Question

Explain the reactions of Kreb’s cycle.

Answer 1

A part of cellular respiration is the Krebs cycle, named after Hans Krebs. The other names are the cycle of citric acid and the cycle of the tricarboxylic acid (TCA cycle). The "Krebs cycle" is a sequence of chemical reactions that all aerobic species use in their cycles of energy conversion.

Complete answer:
In order to join the citric acid cycle, pyruvate is converted into acetyl CoA after glycolysis. Three NADH molecules and one ${FADH_2}$ molecule form at each turn of the cycle. To generate ATP molecules, these carriers can interact with the last portion of aerobic respiration. In each loop, one GTP or ATP is also made. In the synthesis of non-essential amino acids, some of the intermediate compounds in the citric acid cycle can be used; thus, the cycle is amphibolic (both catabolic and anabolic).
Steps in the Citric Acid Cycle:
Step 1: In the first step there is a combination of two-carbon acetyl groups (from acetyl CoA) with a four-carbon molecule of oxaloacetate to form a six-carbon citric acid molecule in a condensation step.
The 2nd step. Citrate loses one molecule of water and absorbs another when citrate is converted into isocitrate, its isomer.
The 3rd and 4th steps. Isocitrate is oxidized in step three, forming a five-carbon molecule, alpha-ketoglutarate, along with the production of carbon dioxide molecules and two electrons that reduce NAD+ to NADH. Oxidation and decarboxylation stages, which release electrons that reduce NAD+ to NADH and release carboxyl groups that form carbon dioxide molecules, are both steps three and four. The product of step three is alpha-ketoglutarate, and the product of step four is a succinyl group. CoA binds with the succinyl group formed in the fourth step of the cycle to form succinyl CoA. The enzyme that catalyzes step four is regulated by inhibition of feedback from ATP, succinyl CoA, and NADH.
step 5. Coenzyme A is substituted by a phosphate group, and a high-energy bond is formed. This energy is used to form either guanosine triphosphate (GTP) or ATP in substrate-level phosphorylation (during the conversion of the succinyl group to succinate).
Step 6. A dehydration process that transforms succinate and fumarate is step six. Two atoms of hydrogen are moved to FAD, forming ${FADH_2}$. The energy stored in these atoms’ electrons is inadequate to decrease NAD+ but adequate to decrease FAD. This carrier stays attached to the enzyme, unlike NADH, and passes the electrons directly to the electron transport chain.
Step 7. During phase seven, water is added to the fumarate, and malate is made. The last step in the cycle of citric acid, by oxidizing malate, regenerates oxaloacetate. There is another NADH molecule made.

Note: In most plants, animals, fungi, and many bacteria, this metabolic process happens. The TCA cycle is carried out in the matrix of intracellular structures called mitochondria in all organisms, except bacteria. In Bacteria citric acid cycle occurs in the cytoplasm.