Cellular Respiration and Enzymes

Cytochrome c reductase (Complex III) is located on the outer membrane of mitochondria in the electron transport chain. Adenylate kinase and ATP synthetase are primarily associated with the inner membrane, while nucleoside diphosphokinase is mainly cytosolic.

Aerobic respiration is the oxidative breakdown of respiratory substrates (like glucose) with the help of oxygen, producing CO2, water, and ATP. Anaerobic respiration occurs without oxygen, fermentation is a type of anaerobic respiration in yeast/bacteria, and respiratory quotient is the ratio of CO2 produced to O2 consumed.

The hexose monophosphate shunt (HMP shunt) is alternatively known as the phosphogluconate pathway or pentose phosphate pathway. It's a metabolic pathway parallel to glycolysis that generates NADPH and pentose sugars.

Malate is oxidised to oxaloacetate using NAD⁺ in the cytosol. In the final reaction of gluconeogenesis, glucose-6-phosphate is hydrolysed by glucose-6-phosphatase to produce glucose. It occurs in the lumen of the endoplasmic reticulum.

According to this theory, the enzyme molecule undergoes configurational or geometric changes in the active site on contact with the substrate.

According to this model, the union between the substrate and the enzyme takes place at the active site more or less in a manner in which a key fits a lock and results in the formation of enzyme-substrate complex.

These enzymes break down large molecules into smaller ones by the introduction of water and breaking of specific covalent bonds. They are hydrolases.

During anaerobic respiration in yeast (fermentation), only 2 ATP molecules are produced per glucose molecule via glycolysis. To produce 38 ATPs, we need 38/2 = 19 glucose molecules. This calculation highlights the inefficiency of anaerobic respiration compared to aerobic respiration, where one glucose yields approximately 38 ATPs. The huge difference explains why organisms prefer aerobic respiration when oxygen is available.

The Krebs cycle involves multiple oxidation steps where acetyl-CoA is oxidized to CO2, with NAD+ and FAD being reduced to NADH and FADH2. The cycle completes when the original oxaloacetate is regenerated through a series of oxidation reactions.

Ubiquinone, also known as Coenzyme Q10 (CoQ10), is a lipid-soluble coenzyme that plays a crucial role in the electron transport chain during cellular respiration. It functions as an electron carrier, shuttling electrons between Complex I/II and Complex III of the mitochondrial respiratory chain. It is not an enzyme, apoenzyme, or primary electron acceptor itself.