Biology Paper 2 November 2004

1. Athe number and sequence of amino acids in its polypeptide chain
2. Bthe folding of its polypeptide chain into a compact three dimensional shape
3. Cthe association of two or more polypeptide chains into one functional molecule
4. Dthe coiling of its polypeptide chain into an alpha helix or beta pleated sheet

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1. Atwo alpha chains of 146 amino acids and two beta chains of 141 amino acids
2. Bfour identical alpha chains of 141 amino acids joined end to end by peptide bonds
3. Cfour identical beta chains of 146 amino acids joined to each other by disulphide bridges
4. Dtwo alpha chains of 141 amino acids and two beta chains of 146 amino acids

1. Apeptide bonds formed between the carboxyl group and the amino group of adjacent chains
2. Bester bonds between the iron of the haem groups and the surrounding polypeptides
3. Chydrogen bonds, ionic bonds and hydrophobic interactions between the chains
4. Dglycosidic bonds linking sugar residues on the surface of each polypeptide chain

1. Aforms a permanent covalent bond with the amino acids of the beta chains
2. Bbinds reversibly to the iron(II) ion at the centre of each haem group
3. Cdissolves in the hydrophobic core formed by the four polypeptide chains
4. Dis converted to water by the iron(II) ion held in each haem group

1. Abreaks the peptide bonds of the primary structure, splitting the enzyme completely into its individual amino acid residues
2. Balters the charges on the acidic and basic groups, breaking the ionic bonds that hold the active site in shape
3. Clowers the kinetic energy of the enzyme and its substrate so that collisions become far less frequent
4. Dremoves the substrate molecules from the solution surrounding the enzyme and its active site

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1. A2
2. B5
3. C7
4. D9

1. Aallows each enzyme to work efficiently in the particular part of the body where it acts
2. Braises the optimum temperature at which each of the enzymes is able to function
3. Cmakes each enzyme able to act on a much wider range of different substrate molecules at once
4. Dkeeps the pH of every body fluid at the same value as the cytoplasm of the cell

1. Arises steadily with substrate concentration and continues to rise without reaching any upper limit at all
2. Brises in proportion to substrate concentration, then levels off once every active site is occupied
3. Cfalls as substrate concentration rises because the substrate blocks the active sites
4. Dstays the same at every substrate concentration because the enzyme is not used up

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1. Aprotein coats that surround and protect the bacterial genetic material
2. Bfolded regions of the cell surface membrane on which respiration occurs
3. Csmall circular pieces of DNA separate from the main bacterial chromosome
4. Dshort lengths of messenger RNA copied from the main bacterial chromosome

1. Ablunt ends on both fragments, so that the two pieces of DNA can be pushed together without any base pairing
2. Bsingle stranded RNA copies of the gene, which are read directly by the bacterial ribosomes
3. Ccomplementary sticky ends, so the cut fragments can pair up by hydrogen bonding between exposed bases
4. Dshorter DNA fragments, which pass more easily through the pores of the bacterial cell wall

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1. Arestriction endonuclease
2. BDNA ligase
3. CDNA polymerase
4. Dreverse transcriptase

1. Athe human cell first converts the mouse gene into the equivalent human gene before using it
2. Bmouse proteins are made from a different set of amino acids from those found in human cells
3. Cthe genetic code is universal, so the same triplets specify the same amino acids in both species
4. Dmouse and human cells contain exactly the same set of genes but express each of them at different rates

1. Aone gene is carried on the X chromosome and its partner is carried on the Y chromosome
2. Bthe same gene appears at several different loci scattered along one homologous chromosome
3. Ctwo completely different genes at separate loci together control one single inherited characteristic in the organism
4. Dthree or more different forms of the gene exist in the population, any two of which may occupy the locus

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1. AI^A I^O or I^O I^O
2. BI^A I^A or I^A I^O
3. CI^A I^B or I^A I^O
4. DI^A I^A or I^A I^B

1. Agroup AB only, since both parents pass on a dominant allele
2. Bgroup A and group AB only, in equal proportions
3. Cgroup A and group B only, in equal proportions
4. Dgroup A, group B, group AB and group O, in equal proportions

1. Ahas a one in four chance of being blood group A, as in any pair of siblings
2. Bmay be any of the four ABO blood groups, since blood group is not inherited
3. Cmust also be blood group A, because the twins carry identical genotypes
4. Dhas a one in two chance of being blood group A, as the alleles segregate again

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1. Aloosely packed rounded cells separated by very large air spaces that act as a reservoir of water vapour
2. Bflattened cells covered by a waxy cuticle that reflects light away from the inner tissues
3. Cclosely packed elongated cells, rich in chloroplasts, near the upper surface where light is brightest
4. Dthick walled dead cells that carry water upwards from the roots to the rest of the leaf

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1. Acarries out the whole of the light dependent stage while the palisade layer carries out the light independent stage
2. Bstores the starch made in the palisade cells until it is exported through the lower epidermis
3. Cabsorbs most of the light falling on the leaf before it can reach the palisade cells above
4. Dprovides air spaces between loosely packed cells and stomata through which carbon dioxide reaches the mesophyll

1. Aare surrounded by a double membrane and contain their own circular DNA and 70S ribosomes
2. Bcontain stacks of thylakoid membranes and store the products of photosynthesis as starch
3. Care bounded by a single membrane and depend entirely on 80S ribosomes in the cytoplasm
4. Dpossess cristae bearing chlorophyll and a matrix in which the Calvin cycle takes place

1. AATP is produced in the chloroplast but is only broken down in the mitochondrion
2. Bcarbon dioxide is released in the chloroplast but is used up in the mitochondrion
3. Coxygen is used up in the chloroplast but is released in the mitochondrion
4. Dcarbon dioxide is used up in the chloroplast but is released in the mitochondrion

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1. Ahas a lower affinity for oxygen, so it hands its oxygen over to haemoglobin in the capillaries
2. Bhas exactly the same affinity for oxygen as haemoglobin but carries four oxygen molecules instead of one
3. Chas a higher affinity for carbon dioxide, which it carries from the muscles back to the lungs
4. Dhas a higher affinity for oxygen, so it releases oxygen only when the partial pressure falls very low

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1. Amuscle oxygen falls rapidly and is almost exhausted early in the dive, while arterial oxygen falls steadily throughout
2. Bmuscle oxygen rises during the dive while arterial oxygen is used up by the working muscles
3. Carterial oxygen falls rapidly during the first few minutes while muscle oxygen stays completely constant for the whole dive
4. Dboth arterial and muscle oxygen fall at the same steady rate until both reach zero together

1. Ablood flow to the muscles is increased so that they can go on contracting aerobically
2. Bthe heart stops beating altogether until the animal returns to the surface to breathe
3. Cthe lungs continue to take up oxygen from the water through the alveolar walls
4. Dblood flow to the muscles is reduced and blood is diverted to the brain and heart

1. Acarbon dioxide only, because respiration has continued aerobically throughout
2. Boxygen, because the muscles have used less of it than usual
3. Clactic acid, because the muscles have been respiring anaerobically
4. Dglycogen, because the liver has released its stores into the blood

1. Athe movement of animals between reserves during the dry season each year
2. Bthe clearing of land for agriculture, settlement and industrial development
3. Cthe natural extinction of species at the end of their evolutionary life span
4. Dan increase in the number of large predators within protected game areas

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1. Ait stops any further mutation from occurring in the populations of the species that are protected
2. Bthe total number of individual organisms living on the earth is then kept exactly the same from one year to the next
3. Cit allows farmers to replace the many wild species of an area with a few high yielding domesticated ones
4. Da wide gene pool is conserved, ecosystems remain stable, and species of economic value survive

1. Aremoving predators from reserves so that the numbers of grazing animals can build up
2. Bsetting up game reserves, enforcing protective laws and joining international trade agreements such as CITES
3. Cclearing large areas of woodland so that the animals that remain have much more open grazing land available to them
4. Dmoving every threatened species into zoos and closing the reserves they came from

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1. AZ
2. BP
3. CR
4. DX

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1. Athe extra oxygen taken in after exercise to remove the lactic acid that has built up
2. Bthe oxygen carried by myoglobin that stays bound to it inside the respiring muscle
3. Cthe difference between the oxygen breathed in and the carbon dioxide breathed out
4. Dthe volume of oxygen still left inside the alveoli at the end of a normal quiet expiration

1. Adrinking water so that the lactic acid is diluted and carried away in the urine
2. Bbreathing deeply and rapidly for several minutes after the exercise has stopped
3. Cholding the breath so that carbon dioxide can build up in the blood once more
4. Dresting until the lactic acid in the muscles is broken down into carbon dioxide alone

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1. Anon-motile heterotrophs whose cell walls contain chitin
2. Bmotile heterotrophs that have no cell wall at all
3. Cmotile autotrophs whose cell walls contain murein
4. Dnon-motile autotrophs whose cell walls contain cellulose

1. Amotile heterotrophs with less developed organ systems
2. Bnon-motile autotrophs with less developed organ systems
3. Cnon-motile heterotrophs with well developed organ systems
4. Dmotile autotrophs with well developed organ systems

1. Ahave rhizoids that anchor the plant and take up water, and can survive long dry periods
2. Bcomplete the whole of their life cycle inside a protective seed coat on dry ground
3. Chave deep roots and lignified xylem vessels that carry water to every part of the plant
4. Dhave a thick waxy cuticle over the whole plant body and reproduce entirely by seed

1. A70S ribosomes, while a eukaryotic cell has 80S ribosomes in its cytoplasm
2. B80S ribosomes, while a eukaryotic cell has 70S ribosomes in its cytoplasm
3. Cno ribosomes at all, while a eukaryotic cell has 80S ribosomes throughout
4. D70S ribosomes, while a eukaryotic cell has no ribosomes outside its nucleus

1. Alinear, naked, and held within a double membrane called the nuclear envelope
2. Bcircular, naked, and not enclosed within a nuclear envelope
3. Clinear, bound to histone proteins, and enclosed within a nuclear envelope
4. Dcircular, bound to histone proteins, and carried on several chromosomes

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1. Ais enclosed in its own double membrane, while the eukaryotic flagellum has no membrane
2. Bcontains a 9 + 2 arrangement of microtubules, while the eukaryotic flagellum contains none of them at all
3. Ccontains no microtubules, while the eukaryotic flagellum has a 9 + 2 arrangement of microtubules
4. Dis made of cellulose fibres, while the eukaryotic flagellum is made of contractile protein

1. Aon infoldings of the cell surface membrane called mesosomes
2. Bon the ribosomes attached to the endoplasmic reticulum
3. Con the cristae of the many mitochondria found in the cytoplasm
4. Dinside the double membrane envelope of the chloroplast

1. A5 to 40 micrometres
2. B0.5 to 5 nanometres
3. C0.5 to 5 millimetres
4. D0.5 to 5 micrometres

1. Atwo layers of protein about 7 nm thick separated by a continuous layer of phospholipid
2. Ba bilayer of phospholipids about 7 nm thick with proteins embedded in and across it
3. Ca single layer of phospholipids about 7 nm thick coated on both sides with cellulose
4. Da solid sheet of protein about 7 nm thick with phospholipid molecules attached to it

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1. Aremoves one chromosome from each pair and destroys it before the cell divides
2. Bhalves the chromosome number, producing haploid cells from a diploid cell
3. Cdoubles the chromosome number, producing diploid cells from a haploid cell
4. Dkeeps the chromosome number the same in the parent cell and the daughter cells

1. Aallows each chromosome to be copied a second time before the cell divides again
2. Bmakes certain that every one of the gametes that is produced receives one complete maternal set of chromosomes
3. Cmeans maternal and paternal chromosomes are assorted independently, giving many different gamete combinations
4. Dkeeps the maternal and paternal chromosomes of each pair together in the same gamete

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1. Aa fall in the overall rate of mitosis in the tissues, so that damaged cells are not replaced quickly enough
2. Bthe repeated production of gametes by meiosis in the reproductive organs of the organism
3. Cexposure to carcinogens such as tobacco tar, which cause mutations in the genes controlling mitosis
4. Dan increase in the number of chloroplasts within the dividing cells of the affected tissue

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1. Ainsulin, by converting glucose to glycogen and storing it
2. Bglucagon, by converting glucose to glycogen and storing it
3. Cinsulin, by converting glycogen to glucose and releasing it
4. Dglucagon, by converting glycogen to glucose and releasing it

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1. Abreaks the peptide bonds of dietary protein so that the amino acids can be absorbed
2. Bconverts the ammonia released by deamination into urea before it leaves the liver in the blood
3. Cmakes the non-essential amino acids by transferring an amino group from one acid to another
4. Dchanges amino acids directly into glycogen for storage in the liver and in the muscles

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1. Amale and female flowers are borne on separate plants
2. Beach flower carries both stamens and carpels together
3. Cthe flowers have no stamens and no carpels at all
4. Dmale and female flowers are borne on the same plant

1. Athe pollen grains of the same plant are too large to be carried to the stigma by insects
2. Bthe stigma of a plant secretes a sugary fluid that dissolves all pollen reaching it
3. Ca pollen grain fails to germinate on a stigma of the same plant, since their genes match
4. Dpollen from another plant of the same species is rejected by the stigma it lands on

1. Athe offspring show much greater genetic variation than those of a cross-pollinated plant
2. Bthe plant produces far more pollen grains than a cross-pollinated plant has to produce
3. Cthe seeds produced are always larger and germinate faster than cross-pollinated seeds
4. Dfertilisation is more reliable, since it does not depend on an outside pollinating agent

1. Ait needs a much larger number of insect visits than cross-pollination needs
2. Bthe pollen has to travel a long distance before it can reach a ripe stigma
3. Cthe flowers must be large, brightly coloured and strongly scented to attract pollinators
4. Dit is a form of inbreeding, so little genetic variation appears in the offspring