Unit 1 Revision NotesWater

Solvent – substances can easily dissolve in it and be transported around plants and animals

Dipolar – The molecule has a negative and positive side; this means it will completely surround and dissolve negative or positive ions. (H =positively charged, O =negatively charged)

Cohesive – attracts molecules of the same type because it is dipolar.

Monosaccharides Single sugar units that provide a rapid source of energy as they are readily

absorbed.

Disaccharides Two sugar units joined together in a condensation reaction, where a water

molecule is removed, creating a glycosidic bond. The glycosidic link can be split by a hydrolysis reaction, where water is

added to the bond.Maltose = Glucose + GlucoseLactose = Glucose + GalactoseSucrose = Glucose + Fructose

Polysaccharides Polymers made up from simple sugar monomers, joined by glycosidic links

into long chains. 2 main types: Starch (plants), Glycogen (animals)

StarchAmylose

Insoluble storage molecule Unbranched chain of glucose Coiled structure-compact

Amylopectin Insoluble storage molecule Long, branched chain of glucose Side branches-easily hydrolysed-glucose released quickly

Glycogen main energy storage molecule in animals multiple side branches (more than amylopectin) very compact molecule – good for storage insoluble in water

Lipids: Triglycerides 1 molecule of glycerol, and 3 hydrophobic fatty acid tails Insoluble in water Joined with ester bonds by condensation reactions and spilt up with

hydrolysis

Saturated Lipids Mainly found in animal fats Melt at higher temperatures No double bonds Every carbon is ‘saturated’ by at least two hydrogen atoms

Unsaturated Lipids Mainly found in plants Melt at lower temperatures Double bonds between carbon atoms in tails, causing the chain to kink 1 double bond = monounsaturated 2 or more double bonds = polyunsaturated

Amino Acids Joined together by peptide bonds to form polypeptides, formed via

condensation reactions

Proteins Made from long chains of amino acids

4 Structural Levels: Primary, Secondary, Tertiary, QuaternaryPrimary Structure

The sequence of amino acids in the polypeptide chain Held together by peptide bonds

Secondary Structure Hydrogen bonds form between the amino acids Coils into an alpha helix or folds into beta pleated sheets

Tertiary Structure Ionic bonds, disulfide bridges and hydrophobic/hydrophilic interactions join

to create a 3D shape

Quaternary Structure For several different polypeptide chains, more bonds are formed between

the individual chains, causing further alteration to the 3D shape

Types of ProteinGlobular

Round and compact Hydrophilic on outside, hydrophobic on inside Soluble Easily transported Example : Haemoglobin

Fibrous Long, insoluble polypeptide chains Tightly coiled to form a rope shape Lots of very strong bonds Example : Collagen

Enzymes Biological catalysts of metabolic reactions Globular proteins Enzyme-Substrate complex

-Lowers the activation energy required-Reduces the repulsion between substrates if they need to be joined

-Puts a strain on bonds, making them break up more easily Lock and Key model

-Like a lock and key, enzymes only work with substrates that fit in their active site

Induced Fit Model-The substrate has to be the right shape to fit the active site-As the Substrate binds to the active site, the active site changes according to the shape of the substrate

Enzymes usually only catalyse one reaction, only one substrate will fit Active site’s shape is determined by the 3D protein structure Enzyme concentration increases the rate of reaction

-only to a certain point, where the substrate is limited and adding more enzymes has no effect

The Circulatory System

The Heart Right = deoxygenated blood to lungs Left = oxygenated blood to body Left Ventricle thicker as has further to push blood

The Cardiac Cycle Cycle of events that occurs as the heart contracts in one heart beat

Diastole Ventricles and atria relax Semi-lunar valves close Atrioventricular valves open Blood flows into atria

Atrial Systole Ventricles are relaxed, atria contract Blood moves into ventricles

Ventricular Systole Atria are relaxed, ventricles Atrioventricular valves close, preventing backflow Blood forced into aorta and pulmonary arteries contract Blood moves into ventricles

Blood Vessels

Artery Carry blood from the heart at high pressure Thick walls, muscular and have elastic tissues Endothelium is folded, allowing the artery to expand

Veins Carry blood to heart Wider lumen, with thinner walls and less elastic tissues Have valves to prevent backflow as pressure is lower

Capillaries Small one cell thick Substances are exchanged between the cells and the capillaries via

diffusion Capillary beds increase the surface area for exchange – increasing the

speed of diffusion

Cardiovascular Disease (CVD)

Atherosclerosis The disease process that leads to Coronary Heart Disease and strokes Blocks or increases the arteries chance of being blocked by thrombosis

(blood clot) This can result in a myocardial infarction or stroke, in which the heart and

brain become starved of oxygen

Atherosclerosis Stages Endothelium cells become damaged due to high blood pressure or smoking Damage causes an inflammatory response – white blood cells move into

the artery wall, and the blood cholesterol accumulates ; atheroma (fatty deposit) builds up

Calcium salts and fibrous tissue form a plaque at the site, narrowing the artery and reducing its elasticity

Plaque makes it difficult for the heart to pump blood, resulting in raised blood pressure

Positive feedback system results – as blood pressure increases, so does damage to the endothelium

Thrombosis Stages Protein called thromoboplastin is releases from the damaged vessel Triggers conversion of prothrombin (protein) into thrombin (enzyme) Thrombin then catalyses the conversion of fibrinogen into fibrin (solid

insoluble fibres) Fibrin fibres tangle to form a mesh in which platelets and red blood cells

get trapped, forming a clot

Lipoproteins and Cholesterol

High Density Lipoproteins (HDLs) Mainly protein Transport cholesterol from body tissues to lover where it is excreted Reduce blood cholesterol level when too high

Low Density Lipoproteins (LDLs) Mainly fatty Transport cholesterol from the liver to the blood, where it circulates until

needed by cells Increases blood cholesterol when too low

Lifestyle Risk Factors for CVD

Diet High level of saturated fats and blood cholesterol increases risk

High Blood Pressure Increases risk of damage to the walls and thus atherosclerosis and

thrombosis

Smoking Carbon monoxide – reduces oxygen in cells, can lead to heart attack or

stroke

Nicotine – makes platelets sticky – increasing chance of thrombosis

Exercise Inactivity increases blood pressure, which increases risk of endothelium

damage

Risk Factors of CVD Beyond Control

Genetics Particular alleles make some people more susceptible to high blood

pressure or high cholesterol levels

Age Risk of developing CVD increases with age

Gender Men are three times more likely to suffer from CVD than pre-menopausal

women There is no difference between men and women post-menopause

Reducing the Risk Factor

Diet Reduce intake of saturated fats

Smoking Quitting smoking

Exercise Doing exercise regularly

Treating CVD : Drug Therapies

Antihypertensives (beta blockers) Reduce high blood pressure, less chance of cell damage

Advantages Can be combined to work more effectively

Can be monitored at to demonstrate effect

Disadvantages Adverse side effects. Example : dizziness, depression and drowsiness

Plant Statins Reduce cholesterol in the blood and atheroma formation

Advantages Reduce risk of suffering from CVD

Disadvantages Can reduce the absorption of vitamins from the gut Hard to obtain enough to reduce cholesterol levels

Anticoagulants (Warafin and Heparin) Reduce blood clotting

Advantages Prevent any new clots forming

Disadvantages Can damage the foetus if taken during pregnancy

Platelet Inhibitory Drugs (Aspirin) Prevent platelets from forming clots

Advantages Can be used to treat people who already suffer from CVD

Disadvantages Side effects. Example : Rash, diarrhoea, and nausea

Cell Membranes

Fluid Mosaic Model Phospholipid molecules form a bi-layer

The phosphate heads are hydrophilic, align on the outside The hydrophobic tails align on the inside

Diffusion Passive (requires no ATP energy) Net movement of particles from an area of high concentration to an area of

lower concentration Moves down the concentration gradient This is too slow for multicellular organisms as the distance to cover is far

larger, they use a different transport medium

Gas Exchange Surfaces

Adapted for efficient diffusion by large surface area to volume ratio thin – short diffusion pathways organism maintains steep concentration gradient of gases across the

surface

Lungs large surface area diffuses out the alveoli through epithelial cells good blood supply from capillaries – exchanging carbon dioxide for new

oxygen

Alveoli provide large surface area for gas exchange

Features of Alveoli for efficient gas exchange large surface area to absorb oxygen moist surface to allow oxygen to dissolve (phospholipid known as lung

surfactant which coats the alveoli and prevents them from collapse) thin lining to allow easy diffusion o gases

Features of Capillaries for efficient gas exchange dense network to carry CO2 and O2

large surface area to transport gases

Factors affecting the Rate of Diffusion larger the Surface Area the faster the particles will exchange the more concentrated the particles on one side of the membrane the

faster they will move to the other less concentrated side

Fick’s Law Rate of Diffusion = ∝ Surface area x concentration difference

Thickness of exchange membrane or barrier Osmosis

passive (requires no ATP energy) the net movement of water molecules from an area of their high

concentration to an area of their low concentration through a partially permeable membrane

Hypertonic = higher water potential Hypotonic = lower water potential Isotonic = no net movement

Facilitated Diffusion some large molecules and charged atoms use carrier and channel proteins

to diffuse across a membrane moves particles down a concentration gradient passive (no ATP required) carrier proteins – molecule attaches to protein, which then changes shape

and releases the molecule on the opposite side of the membrane channel proteins – form pores in the membrane, allowing molecules to

diffuse through them

Active Transport uses ATP energy to move molecules and ions across cell membranes across

a concentration gradient ATP is produced during cellular respiration a molecule attaches to a carrier protein, causing it to change shape,

moving the molecule across the membrane, releasing it on the other side

Endocytosis

used for larger molecules cell takes in substances cell surrounds a substance with its cell membrane membrane pinches off to form a vesicle, containing the ingested substance,

and moving it into the cell

Exocytosis used for larger molecules cells secretes substance vesicles fuse with the cell membrane, releasing their content outside the

cell

Genetics

DNA and RNA Polynucleotides – mononucleotides joined together The sugar in DNA is deoxyribose, and ribose in RNA The mononucleotides are joined through condensation reactions DNA is made of two polynucleotide strands, RNA has one

Complimentary Base Pairing

In DNA Adenine pairs with Thymine Cytosine pairs with Guanine

In RNA Adenine pairs with Uracil Cytosine pairs with Guanine

The strands join together by hydrogen bonding

Purine Adenine

Guanine

Pyrimidine Cytosine Thymine / Uracil

DNA’s Semi-Conservative Replication The DNA helix unzips, using the enzyme DNA topoisomerase forming two

single strands that acts as a template as the helicase breaks the hydrogen bonds between the bases

Free mononucleotides join to each template by complimentary base pairing The mononucleotides are joined by DNA polymerase Hydrogen bonds form between the bases on the original and new strand Each molecule contains one strand of DNA and one new strand

Evidence: Semi – Conservative ModelExperiment conducted by Meselson and Stahl

One test tube contained light nitrogen and one contained heavy nitrogen When spun in a centrifuge, they appeared respectively at the top and

bottom The heavy nitrogen bacteria was then replicated in the light nitrogen broth The DNA when spun in a centrifuge again settled in the middle, suggesting

that the new DNA had one original strand and one new strand

DNA Proteins are made from amino acids A gene is a sequence of bases that codes for the sequence of amino acids A codon (three bases) codes for each amino acid Other codons tell the cell when to start and stop the production of proteins The strands run in opposite directions to each other they are said to be

anti-parallel

Protein Synthesis: Transcription

In the nucleus, hydrogen bonds between DNA strands unzips, catalysed by RNA polymerase

Free RNA nucleotides line up alongside the DNA template with complimentary base pairing

The mRNA moves out of the nucleus through the nuclear pores and attaches to a ribosome in the cytoplasm

Protein Synthesis: Translation In the ribosome, the mRNA codes for amino acids The tRNA then collects these amino acids from the cytoplasm and attaches

itself to the mRNA via complimentary base pairing This continues across the strand of mRNA, with the amino acids joining

together with peptide bonds The process continues until a stop codon is read The protein then is released from the ribosome

Genetic Disorders

Mutations Some mutations in the base sequence of DNA or in DNA replication can

cause genetic disorders The order of DNA bases in a gene determines which protein are created; a

mutation could change the 3D shape of a protein so it does not work properly

The genetic disorders can be inherited

Cystic Fibrosis Caused by recessive allele Causes the production of thick, sticky mucus Caused by a mutation in the CFTR protein - the protein that transports

chloride ions out of cells and into mucus, making it more watery Mutant CFTR is much less efficient, meaning CF sufferers’ mucus is

abnormally thick and sticky This causes problems in the respiratory, digestive and reproductive systems

CF and the Respiratory System

Cilia are unable to move the mucus from the lungs to the throat as it is too thick, blocking the airways

This reduces gas exchange, causing breathing difficulties The mucus also contains many microorganisms which cannot be removed,

increasing the risk of lung infections

CF and the Digestive System Mucus can block the tube that connects the pancreas to the small intestine

- preventing digestive enzymes from absorbing nutrients Mucus can cause cysts in the pancreas, inhibiting the production of

enzymes, reducing the ability to digest food and absorb nutrients

CF and the Reproductive System

Men Tubes in the testicles can be absent or blocked, meaning any sperm

produced cannot be released

Women Thickened cervical mucus prevents, or severely reduces, the sperms

chances of reaching the egg

Testing for CF : Genetic Screening Can confirm a diagnosis Can identify carriers of the genetic disorder Can test embryos Can enable pre-implantation diagnosis when carrying out IVF

Amniocentesis Removing 20cm3 of the amniotic fluid which surrounds the fetus using a

needle and syringe Done at the 16th week of pregnancy Fetal epithelial cells and blood cells can be recovered from the fluid after

spinning it in a centrifuge 2-3 weeks later number of genetic defects can be determined

Chorionic Villus Sampling

A small sample of embryonic tissue is taken from the developing placenta Taken at 8-10 weeks

Testing for CF: Ethics Could lead to far higher incidence of abortion The testing itself can cause miscarriage and is not always accurate Religious standing. For example : Catholics would consider the embryo a

human, thus, aborting the child is a sin

Genetic Disorders

Albinism Inherited, caused by recessive allele Sufferers lack skin, hair and eye pigmentation

Thalassaemia Inherited blood disorder, caused by a recessive allele The sufferer’s blood do not contain efficient levels of oxygen

Experiments

Daphnia Make up a range of different concentrations of caffeine

Transfer one daphnia into the dimple on a cavity slide Place the slide under a microscope, focusing it on the heart Place a small drop of caffeine solution onto the daphnia Count the heart beat for 15 seconds, and times this value by 4 for bpm Keep all other factors. Example : temperature and volume of solution,

constant Repeat the experiment using other solutions Compare the results to see how caffeine affects heart rate

Vitamin C Make at least 6 different Vitamin C solutions of known concentrations Measure out a set volume of DCPIP into a test tube Titrate one of the Vitamin C solutions into the DCPIP drop by drop When the solutions turns colourless, record the volume of Vitamin C

solution that was added Repeat the experiment twice more with the same solution and take an

average of the readings Keep all the other variables constant. Example: Temperature Repeat the above procedure with each solution Use the results to create a calibration curve Next, test the unknown solution in the same way; when you know how

many drops it took to turn the solution colourless, read the calibration curve to determine the solutions concentrations

Beetroot Cut five equal sized pieces of beetroot and rinse them to remove any

pigment Place the pieces on blotting paper before transferring them to five different

test tubes Add 5cm3 of water to each test tube Place the test tubes in water baths at different temperatures (from 100 C to

500C) for 10 minutes Remove the pieces of beetroot from the tubes, using a colorimeter,

measure the absorbance level of the liquid The higher the absorbance, the more pigment released, so the higher the

membrane permeability