Biology Paper 2 November 2003

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1. AGolgi apparatus, which modifies and packages proteins for secretion
2. Brough endoplasmic reticulum, which assembles amino acids into polypeptides
3. Csmooth endoplasmic reticulum, which synthesises and transports lipids
4. Dlysosome, which stores hydrolytic enzymes until worn out organelles are digested

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1. Athe amino group of one amino acid and the carboxyl group of the next
2. Bthe R group of one amino acid and the R group of the next amino acid
3. Cthe amino groups of two neighbouring amino acids in the same chain
4. Dthe carboxyl groups of two neighbouring amino acids in the same chain

1. Aglobular, with parallel strands held side by side by hydrogen bonds along their whole length
2. Bglobular, with four subunits folded round a prosthetic group at the centre of each chain
3. Cfibrous, with three chains wound into a triple helix and no prosthetic group
4. Dfibrous, with a single chain folded into a compact ball around an iron containing haem group

1. Aa single group of chromosomes lies on one equator, with the chromosomes in homologous pairs
2. Bthe chromosomes have already reached the poles and two nuclear envelopes are re-forming
3. Cthe chromosomes are still uncoiled and the nuclear envelope has not yet broken down
4. Dtwo groups of chromosomes lie on two separate equators, divided by a new cell membrane

1. A1
2. B2
3. C4
4. D8

1. Afewer, larger cells, each with half the chromosome number of the parent cell
2. Bcells that differ genetically from one another, so that the tissue can vary
3. Cgametes that fuse together to form new tissue at the growing point of the organism
4. Dmore cells, each with the same chromosomes and the same alleles as the parent cell

1. Aexcited electrons from chlorophyll pass along a chain of carriers, releasing energy to phosphorylate ADP
2. Bchlorophyll absorbs light and is broken down into its component pigments by photolysis
3. Cwater molecules are joined together to release oxygen and the energy that is needed to make ATP
4. Dcarbon dioxide is reduced to triose phosphate using the hydrogen carried by reduced NADP in the stroma of the chloroplast

1. Asplit water molecules into hydrogen ions, electrons and oxygen gas at photosystem II of the grana
2. Bexcite the electrons of chlorophyll a in the thylakoid membranes of the grana
3. Cfix carbon dioxide onto ribulose bisphosphate without any enzyme being needed
4. Dreduce glycerate 3-phosphate to triose phosphate and to regenerate ribulose bisphosphate

1. Ano electron carriers are involved, so no phosphorylation takes place
2. Bthe energy comes from light rather than from the oxidation of a respiratory substrate
3. CATP is made in the intermembrane space rather than on a membrane
4. Dthe energy comes from the oxidation of pyruvate rather than from light

1. Aadenine replaced by guanine
2. Bguanine replaced by adenine
3. Cadenine replaced by thymine
4. Duracil replaced by cytosine

1. Athe change makes the whole gene shorter by one base, so the protein is one amino acid shorter
2. Bevery single base of the gene codes for one amino acid, so one base changed always means one amino acid changed in the protein
3. Cthe triplet containing that base is altered, so a different codon appears on the mRNA and a different amino acid is brought
4. Dthe ribosome reads the gene backwards from the point of the change onwards

1. Ahas a different R group, so the folding, solubility and function of the protein are altered
2. Bcannot form a peptide bond at all, so the whole polypeptide chain is left permanently unfinished
3. Cis not coded for anywhere in the genetic code, so no protein at all can be made
4. Dchanges the primary structure but leaves the tertiary structure completely unaffected

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1. Areabsorption of water under the control of antidiuretic hormone alone
2. Bselective reabsorption of glucose, amino acids and mineral ions into the blood
3. Cultrafiltration of the blood plasma through the capillary wall into the tubule
4. Dsecretion of the hormone renin into the fluid passing along the tubule

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1. Aadrenaline, which reduces the volume of urine by narrowing the collecting duct
2. Bantidiuretic hormone, which makes the wall of the duct less permeable to water
3. Cinsulin, which increases the rate at which water is taken back into the blood
4. Dantidiuretic hormone, which makes the wall of the duct more permeable to water

1. Aa dry mass measurement made by filtering the culture and drying it to constant mass
2. Ba viable count made by spreading a dilution on agar and counting the colonies formed
3. Ca total count made by counting all the cells in a haemocytometer under the microscope
4. Da turbidity measurement made by passing light through the culture in a colorimeter

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1. Athe dead cells are broken down completely, so that they no longer appear in either one of the two columns
2. Bnutrients and oxygen have run out and toxic waste has built up, so cells die and division has stopped
3. Cthe living cells are still dividing rapidly but each new cell is too small to be counted
4. Dthe culture has been diluted, so the same sample now contains fewer cells of either kind

1. Aoffspring differ widely from one another, so a population adapts quickly to any change in its surroundings
2. Bthe population cannot evolve at all, because the genes of the parent cell are never altered
3. Ceach generation carries half the genes of the previous one, so the gene pool shrinks steadily
4. Doffspring are genetically almost identical, so new variation depends on mutation alone

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1. Asmooth muscle
2. Bcartilage
3. Ccilia
4. Dgoblet cells

1. Aare lined with a layer of cartilage that keeps them open and prevents any water loss from them
2. Bhave a dry inner surface, so oxygen passes straight across without dissolving on the way
3. Chave thick muscular walls that pump air in and out and are supplied by a single large blood vessel
4. Dare numerous and thin walled, and are richly supplied with capillaries

1. Abreaking down the walls between them and destroying their elastic fibres, so the surface area falls
2. Bincreasing their number so that each one becomes smaller and less elastic than before
3. Cfilling every one of them with mucus, so that they become blocked but they still keep their elastic recoil
4. Dthickening their walls with extra layers of cells, so their elastic fibres multiply

1. Aa radially symmetrical body, a single body cavity and no true coelom
2. Ba segmented body, jointed appendages and an exoskeleton of chitin
3. Can unsegmented body, tube feet and an internal skeleton of calcium plates
4. Da segmented body, no appendages and a moist skin used for gas exchange

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1. Aa cell wall made of chitin and a nucleus bounded by a double nuclear envelope
2. Bno cell wall at all and many membrane bound organelles in its cytoplasm
3. Ca cell wall of cellulose and one large permanent vacuole that fills most of the cell
4. Da cell wall of murein and a loop of DNA that is not enclosed in a nuclear envelope

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1. Athe enzyme is used up in the reaction and has to be replaced before the next substrate molecule arrives
2. Bthe substrate binds to the active site, forming a complex that lowers the activation energy
3. Cthe substrate binds anywhere on the enzyme surface and is broken down by the heat released
4. Dthe enzyme raises the activation energy so that the reaction can go in one direction only

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1. Araises the pH of the surrounding solution so far that the enzyme is denatured
2. Bresembles the substrate and occupies the active site, keeping substrate molecules out
3. Cbinds to a site well away from the active site and so changes the shape of the active site
4. Dbreaks the peptide bonds of the enzyme, so the enzyme is digested into amino acids

1. Ahas a structure very similar to that of the substrate and competes for the active site
2. Bis converted into a product that then blocks the entrance to the active site
3. Cremoves the substrate from the solution by combining with it before it reaches the enzyme
4. Dbinds at a site other than the active site and distorts the shape of the active site

1. Arestores the rate where the inhibitor is non-competitive, but has little effect where it is competitive
2. Blowers the rate in both cases, because the extra substrate crowds the inhibitor onto the enzyme
3. Crestores the rate where the inhibitor is competitive, but has little effect where it is non-competitive
4. Dhas no effect in either case, because both kinds of inhibitor bind to the active site

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1. Aeach bivalent is always pulled to the same pole as the one lined up next to it on the equator
2. Bthe way each bivalent faces at metaphase I is random and does not affect any other bivalent
3. Cthe chromatids of one chromosome are always separated at anaphase I of meiosis
4. Devery gamete receives a complete set of the chromosomes inherited from the mother

1. Aany one of the many genetically different male gametes may fuse with any one of the female gametes
2. Bthe two gametes exchange lengths of DNA with each other at the moment they fuse
3. Cthe male gamete that reaches the egg cell first is always the one that carries the dominant alleles
4. Dfertilisation restores the haploid number of chromosomes in the zygote that is formed

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1. Athe environment causes new alleles to appear in the individuals that need them most
2. Bindividuals change their own bodies during life and pass those changes to their offspring
3. Cindividuals whose phenotypes suit the environment survive to breed and pass on their alleles
4. Devery individual in the population produces exactly the same number of surviving offspring each year

1. Athe complete loss of every one of the alleles from the gene pool, and so to certain extinction
2. Ban increase in the mutation rate, because the environment alters the DNA directly
3. Can equal number of every phenotype, because selection acts on all of them alike
4. Da change in the frequencies of alleles in the gene pool, and in time to a new species

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1. Afrom the brain along a nerve to the ventricle walls, which then contract before the atria do
2. Bfrom the atrioventricular node across both atria to the sinoatrial node, then down the Purkyne fibres
3. Cfrom the sinoatrial node across both atria to the atrioventricular node, then down the Purkyne fibres
4. Dfrom the Purkyne fibres upwards through the ventricle walls to the sinoatrial node in the atrium

1. Athe heart rate at rest rises, because the heart has to work harder to supply the muscles
2. Bthe number of mitochondria in the heart muscle fibres falls as the fibres grow larger
3. Cthe heart muscle becomes stronger, the chambers enlarge, and the stroke volume increases
4. Dthe heart muscle becomes thinner, the chambers shrink, and the stroke volume decreases

1. Athe heart muscle tires more easily, so it is unable to contract as often as before
2. Bthe blood becomes thinner, so it flows through the vessels without the heart pumping
3. Cthe body needs less oxygen at rest once a person has become physically fit
4. Da larger stroke volume delivers the same cardiac output with fewer beats each minute

1. Alowers the level of cholesterol and saturated fat in the blood and improves circulation
2. Bnarrows the coronary arteries so that blood passes through them at a much higher speed
3. Craises the level of cholesterol in the blood so that the artery walls are strengthened
4. Dremoves the atheroma that has already formed in the coronary arteries within a few days

1. Adecomposers break down dead material and release the energy stored in it as heat
2. Bthe soil absorbs heat during the day and releases it to the roots of plants at night
3. Cproducers absorb sunlight and convert it into chemical energy in organic compounds
4. Dprimary consumers eat the producers and convert their tissues into animal tissue

1. Areturned to the sun by radiation from the surface of the organisms
2. Bconverted into new alleles in the gametes of the organisms concerned
3. Clost as heat in respiration, or passes out in egestion and excretion
4. Dstored permanently in the bones and other hard parts of the consumer

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1. Aincreases at every trophic level as the organisms of that level grow larger
2. Bis stored in the soil and taken up again through the roots of the producers
3. Cpasses through the system once and is lost as heat, so it must be replaced by sunlight
4. Dis recycled endlessly between the organisms and their physical surroundings, as nutrients are

1. Aelephants are poached for their ivory, and they also compete with people for land
2. Blarge predators have increased in number and now take most of the elephant calves
3. Celephants have a very short life span and breed only once in every twenty years
4. Dthe species has no natural predators, so its numbers rise until food runs out

1. Apoaching stops as soon as a single country makes the killing of elephants unlawful
2. Bivory is traded across borders, so an agreement such as CITES is needed to close the market
3. Celephants can be conserved only inside zoos, which are found in many different countries of the world
4. Deach country breeds a different species of elephant that must be crossed with the others