1. What is the net reaction for stage I of glycolysis if the pathway begins with

Question

1. What is the net reaction for stage I of glycolysis if the pathway begins with 2 moles of glucose?
A.   2 Glucose + 2 ATP 2 Glyceraldehyde-3-phosphate + 2 ADP

B.   2 Glucose + 4 ATP 2 Glyceraldehyde-3-phosphate + 2 Dihydroxyacetone phosphate + 4 ADP

C.   2 Glucose + 4 ATP 4 Glyceraldehyde-3-phosphate + 4 ADP

D.   2 Glucose + 2 ATP 2 Glyceraldehyde-3-phosphate + 2 Dihydroxyacetone phosphate + 2 ADP

2. If 2 moles of glucose were converted into 4 moles of pyruvate through the glycolytic pathway, there would be a net yield of ___ ATP.

Explanation / Answer

When one molecule of glucose enters the glycolytic pathway, then it gives rise to 2 products after stage 1 namely Glyceraldehyde-3-phosphate and Dihydroxyacetone phosphate.

Both are interconvertible.

Now, Glucose consumes 1 ATP molecule to convert into Glucose-6-phosphate.

this Glucoe-6-phoaphate is converted into Fructose-6-phosphate under the influence of isomerase enzyme

again Fructose-6phosphate is converted to Fructose-1,6- diphosphate by utilising 1 molecule of ATP

Fructose-1,6-diphosphate is the converted to Glyceraldehyde-3- phosphate and Dihydroxyacetone phosphate by enzyme aldolase.

both the products are interconvertible, but onle glyceraldehyde-3-phosphate proceeds in the further reaction of glycolysis

This Glyceraldehyde-3-phosphate gets converted to 1,3- Diphosphogycerate by Glyceraldehydephosphate dehydrogenase and releases one molecule of NADH2

1,3- Diphosphoglycerate gets converted into 3 phosphoglycerate and releases 1 molecule of ATP

3- Phosphoglycerate is converted to 2-Phosphoglycerate by Phosphoglyceromutase enzyme

2-Phosphoglycerate is converted to Phosphoenol Pyruvate

Phosphoenol Pyruvate again gets converted to Pyruvate, releasing one molecule of ATP by pyruvate kinase enzyme.

So we have net consumption of 2ATP in the process and 4ATP are released because we get 2molecules of Glyceraldehyde-3-phosphate.

Question 1. After stage one of glycolysis using 2 moles of glucose

It will utilise 4ATP molecules and release 2 molecules of Glyceraldehyde-3-phosphate and 2 molecules of Dihydroxyacetone phosphate and 4 molecules of ADP.

So, option 2 is correct.

Question 2. If 4 moles of Pyruvate are produced,

4 ATP is utilised and 8 ATP will be produced.

Then, Net yield will be 8-4 ATP

= 4ATP

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