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Melatonin participates in daily sleep–wake regulation. (i) State the organ that produces melatonin. (ii) A traveller crosses several time zones. Deduce, with a reason, the local time of day when restoring a rise in melatonin would support the usual sleep–wake…
Explain how an impulse in one neuron can cause a response in another neuron at a chemical synapse.
An enzyme is assayed at constant pH and substrate concentration. Explain why activity is lower on either side of the optimum temperature.
Which interaction is a hydrogen bond between two water molecules? A. The covalent O–H link within a single molecule B. An attraction from a partially positive hydrogen to an oxygen on a neighbouring molecule C. A covalent bond directly linking their two oxygen…
Plant energy capture and animal cell functions support life. (a) Outline reasons for using stem cells therapeutically. (b) Describe how leaf cells use light energy. (c) Explain how cells and cell components in blood protect against infectious disease.
A root contains several specialized cell types that originated by division of the same zygote. What generally explains their different functions? A. Each type has retained only one gene B. Different patterns of gene expression produce different proteins C.…
Haemophilia can result from inadequate activity of a blood-clotting protein. (a) Outline how translation produces a polypeptide in a cell. (b) A woman carrying the usual X-linked recessive haemophilia allele has children with a man without that allele.…
Two free amino acids join to make one dipeptide, releasing a water molecule. How is this reaction classified? A. Hydrolysis of a peptide bond B. Reduction of a nucleotide C. Condensation forming a peptide bond D. Replication of a polypeptide
Inheritance and cell division contribute to biological variation. (a) Draw and label one RNA nucleotide. (b) Distinguish mitosis from meiosis. (c) Explain how natural selection can produce antibiotic resistance in a bacterial population.
Which property of glucose permits it to be carried dissolved in blood plasma? A. It is completely non-polar B. Its molecules are too large to interact with water C. Its polar groups interact with water molecules D. It is a lipid with no oxygen atoms