5. Pentose Phosphate Pathway a) Two enzymes act between the oxidative and non-ox

Question

5. Pentose Phosphate Pathway

a) Two enzymes act between the oxidative and non-oxidative phases of the pentose phosphate pathway (PPP) to interconvert five carbon sugars.   Phosphopentose isomerase interconverts ribulose 5-phosphate and ribose 5-phosphate. Phosphopentose epimerase interconverts ribulose 5-phosphate and xylulose 5-phosphate.

In a cell lacking phosphopentose epimerase activity what changes are expected in the levels of fructose 6-phosphate and glyceraldehyde 3-phosphate produced by PPP?

b) The pentose phosphate pathway (PPP) is balanced with glycolysis and gluconeogenesis to meet the immediate needs of a cell. Of the four regulatory modes discussed in class, which would be least affected in cells in which the non-oxidative phase was disrupted by a mutation?

c) Cells with decreased glucose 6-phosphate dehydrogenase activity are more sensitive to oxidative stress because?  

Explanation / Answer

the answer to the above question s are as follows-

a- In a cell lacking phosphopentose epimerase activity,the changes in the levels of fructose-6-phosphate and glyceraldehyde 3-phosphate produced by PPP will be:- decreased levels of both F 6-P and G 3-P

b-If non oxidative phase was disturbed by a mutation, of the four regulatory modes, mode 2 (need both ribose 5-phosphate and NADPH) would be least affected.

c-Cells with decreased glucose 6-phosphate dehydrogenase activity are more sensitive to oxidative stress because they contain elevated levels of oxidized glutathione(GSSG)

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