Biochemistry: Pentose Phosphate Pathway

Questions and Answers

What is the primary function of NADPH in the pentose phosphate pathway?

To provide reducing power for anabolic reactions (correct)

To transport electrons to the electron transport chain

To convert NADH back to NAD+

To fuel catabolic processes

Which compound is specifically synthesized for nucleotide biosynthesis in the pentose phosphate pathway?

Erythrose-4-phosphate

Ribose-5-phosphate (correct)

NADH

NADPH

How does the cell differentiate between anabolic and catabolic pathways?

By converting NADP into NADH

By using ATP for both processes

By utilizing the same pool of nucleotides for both types of metabolism

By relying on different cofactors: NADPH for anabolism and NADH for catabolism (correct)

What type of receptors does nicotine bind to?

Acetylcholine receptors Signup and view all the answers

In which process is most of the NADH produced during glycolysis converted back to NAD+?

At the electron transport chain Signup and view all the answers

What is produced during the reactions involving NAD+?

Electrons and protons Signup and view all the answers

What role do chemical bonds play in the context of electron transport in cells?

They carry energy stored in shared electrons between atoms. Signup and view all the answers

Which of the following accurately describes NADP?

It serves as an oxidant in specific pathways. Signup and view all the answers

Which tissue primarily uses NADPH for fatty acid and steroid biosynthesis?

Liver Signup and view all the answers

What is the primary role of NADPH in erythrocytes?

Reduction of glutathione Signup and view all the answers

In which cells is the highest level of glucose 6-phosphate dehydrogenase found?

Neutrophils Signup and view all the answers

How does the pentose phosphate pathway contribute to the immune response?

By producing superoxide radicals Signup and view all the answers

What metabolic characteristic is associated with cancer cells during low oxygen respiration?

High flux through the pentose phosphate pathway Signup and view all the answers

Which process requires NADPH as the electron source for converting ribonucleotides to deoxyribonucleotides?

Ribonucleotide reduction Signup and view all the answers

Which type of cells primarily use the pentose phosphate pathway to mitigate oxidative stress?

Red blood cells Signup and view all the answers

What is the main product of the pentose phosphate pathway that is important for biosynthetic reactions?

NADPH Signup and view all the answers

What does NADH function as in cellular respiration?

A universal energy carrier Signup and view all the answers

At which wavelength can the absorbance of NADH be monitored?

340 nm Signup and view all the answers

Which pathway is primarily associated with nucleotide biosynthesis?

Pentose phosphate pathway Signup and view all the answers

Which enzyme converts glucose-6-phosphate to 6-phosphogluconolactone?

Gluconolactonase Signup and view all the answers

What type of reactions do the enzymes transketolase and transaldolase primarily catalyze?

Reversible transfers of carbon units Signup and view all the answers

Which of the following is NOT a compound involved in the oxidative phase of the pentose phosphate pathway?

Fructose-6-phosphate Signup and view all the answers

Which product is generated from ribulose-5-phosphate in the non-oxidative phase of the pentose phosphate pathway?

Erythrose-4-phosphate Signup and view all the answers

In the context of catabolic pathways, which process does NOT include NAD+/NADH?

Calvin cycle Signup and view all the answers

Study Notes

Pentose Phosphate Pathway Overview

Anabolic pathway generating NADPH for biosynthesis, including aromatic amino acids and nucleotides.
Produces erythrose-4-phosphate for aromatic amino acid synthesis and ribose-5-phosphate for nucleotide synthesis.

Role of NADPH

NADPH serves as a reducing agent in anabolic reactions, distinguishing it from NADH used in catabolic pathways.
The separation of NADH and NADPH pools prevents competition for nucleotide resources.

Cofactors in Cellular Metabolism

NAD+, NADH, NADP, and NADPH are key cofactors that transfer energy via electrons.
NADH is primarily recycled back to NAD+ in the electron transport chain to generate ATP.
NADP is specifically utilized in pathways requiring NADPH for anabolic reactions.

Nicotine and Acetylcholine Receptors

Nicotine is addictive and interacts with acetylcholine receptors.
Dehydrogenase enzymes involving NAD+ remove electrons and protons, generating NADH, which carries energy throughout the cell.

Phases of the Pentose Phosphate Pathway

Oxidative Phase

Initiated with glucose-6-phosphate and includes key enzymes like gluconolactonase and 6-phosphogluconate dehydrogenase.
Products include ribulose-5-phosphate, essential for nucleotide synthesis.

Non-Oxidative Phase

Involves isomerization and interconversion of sugar phosphates by enzymes like transketolase and transaldolase.
Generates ribose-5-phosphate, erythrose-4-phosphate, and glyceraldehyde-3-phosphate for various biosynthetic needs.

Tissues and Cells Utilizing the Pentose Phosphate Pathway

High PPP enzyme expression in liver, adipose tissue, adrenal cortex, testis, and lactating mammary glands for fatty acid and steroid synthesis.
Erythrocytes produce NADPH for glutathione reduction, protecting proteins from oxidative damage.
Rapidly proliferating cells require NADPH for converting ribonucleotides to deoxyribonucleotides via ribonucleotide reductase.
Neutrophils and macrophages possess high glucose-6-phosphate dehydrogenase activity; utilize NADPH to create superoxide radicals for microbial defense.

Cancer and the Warburg Effect

Cancer cells demonstrate the Warburg effect, favoring low oxygen respiration and increased flux through the pentose phosphate pathway, leading to fermentation products.

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Description

Explore the Pentose Phosphate Pathway's role in generating NADPH for anabolic reactions, including nucleotide and aromatic amino acid synthesis. This quiz also covers the functions of NADPH, key cofactors in metabolism, and the interaction of nicotine with acetylcholine receptors.