅳes them a large surface area for gas exchange.
Muscle cells for movementMuscle cells have protein strands that can slide across each other for conaion. Each cell hasseveral nuclei. There are pes – smooth, skeletal and cardiac.
Tissues A tissue is a group of similar cells, working to perform the same funion, e.g. muscletissue is made om muscle cells.
Organs Different tissues are arranged to form an organ. They work together to perform a particularfunion, e.g. the heart.
Organ Systems A group of organs working together form an organ system, e.g. the circulatorysystem.
. Cell Activities
All cells exchange gases, nuients and other materials between themselves and their surroundings.
Diffusion is the ee movement of particles of a substance (atoms, ions or molecules) om regionsof high concenation to regions of lower concenaion. The process continues until the particlesare evenly distributed. This is movement down a concenation gradient.Diffusion is the usual way in which molecules move into or out of cells.
Concentration gradient refers to the difference in concenation between one region and another.The greater the difference in concenaion, the steeper the concenation gradient, and the fasterthe rate of diffusion. Surfaces qhere gas exchange occurs oen maintain a steep diffusion gradientso that idffusion occuras rapidly. For example:
• across the linging of the air sacs (alveoli) in the lungs of humans• across the surface of cells bordering air spaces in the leaves of plants
Osmosis is a specific pe of diffusion. It is the diffusion of water om a dilute solution to amore concenated soution throuh a partially permeable membrane. Cell membranes are partiallypermeable membranes, and it is by osmosis that water moves into and out of cells.In osmosis, water diffuses om a high water concenation to a low water concenation (seeFigure ).
• Cells placed in distilled water will gain water by osmosis. This is because there is a lowerconcenation of water inside than outside. The cells are said to be turgid.
• Cells placed in a concenated solution will lose water by osmosis. This is because there isa greater concenation of water inside the cell. The cells are said to be flaccid. In severecases the cell membrane is pulled away om the cell wall. The cells are then said to beplasmolysed. Eventually the process may stop because the concenations on both sides ofthe cell membrane have equalised (see Figure ).
Active transport is a chemical process that results in a movement of particles in an opposite dir-eion to that expeed by diffusion. Substances are taken scross a membrane om a region oflow concenation to a region of higher concenation, i.e. against a concenation gradient. Asits name implies, it is an aⅳe process and requires energy supplied by respiration.
S olute,
e.g. sugar
Water
Part ially permeable membrane
Direct ion of water
movement
Dilute solut ion
(High water concentrat ion)Concentrated solut ion
(Low water concentrat ion)
Figure : The process of osmosis.
EnzymesEnzymes are biological catalysts. They speed up the chemical reaions which go on inside lⅳingthings, and are exemely efficient.
Plasmolysed Flaccid Turgid
Vacuole
Source: http://commons.wikimedia.org/wiki/File:Turgor_pressure_on_plant_cells_diagram.svg (Public Domain)
Figure : A plant cell reaing to different pes of turgor pressure.
Enzymes are made inside cells. Once formed, the enzymes may leave the cell and do its job outside.Such enzymes are called extracellular enzymes. They include the digestⅳe enzymes which breakdown food substances in the gut.Other enzymes work inside the cell. They are called intracellular enzymes. Their job is to speedup he chemical reaions occurring in cells, and also conol them.An example of a reaion conolled by an enzyme:
maltose(substrate)maltase(enzyme)−−−−−−−−−−→ glucose(product)
The substance which the enzyme as on it called the substrate – in this case maltose. The newsubstance or substances formed as a result of the reaion are the products. In this case there is justone produ, glucose. The enzyme catalysing this particular reaion is maltase. This reaion cango in either direion – it is reversible. If there is a lot of maltose present compared with glucose,the reaion will go om le to right. If there is a lot of glucose compared to maltose, it will goom right to le. Most metabolic reaions are reversible.
. Properties of Enzymes
. They are always proteinsWe need to take proteins in, ⅵa our food to produce enzymes.
. They are specific in their actionEach enzyme conols one particular reaion, or pe of reaion – maltase will only a onmaltose, and sucrase on sucrose.
. They can be used multiple timesThey are not altered by the reaion that they catalyse. However, they “run down” eventually andhave to be replaced.
. They are destroyed by heatingIn common with all proteins, they are denatured by proteins. Normally this happens at ◦C.
. They are sensitive to pHTheir effeⅳeness depends on the degree of acidi or alkalini of the solution which they arein. Most inacellular enzymes work best in neual conditions.
. How Enzymes Work
Substrate entering
active site of enzyme
Enzyme/substrate
complex
Enzyme/products
complex
Products leaving
active site of enzyme
Products Substrate
Active site
Enzyme changes shape
slightly as substrate binds
Source: http://en.wikipedia.org/wiki/File:Induced_fit_diagram.svg (Public Domain)
Figure : The aion of an enzyme.
Figure shows in a simplified way how enzymes are believed to work. When a substrate moleculehappenes to impa on the aⅳe site of an enzyme, the reaion takes place and the produs leave,eeing up the enzyme for another reaion.Each enzyme’s aⅳe site has a specific shape, into which only one pe of substrate will fit. This iswhy the enzyme is specific in its aion.When an enzyme is denatured by heat, the shape of its aⅳe site changes, so substrates no longerfit in it, and it is not effeⅳe.Anything which helps substrates to come into conta with the enzyme at a faster rate will increasethe rate at which the enzyme can catalyse reaions. Higher temperatures mean that moleculesmove around mroe quickly – a rise in temperature of ◦Ccan double the rate of reaion.Some minerals and ⅵtamins also increase the rate of reaion.Some poisons, such as cyanide and arsenic, inhibit enzymes by blocking the aⅳe site. Somepoisons block aⅳe sites permanently, others temporarily. This is also how some pesticides work.
. Uses for Enzymes
Enzymes can be exaed om organisms in a purified form, and then used in many scientific,domestic and industrial processes. A common useage is in biological washign powders. Variousprotein-digesting (proteases) are added to the washing powder, and they dissolve protein stains.
Biological washing powders are advantageous because they work at relatⅳely low temperatures. Thismeans they are usefulfor washing delicate fabrics, and can save elerici. However, some peopleare allergic to them.Enzymes are normally exaed om microbes, which are grown on a large scale in fermenters.Some examples of enzyme use:
Proteases are used for tenderising meat, skinning fish, remoⅵng hair om hides, and breakingdown proteins in baby foods.
Amylases convert starch to sugar in making syrups, uit juices, chocolates and other food produs.
Cellulase breaks down cellulose and is used for soening vegetables, remoⅵng the seed coat omcereal grain, and exaing agar jelly om seaweed.
Isomerase converts glucose into uose. Fruose is muchsweeter than glucose; this makes ituseful in sweets, syrups and slimming foods, as only small amounts are needed to sweeten theprodu.
Catalase releases oxygen om hydrogen peroⅺde, and is used in making foam rubber om latex.
. Immobilisng EnzymesBiotechnologists have developed a beer method of using enzymes than simply mⅸing the enzymewith the substrate. The enzymes are aachedf to an inert surface, usually glass or plastic beads. Thebeads are then brought into conta with the substrate so that the reaions can take place.One way of bringing the beads into conta with the substrate is to immerse them in a solutionof the substrate, and then wait for the reaion to be completed before colleing the produ andstarting again. This is called batch processing.The other way is to slowly pour a solution of the subate through a column of the beads, andthe colle the produ om the boom. The substrate is aed upon progressⅳely as the solutionickles down the column. This is called continous flow processing, because the produ is colleedall the time. it is more efficient than batch processing.
Nutrition & Balanced DietsNuition is the study of food and feeding processes. Food is the material om which organismsobtain the energy and the raw materials to constru, maintain and repair the body.Plants are autotrophic – they produce their own food, and come at the boom of the food chain.Humans and other animals are heterotrophic (also known as holozoic) – they eat other plants andanimals, and cannot produce their own food.Humans require a balanced diet. This is one which supplies the different pes of food in adequateamounts and the corre proportions, and proⅵdes the body with sufficient energy for its needs. Abalanced diet maintains a healthy and aⅳe life and, where necessary, growth.Humans use food for:
• Energy for body processes (usually obtained om carbohydrates and fats – sometimes om proteinwhen in a state of starvation).
• Building materials, to build the cells of the body (proteins, fats, ⅵtamins, minerals).
• Chemical reaions in the body (proteins, ⅵtamins, minerals, water).
There are seven chemical components of a balanced diet:
Carbohydrates To proⅵde energy.
Sugar Different kinds of food contain different pes of sugar: glucose or uose in uit, laosein milk, or sucrose in ordinary table sugar. The formula for glucose, the simplest possiblesugar, is CHO. It is a monosaccharide – it is made into chains of polysaccharides. Twoglucose molecules bonded together form one maltose molecule.
Starch is found in bread, potatoes and cereals. Starch is a polysaccharide made of a spiral chainof glucose molecules, and is used as the food reserves of plants.
Cellulose is a polysaccharide made of a straight chain of glucose molecules, and is used to buildplant cell walls.
Glycogen is a polysaccharide, and is used as the food reserves of animals, stored in the lⅳer andmuscles.
Fats To proⅵde energy, insulation, and to constru parts of cells.
Animal fats are obtained om lⅳestock, such as cale or pigs. They are eaten in the form ofbuer, dripping or lard. They contain saturated fatty acids, which are unhealthy in largeamounts. Fat contains twice as much energy per gram as carbohydrates and proteins do,and they are solid at room temperature.
Plant fats, or oils, for example olⅳe oil or corn oil, are liquid at room temperature. They containpolyunsaturated fatty acids, which are more healthy than satureated fatty acids.
Proteins To build muscle, make enzymes and hormones, and constru parts of cells. It is nor-mally obtained om the muscles of animals. The disease caused by protein deficiency is calledkwashiorkor. Some plants, such as soya beans and maize, contain relatⅳely large amounts ofprotein compared to other plants, so it is possible to obtain most of the necessary amino acidsom plant-based foods. Proteins are made om amino acids. of which there are differentpes. An organism’s DNA proⅵdes the template for linking amino acids in different orders toproduce proteins (there are a large number of possible combinations). Protein contains Niogenand Sulphur.
Minerals are ions of certain elements (i.e. inorganic), which are needed for particular purposeswithin the body. For example:
Calcium is needed for bone formation. Without calcium, bones are so. Calcium deficiency iscalled rickets.
Iron is required for haemoglobin, in blood. Oxygen is ansported around the body by bindingto haemoglobin. Iron is plentiful in lⅳer and kidneys. Iron deficiency results in anaemia.
Vitamins Various biological compounds required by the body. Some examples:
Vitamin A is neede by the eyes. Vitamin A deficiency is called xerophthalmia and leads toblindness.
Vitamin C keeps the lining of the mouth and gums healthy. It is found in green vegetables, butis destroyed by heating. Lack of it causes scurvy.
Vitamin D is needed to enable calcium to harden bones. Lack of it causes rickets.
Water Makes of -% of the body. The body’s chemical reaions take place in it. Humansneed about lie of water every day.
Fibre Stimulates the smooth passage of food through the gut. Mainly made of cellulose, it aidsfaeces formation.
Too much energy-rich food will cause the indⅳidual to become overweight, while too lile willcause them to become underweight.Malnuition is the result of not haⅵng a properly balanced diet. If the body does not receⅳe thecorre chemical components in the right proportions, it cannot funion efficiently.In humans, as in other animals, complex organic food can enter body cells only if it is first brokendown into smalll soluble molecules. In humans, the stages int his process are:
Ingestion Food is taken into the mouth.
Digestion The breakdown of complex organic foods into small, soluble molecules.
Absorption The uptake of soluble food substances into the body across cell membranes.
Assimilation The use of soluble food substances by cells in the body.
Egestion The removal of undigested food om the body (not to be confused with excretion orsecretion).
In humans, the alimentary canal (gut) is responsible for the ingestion, digestion, absorption andegestion of food.
. Food Tests
Sugar
. Mash the food and add water.
. Add cm3 of the food to a test tube.
. Add cm3 of Benedi’s solution to the test tube.
. Shake the test tube.
. Place the test tube in a waterbath for approⅺmately minutes. If a precipitate develops, sugar ispresent. The colour of the mⅸture gⅳes a rough indication of how much sugar is present: greenis the lowest concenation, yellow higher, brown still higher, and red the highest concenation.
Starch
. Add drops of dilute iodine solution to the food sample.
. If the colout changes to blue-black, starch is present.
Fat
. Pour approⅺmately cm3 of absolute ethanol into a test tube.
. Add a small amount of the food sample to the ethanol.
. Shake the test tube.
. Add approⅺmately cm3 of water to the test tube.
. If the mⅸture turns cloudy white, fat is present.
Protein (Biuret test)
. Mash the food and add water.
. Add cm3 of the food to a test tube.
. Add a small amount of dilute sodium hydroⅺde solution until the mⅸure clears.
. Add a few drops of dilute copper sulphate solution.
. Shake the test tube.
. If the solution turns purple, protein is present.
. Drugs
A drug is something which changes the way the body works. Useful drugs include painkillers andantibiotics. Harmful drugs can be addiⅳe, and harm the body in some way.Addiion can be chemical – when the body becomes adjusted in such a way that it needs the drug,or psychological – when the addied person feels a constant need for the drug.Withdrawal symptoms om a drug include fever, and nausea.
Alcohol
• Reduces aⅳi of nervous system.
• Removes inhibitions, causes relaxation.
• Impairs judgement
• Is poisonous to the lⅳer. Alcohol poisoning causes a coma and death.
Digestion & AbsorptionFood must get into the blood in order to be carried to the bodiy’s cells. Only soluble food cando this. Most food is insoluble, and is broken down into soluble particles through the process ofdigestion, which occurs in the digestⅳe system (see Figure ).Digestⅳe juices break down the food, starting in the mouth with salⅳa (om the salⅳary glands).The food is then swallowed, and other juices om the lⅳer and pancreas are added. Bile is producewdin the lⅳer, and then stored in the gall bladder, before being added to food in the stomach.Muscles keep the walls of the stomach and small intestine moⅵng, mⅸing up the food and digestⅳejuices, and keeping blood mⅵng through the digestⅳe system.When the food has been completely broken down, it is absorbed into the blood in the small intestine,which has a good blood supply and thin walls, which allows food to pass easily into the blood throughthe process of diffusion.Some food cannot be digested, and is egested through the anus.
. Food in chewed and mⅸed with salⅳa in the . ( minute)
Starchsalivary−−−−−→amylase
Sugars
. The carries the chewed-up food to the stomach, using muscular walls which pushfood with a wave of conaion (peristalsis). (– seconds)
. Acid digestⅳe juices, ideal for pepsin (an enzyme that breaks down proteins), are added in the. The food and the digestⅳe juices are mⅸed. (– hours)
Proteinspepsin−−−−→ Amino acids
. More alkaline juices om the pancreas (to neualise the stomach acid) are added in the . There is more mⅸing, then the fully digested food is absorbed into the blood. (–hours)
Starchpancreatic−−−−−−→amylase
Sugars
Fatsbile−−→ Fat droplets
Fat dropletslipase−−−→ Fatty acids and Glycerol
Descending colon
Ascending colon
Transverse colon
Colon
Common
bile duct
Duodenum
Gallbladder
Liver
Oral cavity
SublingualSubmandibular
Parotid
Salivary Glands
Pharynx
Tongue
R sophagus
Pancreas
Stomach
Pancreatic duct
Ileum
(small intestine)
Anus
Rectum
Appendix
Cecum
Source: http://commons.wikimedia.org/wiki/File:Digestive_system_diagram_en.svg (Public Domain)
Figure : The alimentary canal (digestⅳe system).
. Only undigested waste material reaches the . The water is taken back into thebody, leaⅵng solid waste. (– hours)
. Undigested food is stored in the reum, and then the solid waste is egested through the anus asfaeces.
. Teeth
Enamel
Dentine
PulpGum
Cementum
Bone
Blood vessel
Nerve
C
r
o
w
n
R
o
o
t
Source: http://commons.wikimedia.org/wiki/File:Tooth_Section.svg (Public Domain)
Figure : A cross-seion of a human tooth.
An adult teeth has, at most, teeth. Thre are four main pes: , , -and . Incisors are for cuing pieces off food, while canines are for griping it. Pre-molars andmolars are for grinding the food down until it can be swallowed easily.The outside of a tooth is formed by hard enamel. Beneath this is a layer of hard dentine. In thecene is a so area called the pulp caⅵ, which contains small blood vessels and a nerve (see Figure). Tiny channels containing extensions of lⅳing cells tun outom the pulp caⅵ into the dentine.These make the dentine sensitⅳe. The enamel and dentine are made hard by the presence of calciumphosphate, the same substance that makes bones hard.The outside of the root is covered by a material called cement. Aached to the cement are toughfibres which run into the jaw bone. These fibres hold the tooth in its socket; they allow the toothto move slightly, and cushion it om being jarred when it hits something hard.
Tooth Decay
Tooth decay is caused by baeria in the mouth. These baeria form an inⅵsible layer called plaqueon the surface of the teeth.Aer a meal, the baeria feed on any sugar present and turn it into acid. The acid eats into the
teeth. Within approⅺmately one hour the acid is neualised by the salⅳa. However, the decay hasoen already started by this time.Decay usually starts between the teeth and in the creⅵces on the crowns. The acid eats through theenamel into the dentine, allowing baeria to get into the pulp caⅵ. In severe cases the baeriamay spread to the base of the tooth, causing an abscess.Baeria may also get between the tooth and the gum, causing the gum to bleed. Sometimes thefibres aaching the tooth to the jaw are aacked, in which case the tooth gets loose and eventuallyfalls out.There is strong eⅵdence that fluoride helps to prevent tooth decay. It strengthens teeth when theyare forming, and makes the enamel more resistant to acid.Where there is not enough fluoride naturally occuring in public drinking water supplies, it is addedartificially. This has led to a large improvement in the general dental health of the population.
. Duodenum
Food leaⅵng the stomach enters the . Secretions om the lⅳer and pancreas are added(pancreatic juice contains all three pes of digestⅳe enzymes). Bile is stored in the gall bladder,and emulsifies fats. Sodium hydrogen carbonate neualises the stomach acid.
. Small Intestine (Ileum)
Digestion is completed in the (or ), which secretes digestove enzymes, andabsorbs food.The small intestine is covered in millions of tiny protusions called (see Figure ). They increasethe surface area, and so increasing the rate at which the small intestine can absorb food. Each ⅵllushas a thin surface layer, so there is only a short distance for absorption. Inside is a network ofcapillaries to caryy away the absorbed sugars and amino acids. There is also a laeal, to carry awaythe absorbed fatty acids to the lymhpatic system. Conneed to the capillaries is a blood vessel,which carries the absorbed foods to the hepatic portal vein, and then on to the lⅳer.
. Liver
Many cells perform a wide range of funions in the lⅳer, in processing the absorbed foods.
..glucag
on
⇐====⇒insul
inGlycogen stores
Glucose −→ Energy ⅵa Respiration..−→
to other tissue ⅵa the circulation
Thin surface layer
Capillaries
Lacteal
Blood vessel
Figure : A single human ⅵllus om the small intestine.
..−→Synthesis of plasma proteins e.g. fibrinogen
Amino acids −→ Excess are deaminated −→ Urea for excretion..−→
to other tissue ⅵa the circulation
..−→Fat stores
Fatty acids −→ Fats for cell membranes..−→
Energy ⅵa respiration
. Large Intestine
Water and salt are absorbed in the C. Undigested food is stored in the , along withbaeria and some dead cells. This forms faeces and is passed through sphiners out of the anus.
Nutrition in Plants
. Photosynthesis
P is the process by which green plants make glucose and other organic molecles ominorganice molecules, using light energy. The light energy is apped by chlorophyll. The overallprocess for photosynthesis can be summarised as:
Carbon Dioxode +Waterchlorophyll−−−−−−−→light energy
Glucose + Oxygen
Glucose is not the only organic substance made by photosynthesis. Other carbohydrates are alsoformed, which can then be converted to fats, or, by combining with minerals, form amino acids andⅵtamins. Photosynthesis is the source of all organic substances in the plant.
..Carbon dioxide +Waterchlorophyll−−−−−−−→light energy
Glucose and other sugars + Oxygen
.
respired or used tomake:
• starch
• sucrose
• cellulose
• proteins
• fats
• ⅵtamins
• chlorophyll
.excretedorrespired
Products of Photosynthesis Glucose and other sugars:
• Much of the glucose is converted to for temporary storage in the leaf. At night, the starchmay be broken down to the sugar and ansported through th phloem to other parts ofthe plant.
• In the leaf, and throughout the plant, glucose is broken down in to release energy.
• In growing regions, glucose is converted to to make cell walls.
• In the leaf, some glucose is combined with niate to form . These are later incorpor-ated in to to make enzymes and to make struural parts of cells, such as membranes.If there is a shortage of niate, the plant is unable to grown properly, and is weak and unhealthy.
• In the leaf and elsewhere, glucose and other sugars are used to make for struures such ascell membranes and to make which have essential uses for the plant.
• Some glucose is combined with minerals, especially magnesium, to form , the greenpigment used to ap light in photosynthesis.
Oxygen:
• Used in throughout the plant.
• Excreted through stomata as a .
. The Leaf
Cuticle
Upperepidermis
Palisademesophyll
Spongymesophyll
Lowerepidermis
Stoma Guard cells
Xylem
Phloem
Vascularbundle
Source: http://en.wikipedia.org/wiki/File:Leaf_anatomy.svg (CC-BY-SA-2.5)
Figure : A pical leaf.
Each leaf is aached to the stem or branch by a , This leads to the in the leaf. Leavesare covered by a layer of waxy meial called the , which is normally thick and waterproof.It prevents the leaf om losing too much water in hot weather.Immediately under the cuticle is a layer of cells called the . which forms the ‘skin’ ofthe leaf. The epidermis may be pierced by lots of tiny holes called (singular ). Thestomata are mainly on the lower side of the leaf. They allow gases to diffuse in and out of the leaf,and water vapour to escape. Each stoma is flanekd bvy a pair of which can open andclose. They close in hot, dry weather to prevent too much water evaporating om the leaves.
Leaves are generally flat, sometimes large, and oen numerous. The result is that they have a largesurface area for aborbing Carbon dioⅺde and ligt. The veins help to support the leaf, and hold itout flat, so that it can catch the maⅺmum amount of light. In many plants the leaves are positionedin such a way that they don’t shade each other.Between the upper and lower epidermis are ltos of cells which together makes up the .These cells contain , and this is where photosynthesis takes place. The mesophylltowads the upper side of the leaf consists of cells shaped like bricks, and arranged neatly side byside. They are called . The other mesophyll cells are rounded and more irregular intheir arrangement. They are called .Between the mesophyll cells are into which he stomata open. When photosynthesis istaking place, carbon dioⅺde diffuses through the open stomata into the air spaces. It then diffusesinto the cells.Phototsynthessis takes place mainly in the palisade cells. They contain most of the chloroplasts,and they are near the surface of he leaf that gets most light. the chloroplasts are oen clusteredtowards the tops of the cells, in the best position for catching light.The vein is made up of two parts: the towards the top, and the below. The xylembrings water and mineral salts to the elaf. The phloem takes soluble sugar and other produs ofphotosynthesis away om the leaf. Together thexylem and phloem are calld .
Chloroplasts
Chloroplasts are filled with rows of thin interconneed . Millions of molecules are laid out on these membranes.Chlorophyll is a complex organic green which contains , and it plays a ⅵtal rolein photosynthesis, by absorbing blue and red light, but refleing green light.
Stomata
Stomata allow carbon dioⅺde and oxygen to diffuse in and out of leaves. They are also the mainroute by which water vapour excapes om the plant. In hot, dry weather there is a risk that theplant may run short of water. For this reason it is important that the stomata should be able toopen or close according to the weather conditions.When th estoma opens, the guard cells take up water om the neighbouring epidermal cells; as aresult the guard cells swell up and become more turgid. As they swell up they bend, so the gapbetween them widens (see Figure ). They swell up because the inner wall of the guard cells isthicker, and less elastic, than the outer wall.The stoma closes by the reverse rocess. Water passes out of the guard cells, so they become lessturgid. As a result the guard cells straighten, and the gap between them narrows.Around the stoma are sausage-shaped .
outer membrane
intermembrane space
inner membrane
stroma(aqueous fluid)
thylakoid lumen(inside of thylakoid)
thylakoid membrane
granum(stack of thylakoids)
thylakoid(lamella)
starch
ribosome
plastidial DNA
plastoglobule(drop of lipids)
Source: http://commons.wikimedia.org/wiki/File:Chloroplast.svg (CC-BY-SA-(any version) or GNU FDL)
Figure : A chloroplast. On each membrane are many molecules of chlorophyll.
Transport in AnimalsAll organisms which are large require a ansport system, to move substances around the body.Single-celled organisms with low levels of aⅳi do not require ansport systems.Humans have two main ansport systems:
• Circulatory system
• Lymphatic system
. The Circulatory System
Single Circulatory Systems e.g. fish:..Heart
.Gills.Tissues
Blood passes once through the heart on its way around the body.
Double Circulatory Systems e.g. humans:
guard cell
vacuole
chloroplast
epidermal cell
stoma almost closed
stoma wide open
The guard cells have taken
in water by osmosis , as
indicated by the arrows.
Figure : A single stoma.
..Heart.Tissues .Lungs..deoxygenated blood
..oxygenated blood
..oxygenated blood
..deoxygenated blood
Arteries
Aorta takes oxygenated blood om the heart to the body
Pulmonary artery takes deoxygenated blood om the heart to the lungs. The only artery whichcarries deoxygenated blood.
Veins
Superior Vena Cava brings deoxygenated blood om the head and arms back to the heart
Inferior Vena Cava brings deoxygenated blood om the body back to the heart
Pulmonary Vein brings oxygenated blood om the lungs back to the heart. The only vein whichcarries oxygenated blood.
Diastole( l̄ling)
Systole(pumping)
Right and left
ventricles
Antrioventricular
valve
Pulmonary veins
Right and left
Atrium
Pulmonary artery
AortaSemilunar
valve
Anterior
vena cava
Posterior
vena cava
Source: http://commons.wikimedia.org/wiki/File:Human_healthy_pumping_heart_en.svg (Public Domain)
Figure : Diagram of a human heart.
• When the heart is relaxed (), both sides fill up with blood om the veins.
• The aia then cona ( ). So blood is forced into the venicles through thevalves.
• A aion of a second later, the venicles cona ( ). The valves betweenthe aia and venicles close, so blood is squeezed in to the arteries.
• The heart relaxes again and fills up with blood.
Cardiac arrest/Myocardial infarction Heart aack
Atheroschlerosis/atheroma/angina Lack of oxygen to ehart due to fat build-up in coronary arter-ies, leading to chest pain.
Sinoatrial node Group of cells taht regulate heart beat (pacemaker).
Hypertensive High blood pressure
Stroke Atheroschlerosis deprⅳes an arteryin the brain of oxygen.
Lumen
Collagen ̄ bres
Thin layer of muscle
and elast ic ̄ bre
S mooth endothelium
Artery Vein
Capillary
Nucleus of
endothelial cell
S ingle layer of
endothelial cells
Figure : Human blood vessels. The lumen in the artery is much smaller than the lumen in thevein, as the blood is at a much higher pressure.
Composition of the Blood
Plasma is % water. Plasma ansports carbon dioⅺde om the organs to the lungs, solubleprodus om the small intestine to the organs, and urea om the lⅳer to the kidneys. Thefollowing cells are suspended in it:
Red Blood Cells – Erythrocytes Red blood celsl are disc-shaped and biconcave. These cells haveno nucleus, so they can carry more oxygen. Red blood cells contain a chemical called .This combines with oxygen to form oxyhaemoglobin.A red blood cell’s lifespan is about four months. Aer this time it goes to the spleen, which removesworn out red blood cells om circulation.
Source: http://commons.wikimedia.org/wiki/File:Erythrozyten_und_Osmotischer_Druck.svg (Public Domain)
Figure : Red blood cells.
White Blood Cells – Phagocytes & Lymphocytes There are several different pes of white bloodcells. They are all larger than red blood cells, and have a nucleus. Lymphocytes have a nucleus whichoccupies most of the cell.White blood cells prote the body om baeria.Phagocytes can squeeze through capillary walls, move towards baeria, and ingest them.Lymphocytes produce chemicals which destroy baeria, by makign them stick together.
Platelets These are agments of blood cells budded off in the red blood marrow. These cells havea sticky surface, and help to clot the blood at wounds, to stop bleeding.
Blood Clotting
. Blood vessel wall is damaged or broken.
. The protein within the blood vessel wall is exposed. This causes platelets to release an enzyme(thrombin).
. Blood plasma carries a soluble protein called .
. Enzymes secreted by platelets cause soluble fibrinogen to turn into insoluble .
. Fibrin forms long threads which precipitate out of the blood.
. The fibrin threads tangle together and ap red and white blood vessels in the clot.
. The clot dries and hardens, forming a scab.
Tissue Fluid Formation
. Arteriole brings blood into the capillary bed
. The arteriole dⅳides into a network of small capillaries
. Fluid leaks out of the capillaries, especially at the beginning of the capillary bed, and bathes thebody cells.
. The fluid is called . It carries glucose and oxygen om the blood to the cells.
. Tissue fluid containing CO and urea leaks back into the cappillaries at the venous end of thecapillary bed.
. Venule carries blood back to a vein.
. The Lymphatic System
Lymph nodes contain white blood cells, and a as aps for baeria and foreign particles. Tissuefluid containing foreign and waste materials drain into the lymphatic system, pass through a lymphnode, and re-enter the blood circulation.
The Immune System
All cells have protein molecules on their surface membranes called (See Figure ).
Figure : Antigens on a cell.
Lymphocytes (see Figure ) produce . Theseare chemicals which rea to foreign antigens and destroythe foreign cells. Lymphocytes ‘recognise’ antigens on thesurface of body cells and do not produce antibodies againstthem.
Figure : A lymphocyte.
If foreign cells, e.g. baeria, enter the body, lymphocytes recog-nise these as foreign due to their different antigens. The lymph-ocytes will then release antibodies to destroy the baeria.There are thousands of lymphocytes which each produce a dif-ferent antibody. Thus, thousands of different pathogens can bedestroyed. Lymphocytes also produce ‘memory cells’, which re-main in the lymph nodes. These memory cells can produce antobodie very quickly if the sameforeign antigen enters the body again. These antibodies destroy the baeria before they cause alarge infeion – the body is immune to that species of baerium.
Transplants
If a patient needs to have an organ ansplanted into their body, dors must ensure that the antigenson the donor organ are very similar to the patient’s antigens. Otherwise, there is a chance that thepatients lymph nodes will produce antibodies against the organ, rejeing it.Brothers and sisters have similar DNA and are oen used as donors. Patients are kept in sterileconditions aer the operation, and are on drugs to suppress their immune system for the rest oftheir life immunosuppressⅳe drugs).
Transport in PlantsPlants need ansport systems to:
• Move water om the soil to the leaves for use in photosynthesis.
• Move photosynthetic produs om the leaves to other parts of the plant e.g. uit amd growingparts of the plant.
Xylem vessels ansport water om the roots to the leaves. Xylem vessels are long, continuous tubes– it is dead tissue containing . Lignin makes the xylem vessels strong, and is depositedunevenly, which leads to pits in the walls through which water can enter and leave the tubes.
Phloem tubes (sieve tubes) are lⅳing tissue. At the end of each cell making up the tube, the cellwall is perforated to allow easy movement of sucrose. The movement of sucrose om the leavesto where it is needed is called anslocation. Phloem cells contain few organelles. The majoriof aⅳities are performed by a companion cell which proⅵdes energy to the phloem cell.
Root hair cells are found on young roots. They increase the surface area of the root for absorptionof water an mineral ions. They last for approⅺmately one day.
. Osmosis
Water moves by osmosis across the root.Osmosis is the net diffusion of water molecules om a region of high water potential to a region oflow water potential through a partially permeable membrane (down a water potential gradient).Water potential of a substance is a measure of howmuch water there is int it, and how easily the watermolecules can move around. Substances with a lot of water have a high water potential. Substanceswith a lile water have a low water potential. Water moves om areas of high water potential toareas of low water potential.
. TranspirationWater does not move by osmosis in the xylem. The xylem is dead tissue, and there are no cellmembranes. Water moves up the xylem because of anspiration.Transpiration is the loss of water vapour om a leaf through the stomata.
• % of water that is absorbed is lost in anspiration.
• The remaining % is used in photosynthesis.
As water leaves the xylem vessels it reduces the water pressure at the top of the xylemm, so watermoves upwards towards a lower pressure. Transpiration produces a tension (pull).Water molecules are sticky; they stick to each other (), and this helps water to be pulledup the xylem. Transpiration is aided by this cohesion.
Factors Affecting Transpiration
Wind speed Wind removes water vapour om around the stoma, so it increases the water potentialgradient (the water potential of the atmosphere around the toma becomes more negatⅳe) (seeFigure ).higher wind speed, higher transpiration
Humidity The higher the humidi, the lower the water potential gradient, so less water evaporatesom the leaves.higher humidity, lower transpiration
Light intensity During sunlight, stomata open to allow CO in for use in photosynthesis.higher light intensity, higher transpiration
Temperature One a hot day, water evaporates more quickly om the leafhigher temperature, higher transpirationIf the plant loses too much water, it loses turgor pressure in the cells and may wilt – the stomatawill close at this point.
Water supply If there is not enough water, the plant will clsoe its stomata to conserve water.lower water supply, lower transiration
Leaf surface area A greater leaf surface area means more stomata for water to siffuse out of.higher surface area, higher transpiration
Stomata Water is mainly lost through stomata – the more stomata there are, the more anspirationthere is. Most stomata are located on the underside of the leaf.more stomata, higher transpiration
Air spaces More air spaces in the spongy mesophyll of a leaf mean there is mroe space for water tocolle.mroe air spaces, higher transpiration
. Xerophytes
Xerophytes are plants taht are specially adapted to lⅳe in exeme conditions. Some examples ofadaptations:
Thick cuticle stops unconolled evaporation through leaf cells.
Small leaf surface area less surface area for evaporation, e.g. conifer needles, caus spines
Low stomata density smaller surface area for diffusion
Sunken stomata maintains humid air around stomata, e.g. marram grass, cai
Stomatal hairs (trichores) maintains humid air around stomata, e.g. marram grass, couch grass
Rolled leaves maintains humid air around stomata, e.g. marram grass
Extensive roots maⅺmise water uptake, e.g. cai
. Movement of Photosynthetic Products
Photosynthesis occurs in the leaves. It produces glucose – leaves are a . Glucose is convertedinto sucrose for ansport around the plant. Sucrose is a disaccharide. it is less reaⅳe than glucose,and does not get used up as easily as glucose.Sucrose enters the phloem tubes, and is taken to wherever it is needed, e.g. growign shoots, devel-oping uits, roots (anywhere where respiration is happening).The places where sucrose is taken to are called . movement of organic substances is called (also applies to amino acids, lipids etc.).Once at the sink sucrose may be converted to starch for storage (e.g. potatoes), or it may be convertedto other sugars (e.g. uose in uits). In this way very high concenterations of sugars can be builtup without affeing the water potential of cells. Sucrose can also be converted back to glucose forrespiration.
. Systemic Pesticides
Systemic pesticides are absorbed into the plant and ansported throughout the plant in the phloem.The targeted organism (e.g. an inse) feeds on the plant and eats the pesticide and dies.Systemic pesticides are muchmore effeⅳe than conta pesticides, but long term effes on humansare unknown, and consumers may not want to eat produs eated with them.
Respiration & Gaseous ExchangeEvery cell in every lⅳing organism needs energy. Energy is obtained om food by the process ofrespiration. There are two pes of respiration:
. Aerobic Respiration
The break-down of glucose using oxygen to release energy used by cells ( mol Adenosine Tri-phosphate (ATP)).Energy (in the form of ATP) is used in muscle conaion, aⅳe ansport, reaions(building up substances), reaions (destroying substances). Anabolic and catabolic re-aions are together known as reaions. Some energy is released as heat.
Glucose + Oxygen −→ Carbon dioxide +Water + energy
C6H12O6 + 6O2 −→ 6CO2 + 6H2O+ 38mol ATP
CO and HO are byprodus of respiration.
. Anaerobic Respiration
The break-down of glucose without oxygen to release energy used by cells. Less energy is produced( mol ATP).
Yeast
Yeast is a single-celled fungus which can respire anaerobically.
Glucose −→ Ethanol + Carbon dioxode + energy
C6H12O6 −→ 2C2H5OH+ 2CO2 + 2mol ATP
. Calorimeters
Different foods contain different amoutns of energy. Fats contain about twice as much energy ascarbohydrates and proteins. The amount of energy in food can be measured using a calorimeter.
. The Lungs
The alveoli are adapted for efficient gas exchange:
Large surface area Increased by the alveoli. ,, alveoli ≈ m2.
Thin epithelium A Two cell layer separates the air in the alveoli om the blood in the capillaries– only a short distance forgases to diffuse.
Moist Gases dissolve in solution before diffusion – more efficent effusion. Prevents dehydration ofcells.
Blood supply A good blood supply to and om the lungs by a capillary network keeps concenationgradients different by remoⅵng oxygenated blood om the lungs and bringing deoxygenatedblood to the lungs.
Increase in Breathing Rate
ncreased respiration causes an increase in the produion of CO. CO dissolves in water to formcarbonic acid.
CO2 +H2O H2CO3 H+ +HCO−3
H+ ions lower the pH of the blood, and are taken up by oxyhaemoglobin, which then releasesoxygen.Increased CO is deteed by chemoreceptors located in the carotid arteries, aorta, and medulla inthe brain.Chemoreceptors send impulses to the medulla. The medulla then sends impulses to the intercostalmuscles and the diaphragm, causing them to cona more equently (increased ventilation).
Cigarette Smoke
There are three major chemicals in cigaree smoke:
Nicotine • An addiⅳe drug• Higher heart rate• Higher blood rate
Tar • Paralyses the cilia on ciliated cells• Makes goblet cells over-produce mucus• Too much mucus
– Smoker’s cough to remove the mucus– This can damage the alveoli walls, which can lead to emphysema (surface area of alveolireduced, so less oxygen can be absorbed)
• Is a carcinogen (benzene)
Carbon monoxide binds irreversably with haemoglobin, therefore the oxygen carrying capaci ofthe blood is greatly reduced. Smokers have ≈ 10% of their haemoglobin bound to CO – thisforms Carbaminohaemoglobin.
Other smoking-related diseases:
Chronic bronchitis Smoke irritates the bronchi and bronchioles, damages the mucus membranes,and narrows the tubes. It reduces the cilia aion, so mucus cannot be removed, which leads tobaerial infeions. It is more difficult for O to diffuse into the blood.
Excretion & Homeostasis
. Excretion
Excretion is the removal om the body of waste produs of metabolism (which may be toⅺc) andsubstances which are in excess of requirements, e.g. CO and urea. CO is removed ⅵa the lungs.Urea is removed ⅵa the kidneys.
Rhenal artery Brings oxygenated blood full of urea to the kidneys.
Rhenal vein Takes deoxygenated blood which is ee om urea back towards the heart ⅵa the VenaCava.
Kidney Removes unwanted (and excess) substances om the blood, turns them into urine, andpasses the urine on to the bladder. It does this by filtering the blood. cm3 of blood isfiltered by the kidneys every minute.
Ureter Tubes which conne the kidneys to the bladder.
Bladder A muscular bag which can store urine. Can store up to about cm3 before the need tourinate (miuration) becomes compelling.
Sphincter Muscle which, when it conas, urine is prevented om leaⅵng the body, and when itrelaxes, urine can leave the body.
Urethra Tube which carries urien om body.
. Homeostasis
Homeostasis is the maintenance of a constant internal enⅵronment. Examples:
• Body temperature
• Blood pH
• Blood pressure
• Blood glucose concenation
• Blood water concenation
The mechanism by which homeostasis is maintained is by using negatⅳe feedback systems, whichmaintain stabili in the body.
..NORM
.Body detes change and a correⅳemechanism is put in place.
.NORM
.Body detes change and a correⅳemechanism is put in place.
.Rise aboveNorm
.DecreasebelowNorm
.Return toNorm
.Return toNorm
.. (i.e. a change)
.deteed by a
.co-ordinated by a -
.a change occurs in an
.which causes a
Sweating • water evaporates, takes heat om the surface of the skin
Vasodilation • causes more blood to avel to capillaries near skin surface• heat is radiated away om the body• skin appears flushed, because there is more blood flowing through the surface capillaries
Raised hairs • aps air (which insulates) next to skin surface
Vasoconstriction • reduces blood flow to surface capillaries• skin is pale, because there is hardly any blood flowing through surface capillaries
. The Pancreas
The pancreas is both an gland and an gland.
Exocrine gland a gland that secretes externally through a du — the pancreas secretes pancreaticjuice, produced in Acinar cells, into the pancreatic du.
Endocrine gland a gland that secretes hormones direly into the bloodstream — the pancreassecretes the hormones insulin and glucagon, om the Islets of Langerhans, into the bloodstream.
Reproduction
. Asexual Reproduction
• One parent
• Offspring is genetically indentical
• Does not involve gametes
• New diploid cells are produced direly by mitosis (by other diploid cells)
Bacteria
Baeria reproduce by binary fission..
Funghi
ant ibodies
DNA
bacter ium
body cell
nucleus
lymphocyteant ibodies can
bind to the
bacter ial
ant igens, and
destroy the
bacter ium
antibodies do
not bind to body
cell ant igens,
and body cell is
not destroyed
Figure : A lymphocyte indentiing a baerium.
.
.
.nucleus
.cell membrane
.cytoplasm
.cell wall
Figure : A root hair cell
.
.stoma
.leaf underside .boundary layer(water vapour)
Figure : Water vapour build-up around a stoma.
crucible
substrate
thermometer
water
oxygen
Figure : A simple calorimeter – used to measure the energy value of a respiratory substrate.
Trachea
Cardiac notch
Bronchioles
Tertiary bronchi
Secondary bronchi
Primary bronchi
Larynx
Source: http://en.wikipedia.org/wiki/File:Diagrama_de_los_pulmones.svg (GNU FDL)
Figure : The lungs.
Connective tissue
Alveolar sacs
Alveolar duct
Mucous gland
Mucosal lining
Pulmonary vein
Pulmonary arteryAtrium
Alveoli
Capillary beds
Source: http://commons.wikimedia.org/wiki/File:Alveolus_diagram.svg (Public Domain)
Figure : Some alveoli.
Inhalation Exhalation
Source: http://commons.wikimedia.org/wiki/File:Expiration_diagram.svg (Public Domain)
Figure : The aion of breathing.
ci l iated cel l
columnar
epithel ial
cel ls
goblet
cel l
basement
membrane
ci l ia beatingmucus released from
goblet cel l
Figure : Part of the lining of the respiratory passages.
bladder
ur eter
k idney
rhenal
ar teryrhenal
vein
sphincter
ur ethra
adrenal glands
(secrete adrenalin)
Figure : The excretory system.
1. Protein is taken
to alimentary canal.
2. Protein is digested
to amino acids .
3. Amino acids are
absorbed into blood,
and taken to liver in
hepat ic portal vein.
4. Amino acids that are
needed are released into
circulat ion.
5 . Amino acids which
are not needed are
deaminated to ammonia
or a carbohydrate.
6. Ammonia is
converted to urea.
7. Urea is carr ied to
kidney, where it is
filtered from the blood.
Figure : Urea produion.
C COH
OR
H
NH
H
Figure : The Suure of an amino acid. R can stand for anything. The NH part of themolecule (ammonia) is toⅺc, and is converted into urea. Deamination is the removal of the niogen-containing part of the amino acid.
. .
..Bloodvesse
lbrin
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orew
atercan
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underthe
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Ha.
..Fluidcontain
ings
mall
molecules–e.g
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fthe
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wman’scapsule
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..Filate
movesalo
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ubule.
Usefu
lsubsta
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reabsorbed
back
into
theb
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esalts,and
somew
ater(sele
ⅳereabsorptio
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purpose.Th
isrequiresaⅳ
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which
inturn
requiresA
TP.T
hecells
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heRh
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contain
many
mitochondriaforthisp
urpose.
..Sal
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unding
theL
oopof
Henlemeans
thatwater
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seso
utofthe
Loop
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. .Fluidcontain
ingw
ater,saltsand
urea
continu
esalo
ngtheR
henaltube.
. .C
leanbloodpasse
sout
ofthek
idneyⅵ
athe
Rhenalvein.
. .Ur
inee
ⅺtsthe
kidneyⅵ
athe
urete
r.
. Loopof
Henle
.Rh
enal
tubule
Figure:H
owurineisp
roduced–therea
retwoprocesses:ula-filation,and
sele
ⅳereabsorptio
n.
aADH
isah
ormone.
Source: Gray’s Anatomy (Public Domain)
Figure : An indⅳidual glomerulus.
..
. Air ap and airdeteor
.Clean blood
.Venous pressure monitor
. Removed bloodfor cleaning
. Arterial pressuremonitor
.Blood pump
. Heparin pump (toprevent cloing)
. Dialyser inflowpressure monitor
.Used dialysate
.Fresh dialysate
.Dialyser .Patient
Source: http://commons.wikimedia.org/wiki/File:Hemodialysis-en.svg (GNU FDL and CC-BY-SA-ALL)
Figure : Kidney failure – if one or both kidneys fail then dialysis is used or a ansplant performedto keep urea and solute concenation in the blood constant.
Diseased
kidneys
ArteryVein
Transplanted
kidney
Transplanted
ureter
Bladder
Figure : Kidney ansplant may be necessary as Rhenal dialysis is inconvenient for the patient andcostly.
..
enⅵronmental
temperat
ure
.
skin
temperat
ure
.skin
warm
receptors
.skin
coldreceptors
.cereb
alcortex
.anter
iorhypothalamu
s
.sweatin
g. skin
arteriolesdilate.
meta
bolic
rate
decre
ases
.hairso
nbody
lieflat
.poste
riorh
ypothalam
us
.shⅳe
ring
.skin
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ri.
hairraised
.adrenaline
.meta
bolic
rate
incre
ases.
thyroⅺ
ne
. bloodtem
perat
ure
. ︸
︷︷︸
. ︸︷︷
︸
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.inhibi
tion
.inhibi
tion
Figure:A
summaryo
fhow
body
andbloodtem
perat
urea
remain
tained.
