All MCQs

Mitosis preserves chromosome number and supports growth and tissue repair.

Cell membranes are phospholipid bilayers with proteins that regulate transport and signalling.

Several evolutionary forces alter allele frequencies; drift is especially influential in small populations.

Matter cycles, but usable energy flows through ecosystems and declines at successive trophic levels.

Adaptive immunity forms antigen-specific memory cells, the basis of vaccination.

Negative-feedback systems detect deviations and activate responses that restore a regulated range.

Natural selection changes population trait frequencies when heritable variation affects reproductive success.

Aerobic respiration uses glycolysis, the citric acid cycle and oxidative phosphorylation to make ATP.

Light reactions provide ATP and NADPH, while the Calvin cycle fixes carbon into organic molecules.

Enzymes catalyse reactions by lowering activation energy; conditions influence their structure and rate.

DNA replication is semiconservative and uses complementary base pairing.

Meiosis forms haploid cells and generates variation through chromosome segregation and recombination.