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A mutation disrupts the elastic function of titin. Which muscle problem is most directly expected? A. Actin can no longer contain amino acids B. All tendons disappear C. The muscle loses every mitochondrion D. Sarcomeres become more vulnerable to excessive…
Which phloem feature assists transfer between a companion cell and its associated sieve-tube element? A. A thick impermeable wax layer between them B. Numerous plasmodesmata connecting their cytoplasm C. A mature sieve-tube element packed with nuclei D. Closed…
An erythrocyte has delivered oxygen to a hand. In what order does it subsequently pass the labelled locations before entering the aorta? A. Q→P→S→R B. P→Q→R→S C. S→R→Q→P D. R→S→P→Q
A person withdraws a hand from a sharp object. Which structure acts as the effector in this reflex? A. A pain receptor in the skin B. A relay neuron in the spinal cord C. A sensory neuron axon D. A contracting skeletal muscle
Which event initiates a specific antibody-producing response? A. Activation of a matching B cell by antigen and helper-T-cell signals B. Contraction of a skeletal muscle C. Conversion of fibrinogen into fibrin D. Release of hydrochloric acid in the stomach
The shoot changes shape under one-sided illumination. Which set of processes can explain the response? I. Polar positioning of auxin-export proteins redistributes auxin. II. Auxin stimulates proton secretion into the wall. III. Wall acidification permits…
Which environmental change normally favours increased pineal melatonin secretion? A. A rise in dietary calcium B. An increase in blood glucose C. The transition to darkness D. A loud sound at noon
What is a major role of a helper T lymphocyte during an adaptive immune response? A. Activating other immune cells through signalling B. Secreting the bulk of circulating antibody directly C. Engulfing every extracellular pathogen by phagocytosis D. Producing…
In a withdrawal reflex, where would a sensory neuron synapse with a relay neuron in the spinal cord? A. R B. Q C. S D. P
Which sequence summarizes the main stages leading from germ-line precursors to differentiated gametes? A. Differentiation → meiosis → growth → mitosis B. Mitosis → growth → meiosis → differentiation C. Meiosis → mitosis → differentiation → growth D. Growth →…