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Explain the importance of water as a solvent intransport, including its dipole nature:

•A lot of important substances in biological reactions are ionic. (one +ionand one -ion)

•Because water is dipolar, the positive end of a water molecule will beattracted to the negative ion, and the negative end of a water molecule willbe attracted to the positive ion.

•Ths means the ions will get totally surrounded by water molecules - they'lldisolve.

•So water's dipole nature makes it useful as a solvent for other polarmolecules.

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Explain why many animals have a heart andcirculation:

In multicellular organisms, diffusion across the outer membrane wouldbe too slow because of the large distance the substances would haveto travel to reach all the cells. They need glucose and oxygen foraerobic respiration for energy.

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Describe the cardiac cycle:

Ventricular diastole, atrial systole:

Ventricles - relaxed. Atria - Contract. SL valves - closed. AV valves - open.

Ventricular systole, atrial diastole:

Atria - Relaxed. Ventricles - Contract. SL valves - open.. AV valves - closed. Bloodleaves via pulmonary artery and aorta.

Ventricular diastole, atrial diastole:

Ventricles - relaxed. Atria - relaxed. SL valves - closed. AV valves - open. Bloodre-enters via vena cava and pulmonary vein.

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Explain how the structures of the blood vessels relateto their functions.

Ateries

Thick-walled, muscular and have elastic tissue in the walls to cope with the high pressure causedby the heart beat. The inner lining (endothelium) is folded, allowing the artery to expand - highpressure.

Vein

Wider than equivalent arteries, very little elastic or muscle tissue. Contain valves to stop the blood flowingbackwards- low pressure. Blood flow through veins is helped by contraction of the body muscles surroundingthem.

Capillaries

Only one cell thick- speeds up diffusion. Networks of capillaries in tissue - increase surface area.

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Describe the factors that increase the risk of CVD:

Lifestyle factors

•Diet - high in saturated fat. High in salt.

•High blood pressure

•Smoking

•Inactivity

Factors beyond your control

•Genetics

•Age

•Gender

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Relate the structure and operation of the mammalianheart to its function, including the major bloodvessels:

• The left ventricles of the heart has thicker, more muscular walls than the rightventricle, because it needs to contract powerfully to pump blood all the way round thebody. Th right side only needs to get blood to the lngs which are nearby.

• The ventricles have thicker walls than the atria, because they have to push blood out ofthe heart whereas the atria just need to push blood a short disrance into the ventricles.

• The atrioventricular (AV) valves link the atria to the ventricles and stop blood flowingback into the atria when the ventricles contract.

• The semi-lunar (SL) valves link the ventricles to the pulmonary artery and aorta, andstop blood flowing back into the heart after the ventricles contract.

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Evaluate design of studies used to determine healthrisk factors:

•Sample size : Greater sample size - more reliable the results.

•Variables : more variables controlled - more reliable the results.

•Data collection : the less bias - the more reliable the results.

•Controls : presence of controls increases the reliability of theresult.

•Repitition by other scientists : more repititions - more reliableresult.

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Analyse and interpret quantitative data:

Describe the data -

Increases as increases Increases as decreases Decreases as increasesDecreases as decreases

Draw conclusions -

Positive correlation / negative correlation

Check any conclusions are valid -

Be careful that any conclusions match the data

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Analyse data on energy budgets and diet:

Weight Gain :- If energy in take is higher than energyoutput, the excess energy will be truned into fat reservesby the body, so the person will gain weight.

Weight loss:- If energy in take is lower than energy output,the body will have to get more energy from somewhere.It'll turn some of its fat reserves into energy.

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Explain why people's perceptions of risks are oftendifferent from the actal risks:

• Risk can be defined as the chance of somthingunfavourable happening.

• People's perception of risk may be very different fromthe actual risk: People may overestimate the risk- media can make this worse. Some people mayunderestimate the risk - due to lack of information.

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Describe the synthesis of a triglyceride by theformation of ester bonds:

•Triglycerides are formed by condensationreactions and broken up by hydrolysisreactions.

•Three fatty acids and a single glycerolmolecule are joined together by ester bonds.

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Distinguish between monosaccharides, disaccharidesand polysaccharides:

Monosaccharides:

• Carbohydrates are made from monosaccharides.• Glucose is a monosaccharides with six carbon atoms in each molecule.• Structure makes it solube - easily transportable. chemical bonds - lots of energy.

Diaccharides: Two monosaccharides joined together.

• Glycosidic bond - condensation reaction to join - hydrolysis reaction to break.• Maltose - Glucose + Glucose - 1-4 glycosidic bond.• Lactose - Glucose + Galactose - 1-4 glycosidic bond.• Sucrose - Glucose + fructose - 1-2 glycosidic bond.

Polysaccharides: More than two monosaccharides

• Amylose - lots of Glucose - 1-4 glycosidic bonds• Amylopectin - lots of Glucose - 1-4 and 1-6 glycosidic bonds - side branches.• Glycogen - Glucose - 1-4 and 1-6 glycosidic bonds - more side branches

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Health of blood cholesterols levels:

HDLs (high densitiy lipoproteins)

•They are mainly protein.•They transport cholesterol from body tissues to the liver where it's recycled or excreted.•Their function is to reduce total blood cholesterol when the level is too high.

LDLs (low densitiy lipoproteins)

•They are mainly lipid.•Tehy transport cholesterol from the liver to the blood where it circulates untill needed by

cells.•Their function is to increase total blood cholesterol when the level is too low.

High total blood cholesterol level and high LDL level have both been linkedto an increased risk of CVD.

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Describe how monosaccharides join to formdisaccharides and polysaccharides:

• Monosaccharides are joined together byglycosidic bonds in condensation reactions toform diasaccharides and polysaccharides.

• Disaccharides and Polysaccharides arebroken apart by a hydrolysis reaction backinto monosaccharides.

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Discuss whether theree are ethical issues in the useof invertebrates:

•They can't give consent.

•Some people think its more acceptable on invertebrates as thayare simpler organisms - less sophisticated nervous system.

•Some people believe it's unethical to cause distrass or sufferingto any living organism.

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Describe how the effect of caffeine on heart rate inDaphnia can be investigated practically:

1) Make up range of different concentrations of caffeine solutions and a control solution with nocaffeine at all. 2) Transfer one Daphnia into the dimple on a cavity slide. 3) Place the slide onto thestage of a light mcroscope and focus it on the beating heart of the Daphnia. 4) Place a small dropof caffeine solution onto the Daphnia. 5) Count the number of heartbeats in 10 sec and multiplythis by six for beats per min. 6) Repeat this 10 times using the same concentration but differentDaphnia. 7) Don't forget to keep all other factors constant. 8) Repeat the experiment using theother concentrations. 9) Compare the results to see how caffeine concentration affects heart rate

Heart Rate increases as caffeine concentration increases.

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Describe the Benefits and risks of treatments forCVD:

Antihypertensives - Reduce High Blood Pressure

Benefits

•They reduce blood pressure, so there's less chance of damage occurring to the walls ofthe arteries. This reduces the risk of atheromas forming and blood clots developing.

•Different types work indifferent ways, so they can be given in cobination.•Blood pressure can be monitored at home, so they can be given in combination.

Risks

•Palapitations (rapid beating of the heart)•Abnormal heart rhyms•Fainting, headaches and drowsiness•Allergic reactions•Depression

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Describe how to investigate the vitamin C content offood and drink:

First you need to make a calibration curve:

1) Make up several vitamin C solutions of different known concentratons. 2) Measure out a setvolume of DCPIP (blue dye - colourless in vitamin C) into a test tube. 3) Add one of the vitaminC solutions to the DCPIP, drop by drop, using a pipette. 4) Gently shake the test tube for a setlength of time after each drop of vitamin C solution is added. 5) When the solution turns colourless,record the volume of vitamin C solution that has been added. 6) Repeat the experiment twicemore, with the same solution and take and average of the three readings. 7) Make sure you keepall the other variables constant during the experiment. 8) Repeat the above procedure with eachsolution. 9) Use the results to make a line graphn, showing volume of vitamin C solution against itsconcentration - this is the calibration curve. Then you can test the unknown solution in the sameway as the known concentrations and use the graph to finds its concentration.

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Describe the Benefits and risks of treatments forCVD:

Anticoagutants - Reduces the formation of blood clots.

Benifits

•Prevent any existing blood clots from growing any larger.•Prevent any new blood clots from forming.

Risks

•If the patient is badly injured the reduction in blood clotting can cause excessive bleeding,which can lead to fainting or death.

•Allergic reactions.•Osteoporsis (weakened bones)•Swelling of the tissues•Can damage the fetus if taken during pregnacy.

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Describe the Benefits and risks of treatments forCVD:

Plant Satins - reduce cholesterol in the blood.

Benifits

Statins reduce the risk of developing CVD.

Risks

They can reduce the absorbtion of some vitamins from the gut.

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Describe the properties of gas exchange surfaces inliving orpanisms:

Gases diffuse across a surface called the gas exchage surface.

Features that insrease the rate of diffusion:

•Large surface area•Thin - short diffusion pathway•Steep concentration gradient

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Describe the Benefits and risks of treatments forCVD:

Platelet inhibitory Drugs - Reduce formation of Blood clots.

Benefits

• Can be used to treat people who already have blood clots orCVD.

Risks

• Rashes• Diarrhoea• Nausea• Liver function problems• Excessive bleeding after injury.

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Explain the fluid mosaic model of cell membranes:

Cell Membranes - Fluid mosaic structure.

They contain:

•Phospholipid bilayer - fluid (constantly moving)•Protein molecules are scattered through the bilayer, like a mosaic.•Some proteins have a polysaccharide (carbohydrate) chain attached - these are called

glycoprotein.•Some lipids also have a polysaccharide chain attached - glycolipids.•Cholesterol - between phospholipids - makes membrane rigid.

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Explain how the structure of the mammalian lung isadapted for rapid gaseous exchange:

The mammalian lungs have the following features which all help to increase therate of gas exchange:

• Many alveoli provide a large surface area for diffusion to occur across.

• The alveolar epitheluim and capillaret endothelium are each only one cellthick, giving a short diffusion pathway.

• All the alveoli have good blood supply from capillaries - they constantly takeaway oxygen and bring more carbon dioxide, maintaining the concnetrationgradient.

• Breathng in and ot refreshes the air in the alveoli, keeping the concnetrationgradients high.

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Explain what is meant by osmosis:

Osmosis is the diffusion of water molecules across a partallypermeable membrane, from an area of higher concentration to an areaof lower concentration.

Water molecules will diffuse bothe ways through the membrane, butthe net movement of water molecules.

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Describe how membrane structure can beinvestigated:

How to investigate how temperature affects beetroot membrane permeability:

• Cut five equal sized pieces of beetroot and finse them to remove any pigment releasedduring cutting.

• Place the five pieces in five different test tubes, each with 5cm3 of water.• Place each test tube in a water bath at a different temperature, for the same length of time.• Remove the pieces of beetroot from the tubes, leaving just the coloured liquid.• Now you need to use a colourimeter - a machine that passes light through the liquid

and measures how much of that light is absorbed. The higher the absorbance, the morepigment released, so the higher the permeability of the membrane.

Increasing the temperature increases membrane permeability.

Increasing the Alcohol concentration Increases membrane permeabitity.

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Describe the basic structure of mononucleotides andthe structures of DNA and RNA:

Mononucleotides

Phosphate - sugar - Base.

RNA and DNA

•DNA and RNA are polynucletides - lots of mononlucleotides joined together.•The sugar in DNA is deoxyribose and in RNA its ribose sugar.•In DNA there are four bases - adenine (A), thymine (T), cytosine (S) and guanine (G). In

RNA, uracil (U) replaces thymine (T).•The mononucleotides are joined through condensation reactions between the phosphate

of one mononucleotides and the sugar group of another.•Two complementary DNA strands join together by hydrogen bonding between the bases.•Adenine always pairs with thymine (A-T) and guanine aways pairs with cytosine (G-C).•The two DNA strands wind up to form the DNA double-helix.

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Explain what is meant by passive transport, activetransport, endocytosis and exocytosis:

Passive Transport

Diffusion - the net movement of particles from an area of higher concentration to an area lowerconcentration. Passive process - no energy is needed.

Facilitated Diffusion - Larger molecules and charged atoms diffus throgh carrier proteins orchannel proteins in the cell membrane. Passive process - no energy is needed.

Active transport - uses energy to move molecules and ions across the cell membranes, against aconcentration gradient. Attaches to carrier protein. Energy from ATP.

Endocytosis - If too large to be taken into a cell by carrier proteins. Instead surround by a sectionof cell membrane.Membrane then pinches off to form a vesicle inside the cell.

Exocytosis - substances produced by the cell can be released by this method.The vesiclecontaining the substance fuse with the cell membrane and release their contents outside the cell.

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Outline the process of protein synthesis - Translation:

•The mRNA attches itself to a ribosome and transfer RNA (tRNA) molecules carry aminoacids to the ribosome.

•tRNA molecules attach themselves to the mRNA by complementary base pairing.

•The two amino acids attached to the tRNA molecules are joined together by a peptidebond.

•The tRNA molecules move away.

•The chain is ended when there's a stop signal on the mRNA molecules.

•The polypeptide chain moves away form the ribosome and translation is complete.

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Outline the process of protein synthesis -Transcription:

• Hydrogen bonds between the two DNA strans in a gene break, separating the strands,and the DNA molecule uncoils at that point.

• One of the strands is then sed as a template to make and RNA copy (mRNA).

• Free RNA mononucleotides line up alongside the template strand. Once the RNAmononucleotides have paired up with their complementary bases on the DNA strandthey're joined together, forming an mRNA molecule.

• The mRNA moves out of the nucleus through a nuclear pore, and attaches to a ribosomein the cytoplasm. DNA re-forms.

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Explain the mechanism of action and specificity ofenzymes:

Induced Fit

The subsrate doesn't only have to be the right shape to fit the active site, it has to make the activesite change shape in the right way as well.

Specificity

•Enzymes are very specific - they usually only catalyse one reaction.•This is because only one substrate will fit into the active site.•The active site's shape is determined by the enzyme's 3D struture.•Each different enzyme has a different 3D struture and so a different shaped active site.•If the substrate doesn't match the active site, the reaction won't be catalysed.•If the 3D struture of a protein is altered in any way, the shape of the active site will change.

This means the substrate won't fit into the active site and the enzyme will no longer beable to carry out its function.

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Explain the nature of the genetic code:

A gene is a sequence of bases that codes for the sequence of amino acids in a protein.

• Polypeptide chains (proteins) are made from amino acids.

• Different proteins have a different number and order of amino acids.

• It is the order of monomucleotide bases in a gene that determines the order of amino acidsin a particular protein.

• Each amino acids coded for by a sequence of three bases in a gene.

• Different seqences of bases cade for different amino acids.

• Some amino acids are coded for by more than one triplet.

• Other triplets are used to tell the cell when to start and stop production of the polypeptidechain - these are called start and stop signals.

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Explain how errors in DNA replication can give rise tomutations:

Mutations are changes to the base sequence of DNA.

Types of Errors

•Substitution - one base is substitued with another.•Deletion - one base is deleted.•Insertion - an extra base is added.•Duplication - one or more bases are repeated.•Inversion - a sequence of bases is reversed.

Cystic fibrosis is a genetic disorder caused by a mutation in a gene. The protein the gene codesfor is important for mucus production.

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Describe DNA replication:

• The DNA helix unzips to form two single strands. Each single strand acts as a templatefor a new strand.

• Free-floating monomucleotides join to each original template strand by complementarybase pairing - A with T, G with C.

• The mononucleotides on the new strand are joined together by enzyme DNA polymerase.Hydrogen bonds form between the bases on the original and new strand.

• Each new DNA molecule contains one strand from the original DNA molecule and onenew strand.

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Explain how cystic fibrosis impairs the functioning ofthe gaseous exchange:

•The cilia are unable to move the mucus towards the troat because it is so thick and sticky.

•This means the mucus builds up in the airways.

•Some airways can become completely blocked by mucus - gas exchange can't take placein area below the blockage.

•This means that the surface area available for gas exchange is reduced, causing breathingdifficulties.

•Sufferers are also more prone to lung in fections as mucus containing microorganismscan't be removed.

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Explain the terms:

Gene - A sequence of bases on a DNA molecule that codes for a protein, which results in acharacteristic.

Allele - A different version of a gene.

Genotype - The alleles a person has.

Phenotype - The characteristics the alleles produce.

Dominant - An allele whose characteristic appears in the phenotype even when there's only onecopy.

Recessive - An allele whose charateristics only appears in the phenotype if two copies are present.

Homozygote - An organism that carries two copies of the same allele.

Heterozygote - An organism that carriers two different alleles.

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Explain how cystic fibrosis impairs the functioning ofthe Reproductive system:

In men, the tubes connecting the testicles to the penis are absent in some sufferesand can become blocked by thinck mucus in others. This means that any spermproduced can't reach the penis.

In women, thickened cervical mucus can prevent the sperm from reaching theegg. The sperm has to travel through this mucus to reach the egg - thick mucusreduces the motility of the sperm, reducing it's chances of making it to the egg.

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Explain how cystic fibrosis impairs the functioning ofthe digestive system:

• The tube that connects the pancreas to the small intestine can become blocked withmucus - preventing digestive enzymes produced by the pancreas form reaching the smallin testine. this reduces the sufferers ability to digest food and so fewer nutrients can beabsorbed.

• The mucus can cause cysts to form in the pancreas. These inhibit the production ofenzymes, which also reduces the ability to digest food and absorb nutrients.

• The mucus lining the small intestine is abnormally thick - this inhibit the absorption ofnutrients.

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Explain the uses of genetic screening: Identificationof Carriers

•Carrier testing is offered to individuals with a family history of genetic disorders.•It shows whether people without a disorder carry an allele that can cause a disorder.•Couples can be tested before having children to determine the chances of any future

children having the disorder.•Carrier testing allows people to make informed decisions about things like whether to have

children and whether to carry out prenatal testing if the woman is pregnant.

Social and Ethical issues:

•Finding out you're a carrier may cause emotional stress.•The tests aren't always 100% accurate.•There are concerns thath the results of genetic tests could be used by emplors or life

insurance companies.

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Describe the principle of gene therapy:

Gene therapy involves altering the alleles inside cells to curegenetic disorders.

Somatic theraphy - this involves changing the alleles in body cells.

Germ line therapy - this involves changing the allels in the sex cells.

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Explain the uses of genetic screening - Prenataltesting:

Prenatal tests involve screening unborn babies for genetic disorders.

Amniocentesis

Carried out at 15 - 16 weeks. Sample of amniotic fluid is obtained using a very fine needle. Thisfluid contains fetal cells. The cells contain DNA, which can be analysed.

Chorionic villus sampling (CVS)

This is carried out at 8 - 12 weeks. A sample of cells is taken from the chorionic villi (cord) usinga fine needle or a catheter. The cells contain fetal DNA, which can be analysed.

Social and Ethical issues:

•Prenatal tests slightly increase the risk of miscarriage (by 1%)•Fasle results could provide incorrect information.•Some people consider it unethical to abort a fetus because it has a genetic disorder.

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Explain the uses of genetic screening -Preimplantation Genetic Diagnosis:

PGD is carried out on embroyos produced by IVF. It involves screening embryos for geneticdisorders before they're implanted into the woman. This aviods the issue of abortion.

Social and Ethical issues:

• It can be used to find out other characteristics - leading to concerns of designer babies.• False results could provide incorrect information.