(ES10.1- for each metabolic pathway we consider, be able to state 1) what goes in, 2) what comes out, 3) the energy yield, and 4) where in the cell it occurs) For each of the pathways listed below, write a numbered list identifying- 1) What is(are) the main substrate(s) for that pathway

A. Glycolysis refers to the catabolic process that comprises the dissociation of the glucose molecule into a ten-step pathway. It is the initial step of cellular respiration.  

1. The main substrate of glycolysis is the one molecule of glucose.  

2. Two molecules of pyruvate are the final product of the process.  

3. In the process, initially, two ATPs are used in the preparatory phase for the steps of phosphorylation. Later in the pay off phase, two NADH and four ATP molecules are produced. Thus, the net yield of ATP is 2 and 2 NADH.  

4. The cytosol is the location where glycolysis takes place.  

B. Pyruvate oxidation: In the existence of oxygen, the product of glycolysis is oxidized and decarboxylated by the enzyme known as pyruvate dehydrogenase complex. The product formed in the process is Acetyl-CoA, which is further used in the citric acid cycle.  

1. The two molecules of pyruvate are the main substrate for pyruvate oxidation.  

2. The final product formed in the process is two molecules of Acetyl-CoA with the discharging of two molecules of carbon dioxide.  

3. In the process, the production of two molecules of NADH takes place because of the oxidative decarboxylation reaction.  

4. The process takes place in the mitochondrial matrix.  

C. Citric acid cycle: It is also known as the tricarboxylic acid cycle as the first product produced in the citric acid, also called Kreb's cycle. It is a part of the cellular respiration procedure. This cycle helps in the generation of the intermediates for different biochemical pathways in the cell and is accountable for the generation of the reduced energy carrier molecules like NADH.  

1. The two molecules of acetyl-CoA are the main substrate for the process and the two moles of oxaloacetate that produce two molecules of the citric acid cycle.  

2. In the cycle, the last product produced is oxaloacetate, which reacts with acetyl-CoA to generate citric acid.  

3. In the process formation of two molecules of FADH2, 6 molecules of NADH, and two molecules of GTP takes place.  

4. The cycle takes place in the mitochondrial matrix.  

D. Fatty acid beta-oxidation: Beta oxidation refers to the oxidation that takes place at the beta carbon of the fatty acid at the time of its degradation. The degradation of fatty acids takes place in the mitochondrial matrix via a four-step pathway, in which oxidation and withdrawal of two molecules of carbon take place from the fatty acid chain in each round of oxidation.  

1. The main substrate is unsaturated and saturated even and odd-numbered fatty acids.  

2. The final product produced in the process is acetyl-CoA and propionyl CoA.  

3. Each round of beta-oxidation produces 1 molecule of FADH2, NADH, and acetyl-CoA.  

4. Mitochondrial matrix is the location where beta-oxidation takes place.  

E. Calvin-Benson Cycle: Also known as the dark reaction. It uses the ATP and NADPH produced in the light reaction for the reduction of the intermediate product 3-phosphoglyceric acid, and regeneration of the initial substrate Ribulose-1,5-bisphosphate while fixing the molecule of CO2 to generate glucose. It is an anabolic process.  

1. Three molecules of carbon dioxide and three molecules of ribulose-1,5-bisphosphate is the main substrate of the process.  

2. The final product is the one molecule of Glyceraldehyde-3-phosphate, which is used for the generation of the glucose molecule, and the other 5 molecules of glyceraldehyde-3-phosphate for the regeneration of ribulose-1,5-bisphosphate.  

3. 6 molecules of NADP and 9 molecules of ADP are generated in the process.  

4. The cycle takes place in the stroma of the chloroplast.  

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