Respiration MCQs for NEET — Botany Questions with Answers

(b) In fermentation, the incomplete oxidation of glucose is achieved under anaerobic conditions by set of reactions, where pyruvic acid is converted to CO₂ and ethanol. The enzyme pyruvic acid, decarboxylase and alcohol dehydrogenase catalyse these reactions. In animal cells also, like muscles during exercise, where oxygen is inadequate for cellular respiration, pyruvic acid is reduced to lactic acid by lactate dehydrogenase. The reducing agent is NADH + H⁺, which is reoxidised to NAD⁺, in both the processes

An amphibolic pathway is a biochemical pathway that serves both anabolic and catabolic processes. An important example of an amphibolic pathway is the Krebs cycle, which involves both the catabolism of carbohydrates and fatty acid and the synthesis of anabolic precursors for amino acid synthesis. eg, $\mathrm{\alpha }$-ketoglutarate and oxaloacetate.

The production of ATP with the help of energy liberated during oxidation of reduced coenzymes and terminal oxidation is called oxidative phosphorylation. Peter Mitchell (1961) put forward a hypothesis known as chemiosmotic hypothesis for ATP synthesis. According to this when electrons flow from dual proton, electron carrier to a non-hydrogen carrier the H⁺ are released and expelled into the intermembrane space and thus, creates a proton gradient with higher concentration of H⁺ in the inter membranous space than the matrix. Due to proton motive force the protons flow back and energy liberated during this back flow of protons activate ATPase present in F₁ head to synthesize ATP. 

(d) Cell organelles and nucleus are absent in mature red blood cells, therefore, aerobic respiration do not take place.

(d) Succinate dehydrogenase enzyme is present on inner membrane of mitochondria and catalysed the oxidation of succinate to fumarate.

(a) Glycolysis, Krebs cycle and electron transport system are meant for ATP synthesis in different steps. ATP is the energy currency of cell.

One mole of ATP liberates 12 kcal of energy. So 686 kcal will liberate 686/12 = 57.1 ATP molecules.

(c): TCA cycle is the cyclic biochemical catabolic pathway for the oxidation of fuel molecule through acetyl CoA which is completely oxidized to carbon dioxide and water. Kreb's cycle operates in the mitochondrial matrix because it contains complex mixture of soluble enzymes that catalyse the respiration of pyruvic acid and other smali molecules. The cycle consists of 9 enzymatic steps, four of which are dehydrogenations

(a) : In Krebs cycle, GTP is formed during the conversion of succinyl CoA to succinic acid or succinate. The enzyme required for this reaction is succinyl thiokinase. The phosphorylation in this reaction is substrate level phosphorylation where ATP synthesis is directly linked to the liberation of energy.

(b) In respiraion, from 180gm of glucose 264 gm CO₂+ 108gm H₂O + 686 Kcal energy is formed.

${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6 + 6{\mathrm{O}}_2 \stackrel{ }{\to }6{\mathrm{CO}}_2 + 6{\mathrm{H}}_2\mathrm{O} \mathrm{Kcal}$

Atomic weight of C =12, H = 1, O=16

$$\begin{gathered} {\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6 = (12 \times 6 + 12 \times 1 + 16 \times 6) \\ = 180 \mathrm{gm} \\ 6{\mathrm{CO}}_2 = 6(12 + 16 \times 2) \\ = 264 \mathrm{gm} \\ 6{\mathrm{H}}_2\mathrm{O} =6(2 \times 1 + 16) \\ = 108 \mathrm{gm} \\ \therefore \mathrm{From} 1 \mathrm{molecule} \mathrm{or} 180 \mathrm{gm} \mathrm{of} \mathrm{glucose}, \mathrm{through} \\ \mathrm{respiration}, 264 \mathrm{gm} {\mathrm{CO}}_2, 108\mathrm{gm} {\mathrm{H}}_2\mathrm{O} \mathrm{and} 686 \mathrm{Kcal} \mathrm{energy} \mathrm{are} \mathrm{formed}. \end{gathered}$$