Biology Unit 1, Revision

Front 1

how the DNA replicates?

Back 1

1, two strands of DNA will unzip along the line of hydrogen bond. this is brought about helicase. the strands act as templates for the new DNA strands.
2, the exposed base will attract free DNA nucleotides and new hydrogen bonds are formed between matching pairs. the enzyme DNA polymerase and DNA ligase join the nucleotides together to form new DNA strands.
3, the result is two new strands of DNA identical with the original piece.

Front 2

Explain why many animals have a heart and circulation (mass transport to overcome limitations of diffusion)

Back 2

1, Large and multicellular means small SA:vol ratio (54)
2, Cells can be specialised (6)

Front 3

Explain how the structures of blood capillaries, arteries and veins relate to their functions

Back 3

1, Capillaries – small, wall single cell thick. Rapid diffusion, leaky for tissue fluid formation (9)
2, Arteries. – narrow lumen, thick walls (collagen, elastic fibres, smooth muscle), no valves (8). Stretch during systole, maintain high pressure (9)
3, Veins – wide lumen, thin walls (less collagen, few elastic fibres, little muscle), valves (8). Low pressure, valves prevent back flow, flow due to skeletal muscle contraction and low pressure in thorax (9).

Front 4

Relate the structure and operation of the mammalian heart to its function (the cardiac cycle including diastole, atrial systole and ventricular systole)

Back 4

1, Diastole – muscle at rest, semi lunar valves prevent back flow, blood entering from veins into atria and ventricles due to elastic recoil of heart, atrio ventricular valves open.
2, Atrial systole – atrial muscle contracts, blood fills ventricles.
3, Ventricular systole – ventricular muscle contracts, pressure closes atrio ventricular valves and opens semi lunar valves.
4, Thickness of chamber walls related to function (10-11).

Front 5

Explain the course of events that leads to atherosclerosis (endothelial damage, inflammatory response, plaque formation, raised blood pressure)

Back 5

1, Fatty deposits (plaques) narrowing and hardening arteries. Increases risk of blockage by blood clots, restricts blood flow.
2, Damaged endothelial cells due to high BP or toxins (eg from cigarettes).
3, Inflammatory response – WBC accumulate and collect cholesterol to form atheroma.
4, Calcium salts and fibrous tissue added to form plaque.
5, BP increases – positive feedback (11).

Front 6

Describe the blood clotting process (thromboplastin release, conversion of prothrombin to thrombin and fibrinogen to fibrin) and its role in CVD

Back 6

1, Thromboplastin released from platelets and damaged tissue.
2, Converts prothrombin to thrombin.
3, Converts fibrinogen to fibrin, which makes clots form (13).

Front 7

Describe the symptoms of CVD, ie coronary heart disease (CHD) and stroke, and the factors which increase the risk of CVD (genetic, diet, age, gender, high blood pressure, smoking and inactivity)

Back 7

 Stroke, (12).
 Angina, heart attack and arrhythmia (14-15).
 Risk increases with age, higher in men (25).
 Some genetic element, but many genes involved (26)
 High blood pressure and endothelial damage (26).
 Diet and obesity, cholesterol (30, 39-41).
 Smoking and inactivity (42).

Front 8

Describe what is meant by blood pressure and explain the role of high blood pressure in CVD

Back 8

 Hypertension (26), systolic and diastolic pressure, normal values.

Front 9

Describe the normal electrical activity of the heart, including the roles of the sino-atrial node (SAN), the atrio-ventricular node (AVN) and the bundle of His, and how the use of electrocardiograms (ECGs) can aid the diagnosis of CVD and other heart conditions

Back 9

 SAN (in right atrium) – pacemaker – starts wave of depolarisation (16).
 AVN (between atria and ventricles) passes wave to ventricles after short delay. Uses Purkyne fibres in bundle of His to reach apex first (16).
 ECG measures activity from outside chest.
 Know what the trace shows (P is atrial wave, QRS is ventricular, T is repolarisation in diastole). Know abnormal patterns (18-19).

Front 10

Analyse quantitative data on illness and mortality rates to determine health risks and recognise that it is important to distinguish between correlation and causation

Back 10

 Calculating probabilities, estimating risk (20).
 Correlation and causation – know the difference (24).

Front 11

Explain why people’s perceptions of risks are often different from the actual risks

Back 11

 Reasons for overestimating risk (22).

Front 12

Analyse data on energy budgets and diet so as to be able to discuss the consequences of energy imbalance

Back 12

BMR and energy requirements (38).
 BMI and obesity (39).

Front 13

Distinguish between monosaccharides, disaccharides and polysaccharides (glycogen and starch – amylose and amylopectin) in terms of their structure and their role in providing and storing energy (β-glucose and cellulose are not required at this stage). Students should recognise the structural formulae for α-glucose and maltose and the monomers which make up sucrose and lactose

Back 13

 Monosaccharides (alpha glucose 32) immediate energy supply in respiration, disaccharides (maltose – glucose amd glucose, 33 , sucrose – glucose and fructose, lactose – glucose and galactose).
 Glycogen in animals and bacteria. Storage, polymer of glucose, many side branches make it easy to break down 1-4 and 1-6 bonds (35).
 Starch in plants. Amylose straight chain polymer of glucose with only 1-4 bonds, amylopectin branched with 1-4 and 1-6 (35).

Front 14

Describe how monosaccharides join to form polysaccharides through condensation reactions forming glycosidic bonds, and how these can be split through hydrolysis reactions

Back 14

1.1.13

Front 15

Recognise that glycerol with three fatty acids attached is a lipid and specifically a triglyceride, describe the formation of ester bonds in condensation reactions and recognise differences between saturated and unsaturated lipids

Back 15

1.1.14

Front 16

Calculate body mass indices (BMIs) using the formula BMI = body mass (kg)/height2 (m) and explain their significance

Back 16

 BMI calculations and importance (39). 20-24.9 normal.

Front 17

Discuss the possible significance for health of blood cholesterol levels and levels of high-density lipoproteins and low-density lipoproteins (HDLs and LDLs)

Back 17

 Lipoprotein used to transport cholesterol. High levels linked to CHD.
 LDL include saturated fats, stay in circulation when in excess and end up in plaques (31).
 HDL include unsaturated fats – transport cholesterol to liver for breakdown and lowers blood cholesterol (41).

Front 18

Describe how the effect of caffeine on heart rate in Daphnia can be investigated practically

Back 18

 Activity 1.21 – know the procedure.

Front 19

Discuss how individuals, by changing their diet, taking exercise and not smoking, can reduce their risk of coronary heart disease.

Back 19

Sensible advice pages 45-49.

Front 20

Describe the properties of gas exchange surfaces (large surface to volume ratio, thickness of surface, difference in concentration) and explain how the structure of the lung provides a large surface area to volume ratio

Back 20

Alveoli provide large SA, circulation of blood and breathing maintain diffusion gradients, really thin layer of cells in alveoli presents minimum barrier.
 Fick’s law not specified, but it has been given in a question.

Front 21

Describe the structure of the unit membrane (fluid mosaic model) and how its structure depends on the properties of the phospholipids

Back 21

Phospholipid bilayer, hydrophobic tails and hydrophilic heads cause stability but fluidity in plane of membrane.
 Mosaic provided by glycoproteins (in one layer or both).
 Cholesterol to limit fluidity.
 Functions of proteins – signaling and recognition, enzymes, transport.


Front 22

Describe how the effect of temperature on membrane structure can be investigated practically

Back 22

 Activity 2.7 – know the technique.

Front 23

Explain what is meant by osmosis in terms of the diffusion of free water molecules through a partially permeable membrane (consideration of water potential is not required)

Back 23

Osmosis is movement of water across a partially permeable membrane. Depends on concentration of free water molecules, so since more solute molecules mean fewer free water molecules the gradient will be towards a more dilute solution.

Front 24

Explain what is meant by passive transport (diffusion, facilitated diffusion), active transport (including the role of ATP), endocytosis and exocytosis and describe the involvement of carrier and channel proteins in membrane transport

Back 24

 Diffusion – movement of particles from higher to lower concentration. Passive – no energy provided by cell – small and uncharged molecules can cross the membrane (eg oxygen, carbon dioxide) Follows diffusion gradient (62).
 Facilitated diffusion – larger charged particles need water-filled channels provided by membrane channel proteins. Still passive, can allow control when only certain particles allowed through. Can also be gated to open and close. Carrier proteins are a bit more complicated since they change shape to pass particles across the membrane. Follows diffusion gradient (62).
 Active transport – active, required energy from ATP provided by cell. Uses carrier proteins in membrane, against diffusion gradient (64).
 Exocytosis and endocytosis – bulk transport out and in. Vesicles form inside cell and fuse with membrane to transport out, bits of extracellular fluid engulfed to bring stuff in. Requires energy so active (65).
 Nice summary of transport methods on 65.

Front 25

Describe the basic structure of mononucleotides as a phosphate group, deoxyribose or ribose and a base eg thymine, uracil, cytosine, adenine and guanine. Describe the structures of DNA and RNA as polynucleotides composed of mononucleotides linked in condensation reactions. Describe complementary base pairing and the hydrogen bonding involved in the formation of the DNA double helix

Back 25

Polymer is produced by making the sugar-phosphate backbone, bases are not involved.
 Complementary bases pair A-T, (A-U in RNA), C-G. Due to shape and number of hydrogen bonds possible. H-bonds between bases links two polymer strands together to form double helix in DNA.

Front 26

Explain the process of protein synthesis (transcription, translation, transfer RNA, messenger RNA, ribosomes, the role of start and stop codons) explain the roles of the template (antisense) DNA strand in transcription, codons on messenger RNA and anticodons on transfer RNAs

Back 26

Some triplets code for start or stop (beginning and end of a gene) (76).
 Transcription – making a copy of the base sequence on the template strand of DNA.
 Result is mRNA which can move to cytoplasm, leaving DNA in place for another day (77).
 Transcription because language is the same – bases.
 Translation – converting base sequence to sequence of amino acids, so changing language. tRNA is the translator – it know swhich amino acid to carry for a given triplet (anticodon when on tRNA). Matches anticodon with codon on mRNA to supply correct amino acid.
 Occurs on a ribosome in the cytoplasm.
 Peptide bonds link amino acids in order specified by mRNA (and therefore DNA) (77- 80).

Front 27

Explain the nature of the genetic code (triplet code, non-overlapping and degenerate) and describe a gene as being a sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain

Back 27

 Triplet code – three bases on a strand code for one amino acid
 22 amino acids and 64 codes, so degenerate code – some amino acids have more than one code.
 Learn this definition of a gene – sequence bounded by start codon and stop codon (76).

Front 28

Describe the basic structure of an amino acid (structure of specific amino acids are not required). Describe the formation of polypeptides and proteins as amino acid monomers linked by peptide bonds in condensation reactions. Explain the significance of a protein’s primary structure in determining its three-dimensional structure and properties as a globular or fibrous protein

Back 28

Primary structure is sequence of amino acids. Different properties of R groups determine properties of polypeptide, causing folding etc (57).
 Globular proteins tightly folded and soluble in water. 3D (tertiary structure) shape crucial, eg enzymes are globular proteins.
 Fibrous proteins don’t fold – stay as chains and often cross linked together into strands. Insoluble, eg keratin in hair, collagen in tendons, bones, skin and blood vessels (59).

Front 29

Explain the mechanism of action and specificity of enzymes in terms of their three dimensional structure and explain that enzymes are biological catalysts that reduce activation energy

Back 29

Enzymes have properties of catalysts (make reaction more likely to occur without being changed by it), but are also protein.
 Active site shape and charge distribution important (tertiary protein structure, 3D shape).
 Physical contact required between active site and substrate (enzyme + substrate, enzyme-substrate complex, enzyme + products) (70).
 Induced fit theory – substrate fits active site a bit, then induces it to fit better as it binds (70).
 Lock and key hypothesis – links shapes of substrate and active site (70).
 Specificity of enzymes explained by shape of active site.
 Activation energy – energy needed to start a reaction. Enzymes reduce activation energy needed to normal body conditions (71).

Front 30

Describe how enzyme concentrations and substrate concentrations can affect the rates of reactions and how the effect of enzyme concentration on reaction rate can be investigated practically

Back 30

Activity 2.10, core practical.
 All about number of enzyme-substrate complexes that can be formed.
 Note that the enzyme concentration graph is about initial rate, ie when plenty of substrate around (72).
1.2.12

Front 31

Describe the process of DNA replication (semi-conservative, including the role of DNA polymerase)

Back 31

Replication is copying of DNA. Compare it with transcription.
 Semi conservative – each new DNA molecule has one old strand and one new strand.
 Controlled by DNA polymerase – splits original pair of strands and promotes pairing of new nucleotides with exposed bases.

Front 32

Explain how errors in DNA replication can give rise to mutations and explain how CF results from one of a number of possible gene mutations

Back 32

Gene mutation is change in the base sequence of a gene.
 Changing a triplet can change the amino acid code of mRNA, so polypeptide is different. This might affect 3D structure, which is crucial to function (82).
 Lots of different mutations of the same gene cause CF. The effect of the mutation on the shape (and therefore function) of the CFTR protein determines the severity of the CF (82).

Front 33

Explain the terms genotype, phenotype, recessive, dominant, homozygote and heterozygote and use a knowledge of genetics (including the interpretation of pedigree diagrams) to answer questions about monohybrid inheritance including CF, albinism, thalassaemia and garden pea height and seed morphology

Back 33

Genotype – alleles present whether expressed or not.
 Phenotype – observable effect of the genotype (what it looks like) (84-85).
 Allele – possible form of a gene.
 Recessive – allele expressed only when homozygous.
 Dominant – allele expressed whenever present.
 Homozygote – individual possessing only one type of allele for a gene (eg FF, ff).
 Heterozygote – individual having different alleles for a gene (eg Ff) (85).
 Monohybrid – inheritance pattern of a single gene.
 Remember – genotypes of individuals have two letters (alleles), gametes are haploid and only have one.
 CF – recessive, normal is dominant.
 Thalassaemia – book says it’s recessive, then says the heterozygote is different so it could be codominant.
 Albinism is recessive.
 Know about yellow and green, tall and short peas.

Front 34

Explain how the expression of the CF gene impairs the functioning of the gaseous exchange, digestive and reproductive systems

Back 34

Gas exchange – sticky mucus can’t be removed by cilia. Pathogens grow in mucus (especially anaerobes where oxygen can’t penetrate). DNA from dead white cells attacking pathogens makes mucus thicker (53-54). Mucus blocks bronchioles so some alveoli not ventilated. Can be harder to get air out, so parts of lung overinflate and lose elasticity (56).
 Digestion – mucus blocks pancreatic duct so enzymes not released into duodenum. Food not properly digested and can’t be absorbed. Enzymes trapped in pancreas can cause damage, possibly diabetes if islets of Langerhans affected.
 Reproduction – mucus blocks cervix to prevent sperm reaching egg, males can lack vas deferens or have it blocked by mucus, so sperm can’t reach the urethra (73).

Front 35

Describe the principles of gene therapy and distinguish between somatic and germ line therapy

Back 35

Gene therapy – normal copies of the gene inserted into cells that need to express it (eg lining of lung). Inserted gene is transcribed and translated, and functioning protein is produced (88).
 Can use virus particles or liposomes to get gene into cells (88).
 Not very successful – hard to get gene into enough cells, and cells are constantly replaced so treatment needs to be repeated regularly.
 Somatic gene therapy treats cells that never make gametes. Inserted genes are never passed to next generation.
 Germ line therapy modifies eggs or sperm so that every cell will be changed, including those in testes and ovaries, so the genes will be passed on and become a part of the species genotype. Currently illegal (89).

Front 36

Describe how gel electrophoresis can be used to separate DNA fragments of different length

Back 36

Technique is summarised on page 91.
 Chop up DNA with restriction enzymes.
 Load on agarose gel, apply current to draw DNA towards positive electrode, speed depends on size of fragment.
 Transfer to nylon sheet (southern blotting), apply probe or stain to see the fragments.

Front 37

Describe how the genetic profiles produced by gel electrophoresis can be used in genetic screening using gene probes

Back 37

Gene probe -single strand of DNA with complementary base sequence to known gene sequence.
 Apply to gel, wash off anything that hasn’t bound to DNA. Usually radioactive, so can detect whether they’ve stuck to the DNA.


Front 38

Explain the uses of genetic screening in the identification of carriers, prenatal testing (amniocentesis and chorionic villus sampling) and embryo testing

Back 38

 Test potential parents to see if they have a recessive mutation. Allows assessment of risk.
 Testing embryo or foetus – amniocentesis samples fluid around foetus containing some foetal cells. Done at 15-17 weeks, 1% risk of abortion. CVS sample placenta which includes foetal cells. Done at 8-12 weeks, 1-2% risk.
 PIGD – preimplantation genetic diagnosis. Done using IVF, cell from embryo taken at 8-16 cell stage, tested and only implanted in uterus if found to be normal. Expensive and unreliable.

Front 39

Discuss the social, ethical, moral and cultural issues related to genetic screening.

Back 39

 Rights of embryo – some cultures deem them to have full rights at conception, so any tinkering is wrong (no consent, abortion not allowed).
 Duties – eg of parent to prevent harm at any stage of development. Maybe to avoid misery of particularly bad disorder.
 Four frameworks on pages 94-95 – Rights and duties, maximising good, decision making, virtuous lives.

Front 40

using the information in the graph, describe what the results of this trial show

Back 40

1, the volume of A decresed on average by..while the volume of B increased by...
2, the range of the mean change for A is much larger than B.

Front 41

why the result of a trial do NOT indicate..?

Back 41

1, sample size
2, error bars overlap
3, other variables
4, two month is too short
5, the experiment does not tell us whether the reduction is permanant or not.

Front 42

in each strand of the DNA, the mononucleotides are held together by?

Back 42

phosphodiester/phospho(di)ester/covalent bond

Front 43

why many animals have a circulatory system?

Back 43

a circulatory system overcomes the limitation of diffusion and it helps to transfer oxygen and heat aroud the body

Front 44

why a mammalian heart is divided into a right and left side?

Back 44

1, it keeps oxygenated and deoxygenated blood seperate
2, this results in as much oxygen as possible being carried to the cells
3, there is need for difference pressures in each side of the heart

Front 45

why a person with beta thalassaemia has symptoms of anaemia?

Back 45

1, mutation cause different base sequence
2, difference sequence of amino acids
3, haemoglobin/protein/polypeptide being the wrong shape
4, haemoglobin no longer binds oxygen
5, less/no oxygen supplied to the cells
6, respiration
7, breathlessness due to body trying to take in more oxygen
8, tiredness due to lack of energy

Front 46

suggest how gene therapy could be carried out to treat thalassaemia disorder?

Back 46

1, use correct allele
2, for haemoglobin
3, introduction of allele into cells
4, cells named as bone marrow
5, use of vector to introduce gene into cells
6, virus/liposome used as vector
7, injection into bone marrow/mode of delivery of vector
8, need for repeated treatment

Front 47

experiment carried out to investigate the permeability of cell membranes?

Back 47

1. use beetroot tissue;
2. washing beetroot thoroughly ;
3. waterbath to maintain and change temperature ;
4. range at least 5 temperatures / alcohol concentrations ;
5. appropriate controlled variable named e.g.
length of time, size of beetroot ;
6. indication of what is being used to judge
permeability colour of solution,
absorbance, transmission ;
7. description of how permeability can be
assessed e.g. use of colorimeter, standard
solutions ;
8. repeats the experiment ;

Front 48

describe what relationship if any there is between the permeability of this cell membrane and the solubility of the molecules in oil compared with water?

Back 48

permeability of cell membrane increases as the
solubility (in oil relative to water) increases / eq ;

Front 49

knowledge of the structure and properties of cell membranes to explain the results of investigation(differed molecules in their size and in their solubility in oil compared with their solubility in water. the higher the solubility, the more soluble the molecule is in oil compared with water)

Back 49

1. reference to phospholipid bilayer ;
2. reference to hydrophobic nature (of bilayer /
tails) ;
3. idea that {non-polar molecules / molecules that
have high solubility in oil compared with water}
will pass through the membrane more readily
OR
idea that {polar molecules / molecules with
low solubility in oil relative to water} will pass
through less readily ;
4. idea that permeability linked to readiness to
dissolve ;
5. reference to {fluidity / movement} of
phospholipids ;

Front 50

describe its structure(Omega 3)

Back 50

1. reference to {COOH/ carboxylic/ acid}
grouping (at one end) ;
2. (long hydro)carbon chain / eq ;
3. 18 carbons / 17 carbons in hydrocarbon chain
/ eq ;
4. Correct reference to (poly) unsaturated ;
5. 3 carbon-carbon double bonds / 4 double
bonds ;
6. kinked structure / eq ;

Front 51

dietary factors that increase the risk of CVD?

Back 51

1) high {salt / sodium}
2) high cholesterol
3) high saturated fat / high trans-fat
4) high calories
5) high alcohol
6) low fibre / low NSP
7) low antioxidants / low vitamin C / low
vitamin E ;

Front 52

risk of using antihypertensives?

Back 52

blood pressure falls too low / coughs / swelling of
ankles / impotence / tiredness / constipation /
headache / confusion / depression / excessively
low heart rate / allergy / stroke / provoked type II
diabetes / frequent urination / fainting / dizziness
/ vomiting / dry mouth / breathing difficulties /
irregular heart rate / chest pain / hives / rash /
dehydration / reduced circulation effects / low
potassium / blurred vision / eq ;

Front 53

explain the meaning of the term primary structure?

Back 53

1. {sequence / order} of amino acids ;
2. joined by peptide bonds ;

Front 54

explain the importance of the primary structure of an enzyme to its function?

Back 54

1. idea that primary structure determines
(three-dimensional) folding / eq ;
2. reference to types of amino acids determine
{types of bonds / (other than peptide bonds)
/ named bond};
3. reference to position of amino acids
determines position of{bonds / correctly
named bond} ;
4. correct reference to two cys (amino acids)
form bonds ;
5. idea that {shape / position / eq} of active site
is determined by position of amino acids ;
6. reference to shape of active site being
correct to bind to substrate ;
7. reference to {amino acids / R groups}
involved in {chemical reaction / eq} ;
8. reference to {globular/ soluble / enzyme
}molecules being {relatively short /small /
made up of relatively few amino acids} ;
9. reference to {globular / soluble proteins/
enzyme} having relatively high number of {
polar / small{ { amino acids / R groups} ;
10. reference to {polar R groups / eq} facing
outwards ;

Front 55

describe the roles of messenger RNA in protein synthesis?

Back 55

1. mRNA as a copy of the genetic code of the protein being synthesized ;
2. moves out of the nucleus to ribosomes
3. it acts as a template and it has the instructions for translation ;

Front 56

describe the roles of transfer RNA in protein synthesis?

Back 56

1. translation ;
2. binds to an amino acid and takes it to the ribosome and mRNA ;
3. tRNA being specific to amino acid ;
4. holds the amino acid in place ;

Front 57

explain why the maximum blood pressure is higher in the left ventricle than in the right ventricle?

Back 57

-left ventricle has more/thicker muscle
-blood from the left ventricle has to devide between more capillaries
-left ventricle has to pump blood further

Front 58

explain why blood pressure varies in a ventricle during the cardiac cycle?

Back 58

-pressure increases as blood is forced into ventricle during atrial systole
-pressure starts to decrease due to blood loss into artery
-blood pressure decreases during diastole

Front 59

factors that increase the risk of having hypertension?

Back 59

smoking, stress, alcohol

Front 60

explain how a coronary bypass could restore normal heart function?

Back 60

1, allow blood/metabolite/oxygen
2, to reach cardiac muscle tissues
3, heart muscle/region beyond block able to work more efficiently
4, enables aerobic respiration
5, removal of lactic acid/lactate/eq

Front 61

how ions such as Ca2+ pass through the cell surface membrane by facilitated diffusion?

Back 61

1. (ion / Ca2+) {binds / eq} to protein (in membrane) /
{named / channel / carrier} protein ;
2. reference to {specificity / eq} of protein to {ion /
Ca2+} ;
3. protein spans the membrane / eq ;
4. protein changes shape / description of shape change
/ eq ;
5. (ion / Ca2+) moves across from a region of high
concentration to a region of lower concentration /
down a concentration gradient / eq ;
6. until both sides are equal / eq ;

Front 62

describe the uptake of Ca2+ ions by the cell over the 10 minute period at 30C

Back 62

1. {linear / rapid / steady / eq} increase for first {3½ / 4}
minutes ;
2. uptake slows after {3½ / 4 / {next 2 / eq}} minutes ;
3. no further {increase / uptake} after {5.5 / 6 minutes} ;
4. credit correct manipulation of the data e.g. uptake is
1.8 to 2 au min -1 ;

Front 63

explain what is meant by the term cardiac cycle?

Back 63

1. sequence of events from one beat to the next beat / eq ;
2. reference to {contraction / systole} and {relaxation /
diastole} ;
3. correct detail of sequence e.g. atrial systole → ventricular
systole → diastole / approx 30% of time spent in systole
and 70% in diastole ;
4. correct detail of electrical regulation of cardiac cycle/eq;

Front 64

two components of DNA, other than the bases?

Back 64

pentose suger(deoxyribose), phosphate

Front 65

describe and explain the changes in the concentration of pigment as the temperature increased from 20C to 80C.

Back 65

1, concentration increases as temperature rises up to 80C
2, correct manipulation of data
3, increase in kinctic energy
4, due to channel proteins denaturing
5, all proteins denatured by 80C
6, reference to diffusion of pigments through bilayer
7, only a little pigment leaks out up to 50C because most membrane proteins closed

Front 66

suggest why the concentration of pigment levelled out at 50% of the original pigment concentration after 80C

Back 66

1, dynamic equilibrium has been achieved
2, equal concentrations of pigment in water and beetroot (no concentration gradient)
3, reference to volume of water used
4, correct reference to experimental error/reliability of data

Front 67

name two mechanisms by which amino acids can move through the cell surface membrane?

Back 67

1,active transport/uptake, 2,facilitated diffusion
3, endocytosis, pinocytosis, endopinocytosis

Front 68

the stage of protein synthesis that occurs at the ribosmes?

Back 68

translation

Front 69

suggest molecules other than amino acids and water, that maybe found at the ribosomes and that are involved in protein synthesis

Back 69

1, ATP/ADP
2, mRNA
3, tRNA
4, rRNA

Front 70

how blood is moved through veins?

Back 70

1, skelatal muscle contracts
2, squeezes vein
3, blood is forced in both directions
4, (one way) valves present
5, prevent backflow
6, reference to role of thorax
7, lower pressure in heart during diastole

Front 71

give two structural features of a capillary that enable it to exchange materials rapidly between the blood and the surrouding body tissues?

Back 71

1, the walls of a capillary is only one cell thin
2, small lumen/small diameter
3, pores present

Front 72

suggest why the waxy surface of the oranges is removed before they are submerged in pectinase?

Back 72

1, waxy layer is waterproof
2, enzyme/pectinase in solution
3, therefore enzyme/pectinase unable to pass through waxy layer/unable to get to pectin/polysaccharide/carbohydrate
4, pectinase is specific and will not digest lipid/waxy surface

Front 73

explain why pectinase does not hydrolyse the cellulose found in the orange peel cell walls?

Back 73

1, shape of enzyme/pectinase active site
2, fits pectin/does not fit cellulose/reference to specificity of enzymes

Front 74

suggest why chopping up the oranges could speed up hydrolysis?

Back 74

1, increase the surface area
2, more substrate/pectin available/increases the number of enzyme-substrate complexes/collisions between enzyme/and substrate

Front 75

the pectinase shows a small increase in concentration over the 12 hours of the hydrolysis, suggest why the concentration of the pectinase increases slightly?

Back 75

1, hydrolysis uses up water
2, evaporation of water
3, idea of same number of the enzyme/pectinase molecules but in less solvent/water
4, pectinase released from orange tissues
5, correct referece to osmosis into orange

Front 76

give variables that the student controlled by using the same daphnia?

Back 76

1, genetype
2, age
3, size
4, gender
5, physiological state
6, pre-treatment
7, absorption rate

Front 77

reasons why the Daphnia heart rate was higher at the end of the investigation compared to the 180 beats per minute at the start?

Back 77

1, variation due to chance
2, still some caffeine present within the organism/still some caffeine present on the surface
3, idea of time to recover from effect of caffeine
4, inaccuracy of measurements

Front 78

the investigation was repeated using DNA polymerase and starch solution but no reaction took place, explain why no reaction took place?

Back 78

1, DNA polymerase has a different shaped active site/starch shape different to DNA polymerase active site
2, so starch cannot bind
3, enzyme-substrate complexes cannot form
4, reference to specificty

Front 79

explain the term fluid mosaic

Back 79

fluid-phospholipid molecules can move within phospholipid layer
mosaic-proteins/glycoproteins dotted throughout the membrane/bilayer

Front 80

one function of glycoprotein?

Back 80

act as receptors

Front 81

the structure of a phospholipid molecule?

Back 81

1, two fatty acid tails
2, glycerol
3, phosphate

Front 82

how different types of lipoproteins can affect the health of the body?

Back 82

1, LDLs carry most cholestoral/HDLs more protein/eq
2, LDLs bind to receptors on cell membranes
3, if in high concentration, they overload receptors
4, results in high blood cholestorol
5, high risk of athroma/atherosclerosis
6, HDLs transport cholesterol to liver
7, cholesterols broken down therefore less risks of atherosclerosis

Front 83

how embolisation helps to destroy a tumour?

Back 83

1, the blood cannot pass through the artery to transport oxygen and substances to the tumour cells
2, anerobic resperation
3, build up of lactic acid
4, the tumour is destroyed

Front 84

describe the effect of cystic fibrosis on the male reproductive system?

Back 84

1, impairs functioning of male reproductive system
2, commonly causes a lack of vas deferens/sperm ducts
3, therefore no sperm released
4, if vas deferens present, lumen narrowed
5, so fewer than normal sperm released

Front 85

Describe three reasons why you love your wife.

Back 85

Points awarded for truthfulness, sentiment, inventiveness, and overall emotion.

Hint 85

Points awarded for truthfulness, sentiment, inventiveness, and overall emotion.

Front 86

unsaturated lipids have what kind of bonds?2

Back 86

have double bonds between carbon atoms and between carbon and oxygen atoms

Front 87

draw a diagram to show two mononucleotides joined together in a single strand of DNA

Back 87

1. phosphate and base joined to pentose sugar ;
2. base correctly joined to sugar ;
3. phosphate correctly joined to two pentose sugars ;

Front 88

name two method of prenatal testing and explain how it can be used to detect cystic fibrosis

Back 88

EITHER
1. amniocentesis ;
2. amniotic fluid removed (from amniotic sac of mother) / eq ;
3. {fetal / embryonic} cells present in amniotic fluid /{fetal / embryonic} cells needed ;
4. DNA can be analysed / eq ;
5. to detect {defective / eq} gene(s) (in sample) / eq ;
OR
1. chorionic villus sampling ;
2. placental tissue removed (from womb of mother) / eq ;
3. fetal cells present in {placenta / placental tissue / chorionic tissue} / fetal cells needed ;
4. DNA can be analysed / eq ;
5. to detect {defective / eq} gene(s) (in sample) / eq ;

Front 89

describe one benefit and one risk, to a pregnant woman, of prenatal testing

Back 89

Benefit:
1. gives information about abnormalities (in fetus) / eq ;
2. {opportunity for choice / eq} / {consider termination / eq} / time for {preparation / treatment / eq } / {peace of mind / eq} ;
Risk:
3. possibility of miscarriage (due to procedure) / eq ;
4. {potentially a healthy baby would be lost / eq} / {risk to mother / eq} ;
OR
3. idea of {false positive / false negative} result ;
4. wrong decision made / description of wrong decision ;
OR
3. {damage / harm} to fetus ;
4. subsequent health issues / miscarriages / eq ;

Front 90

discuss either one ethical issue or one social issue relating to the use of prenatal testing

Back 90

1. idea that a fetus is living ;
2. abortion is {wrong / murder} / eq ;
OR
1. who has right to decide if tests should be performed / eq ;
2. implications of medical costs / disagreements over next step ;
OR
1. issues relating to confidentiality of {parents / child} / eq ;
2. idea that {some other abnormality may be found / paternal DNA does not match / other family members have right to know results} ;
OR
1. that or some other abnormality may be found ;
2. comment on possible problems with {future employment / insurance / what constitutes a serious condition} / eq ;
OR
1. not fully understanding possible risks of prenatal testing;
2. possibility of {miscarriage / harm to child} / eq;
OR
1. {who has the right to make the decision for the fetus / fetus has decision rights} (if the test is positive) ;
2. {denying them the opportunity to live / fetus should be allowed to live / fetus has a right to live} ;

Front 91

describe the roles of the atrioventricular(bicuspid and tricuspid) valves during the cardiac cycle

Back 91

1. valves {separate / eq} atria from ventricles ;
2. open during atrial {systole / contraction } / eq ;
3. so that blood can pass through to ventricles / eq ;
4. closed during ventricular {systole / contraction} eq ;
5. to prevent {blood being forced back / backflow / eq} (up into atria) / to maintain pressure in ventricles ;
6. open during diastole / eq ;
7. so that ventricles can start to fill up (as atria are filling) ;

Front 92

bicuspid valve

Back 92

valve found between the left atrium and left ventricle of the heart, one of the atrioventricular valves

Front 93

tricuspid valve

Back 93

valve found between the right atrium and the right ventricle of the heart, one of the atrioventricular valves

Front 94

during the cardiac cycle, the pressure in the right ventricle rises to a maximum of about 3.3kPa, suggest reasons for the difference between this pressure and the maximum pressure in the left ventricle, as shown in the graph.

Back 94

1. correct reference to pressure differences e.g. left is higher ;
2. left ventricle pumps blood {all around body / to rest of body / many arteries / systemic} / eq ;
3. right ventricle pumps blood to {lungs / pulmonary system / eq} ;
4. idea that if blood under high pressure there would be {damage / eq} to {lungs / capillaries / eq} ;
5. reference to lots of muscle (contracting in left ventricle) / reference to thick wall (of left ventricle) ;

Front 95

distinguish between the terms causation and correlation

Back 95

Causation:
when a change in one variable is responsible for a change in another variable / eq ;
Correlation:
(relationship between two variables such that) a change in one of the variables is reflected by a change in the other variable / eq ;

Front 96

using the information in the table above, describe the relationship between ethnic group, cholesterol levels and the percentage of the population with high blood pressure

Back 96

1. {no relationship / little difference} between ethnic group and cholesterol level / eq ;
2. {more / higher percentage of} black and African Americans have {highest / higher} blood pressure than both White and Mexican Americans / eq ;

Front 97

suggest one reason why the data on the American indian and alaskan native population are described as statistically unreliable

Back 97

not enough people surveyed / eq ;

Front 98

a student concluded from the results for gender, shown in the table below, that higher cholesterol levels cause lower blood pressure. using the information in both tables, explain why this is not a valid conclusion

Back 98

1. idea that {other variables present / other variables need considering / no information available about other variables} (for a causal relationship) ;
2. named variable (e.g. genetics, ethnic group, mass of individuals, age of individuals, diet, smoking, exercise) ;
3. idea that cholesterol level of 204 mg dm-3 may not be significantly lower than 207 mg dm-3 ;
4. idea that {30% may not be significantly different from 26% / two values are not very different} ;
5. no information on how many tested / survey not repeated elsewhere ;

Front 99

compare the mortality rate from coronary heart disease in males with that of females, between 1995 and 2001.

Back 99

1. both decrease ;
2. mortality rate in men is higher than that in women (throughout time period) / eq ;
3. this difference is greater at the start of the time period than at the end / eq ;
4. a valid comparison made about the difference in the changes e.g. between 1997 and 1998 the rate stays constant for males but falls for women / fall in mortality rate in men is steeper than the fall in women / decrease in mortality rate is greater in men than women /
the decrease in men is less uniform than in
women ;
5. correct manipulation of figures to quantify any of the above ;

Front 100

the graph shows a change in the number of deaths from coronary heart disease between 1995 and 2001, suggest three reasons for this change

Back 100

1. {people more aware of the dangers / better health education} / appropriate named example /eq ;
2. less stress /eq ;
3. {better / more} screening / eq ;
4. better treatments / eq ;
5. more exercise being taken / eq ;
6. changed diet / less obesity / eq ;
7. less alcohol intake / eq ;
8. decrease in smoking ;
9. change in population genetics / eq ;

Front 101

one cause of coronary heart disease is atherosclerosis, describe how atherosclerosis develops.

Back 101

1. damage to {endothelial cells / epithelial cells /cells lining artery (wall)} ;
2. reference to inflammatory response ;
3. reference to (accumulation of) white blood cells in (damaged area) ;
4. {build up / eq} of cholesterol (in damaged area) ;
5. reference to build up of {calcium salts / fibrous tissue / fibrin / platelets} ;
6. reference to formation of {atheroma / plaque} ;
7. reference to {loss of elasticity (of artery) / narrowing of lumen} / eq ;
8. idea that this process is self–perpetuating ;

Front 102

using the information in the graph, describe the effect of storage time on the vitamin C content of the camu-camu fruit.

Back 102

1. vitamin C content decreases during first {145 / 150} days of storage / eq ;
2. no further decrease in vitamin C content (after first {145 / 150} days) / eq ;
3. idea that decrease is {fastest / greatest} up to 25 days ;
4. rate of decrease decreases with time / eq ;
5. correct manipulation of figures ;

Front 103

describe how an investigation could be carried out to compare the effect of storage time on the vitamin C content of the parana state camu-camu fruit with those from the amazon region

Back 103

1. reference to DCPIP ;
2. reference to use of (camu-camu) juice ;
3. idea of titrating juice with DCPIP ;
4. correct reference to colour change e.g. from blue to {colourless / pink} ;
5. use of calibration curve to determine vitamin C concentration / comparison with standard vitamin C ;
6. reference to procedure being repeated at (regular) time intervals e.g. everyday ;
7. reference to replication ;
8. description of one controlled variable ;
9. reference to drawing graph of both sets of results ;

Front 104

distinguish between the terms allele and gene

Back 104

1. an allele is the {different form / eq} of a gene / eq ;
2. a gene is {a section of DNA / sequence of bases} that codes for a {polypeptide / eq} /occupies a particular {locus / eq} on a chromosome / eq ;

Front 105

explain the meaning of the term recessive allele

Back 105

(allele) that is only expressed (in the phenotype of an organism) if the dominant allele is not present / eq ;

Front 106

explain the meaning of the term homozygous

Back 106

alleles (of a particular gene) are the same / eq ;

Front 107

name the members of this family who are definitely carriers of albinism, giving reasons for your answer.

Back 107

1. Cara and Jasjeet ;
2. {Naveeda / one child} is an albino so must have inherited an albino allele from each parent / eq ;
3. Daniel ;
4. Cara must have inherited the albino allele from her father (as Susan was an unaffected homozygote) / eq ;

Front 108

suggest why the incidence of albinism in squirrels is lower than the incidence in humans, giving a reason for your answer.

Back 108

1. idea that {fewer albino squirrels survive / squirrels may not breed so frequently} ;
2. a suitable reason given (e.g. more predation, less camouflage) ;
3. idea of {frequency of albinism allele in squirrel (population) is lower / chances of two squirrels with the allele less likely to mate} ;
4. comment on the lower mutation rate (in squirrels) ;

Front 109

explain why melanin cannot be produced in the absence of the enzyme tyrosinase

Back 109

1. idea that dihydroxyphenyalanine cannot be synthesized from tyrosine if tyrosinase is absent ;
2. idea that precursor of melanin is dihydroxyphenylalanine / melanin only made if DHPA present ;
3. enzymes are (substrate) specific therefore no other enzyme will breakdown tyrosine / tyrosine does not breakdown on its own ;

Front 110

explain the meaning of the term osmosis

Back 110

1. {movement / diffusion / eq} of water through a partially permeable membrane / eq ;
2. from a region with more free water to a region with less free water / down water concentration gradient / eq ;

Front 111

explain why thee piece of potato placed in 0.2 mol dm-3 sucrose solution had the largest change in mass

Back 111

1. due to high uptake of more water / eq ;
2. as higher water concentration outside potato / eq ;
3. idea of largest difference in concentrations of solutions ;

Front 112

the student suggested that there would be no change in the mass of a piece of potato placed in a sucrose solution of 0.75 mol dm-3, give an explanation for this suggestion

Back 112

EITHER
1. {mass increased / positive change} at 0.6 and {mass decreased / negative change} at 0.8 (mol dm-3 ) ;
2. idea that concentration is closer to 0.8 than 0.6 mol dm-3 as the decrease in mass is greater than the increase in mass – 0.11 is closer to zero than + 0.31 ;
3. idea of no net movement of water ;
OR
1. results were plotted onto a graph ;
2. the line crossed the x axis at 0.75 mol dm-3 eq ;
3. idea of no net movement of water ;

Front 113

the student repeated this investigation using another potato and the results were different. the student concluded that there was a difference in water content of the two potatoes. suggest two reasons for this difference in water content

Back 113

Any two from:
age,
{type / variety / genotypes / country of origin / eq}, storage time,
growth conditions,
part of potato used,
damage,
sprouting,
{storage conditions / temperature / humidity / light /
eq} ;;

Front 114

suggest two reasons why measuring the change in length would not be as accurate as weighing the potato pieces

Back 114

Any two from:
potato pieces are not straight,
potato widths are different,
edges may not be cut straight,
rulers are {subjective / analogues},
change in length is small,
only measuring changes in one plane ;;

Front 115

explain how a gene mutation may result in a protein that does not function normally.

Back 115

1, gene mutation is change in the genetic code.
2, changes mRNA and codon
3, thus different amino acid included
4, different sequence of amino acid and primary structure of protein
5, different R groups
6, change the covalent bond in protein
7, protein forms different structure, including secondary, tertiary, quaterary
8, different 3 D shape

Front 116

mammalian gametes are formed by meiosis and have the ability to fuse to form a zygote. explain why it is important that gametes are produced by meiosis.

Back 116

1, it halves the chromosome number, one of each pair in gamete/haploid cells. the diploid number is maintained in the zygote
2, randomly assorts the chromosomes/genes, provides genetic variation

Front 117

explain how the genetic material from a mammalian sperm cell is able to enter an ovum to bring about the process of fertilisation.

Back 117

1, acrosome present
2, digestive enzymes
3, breakdown jelly surrending ovum, allow head to reach the ovum membrane
4, genetic material passing through ovum membrane

Front 118

suggest why, during the first four divisions, the embryo does not increase in volume even though the total number of cells increase.

Back 118

because the cells do not increase in volume/no new cytoplasm is produced.

Front 119

outline the events that occur in mitosis from the start of prophase up to the end of metaphase

Back 119

1, chromosomes coil and condenses, thus become visible
2, each chromosome becomes visible as two chromatids
3, nuclear membrane breaks down
4, centrioles position themselves at opposite end of the cell
5, spindles formed from the microtubules between centrioles
6, chromosomes on the equator
7, attached by centromeres

Front 120

suggest three reasons why a range of blood LDL is given in the table for the hh genotype, rather than a single level

Back 120

1, because LDL levels vary
2, before/after a meal/diet
3, age
4, gender
5, genetics
6, accuracy of test/measuring equipment
7, variation within a population

Front 121

explain how a deletion in the DNA base sequence, that codes for the LDL receptor protein, can make a receptor protein that is non-functional

Back 121

1, deletion can lead to change/loss of amino acid sequence/primary structure of protein
2, changes tertiary structure of protein
3, shape important in function and recognition and binding of LDL, hence non-functional
4, frame shift

Front 122

suggest which of the three samples comes from the person with the HH genotype. give one reason for your answer

Back 122

smaller, lighter fragment of DNA because it is a deletion, therefore, it moves further/faster towards the postive terminal, the line is twice as thick meaning that it is homozygous

Front 123

the pectinase shows a small increase in concentration over the 12 hours of the hydrolysis. suggest why the concentration of the pectinase increases slightly.

Back 123

1, hydrolysis uses up water
2, evaporation of water
3, same number of enzyme/pectinase molecules but in less solvent/water
4, pectinase releasesd from orange tissue
5, osmosis into orange

Front 124

explain what is meant by stem cell

Back 124

Stem cell is a cell which can divide and can differentiate into different types of cell. Primal cells have retained the ability to divide and differentiate from an earlier stage

Front 125

suggest two advantages of using stem cells, as an alternative to organ transplants

Back 125

1, overcome problems of shortage of donors
2, can use patients' own stem cells therefore no immunity problem
3, necessary sugery less invasive/drastic/life threatening/recovery time
4, probably less expensive

Front 126

explain how embryonic stem cells used in some types of medical research are produced and obtained?

Back 126

1, by fertilisation of ova by sperm in vitro, 2, usually there are spare fertilised ova from IVF treatment

Front 127

explain how acrosome helps to bring about fertilisation

Back 127

1, release digestive enzymes
2, dissolves pathway through follide cells jally layer/zona pellucida

Front 128

explain how mitochondria in a sperm helps to bring about fertilisation

Back 128

1, provide energy
2, for movement/ to enable sperm to reach ovum