Tag: biology

The process by which the energy of glucose is released under aerobic respiration, was discovered by Hans Krebs. The Krebs cycle is a part of cellular respiration. It is a series of chemical reactions used by all aerobic organisms to generate energy.

Aerobic respiratory pathway is appropriately called amphibolic pathway. It contains both catabolic and anabolic reactions. The pathway is catabolic because in this pathway, glucose is broken down into carbon dioxide and water. It is also anabolic pathway as energy rich ATP molecule is produced during this pathway. These ATP molecules are later used to carry out various reaction. 

The Krebs cycle is a major metabolic pathway that releases energy in the form of NADH, FADH2, and ATP/GTP. While it is a central hub, it is primarily responsible for the oxidation of acetyl-CoA.

The citric acid cycle starts with the condensation of acetyl group with oxalo acetic acid and water to yield citric acid. The reaction is catalysed by the enzyme citrate synthase and a molecule of CoA is released.

So the correct option is 'citric acid'.

The enzymes for the Krebs cycle are located within the mitochondrial matrix in eukaryotic cells.

In the Krebs cycle, each acetyl CoA oxidation yields 3 NADH, 1 FADH2, and 1 GTP (equivalent to 1 ATP), which collectively generate 12 ATP molecules through oxidative phosphorylation in older traditional calculations often referenced in textbooks. Thus, the formation of 12 ATP from each acetyl CoA is the standard representation for this pathway.

Glycolysis has 1 oxidation step (G3P to 1,3-BPG), the link reaction has 1 (pyruvate to acetyl-CoA), and the Krebs cycle has 4 (isocitrate to alpha-ketoglutarate, alpha-ketoglutarate to succinyl-CoA, succinate to fumarate, and malate to oxaloacetate).

The same respiratory process which acts as a catabolic pathway for respiratory substrates also acts as an anabolic pathway for the synthesis of various intermediary metabolic products and secondary metabolites. The respiratory pathway, therefore, acts both as catabolic as well as an anabolic pathway. Thus, it is better to call it the amphibolic pathway rather than a catabolic pathway alone.

Fatty acid synthesis takes place in the cytoplasm of the cell. It is the creation of fatty acids from acetyl-CoA and NADPH through the action of enzymes called fatty acid synthases. Most of the acetyl-CoA which is converted into fatty acids is derived from carbohydrates via the glycolytic pathway. 

The Kreb’s Cycle gives 3 moles of NADH, 1 mole of FADH and 1 mole of ATP per cycle of substrate i.e per 1 mole of Acetyl CoA. However net ATP i.e after ETS which would make the answer to 12 ATP(9+2+1) respectively.