Cell Respiration · Paper 2 — Free Biology HL Practice Questions

The below shows a simplified overview of aerobic respiration in a eukaryotic cell. Use the following ATP yields for parts (b) and (c): glycolysis $= 2\,\text{ATP}$; link reaction $= 0\,\text{ATP}$; Krebs cycle $= 2\,\text{ATP}$; oxidative phosphorylation $= 28\,\text{ATP}$.

A researcher investigates aerobic cell respiration using isolated rat liver mitochondria. The mitochondria are supplied with pyruvate, ADP, and inorganic phosphate ($\text{P}_\text{i}$). Oxygen consumption is measured over 10 minutes; $0.5\,\mu\text{mol}$ of $\text{O}_2$ is consumed. Assume: complete oxidation of one pyruvate via the link reaction and Krebs cycle yields $4\,\text{NADH}$, $1\,\text{FADH}_2$, and $1\,\text{ATP}$ (substrate-level phosphorylation). Each NADH yields $2.5\,\text{ATP}$; each FADH₂ yields $1.5\,\text{ATP}$. Each $\text{O}_2$ molecule accepts $4$ electrons; each NADH or FADH₂ donates $2$ electrons to the electron transport chain.