Question

1. Describe the function of the following enzymes: glycogen phosphorylase, glycogen synthase, protein kinase a, adenylate kinase, branching enzyme

2. a. Why do cell extracts require NAD⁺ to convert glucose to pyruvate? What intermediates accumulate when NAD⁺ is absent? Explain. b.Why does the rate at which glucose is converted to pyruvate decrease when citrate is added?

3. Define gluconeogenesis. What molecules are good substrates for gluconeogenesis? Biosynthetic and catabolic pathways are rarely identical. Is this true for gluconeogenesis vs. glycolysis? Explain.   

4. a. How does a D-glucose differ from B D-glucose? b.What is the difference between a 1-6 bond between two glucose molecules and a 1-4 bond? c.What is the difference between fructose and glucose? d.How does ribose differ from glucose? e.Carbohydrates (glucose, for example) are frequently phosphorylated upon entering a cell. Why?

5. Determine whether the following statements regarding free energy change are true or false. If false, change them to make the statement true.

Free energy change is a measure of the speed of the reaction.

Free energy change is a measure of the maximum amount of work available from the reaction.

Free energy change is a constant for a reaction under any conditions.

Free energy change is equal to zero at equilibrium.

The hydrolysis of ATP proceeds with a negative G.

Answer 1

1) Glycogen phosporylase:-It catalyse conversion of glycogen into glucose.

Glycogen synthase:-It catalyse conversion of glucose into glycogen.

Protein kinase a:- It regulate glycogen,sugar in the cell.

Adenylate kinase:-It catalyse interconversion of adenine nucleotide i.e. 2 molecules of ADP into ATP and AMP

Branchin enzymes:-It catalyse the transfer of carbohydrate unit from one molecule to another. It is also known as glycosyltransferase.

2)a) NAD⁺ will form energy rich molecule that is NADH and second half of glycolysis require energy rich molecules. There is conversion of glyceraldehyde-3-phosphate into 1-3-biphosphoglycerate in the presence of NAD⁺.In the absence of NAD⁺ glycolysis will stop.

b)There is decrease in the rate of glycolysis on the addition of citrate because citrate inhibit phosphofructokinase that is reqired in the glycolysis during the conversion of fructose-6-phosphate into fructose-1-6-biphosphate.

3) Gluconeogensis:-It is the generation of glucose from non-carbohydrate carbons substrate. Lactate(pyruvate), glycerol, alanine, glutamine,glucogenic amino acids are good substrate for the gluconeogenesis.

Yes it is true that biosythetic and catabolylic pathways are rarely identical in case of gluconeogenesis and glycolysis.Gluconeogegesis is a biosynthetic pathway in which formation of glucose occure from pyruvate and glycolysis is a catabolic pathway in which breakdown of glucose occures into pyruvate.First seven steps in the gluconeogenesis are the reversal of the reaction that are in the glycolysis pathways but other step are different.So mechanism is somewhat similar but not identical.

5) Free energy change is a measure of the speed of the reaction.False because it gives us information weather or not a given reaction will occure.it tells us nothing about the speed of the reaction.

Free energy change is a measure of the maximum amount of work available from the reaction. True

Free energy change is a constant for a reaction under any conditions.

Free energy change is equal to zero at equilibrium. true

The hydrolysis of ATP proceeds with a negative G. true