Biochemical process of light independent stage of photosynthesis

In this stage carbon (IV) dioxide from atmosphere is captured and modified by addition of hydrogen to form carbohydrates and other organic compounds (amino acids and lipids). Carbon (IV) dioxide combines with ribulose-1, 5-bisphosphate to form unstable six carbons sugar which eventually breaks down to two (2) molecules of glycerate-3-phospahte, check it here;

Two molecules of glycerate-3-phospate are phosphorylated by ATP to form two (2) molecules of glycerate disphosphate, NADPH catalyzes them, reducing them to two molecules glyceraladehyde-3-phospate. One molecule of glyceraldehyde-3-phosphate is quickly converted to glucose, amino acids, lipids and other carbohydrates while the other molecule is utilized in the synthesis of ribulose-1,5-bisphospahte. This process is as follow;

 

In this process, first stable molecule is glycerate-3-phosphate. Energy carriers (ATP and NADPH) are used to reduce glycerate-3-phosphate  to form  12 molecules glyceraldehyde 3-phosphate, in which two molecules of 12 molecules are removed from the cycle to form glucose while the remaining 10 molecules  for the formation of ribulose-1,5-bisphosphate. 

Note: ADP, Pi (orthophosphate, NADP+, RUBP (Ribulose-1, 5-bisphosphate) are recycled for the next process.

QUESTIONS

(1)   In the process of photosynthesis, how many molecules of glyceraldehyde-3-phosphate are used in the formation of glucose and ribulose-1, 5-bisphosphate?

(2)   State two (2) and one (1) step(s) in glycolytic pathway and pentose phosphate pathway respectively which are somewhat related to the process of photosynthesis. Name enzymes which are involved at those specific steps.

ANSWERS

1.      In question one above, the answers are; two (2) and ten (10) molecules of glyceraldehye-3-phosphate are used to form glucose and ribulose-1, 5-bisphosphate respectively. As stated above.   

2.      In question two, steps are; step number three (3) where fructose-1, 6-bisphosphate is converted to Dihydroxyacteone and glyceraldehyde-3-phosphate. This step is catalyzed by aldolase enzyme. In both process (photosynthesis and glycolytic pathway) there exists glyceraldehye-3-phosphate and that is what bring the relationship. This picture below shows how(glycolytic pathway step three(3) ) occurs;

In step number six of glycolytic pathway, there is relationship between glycolytic pathway and photosynthesis process represent by gycerate-3-phosphate (phosphoglycerate isomer). Where 1, 3-bisphosphate is converted to 3-phosphateglycerate, a reaction catalyzed by phosphoglycerate kinase. See it in this diagram;

In pentose phosphate pathway, the relationship is exhibited by ribulose-1, 5-bisphosphate, which is formed from 6-phosphogluconate, a reaction catalyzed by 6-phosphogluconate dehydrogenase. See it here (in step 3 of Pentose Phosphate Pathway);