3-L1

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

In which pathway does NAD act as a hydrogen acceptor?

EM pathway (correct)

Glycolysis

Pentose Phosphate Pathway

HMP pathway

What is formed in the EM pathway?

CO2 but not ATP

Neither CO2 nor ATP

ATP but not CO2 (correct)

CO2 and ATP

How many molecules of NADPH are formed per molecule of glucose 6-phosphate?

Three

One

Four

Two (correct)

In which pathway is ATP required but not produced?

HMP pathway Signup and view all the answers

What is the product of the second dehydrogenation reaction in the Pentose Phosphate Pathway?

Ribulose 5-phosphate Signup and view all the answers

What is the product of the oxidative reactions of the pentose phosphate pathway?

NADPH + H+ and CO₂ Signup and view all the answers

What is the function of the stage 2 nonoxidative reactions of the pentose phosphate pathway?

To convert ribulose 5-phosphate to various sugar molecules Signup and view all the answers

What is the reactant of the enzyme phosphogluconate dehydrogenase?

6-phosphogluconate Signup and view all the answers

What percentage of glucose is shunted through the pentose phosphate pathway daily?

10% Signup and view all the answers

What is the primary location of the pentose phosphate pathway?

Cytosol Signup and view all the answers

What is the primary purpose of the pentose phosphate pathway?

Generation of NADPH and pentose phosphates Signup and view all the answers

How many molecules of glucose-6-phosphate enter the pentose phosphate pathway?

3 Signup and view all the answers

What is the byproduct of the pentose phosphate pathway that is used for nucleotide synthesis?

Pentose phosphates Signup and view all the answers

What is the role of NADPH in hemoglobin?

To keep the iron in the reduced state (ferrous) Signup and view all the answers

What is the consequence of diminished G6PD activity in cells?

Decrease in the cellular detoxification of free radicals Signup and view all the answers

What is the primary function of NADPH in the lens of the eye?

To maintain the transparency of the lens Signup and view all the answers

What is the result of the inability to detoxify oxidizing agents in G6PD deficiency?

All of the above Signup and view all the answers

What is the role of NADPH in macrophage activity?

To produce superoxide anion radical Signup and view all the answers

In which organs is the oxidative reaction of the pentose phosphate pathway active?

Liver, lactating mammary glands, and adrenal cortex Signup and view all the answers

What is the role of NADPH in erythrocytes?

Maintaining membrane integrity Signup and view all the answers

What is the function of NADPH in the nonoxidative reactions of the pentose phosphate pathway?

Synthesizing nucleotides and nucleic acids Signup and view all the answers

Which organs require NADPH for the biosynthesis of fatty acids and steroids?

Adrenal cortex and adipose tissue Signup and view all the answers

What is the role of NADPH in free radical scavenging?

Reducing glutathione Signup and view all the answers

In which organs is the pentose phosphate pathway involved in nucleotide synthesis?

All cell types Signup and view all the answers

What is the role of NADPH in the adrenal cortex?

Synthesizing steroids Signup and view all the answers

What is the role of glutathione in erythrocytes?

Detoxifying free radicals Signup and view all the answers

In which organs is the pentose phosphate pathway involved in fatty acid synthesis?

Adipose tissue and liver Signup and view all the answers

Study Notes

Prevention of Methemoglobinemia

NADPH is essential for keeping hemoglobin iron in a reduced state (ferrous) to prevent methemoglobinemia, which impairs oxygen transport.

Role of NADPH in Eye Health

NADPH maintains lens transparency by supporting lens protein health.

Macrophage Function

NADPH enables macrophages to produce superoxide anion radicals, crucial for bacterial elimination.

Clinical Significance of HMP Pathway

Glucose 6-phosphate dehydrogenase (G6PD) deficiency is the most common enzyme deficiency, inherited in an X-linked manner.
It leads to hemolytic anemia due to an inability to detoxify oxidizing agents.
Reduced G6PD activity decreases NADPH formation, impairing cellular detoxification of free radicals and peroxides.
Symptoms of G6PD deficiency include anemia, jaundice, and dark urine.

Key Differences Between Pathways

Embden-Meyerhof Pathway (Glycolysis)
- Occurs in all tissues.
- NAD is the hydrogen acceptor and ATP is both required and produced.
- CO2 is not formed.
Hexose Monophosphate Shunt (HMP) Pathway
- Occurs in specialized tissues for specific functions.
- NADP is the hydrogen acceptor; ATP is required but not produced.
- CO2 is produced.

Reactions in Pentose Phosphate Pathway

Stage 1: Oxidative Reactions (Irreversible)
- Involve dehydrogenation of glucose 6-phosphate, hydration of phosphogluconolactone, and formation of ribulose 5-phosphate.
- Each cycle converts glucose 6-phosphate to ribulose 5-phosphate, CO2, and two NADPH molecules.
Stage 2: Nonoxidative Reactions (Reversible)
- Ribulose 5-phosphate can be converted into ribose 5-phosphate for nucleotide synthesis or intermediates of glycolysis (fructose 6-phosphate, glyceraldehyde 3-phosphate).

Definition and Significance of the HMP Pathway

Known as the pentose phosphate pathway; serves as an alternative route for glucose oxidation.
Approximately 10% of daily glucose is diverted to this pathway, occurring in the cytosol.
Major objectives include generating NADPH for biochemical reduction and pentose phosphates for nucleotide synthesis.
Each cycle processes three glucose-6-phosphates, yielding CO2 and five-carbon residues generating glucose 6-phosphate and glyceraldehyde 3-phosphate.

Physiological Significance of the HMP Pathway

Oxidative reactions occur primarily in:
- Liver
- Lactating mammary glands
- Adipose tissue (fatty acid biosynthesis)
- Adrenal cortex (steroid synthesis)
- Erythrocytes (glutathione reduction)
- Testes and ovaries
- Lens of eyes
Nonoxidative reactions happen in all cell types for synthesizing nucleotides and nucleic acids.

Functions of NADPH

Provides reducing equivalents to support biosynthesis of fatty acids, cholesterol, and steroids.
Aids in free radical scavenging, enhancing regeneration of reduced glutathione reductase to eliminate free radicals (like superoxide and hydrogen peroxide).
Ensures erythrocyte membrane integrity by maintaining glutathione in a reduced state, detoxifying free radicals within red blood cells.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on the Embden-Meyerhof-Parnas pathway and the Hexose Monophosphate Shunt pathway. Identify the key differences between these two pathways, including the tissues in which they occur, the acceptors of hydrogen, and the production of ATP and CO2.