Lecture 10 - TCA cycle Flashcards

1
Q

What does TCA stand for?

A

tricarboxylic acid

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2
Q

What are the other names for the TCA cycle?

A

Citric acid cycle; Krebs cycle

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3
Q

What is the first step? (i.e., what happens to pyruvate?

A

it’s converted to acetyl coenzyme A by oxidative decarboxylation

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4
Q

What is decarboxylation?

A

a chemical reaction that removes a carboxyl group and releases carbon dioxide

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5
Q

What begins the TCA cycle?

A

the entry of acetate as acetyl CoA

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6
Q

What are the products of the TCA cycle?

A

CO2, ATP, NADH and FADH2

Acetyl CoA -> 3 NADH + FADH2 + ATP + 2 CO2

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7
Q

What were the 3 important enzymes mentioned?

A

CAC-3: isocitrate dehydrogenase
CAC-4: alpha-ketoglutarate dehydrogenase
CAC-6: succinate dehydrogenase

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8
Q

What enzyme is inhibited by its products? What are the products? What else inhibits it?

A

oxoglutarate/ alpha-ketoglutarate dehydrogenase

succinyl CoA and NADH

high energy charge in cell is also inhibitive

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9
Q

What are the allosteric activators of oxoglutarate dehydrogenase?

A

ADP and calcium ions

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10
Q

What is an allosteric regulator?

A

a substance that binds to a site on an enzyme distinct from the active site

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11
Q

True or false: succinate dehydrogenase is not the only enzyme that participates in both the citric acid cycle and the electron transport chain

A

false

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12
Q

What else does the TCA cycle play an important role in?

A

the catabolism of proteins and lipids

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13
Q

Catabolism of TAG molecules

A

begins with their hydrolysis to glycerol and free fatty acids

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14
Q

Fatty acids and the TCA cycle

A

fatty acids are linked to coenzyme A to form fatty acyl CoAs, which are then degraded by beta oxidation, a catabolic process that generates acetyl CoA and the reduced coenzymes NADH and FADH2

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15
Q

Proteins and the TCA cycle

A
  • free amino acids can be catabolized for energy
  • protein catabolism beings with hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain – proteolysis
  • the enzymes responsible = proteases
  • all of the pathways for amino acid catabolism eventually lead to pyruvate, acetyl CoA, or a few key intermediates in the citric acid cycle

**amino acids can fuel the Krebs cycle

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16
Q

Cataplerotic vs anaplerotic pathways

A

cataplerotic: TCA intermediates lost to this pathway to provide precursors for biosynthesis
anaplerotic: regenerate TCA intermediates