Enzymes and Metabolism · Paper 1 — Free Biology HL Practice Questions

A student investigates the effect of a new drug on the enzyme lactase by measuring the rate of lactose digestion at various substrate concentrations, with and without the drug. The drug reduces $V_{max}$ without changing $K_m$. Which type of inhibition does this most likely represent, and where does the inhibitor bind?

In human cells, hexokinase catalyses the phosphorylation of glucose to glucose-6-phosphate. Glucose-6-phosphate binds to hexokinase at a site other than the active site, causing a conformational change that reduces enzyme activity. Which type of enzyme regulation does this represent?

In an experiment on lactate dehydrogenase (LDH) from human muscle tissue, initial reaction velocity is measured at varying pyruvate concentrations with and without a fixed concentration of an inhibitor. In the presence of the inhibitor, $V_{max}$ remains unchanged while $K_m$ increases from $0.5 \ \text{mmol dm}^{-3}$ to $2.0 \ \text{mmol dm}^{-3}$. Which type of inhibition is occurring?