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24 Cards in this Set

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What are the regulatory points in the citric acid cycle?

Four points...
1. Pyruvate dehydrogenase
2. Citrate synthase
3. Isocitrate dehydrogenase
4. α-ketoglutarate dehydrogenase
What allosterically regulates citrate synthase,isocitrate dehydrogenase, and
α-ketoglutarate dehydrogenase?

How is it repressed/activated?
1. Repressed by high energy levels (ATP, NADH)

2. Activated by low energy levels (ADP, NAD+)
What molecules inhibit citrate synthase and α-ketoglutarate through feedback inhibition?

Two molecules...
1. Citrate

2. Succinyl CoA
What happens to the citric acid cycle if all of the intermediates are use for biosynthesis?
Cycle will stop
Will adding more acetyl-CoA replenish the intermediates in the citric acid cycle?
No it will not because the pathway is cyclic
How are intermediates in the citric acid cycle replenished?
Anaplerotic reactions
What are anaplerotic reactions?
Four ways to convert either pyruvate or PEP directly to citric acid cycle intermediates without passing through acetyl-CoA
What are the enzymes for each anaplerotic reaction?

Four molecules...
1. Pyruvate carboxylase
2. PEP carboxykinase
3. PEP carboxylase
4. Malic enzyme
What is the product of the anaplerotic reaction using pyruvate carboxylase?
Oxaolacetate
What intermediate is formed from the anaplerotic reaction catalyzed by PEP carboxykinase?
Oxaolacetate
PEP carboxylase catalyzes an anaplerotic reaction that produces what intermediate?
Oxaolacetate
The malic enzyme catalyzes an anaplerotic reaction that converts pyruvate into what intermediate?
Malate
What is biotin?
Biotin is the cofactor for carrying oxidized single carbons
What compound are fatty acids degraded into?
Acetyl-CoA
What does the glyoxylate shunt allow to happen?
Shunt converts fat to glucose
How is the glyoxylate shunt able to convert fat to glucose?
It bypasses the two steps in the citric acid cycle that release CO2 so that there's a net increase in C
Can mammals make glucose from fat?

Why or why not?
No because we do not have isocitrate lyase and malate synthase
Where is the glyoxylate shunt located in plants?
In the glyoxysome organelle next to the mitochondria
What is the function of the glyoxylate shunt?

Two functions...
1. It splits isocitrate and directly form malate and succinate

2. It allows the reversal of the pyruvate dehydrogenase step
What happens to isocitrate after it is split?

Two things...
1. Succinate is converted to PEP and used for gluconeogenisis

2. Malate is used to keep the citric acid cycle running
What vitamin is biotin?

Why is a lack of biotin uncommon?
Vitamin H

The bacteria in our intestines makes biotin
What is pantothenate?
Vitamin B-5
What is pantothenate required for?

Two things...
1. Acetyl-CoA

2. Acyl carrier protein
What is the difference between biotin and TPP?
Biotin's active site is CO2

TPP's active site is an acetaldehyde