Krebs Cycle Biochemistry 2 Past Paper 2024 PDF

‫‪J‬‬ ‫‪154‬‬ ‫‪.‬‬ ‫)‬ ‫‪d‬‬ ‫‪E‬‬ ‫‪3·Chemistry 2‬‬ ‫‪t‬‬ ‫"‬...

‫‪J‬‬ ‫‪154‬‬ ‫‪.‬‬ ‫)‬ ‫‪d‬‬ ‫‪E‬‬ ‫‪3·Chemistry 2‬‬ ‫‪t‬‬ ‫"‬ ‫‪=-‬‬ ‫‪g‬‬ ‫‪n‬‬ ‫الشجاعة ال تعني عدم الخوف‪ ،‬ولكنها تعني الصمود والثبات إلى النهاية‪.‬‬ ‫&‬ ‫‪-‬‬‫‪--‬‬ ‫‪zi‬‬ ‫‪I‬‬ ‫‪-‬‬ ‫‪6‬‬ ‫‪I‬‬ ‫‪W‬‬ ‫‪I‬‬ ‫‪-‬‬ ‫=‬ ‫=‬ ‫‪r‬‬  Krebs cycle Citric acid cycle or TCA Cycle Is the second major step in oxidative phosphorylation. → After glycolysis breaks glucose into smaller 3 carbon molecules →the Krebs cycle transfers the energy from these molecules to electron carriers will be used in the electron transport chain to produce ATP. TCA cycle involves the oxidation of acetyl CoA → CO2 and H2O. - TCA cycle -the central metabolic pathway. - The TCA cycle is the final oxidative pathway for carbohydrates, fats, amino acids. - TCA cycle supplies energy & also provides many intermediates required for the synthesis of amino acids, glucose, heme. - TCA cycle is the most important central pathway connecting almost all the individual metabolic pathways. ‫وليد خالد‬.‫د‬ Page 2  - The Krebs cycle is the second of 4-different processes which must happen to extract the energy from glucose. - The Krebs cycle consists of Eight steps reactions 9-sequential process. KREB’s Cycle Place - Krebs cycle happens only within the mitochondrial matrix. - Pyruvate is formed in the cytosol of the cell → imported into the mitochondria → converted to acetyl CoA and imported into the mitochondrial matrix. The mitochondrial matrix is the innermost part of the mitochondria. ‫وليد خالد‬.‫د‬ Page 3  In carbohydrate metabolism 1 - Glycolysis to produce pyruvate. 2 - Pyruvate is oxidized to acetyl-CoA. 3 - Acety1-CoA enters the citric acid cycle. Function and Regulation 1 - Amphibolic Function TCA cycle has both anabolic and catabolic functions. A - Catabolic role It is the final common pathway for oxidation of carbohydrate, lipids and proteins with energy production. B - Anabolic role Source of the intermediates used in biosynthesis : 1 - Oxaloacetic acid is used in gluconeogenesis. 2 – α -ketoglutarate is used for synthesis of some non essential amino acids. 3- Succinyl CoA is used in heme synthesis. ‫وليد خالد‬.‫د‬ Page 5  Regulation of TCA Cycle Three regulatory enzymes 1 - Citrate synthase. 2 - Isocitrate dehydrogenase. 3 - α-ketoglutarate dehydrogenase. → Citrate synthase is inhibited by ATP, NADH, acyl CoA & succinyl CoA. → Isocitrate dehydrogenase is activated by ADP & inhibited by ATP and NADH. → α -ketoglutarate dehydrogenase is inhibited by succinyl CoA & NADH. Availability of ADP is very important for TCA cycle to proceed ‫وليد خالد‬.‫د‬ Page 6 ‫د‪.‬وليد خالد‬ ‫‪Page 7‬‬