Cellular Respiration by Berta Chaya https://padlet.com/rchaya84/edrrb5pk64jf Reflection: Importance of Glycolysis, Link Reaction & Krebs Cycle en-us 2016-06-15 05:45:03 UTC 2025-10-24 20:53:02 UTC hello@padlet.com l adrianazhar_aa https://padlet.com/rchaya84/edrrb5pk64jf/wish/114886880 2016-06-17 05:02:55 UTC https://padlet.com/rchaya84/edrrb5pk64jf/wish/114886880 Glycolysis https://padlet.com/rchaya84/edrrb5pk64jf/wish/115658797 This is the first stage of cellular respiration in which it involves the aerobic catabolism of glucose. This process occurs outside of the mitchondrial matrix, that is, in the cytosol . Glucose is firstly phosphorylated into glucose 6-phosphate (G6P) with the breakdown of an ATP molecule into ADP. Then G6P undergoes isomerization and forms fructose 6-phosphate with help of isomerase. Fructose 6-phosphate further undergoes phosphorylation and forms fructose 1,6-diphosphate with another consumption of a molecule of ATP. Then, cleavage of fructose 1,6-diphosphate happened where it splits into glyceraldehyde 3-phosphate (G3P) and dihydroxyacetone phosphate. Next, G3P is oxidized by hydrogen removal and transferred to NAD+ to form NADH. An inorganic phosphate attache to G3P carbon skeleton and forming 1,3-biphosphoglycerate. Then, 1,3-biphosphoglycerate is hydrolyzed to form  3PG and ATP is formed through substrate level phosphorylation. 3PG is then isomerized into 2PG, which eventually converted to phosphoenolpyvurate (PEP). Lastly,  PEP will be converted to pyruvate , ADP is phosphorylated to form an ATP molecule through substrate level phosphorylation.

]]> 2016-06-29 09:13:40 UTC https://padlet.com/rchaya84/edrrb5pk64jf/wish/115658797 Link Reaction https://padlet.com/rchaya84/edrrb5pk64jf/wish/115817687 This is the second stage of cellular respiration that involves oxidative decarboxylation of pyruvate. It is an aerobic process as it involves the presence of oxygen. This process occurs in the mitochondrial matrix. Pyruvate (3C), which is the product of glycolysis, is converted into a 2-carbon molecule, acetyl-CoA (acetyl coenzyme A) with the help of enzyme pyruvate dehydrogenase. Coenzyme A is to help acetyl group (2C) molecule to enter Stage 3 : Krebs Cycle before detaching it to be used again. During this process, two hydrogen atoms are lost and are transferred to NAD+ to form NADH. Simultaneously, pyruvate losses one carbon atom to produce carbon dioxide. Link reaction repeats twice for each molecule of glucose oxidised (2 pyruvate from glycolysis). Hence, the total production from this process is 2 NADH, 2 acetyl CoA and 2 carbon dioxide molecules.]]> 2016-07-01 14:43:14 UTC https://padlet.com/rchaya84/edrrb5pk64jf/wish/115817687 Krebs Cycle https://padlet.com/rchaya84/edrrb5pk64jf/wish/116095378 This is the third stage in the cellular respiration which is also known as citric acid cycle or tricarboxylic acid cycle. This stage is an aerobic process as it occurs in the mitochondrial matrix and only in the presence of oxygen. This stage involves in the formation of NADH and FADH2. It also functions to carry high energy electron and hydrogen ions to Stage 4 : Electron Transport Chain. In this process, the acetyl-CoA which is produced in the link reaction combines with the oxalocetate in a process called condensation. This reaction produces citrate which contains six carbons. The citrate undergoes isomerization to become isocitrate. Then, the the isocitrate goes through a process called oxidative decarboxylation to form α-ketoglutarate. In this process, NAD+ is reduced to NADH and one molecule of carbon dioxide is released. One molecule of carbon is also removed in this process. α-ketoglutarate undergoes the same process to produce succinyl CoA (4C). NAD+ is reduced to NADH and one molecule of carbon dioxide is released. One molecule of carbon is also removed. Next, the succinyl CoA undergoes substrate level phosphorylation to produce succinate. Unstable bond between succinyl CoA breaks and form succinate (4C). CoA that detached from succinyl group is replaced by phosphate group (Pi), then transfer the phosphate group to GDP to form GTP. GTP then transfer its phosphate group to ADP to yield ATP. Succinate then changes to fumarate through a process called oxidation. This process is the only process that produces FADH2 by reducing FAD+, another coenzymes in the cellular respiration process. The next process is hydration where fumarate is hydrolyzed  to malate. Finally, malate undergoes oxidation to form oxalocetate again. In this process, NAD+ is reduced to NADH.

The cycle is repeated and completed twice for each molecule of glucose oxidised. Overall, 6NADH, 2FADH2, 2GTP and 4 carbon dioxide are produced in Krebs Cycle.


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