Cataplerotic and Anaplerotic Reactions Quiz

Questions and Answers

What are cataplerotic reactions?

A series of reactions that deplete CAC intermediates.

What are sterols?

They are cholesterol-based substances like cortisol, testosterone, and estrogen.

What are the cataplerotic reactions?

Phosphoenolpyruvate carboxykinase, 2. Aspartate transaminase, 3. ATP citrate lyase, 4. Glutamate dehydrogenase, 5. Aminolevulinate synthase.

What are the situations in which the cataplerotic reactions will be active?

DNA synthesis, RBC synthesis, storing energy as fatty acids, need for glucose, after a meal, excess production of ATP, steroid signaling. Signup and view all the answers

What are anaplerotic reactions?

A series of reactions that build up CAC intermediates. Signup and view all the answers

What are the anaplerotic reactions?

<ol> <li>Pyruvate carboxylase, 2. Beta oxidation, 3. Glutamate dehydrogenase, 4. Aspartate transaminase, 5. Adenylosuccinate lyase.</li> </ol> Signup and view all the answers

What does phosphoenolpyruvate carboxykinase do?

Phosphorylates oxaloacetate while releasing CO2. Signup and view all the answers

What is the reaction that phosphoenolpyruvate carboxykinase catalyzes?

GTP + oxaloacetate -> GDP + PEP + CO2. Signup and view all the answers

What does ATP citrate lyase do?

Activates citrate while consuming ATP. Signup and view all the answers

What is the reaction that ATP citrate lyase catalyzes?

citrate + ATP + CoA -> oxaloacetate + ADP + Pi + acetyl CoA. Signup and view all the answers

Is ATP citrate lyase cataplerotic or anaplerotic?

False Signup and view all the answers

What does Delta-aminolevulinate synthase do?

Synthesizes delta-aminolevulinate (ALA), the first step in heme formation. Signup and view all the answers

How is the Delta-aminolevulinate synthase the first step in heme formation?

Heme is a cage of all of the delta-aminolevulinate acid and the iron atom sits on the inside. Signup and view all the answers

What does each of the catapleronic reactions go to?

<ol> <li>Phosphoenolpyruvate carboxykinase = glucose, 2. Aspartate transaminase = amino acids, 3. ATP citrate lyase = fatty acids, sterols, 4. Glutamate dehydrogenase = nucleic acids, 5. Aminolevulinate synthase = heme.</li> </ol> Signup and view all the answers

What does adenylosuccinate lyase do?

Breaks down adenylosuccinate for nucleotide synthesis. Signup and view all the answers

What is the reaction for the breakdown of adenylosuccinate?

adenylosuccinate -> AMP + fumarate. Signup and view all the answers

What is the breakdown of SAICAR?

SAICAR -> AICAR + fumarate. Signup and view all the answers

What does malic enzyme do?

Pyruvate + HCO3- + NADPH + H+ -> L-malate + NADP+ + H2O. Signup and view all the answers

What is malic enzyme's full name?

Malate dehydrogenase (oxaloacetate decarboxylating). Signup and view all the answers

What is malate dehydrogenase similar to?

Pyruvate carboxylase. Signup and view all the answers

What changes the malate dehydrogenase varieties?

The cofactor (NAD or NADP), substrate (pyruvate or oxaloacetate), location (cytoplasmic, mitochondrial), or role (shuttle, TCA, anaplerotic/generate NADPH, gluconeogenesis, anaplerotic). Signup and view all the answers

What does pyruvate carboxylase do?

Adds carbon to pyruvate. Signup and view all the answers

What is the pyruvate carboxylase reaction?

pyruvate + ATP + HCO3- -> 2H+ + ADP + Pi + oxaloacetate. Signup and view all the answers

How is the pyruvate carboxylase regulated?

Regulated by acetyl CoA. Signup and view all the answers

What does beta oxidation do?

Breakdown of fatty acid chains. Signup and view all the answers

What happens when the fatty acid has an odd number of carbons during beta oxidation?

Instead of acetyl-CoA, it produces propionyl CoA (3 carbons), which is then converted into succinyl CoA if you add CO2. Signup and view all the answers

What does Aspartate Transaminase do?

Reversible transfer of NH4. Signup and view all the answers

Is Aspartate transaminase anaplerotic or cataplerotic?

True Signup and view all the answers

What does glutamate dehydrogenase do?

Removes hydrogen from glutamate. Signup and view all the answers

How is glutamate dehydrogenase similar to aspartate transaminase?

Both are reversible and can be anaplerotic or cataplerotic depending on the direction of the reaction. Signup and view all the answers

What is the TCA?

It is an amphiplerotic mechanism, our body is a mixture of catabolism and anabolism that is mediated by the TCA. Signup and view all the answers

Study Notes

Cataplerotic Reactions

Deplete citric acid cycle (CAC) intermediates, known as "emptying reactions."
Intermediates are diverted for biosynthesis of important molecules.
Active during DNA synthesis, RBC production, storage of energy as fatty acids, post-meal scenarios, and steroid signaling.
Key cataplerotic reactions include:
- Phosphoenolpyruvate carboxykinase (converts oxaloacetate to phosphoenolpyruvate)
- Aspartate transaminase (transfers amino groups)
- ATP citrate lyase (breaks down citrate into oxaloacetate and acetyl CoA)
- Glutamate dehydrogenase (removes hydrogen from glutamate)
- Delta-aminolevulinate synthase (first step in heme formation)

Anaplerotic Reactions

Build up CAC intermediates, balancing their depletion for biosynthesis.
Promote the replenishment of intermediates used in various metabolic pathways.
Key anaplerotic reactions include:
- Pyruvate carboxylase (adds carbon to pyruvate)
- Beta oxidation of fatty acids (releases acetyl CoA)
- Glutamate dehydrogenase (also acts in anaplerotic direction)
- Aspartate transaminase (can function in both directions)
- Adenylosuccinate lyase (involved in nucleotide synthesis)

Enzyme Functions and Roles

Phosphoenolpyruvate carboxykinase
- Catalyzes reaction: GTP + oxaloacetate → GDP + PEP + CO2.
- Converts oxaloacetate to phosphoenolpyruvate during gluconeogenesis.
ATP Citrate Lyase
- Breaks down citrate in the cytoplasm while consuming ATP.
- Reaction: citrate + ATP + CoA → oxaloacetate + ADP + Pi + acetyl CoA.
- Functions in fatty acid and sterol biosynthesis.
Delta-Aminolevulinate Synthase
- Key in heme formation, synthesizes delta-aminolevulinate (ALA) from precursor molecules.
Adenylosuccinate Lyase
- Catalyzes breakdown of adenylosuccinate into AMP and fumarate.
Malic Enzyme
- Converts pyruvate to L-malate while producing NADP+.
- Similar in function to pyruvate carboxylase.

Additional Key Concepts

Beta Oxidation
- Breaks down fatty acids, releasing acetyl CoA at each step.
- When fatty acids have odd carbon numbers, results in propionyl CoA, which is converted to succinyl CoA.
Aspartate Transaminase
- Catalyzes the reversible transfer of amino groups between aspartate and α-ketoglutarate.
- Functions in both cataplerotic and anaplerotic capacities, making it amphiplerotic.
Glutamate Dehydrogenase
- Removes hydrogen from glutamate, can utilize NAD or NADP.
- Also amphiplerotic, functioning depending on reaction direction.
TCA Cycle
- Functions as an amphiplerotic mechanism, balancing catabolic and anabolic processes in the body.

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Test your knowledge on cataplerotic and anaplerotic reactions with these flashcards. Explore definitions, key reactions, and understand the role of sterols in the metabolic pathways. Perfect for students of biochemistry and related fields.