BB 491 The Pentose Phosphate Pathway

What are the two different phases present in the Pentose Phosphate Pathway?

• The anabolic pathway

• Oxidative pathway

• The active pathway

• Non-oxidative pathway

• The catabolic pathway

Describe the first step of the oxidative phase of the Pentose Phosphate Pathway:

• Glucose 6-phosphate + Glucose 6-phosphate dehydrogenase + NADP+ ---> 6-phosphogluconoactone + NADPH

• 6-phosphogluconoactone + gluconolactonase + H2O ---> 6-phosphogluconate + H+

• 6-phosphogluconate + 6-phosphogluconate dehydrogenase + NADP+ ---> ribulose-5-phosphate + NADPH + CO2

Describe the second step of the oxidative phase of the Pentose Phosphate Pathway:

• Glucose 6-phosphate + Glucose 6-phosphate dehydrogenase + NADP+ ---> 6-phosphogluconoactone + NADPH

• 6-phosphogluconoactone + gluconolactonase + H2O ---> 6-phosphogluconate + H+

• 6-phosphogluconate + 6-phosphogluconate dehydrogenase + NADP+ ---> ribulose-5-phosphate + NADPH + CO2

Describe the third step of the oxidative phase of the Pentose Phosphate Pathway:

• Glucose 6-phosphate + Glucose 6-phosphate dehydrogenase + NADP+ ---> 6-phosphogluconoactone + NADPH

• 6-phosphogluconoactone + gluconolactonase + H2O ---> 6-phosphogluconate + H+

• 6-phosphogluconate + 6-phosphogluconate dehydrogenase + NADP+ ---> ribulose-5-phosphate + NADPH + CO2

What is the first steps of the non-oxidative phase of the Pentose Phosphate Pathway? (There are two correct answers)

• Glyceraldehyde 3-phosphate + sedoheptulose + transaldolase ---> Fructose 6-phosphate + Erythrose 4-phosphate + xylulose-5-phosphate

• Ribose-5-phosphate + xylulose-5-phosphate + transhetolase ---> Glyceraldehyde + Sedoheptulose 7-phosphate

• Ribulose 5-phosphate + ribulose 5-phosphate isomerase ---> Ribose-5-phosphate

• Erythrose-4-phosphate + xylulose-5-phosphate + transhetolase ---> Glyceraldehyde 3-phosphate + fructose 6-phosphate

• Ribulose 5-phosphate + ribulose 5-phosphate-3-epimerase ---> Xylulose-5-phosphate

What is the second step of the non-oxidative phase of the Pentose Phosphate Pathway?

• Ribulose 5-phosphate + ribulose-5-phosphate-3-epimerase ---> Xylulose-5-phosphate

• Glyceraldehyde 3-phosphate + sedoheptulose + transaldolase ---> Fructose 6-phosphate + Erythrose 4-phosphate + xylulose-5-phosphate

• Ribulose 5-phosphate + ribulose 5-phosphate isomerase ---> Ribose-5-phosphate

• Erythrose-4-phosphate + xylulose-5-phosphate + transhetolase ---> Glyceraldehyde 3-phosphate + fructose 6-phosphate

• Ribose-5-phosphate + xylulose-5-phosphate + transhetolase ---> Glyceraldehyde + Sedoheptulose 7-phosphate

What is the third step of the non-oxidative phase of the Pentose Phosphate Pathway?

• Ribulose 5-phosphate + ribulose-5-phosphate-3-epimerase ---> Xylulose-5-phosphate

• Glyceraldehyde 3-phosphate + sedoheptulose + transaldolase ---> Fructose 6-phosphate + Erythrose 4-phosphate + xylulose-5-phosphate

• Ribulose 5-phosphate + ribulose 5-phosphate isomerase ---> Ribose-5-phosphate

• Erythrose-4-phosphate + xylulose-5-phosphate + transhetolase ---> Glyceraldehyde 3-phosphate + fructose 6-phosphate

• Ribose-5-phosphate + xylulose-5-phosphate + transhetolase ---> Glyceraldehyde + Sedoheptulose 7-phosphate

What is the fourth step of the non-oxidative phase of the Pentose Phosphate Pathway?

• Ribulose 5-phosphate + ribulose-5-phosphate-3-epimerase ---> Xylulose-5-phosphate

• Glyceraldehyde 3-phosphate + sedoheptulose + transaldolase ---> Fructose 6-phosphate + Erythrose 4-phosphate + xylulose-5-phosphate

• Ribulose 5-phosphate + ribulose 5-phosphate isomerase ---> Ribose-5-phosphate

• Erythrose-4-phosphate + xylulose-5-phosphate + transhetolase ---> Glyceraldehyde 3-phosphate + fructose 6-phosphate

• Ribose-5-phosphate + xylulose-5-phosphate + transhetolase ---> Glyceraldehyde + Sedoheptulose 7-phosphate

What is the rate limiting step of the Pentose Phosphate Pathway?

• When riboluse-5-phosphate is converted into ribose-5-phosphate.

• When 6-phosphogluconate is converted into ribulose-5-phosphate.

• When Glucose 6-phosphate is converted into 6-Phosphogluconolactone.

• When 6-phosphogluconalctone is converted into 6-phosphogluconate.

Where does the Pentose Phosphate Pathway get its Glucose 6-phosphate?

• From the fifth step of the urea cycle.

• From the first step of glyolysis.

• From the third step of the CAC.

• From the second step of the Calvin cycle.