📋 MDCAT Past Paper Biology Recap

1-B   2-B   3-B   4-B  |  5 = Prophase I   6 = lowers   7 = how water is pulled up through the xylem via transpiration from the leaves   8 = homeostasis is the body's regulatory maintenance of a stable internal environment despite external changes   9 = because hydrolysing its terminal phosphate bond releases usable energy that powers cellular reactions  |  10 = In competitive enzyme inhibition, an inhibitor occupies the active site but can be displaced by adding enough substrate, since substrate and inhibitor compete for the same binding location; similarly, in the Bohr effect, rising CO2 (via lowered pH) changes haemoglobin's shape so it binds oxygen more weakly, but this is also reversible — as CO2 falls again (e.g. in the lungs), haemoglobin's oxygen affinity increases again — in both cases, a reversible change in one molecule's concentration shifts a binding equilibrium at a separate site rather than permanently altering the protein.