Respiration MCQs for NEET — Botany Questions with Answers

During the decarboxylation of pyruvic acid, pyruvate is converted into acetyl CoA. This process involves the removal of a carbon dioxide molecule (decarboxylation) and the subsequent formation of acetyl CoA, which then enters the Krebs cycle for further energy production.

During glycolysis, one glucose molecule is broken down into two molecules of pyruvate. In this process, two molecules of NAD+ are reduced to form two molecules of NADH. Therefore, the number of reduced coenzymes NADH produced during glycolysis is 2.

The net gain of glycolysis includes the production of 2 ATP molecules and 2 NADH molecules per glucose molecule. Although 4 ATPs are produced, 2 ATPs are consumed in the initial steps, resulting in a net gain of 2 ATPs and 2 NADH molecules.

In cellular respiration, oxygen is used in the Electron Transport System (ETS). Oxygen acts as the final electron acceptor at the end of the ETS, where it combines with electrons and protons to form water.

In the Electron Transport System (ETS), each molecule of NADH + H⁺ produces 3 ATP molecules. This is because NADH enters the ETS at the first complex, resulting in the pumping of protons at three points, which ultimately generates 3 ATP molecules per NADH molecule.

Fermentation is the primary mode of energy production in yeast. Yeast cells perform anaerobic respiration (fermentation) to produce energy in the form of ATP along with byproducts like ethanol and carbon dioxide, especially in the absence of oxygen.

The citric acid cycle, also known as the Krebs cycle, was proposed by Hans Krebs in 1937. This series of chemical reactions is a key part of cellular respiration, where acetyl-CoA is oxidized to produce energy in the form of ATP, NADH, and FADH2.

In one turn of the Krebs cycle, 1 molecule of FADH2 is produced. The cycle involves the oxidation of acetyl-CoA and produces multiple energy carriers: 3 NADH, 1 FADH2, and 1 ATP (or GTP).

In the Electron Transport System (ETS), one molecule of FADH2 contributes to the production of approximately 2 ATP molecules. FADH2 enters the ETS at Complex II, bypassing Complex I, leading to the generation of fewer ATP compared to NADH.