Question

When a poison such as cyanide blocks the electron transport chain, glycolysis and the citric acid cycle also eventually stop working. Which of the following is the best explanation for this?a) The uptake of oxygen stops because electron transport was inhibited b) They run out of ADP c) A high level of NADH is present in the cell d) Electrons are no longer available from the electron transport chain to power glycolysis and the citric acid cycle e) NAD⁺ and FAD are not available for glycolysis and the citric acid cycle to continue

Answer 1

Cyanide increases the pH in the intermembrane space and inhibits ATP synthesis by blocking the electron transport chain, leading to a build-up of NADH. This prevents the oxidation of NADH to NAD+, halting glycolysis and the citric acid cycle, as they require oxidized NAD+ and FAD to function.

Step-by-step explanation:

When cyanide inhibits cytochrome c oxidase, it effectively halts the electron transport chain (ETC). As a consequence, the pH of the intermembrane space would increase, due to a decrease in the influx of protons (H+) from the mitochondrial matrix to the intermembrane space. This disruption in proton gradient affects ATP synthesis negatively by inhibiting ATP synthase, the enzyme responsible for producing ATP using the proton gradient. Without this gradient, ATP synthesis stalls, leading to a depletion of energy within the cell.

The best explanation for why glycolysis and the citric acid cycle also stop when the electron transport chain is inhibited by cyanide is that there is a high level of NADH in the cell, and NAD+ and FAD are not available in their oxidized forms to accept electrons. These components are essential for the continuation of glycolysis and the citric acid cycle, as they act as electron acceptors during various steps of these metabolic processes. When the ETC is blocked, NADH and FADH2 cannot be oxidized back to NAD+ and FAD, causing these cycles to halt.

Answer 2

NAD⁺ and FAD are not available for glycolysis and the citric acid cycle to continue.

Explanation:

The glycolysis, citric acid cycle and the Electron transport chain all together makes up the aerobic respiration. The glycolysis and Kreb's Cycle produces a lot of reduced hydrogen ion transporters like NADH and FADH which are then transported to the inner Mitochondrial membrane which are then oxidised back to the NAD and FAD forms by accepting their hydrogens by either complex 1 or complex 2. Now the cyanide blocks the electron transport chain which means there's noone to accept those hydrogens. So there will be enormous NADH and FADH in cell, but there will be reduced or nil NAD and FAD. This will lead to disappearance of hydrogen ion acceptors which are essential to carry out Kreb's Cycle and glycolysis. So this will lead to stoppage of them.