NEET Practice Questions (MCQs) with Answers & Solutions

P-219, Para 2

P-220; Photorespiration; Para 2

P-223 Factors Affecting Photosynthesis- Temperature; Para 1

Oxidative phosphorylation is the process of formation of ATP from ADP and inorganic phosphate (P₁) in the presence of oxygen. It occurs mainly in the Electron Transport Chain (ETC) of cellular respiration. 

Acetyl Co-A is common to respiration mediated breakdown of fats, carbohydrates and proteins. Glucose and fructose are phosphorylated to give rise to glucose-6-phosphate by the activity of the enzyme hexokinase.

Glucose-6-phosphate then converts into fructose 6 phosphate and further to fructose 1-6-bisphosphate. Pyruvic acid is the end product of glycolysis. 

(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.