Question

2. Contrast the glycolysis and citric acid cycle pathways in terms of a) the overall reactants and products in each pathway, b) number of all energy molecules produced in each pathway, c) the key enzymes that are regulated and molecules which regulate them in each pathway and d) the location of each pathway (2 pts)

Answer 1

• Glycolysis cycle is a linear chain of reactions. All about breakdown of Glucose (the food we have taken is in the form of glucose) into 2 molecules of Pyruvate. This cycle is energy yielding cycle. A total of 4 ATP and 2 NADH are produced at the end of the cycle. And Pyruvate produced goes in the citric acid cycle, it converts into Acetyl coA and that initiates the TCA or citric acid cycle.

The Key enzymes which regulate the rate of glycolytic pathway are Hexokinase, Phosphofructokinase and Pyruvate kinase. The reactions catalyzed by these enzymes are irreversible. Hexokinase starts the cycle by converting Glucose into Glucose-6-phosphate, this is an energy consuming reaction. Phosphofructokinase converts Fructose-6-phosphate into Fructose-1,6-bisphosphate, again it's an energy consuming reaction. Pyruvate kinase ends the cycle by converting Phosphoenol pyruvate into Pyruvate. In this reaction 2 molecules of ATPs are produced.

• Kreb's cycle is cyclic and starts with the Acetyl coA and oxaloacetate. The product of 1 acetyl coA in the cycle gives 2 molecules of CO2, 3 NADH, 1 FADH2 and 1 ATP.  

	Glycolysis cycle	Citric acid cycle
Reactant and product	Glucose molecule breaks down to make 2 molecule of pyruvate.	2 molecules of Acetyl coA with oxaloacetate initiates the cycle and gives 4 molecules of Co2
Energy produced	Glucose -------> 4 molecules of ATP + NADH	2 ACetyl coA ------> 6NADH + 2FADH2 + 2ATP NADH and FADH2 goes to Electron transport chain and yields 3 and 2 ATPs respectively.
Location	In the cytosol	In mitochondrial matrix