Biology Paper 3 November 2023

1. Amoves water down a water potential gradient, which osmosis does not.
2. Boccurs only in plant cells, while osmosis occurs in cells generally.
3. Crequires ATP, while osmosis is a passive process.
4. Dis a passive process that needs no metabolic energy, unlike osmosis.

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1. Ahigher solute concentration to a region of lower solute concentration, through any membrane.
2. Bhigher water potential to a region of lower water potential, through a partially permeable membrane.
3. Clower solute potential to a region of higher solute potential, without any membrane present.
4. Dlower water potential to a region of higher water potential, through a partially permeable membrane.

1. Acauses the phospholipid tails to pack more closely together, solidifying the membrane.
2. Brestricts the movement of phospholipids, reducing membrane fluidity.
3. Cincreases the membrane's permeability to glucose directly.
4. Dbreaks down to release extra energy for active transport.

1. ABoth a lysosome and a ribosome are bounded by a double membrane and contain hydrolytic enzymes.
2. BNeither a lysosome nor a ribosome is involved in the digestion or synthesis of cell contents.
3. CA lysosome is bounded by a single membrane and contains hydrolytic enzymes; a ribosome has no surrounding membrane and is the site of protein synthesis.
4. DA lysosome has no surrounding membrane and is the site of protein synthesis; a ribosome is bounded by a single membrane and contains hydrolytic enzymes.

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1. Athree hydrophobic fatty acid tails attached to a hydrophilic phosphate head.
2. Btwo hydrophilic fatty acid tails and one hydrophobic phosphate head.
3. Cone hydrophilic phosphate head and two hydrophobic fatty acid tails.
4. Da hydrophilic glycerol backbone and no hydrophobic region at all.

1. Ano consistent arrangement, since phospholipids distribute randomly through the membrane.
2. Bhydrophilic heads facing each other in the centre and hydrophobic tails facing the water on both sides.
3. Chydrophobic tails facing each other in the centre and hydrophilic heads facing the water on both sides.
4. Dhydrophobic tails facing the water on one side only and hydrophilic heads facing the water on the other.

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1. Athe active site is a rigid shape that exactly matches the substrate before any binding occurs.
2. Bthe active site changes shape as the substrate binds, moulding around it to fit more closely.
3. Cthe substrate's shape changes permanently to match a fixed, unchanging active site.
4. Dthe active site forms only after the substrate has already reacted and left the enzyme.

1. Athe presence of an iron ion in each of its four haem groups.
2. Bits quaternary structure of four separate, non-interacting polypeptide chains that each bind oxygen completely independently of the others.
3. Ccooperative binding, in which binding of one oxygen molecule makes further binding easier.
4. Dits solubility in the aqueous cytoplasm of the red blood cell.

1. Aprovides many free ends at which enzymes can act simultaneously to release glucose quickly.
2. Bgives it a fixed chain length that is identical in every glycogen molecule, regardless of the tissue or organism it is found in.
3. Cmakes it highly soluble, raising the osmotic pressure of the cytoplasm.
4. Dprevents any enzyme from acting on it under normal conditions.

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1. AThey are found only in gametes and never occur in ordinary body cells.
2. BThey are always identical in the alleles they carry at every locus.
3. COne is always longer than the other, with the centromere in a different position and often a different overall banding pattern.
4. DThey carry the same genes in the same sequence, though the alleles present may differ.

1. AThe nuclear envelope breaks down and the nucleolus disappears.
2. BSister chromatids separate and move to opposite poles.
3. CA new nuclear envelope re-forms around each set of chromosomes.
4. DChromosomes line up individually along the equator of the cell.

1. Ahalves the chromosome number, so fertilisation restores the diploid number in the offspring.
2. Bdoubles the chromosome number in each gamete that is produced.
3. Celiminates the need for fertilisation between two separate gametes.
4. Dproduces four gametes that are always genetically identical to the parent cell and to each other, with no variation at all.

1. Aprevent any genetic variation from arising in the next generation.
2. Bgenerate new combinations of alleles, increasing genetic variation among offspring.
3. Ckeep every gamete produced genetically identical to the parent cell.
4. Doccur only in organisms that reproduce asexually.

1. Aalways increases the range of variation in a population over successive generations.
2. Bfavours the intermediate phenotype and selects against both extremes.
3. Cfavours one phenotypic extreme over both the other extreme and the population mean.
4. Donly occurs when the environment is changing rapidly in one particular direction.

1. Amore than one codon can specify the same amino acid.
2. Bit differs completely between unrelated species.
3. Ccodons overlap so that one base is shared between two codons.
4. Deach codon can specify more than one amino acid at once.

1. Acodons can be read starting from any one of their three base positions.
2. Bstart and stop codons are each read twice within every gene.
3. Cthe same three bases can be read as part of two different codons.
4. Deach base forms part of only one codon as the sequence is read.

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1. ADNA is negatively charged, due to its phosphate groups.
2. BDNA is positively charged, due to its sugar-phosphate backbone.
3. Cthe gel matrix actively pushes fragments toward the positive electrode.
4. Dan electric current has no real effect on the charge of DNA.

1. Alarger fragments are specifically repelled by the positive electrode.
2. Bthe gel acts as a molecular sieve, and smaller fragments pass more easily through its pores.
3. Csmaller fragments carry a stronger negative charge than larger fragments.
4. Dsmaller fragments do not get separated by size at all and instead simply dissolve completely into the surrounding buffer solution.

1. ATranscription requires tRNA and ribosomes; translation requires RNA polymerase.
2. BBoth transcription and translation take place exclusively inside the nucleus.
3. CTranscription makes a polypeptide from mRNA at ribosomes; translation makes mRNA from a DNA template in the nucleus.
4. DTranscription makes mRNA from a DNA template in the nucleus; translation makes a polypeptide from mRNA at ribosomes.

1. AATP and NADPH, with oxygen released as a by-product.
2. BATP and oxygen, with the electrons passed permanently to NADP+.
3. CNADPH only, with no ATP produced at all.
4. DATP only, with the electrons returned to photosystem I.

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1. Aconverted directly into carbon dioxide and water with no enzyme involved.
2. Bhydrolysed into two separate molecules of lactate.
3. Cphosphorylated using ATP produced earlier in glycolysis.
4. Ddecarboxylated and dehydrogenated, reducing NAD+ to NADH.

1. Areleases a very large, fixed amount of energy in one single burst that cannot be recovered or reused once it has been released.
2. Bcannot diffuse through the cytoplasm to reach where energy is needed.
3. Creleases energy in small, manageable amounts and can be readily regenerated from ADP and phosphate.
4. Dis found only in animal cells, never in plants or microorganisms.

1. Ainherited only from the father, through the sperm's mitochondria.
2. Babsent from the egg cell and only added to the zygote after fertilisation.
3. Cidentical in sequence to nuclear DNA from the same organism.
4. Dinherited only from the mother, making it useful for tracing maternal lineage.

1. Asperm are collected from the testes and left to mature in culture before use.
2. Beggs collected from the ovaries are combined with sperm in a dish, outside the body.
3. Can embryo is transferred into the uterus before fertilisation has occurred.
4. Dfertilisation occurs naturally inside the ovary itself, without any laboratory intervention or handling of the egg.

1. Aplaced directly into the ovary to continue its development there.
2. Bpassed by catheter through the cervix into a hormonally prepared uterus.
3. Cfrozen permanently and never subsequently transferred into a uterus.
4. Dimplanted directly into the fallopian tube through a surgical incision.

1. Ahave red blood cells that sickle and are removed along with the parasite inside, giving some protection against severe malaria.
2. Bpass the sickle-cell allele only to their daughters, never to sons.
3. Csuffer from severe sickle-cell anaemia, which itself deters mosquito bites.
4. Dare completely immune to malaria and are never infected by the parasite.

1. Athey are the primary source of antibiotics used in modern medicine.
2. Bthey are entirely immune to being classified as agricultural weeds.
3. Cthey are grown commercially as a staple cereal crop worldwide.
4. Dtheir fossilised relatives contributed to the formation of coal deposits.

1. Awithstand and smooth out the high pressure pulses generated by the heart.
2. Ballow valves to form at regular intervals along its length.
3. Cincrease the width of the lumen so as to reduce the blood pressure carried within the vessel.
4. Dprevent any elastic recoil from occurring between heartbeats.

1. Aa thicker wall overall and a narrower lumen.
2. Bno lumen at all, since blood flows through solid tissue.
3. Cvalves along its length and a thinner wall relative to its lumen.
4. Da thicker tunica media containing more smooth muscle.

1. Ain a ganglion, off to one side of the axon, outside the central nervous system.
2. Binside the effector organ that the neuron eventually supplies.
3. Cwithin the grey matter of the central nervous system.
4. Dat the neuromuscular junction, next to the effector it supplies.

1. Aconservationists routinely encourage farmers to clear more natural habitat for farmland.
2. Bfarmers are never affected in any way by restrictions on protected areas.
3. Cwild animals raiding crops cause direct economic loss to farmers.
4. Dprotected predators are legally required to be relocated onto farmland.