Lecture 17

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Which of the following is NOT a key intermediate in the Pentose Phosphate Pathway?

6-Phosphogluconate

Fructose-1,6-bisphosphate (correct)

Glucose-6-phosphate

Ribulose-5-phosphate

What is the role of the enzyme glucose-6-phosphate dehydrogenase (G6PD) in the Pentose Phosphate Pathway?

It catalyzes the conversion of 6-phosphogluconate to ribulose-5-phosphate

It catalyzes the conversion of glucose-6-phosphate to 6-phosphogluconate (correct)

It catalyzes the conversion of ribulose-5-phosphate to ribose-5-phosphate

It catalyzes the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate

Which of the following is a key function of the NADPH produced in the Pentose Phosphate Pathway?

Energy production through the electron transport chain

Conversion of pyruvate to acetyl-CoA

Oxidation of glucose to carbon dioxide and water

Reductive biosynthesis of fatty acids and cholesterol (correct)

How does the Pentose Phosphate Pathway connect to the glycolytic pathway?

The PPP generates fructose-6-phosphate for entry into glycolysis Signup and view all the answers

What is the fate of pentose sugars in tissues such as bone marrow and rapidly dividing cells that require ribose-5-phosphate?

They are converted to CO2, NADPH, and ribose 5-phosphate. Signup and view all the answers

In which tissues does the pentose phosphate pathway end with the production of ribose 5-phosphate, NADPH, and CO2?

Bone marrow Signup and view all the answers

Which of the following is a function of NADPH in the pentose phosphate pathway?

Fatty acid synthesis in adipose tissue Signup and view all the answers

What is the role of ribose 5-phosphate in the pentose phosphate pathway?

Used for nucleotide and coenzyme synthesis Signup and view all the answers

Which phase of the pentose phosphate pathway recycles pentose phosphates into glucose phosphate?

Non-oxidative phase Signup and view all the answers

What is the initial conversion in the non-oxidative phase of the pentose phosphate pathway from ribulose 5-phosphate?

Epimerization into xylulose 5-phosphate Signup and view all the answers

What is the main function of Transketolase in the pentose phosphate pathway?

Transfer a two-carbon fragment from a ketose donor to an aldose acceptor Signup and view all the answers

Which enzyme is responsible for the conversion of sedoheptulose 7-phosphate to fructose 6-phosphate in the pentose phosphate pathway?

Transaldolase Signup and view all the answers

What are the products of the reaction catalyzed by Transketolase in the nonoxidative phase of the pentose phosphate pathway?

Glyceraldehyde 3-phosphate and sedoheptulose 7-phosphate Signup and view all the answers

Which process leads to the conversion of two pentose phosphates to a triose phosphate and a seven-carbon sugar phosphate?

Pentose phosphate pathway Signup and view all the answers

What is the role of Transaldolase in the nonoxidative phase of the pentose phosphate pathway?

Condense sedoheptulose 7-phosphate with glyceraldehyde 3-phosphate Signup and view all the answers

In the pentose phosphate pathway, which enzyme is required a second time for a reaction?

Transketolase Signup and view all the answers

What is the net effect of two iterations of the transaldolase reaction and previous reactions mentioned in the text?

5 Glucose-6-P + Pi Signup and view all the answers

What is the role of NADPH in regulating partitioning between glycolysis and the pentose phosphate pathway?

Inhibitor of the pentose phosphate pathway Signup and view all the answers

Which molecule does donor xylulose 5-phosphate contribute a two-carbon fragment to, during the transaldolase reaction?

Erythrose 4-phosphate Signup and view all the answers

When is glucose directed towards glycolysis according to the text?

When NADPH level is high Signup and view all the answers

What happens when NADPH is forming faster than it is being used for biosynthesis and glutathione reduction?

[NADP+] rises Signup and view all the answers

What determines which pathway glucose enters according to the text?

[NADPH] concentration Signup and view all the answers

Which of the following statements about the role of NADPH in protecting cells against highly reactive oxygen derivatives is correct?

NADPH is an electron donor used in the reductive biosynthesis of fatty acids and steroids, as well as in the repair of oxidative damage. Signup and view all the answers

Which of the following statements about the role of glutathione (GSH) in protecting cells against highly reactive oxygen derivatives is correct?

GSH is a tripeptide that protects cells by scavenging hydrogen peroxide and hydroxyl free radicals, and its regeneration from the oxidized form (GSSG) requires NADPH. Signup and view all the answers

What is the potential consequence of glucose-6-phosphate dehydrogenase (G6PD) deficiency in cases of high oxidative stress?

It can be fatal due to the inability to regenerate GSH from its oxidized form (GSSG), leading to a lack of protection against reactive oxygen species. Signup and view all the answers

Which of the following statements about the products of the oxidative phase of the pentose phosphate pathway is correct?

The main products are NADPH and ribose-5-phosphate, where NADPH is used in reductive biosynthesis and repair of oxidative damage, while ribose-5-phosphate is a precursor for nucleotides and coenzymes. Signup and view all the answers

What is the role of the enzymes transketolase and transaldolase in the pentose phosphate pathway?

They are involved in the non-oxidative phase of the pathway, recycling six molecules of the pentose phosphate into five molecules of the hexose phosphate. Signup and view all the answers

Which of the following statements about the relationship between the pentose phosphate pathway, glycolysis, and gluconeogenesis is correct?

The pentose phosphate pathway is a branched pathway that diverges from glycolysis, allowing cells to generate NADPH and ribose-5-phosphate. Signup and view all the answers