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Dodaj cały arkusz do zestawuCompared with nearby land, a deep lake changes temperature slowly when the same amount of energy is supplied per kilogram. Which explanation accounts for this thermal stability? A. Breaking covalent O–H bonds gives water a low heat capacity B. Hydrogen bonds…
An electron-microscope model of chromatin shows repeated bead-like units along a DNA molecule. What is the basic composition of one nucleosome? A. An entire chromosome enclosed by its nuclear membrane B. A ribosome attached to several amino acids C. A lipid…
A plant cell deposits cellulose microfibrils outside its plasma membrane. What is their principal contribution? A. They catalyse respiration in the mitochondria B. They store the cell’s genetic information C. They resist stretching and reinforce the cell wall…
A soluble globular enzyme has many charged and polar side chains exposed on its surface, while most non-polar side chains are buried. Which inference follows? A. The buried side chains are all linked by disulfide bonds B. Surface polar groups can form hydrogen…
Which metabolic transformation is catabolic? A. Incorporating glucose into a growing glycogen chain B. Hydrolysis of a starch molecule into smaller sugar units C. Producing a triglyceride from glycerol and fatty acids D. Joining amino acids into a polypeptide
A blue carbon-dioxide indicator becomes yellow when dissolved carbon dioxide accumulates. Identical sealed jars start blue. Which treatment is most likely to retain the blue colour if illumination is sufficient for net photosynthesis? A. An aquatic plant and a…
Which electron-transfer event is correctly placed in the light-dependent reactions of photosynthesis? A. Photosystem II receives electrons directly from triose phosphate B. ATP donates its phosphate electrons to reduce water C. Electrons leaving photosystem I…
During Calvin-cycle operation, four triose-phosphate molecules leave the cycle and provide carbon for two hexose molecules. How many RuBP molecules must be regenerated during this net production? A. 12 B. 20 C. 4 D. 8
Each panel proposes the strand composition of two DNA molecules after one round of replication. Which panel represents semiconservative replication? A. Panels Q and R B. Panel Q only C. Panel R only D. Panel P only
The upper strand is the template for transcription. Read the sequence in the indicated triplet frame. Template: 3′–TAC GGA CTT ACG TTT CGC–5′ Other strand: 5′–ATG CCT GAA TGC AAA GCG–3′ Codon | Amino acid AUG | Met CCU | Pro GAA | Glu UGC | Cys UAC | Tyr GGA |…
Researchers disable a gene in a laboratory strain and compare its phenotype with an otherwise similar strain in which the gene remains active. What is the main purpose? A. To ensure that all mutations in the genome are removed B. To manufacture additional…
A membrane-protein preparation is rapidly frozen so that molecules can be imaged in stable conformations using an electron beam. Which method is being used? A. Fluorescence microscopy of living cells B. Light microscopy with a visible stain C. Cryogenic…
Which event distinguishes lysogenic infection from an immediately lytic infection by a temperate bacteriophage? A. The host supplies no energy to viral processes B. The phage genome becomes a prophage within the host chromosome C. The viral genome is never…
A cell maintains the ion concentrations shown. Which mechanism can sustain these opposing gradients? Ion | Cytosol / mmol L⁻¹ | External fluid / mmol L⁻¹ Potassium | 142 | 4.5 Sodium | 12 | 138 A. Passive movement of both ions through permanently open channels…
Clathrin assembles on the cytoplasmic surface of a patch of membrane. What does this coat contribute to vesicle formation? A. It forms a scaffold that helps curve the membrane into a bud B. It breaks all phospholipid tails into amino acids C. It pumps water…
Early embryonic cells receive different concentrations of signalling molecules according to their positions. Which outcome can these gradients direct? A. Immediate loss of all chromosomes B. Replication of only the mitochondrial genome C. Development of…
A neonicotinoid insecticide disrupts communication between neurons in an insect. What molecular interaction is responsible? A. Cleaving acetylcholine into glucose and phosphate B. Blocking protein synthesis in the insect’s bacterial symbionts C. Binding to…
In this constructed dataset, exercise begins at 0 minutes and epinephrine infusion begins at 25 minutes. Which signalling event can account for the subsequent difference from the control? A. The receptor permanently destroys cyclic AMP B. A receptor activates…
Which event can occur in both mitosis and meiosis? A. A diploid chromosome number is halved in each daughter nucleus B. Homologous chromosomes form bivalents before the first division C. Exchange of chromosome segments is obligatory in every division D.…
Identical twins differ in methyl-group attachment to amino-acid residues of proteins associated with one chromosome. Which interpretation best fits the observation? A. One twin has a different order of DNA bases at every gene B. Both twins must have identical…
Which pairing describes a mechanism and a possible consequence in the formation of species? A. Increased interbreeding — guaranteed reproductive isolation B. Permanent mixing of gene pools — prevention of all allele-frequency change C. Reduced gene flow…
Which molecular comparison was central to distinguishing Bacteria, Archaea and Eukarya as major domains? A. Measuring the concentration of messenger RNA in growing cultures B. Counting the amino acids in one dietary protein C. Comparing the colours of membrane…
Destruction of walls between neighbouring alveoli leaves larger air spaces in a lung. What direct effect impairs gas exchange? A. The total respiratory surface area is reduced B. The diffusion path through every remaining cell becomes zero C. The blood gains…
Which pair of changes would tend to increase transpiration from a well-watered plant with open stomata? A. Lower light availability and higher relative humidity B. Lower air temperature and higher relative humidity C. Higher relative humidity and slower air…
The drawing represents a shortened sarcomere. Which labelled feature increases in length when the sarcomere relaxes and stretches back? A. R, the length of a thin filament B. P, the distance between the two Z-discs C. S, the width of the central line D. Q, the…
A plant signal accumulates around ripening bananas and promotes ripening in nearby fruit. Which substance acts directly in this response? A. Glucagon B. Ethylene C. Melatonin D. Testosterone
A bacterial isolate is no longer killed by an antibiotic that inhibited an earlier isolate of the same species. Which biological change could explain the difference? A. A mutation has altered a bacterial target so the drug binds less effectively B. The…
After rapid travel across time zones, a person remains alert late into the local night. Which endocrine mismatch can contribute? A. Excess melanin released from the hypothalamus B. Release of oxytocin from the thyroid at sunset C. Loss of insulin release from…
In an apple variety, pollen sharing the relevant incompatibility specificity with the maternal plant is rejected. What is a reproductive benefit of this mechanism? A. It prevents all changes in allele frequency B. It ensures that every ovule is fertilised by…
A diploid primary spermatocyte in a mammal contains 40 chromosomes. After normal meiosis and differentiation, what is produced? A. Two sperm cells with 40 chromosomes each B. Four sperm cells with 20 chromosomes each C. Four sperm cells with 40 chromosomes…
In a snapdragon line showing incomplete dominance, crimson homozygotes and ivory homozygotes produce pale-rose heterozygotes. A pale-rose plant is crossed with an ivory plant. Which result is expected? A. Only crimson offspring B. Crimson and ivory offspring…
Let P represent a functional allele and p a recessive allele associated with phenylketonuria. Which combination identifies the affected genotype and the disrupted metabolic conversion? A. PP; tyrosine cannot be converted into glucose B. Pp; phenylalanine…
Which observation would support calling two structures analogous? A. They perform similar roles but their specialised forms arose independently B. They occur only in members of one species C. They have identical DNA sequences at every locus D. They differ in…
A horse and a donkey produce a mule. Which description identifies the process that produced this offspring? A. Isolation of two populations before mating can occur B. Asexual reproduction from one parent C. Interbreeding between members of different species D.…
Which climatic description is most consistent with tundra? A. Low annual precipitation, long cold winters and a short growing season B. High rainfall and high temperatures throughout the year C. High rainfall and frost-free conditions throughout the year D.…
Photosynthetic symbionts live within a reef-building coral. Which transfer provides a benefit to the symbionts? A. Carbon dioxide released by coral respiration supplies carbon for photosynthesis B. Coral cells provide sunlight by respiration C. The symbionts…
In an iron-limited marine region, adding iron briefly stimulates phytoplankton growth. What is a plausible immediate consequence? A. Reduced primary production because the limiting nutrient was added B. Increased photosynthetic uptake of carbon dioxide from…
Which statement correctly distinguishes two sources of heritable variation? A. Mutation can generate new alleles, whereas sexual reproduction reshuffles alleles into new combinations B. Fertilisation prevents offspring from differing genetically C. Meiosis…
Which land-use change would tend to reduce an area’s capacity to remove and store atmospheric carbon? A. Allowing native woodland to regenerate B. Restoring a drained peat-forming wetland C. Clearing a mature forest and keeping the ground sparsely vegetated D.…
Strong warming of surface seawater can increase its density contrast with deeper water. Which consequence can follow? A. Reduced delivery of nutrients from depth into the sunlit layer B. A necessary increase in oxygen production by all marine ecosystems C.…
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