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Chem > Citric Acid Cycle > Flashcards

Citric Acid Cycle Flashcards

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1
Q

How many enery capture steps in the CAC

A

5

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2
Q

What’s the first step of the CAC

- substrates + products/ enzymes/ irreversible or reversible

A
  • first step is hydrolysis of the thioester bond
  • irreversible conversion of A.Coa/OAA to citrate via the enzyme citrate synthase
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3
Q

What task does a synthase perform

A

joing 2 molecules together without ATP or NTP

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4
Q

Is the first step in the CAC exergonic or endergonic? Why

A

Exergonic, because of the release of energy of the thioester bond

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5
Q

What happens if there is an increase in citrate concentration?

A

the citrate is take to the cytosol to be used for Fatty acids

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6
Q

Why is citrate converted to isocitrate

A

because the tertiary hydroxyl group is hard to oxidized, so an isomerization occurs

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7
Q

what is the 3 steps of the CAC?

- important notes/ enzymes/ S&P/Rev or IRRev

A
  • isocitrate is converted to A-ketoglutarate
  • via a decarboxylation and oxidation
  • Enzyme: Isocitrate dehydrogenase
  • irreversible step
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8
Q

How does Mn2+ help with the decarboxylation of isocitrate

A
  • it increases electron withdrawing group for decarboxylate
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9
Q

Where are the 2 forms of ioscitrate dehydrogenase and why do they reside there?

A
  1. Resides in the matrix of the mitochandria for CAC, NAD+ dependent enzyme
    - Able to dump electrons onto NAD=
  2. Resides in the cytosol for NADP+ dependent enzyme
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10
Q

Write the balanced equation of Isocitrates conversion

A

Isocitrate + NAD+ –> A Ketoglutarate + NADH + CO2

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11
Q

What makes pyruvate and A-KG, A-keto acids

A

They are 1 bond away from the carbonyl group making them a-keto acids

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12
Q

What cosubstrate is typically involved in the conversion of hydroxyl groups to carbonyl groups?

A

NAD+ and NADPH

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13
Q

What occurs in the 4th step of the CAC

A
  • A-ketoglutarate is converted into Succinyl CoA
  • enzyme: A-ketoglutarate dehydrogenase
  • Irreversible step
  • Thioester bond formed, decarboxylation and oxidation
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14
Q

What is complex is A-ketoglutarate dehydrogenase most similar to

A

PDH complex

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15
Q

How is A-ketoglutarate dehydrogenase regulated?

A

Via allostery

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16
Q

What are the difference between PDH and A-KG dehydrogenase?

A
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17
Q

what is the 5th step of CAC

A
  • conversion of Succinyl-Coa to succinate
  • transfer of thioester to high energy molecule
  • SLP
  • Succinyl-CoA synthetase
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18
Q

How does the energy capture step of succinyl-CoA occur

A
  • Breaking of thioester bond to form an anhydride bond
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19
Q

Why does GDP need to be regenerated? How does this occur in the CAC

A
  • has to be regenrated for reaction to work
  • GDP is made into GTP which it transfers it Triphospate onto ADP making ATP via nuclotide diphosphate kinase
20
Q

What do nucleotide diphosphate kinase do?

A
  • transfer of phosphate
21
Q

What does a synthetase do?

A

joins two molecules with the participation of ATP and NTP

22
Q

How many high energy bonds in the Succinyl- CoA sythetase reaction?

A

4

23
Q

Explain the succinyl- CoA synthetase reation

A
  1. Formation of succinyl phosphate
    Pi + Succinyl- CoA(thioester) <-> succinyl-phosphate (mixed anhydride) + CoASH
  2. Formation of phophoryl His
    Enzymer-His + S.P <-> 3-phopho-His (phosphoamide) + Succinate
  3. Phosphoryl tranfer to GDP forming GTP (SLP Step)
    GDP + 3-phospho-His <-> GTP (phosphoanhydride)
24
Q

What is the importance of the last 3 steps of the CAC?

A

they convert methylene group of Succinate to carbonyl group of OAA

25
Q

Where does FAD typically show up in reactions

A

oxidations of alkanes to alkenes

26
Q

What are the products of the Citric Acid Cycle?

A

3 NADH
1 GTP (ATP)
2 CO2
1 FADH2

27
Q

Write a balanced equation for the CAC

A

A.CoA +3 NAD+ GDP + Pi + FAD H20 –> 2 CO2 + NADH + FADH2 + GTP + CoA

28
Q

Why cant mammals convert FA into glucose?

A

Fatty acids are broken down into ACoA, there is no net gain of carbons therefore cannot be used as glucose

29
Q

Where can FA’s enter in the CAC

A

As succinyl CoA, last 3 carbons of uneven fatty acids

30
Q

What makes CAC an Amphibolic pathway?

A
  • Catabolic processes such as oxidative catabolism of carbs, fa, and aa
  • Anabolic process for aa syntheses, purine and pyrimidine biosynthesis, gluconeogensis, FA and sterol syntheisis
31
Q

What processes in catapleurotic?

A
  • OAA can be used for glucose
  • Malate can be used for glucose
  • Citrate for FA aand cholestrol
  • A-KG for AA
32
Q

Which processes are anapleurotic

A
  • CO2, fatty acids for Succinyl- Coa
  • Amino acids at A-KG
33
Q

Why are anaplerotic reactions important in the CAC

A
  • needed to replenish the CAC for anabolic process
34
Q

What is the most important anaphlerotic process in mammales

A

pyruvate carboxylation

35
Q

What transmination reaction occurs with pyruvate?

A

Alanine

36
Q

What transmination reaction occurs with OAA?

A

Asparatate

37
Q

What transmination reaction occurs with A-KG

A

glutamate

38
Q

Under what conditions will pyruvate be turned into OAA?

A
  • starvation
  • Exercise
39
Q

Under what conditions is pyruvate converted to A.CoA

A

Heavy fatty acids and amino acid metabolism

- acetyl CoA iacticates pyruvate carboxylase

40
Q

Describe the process the occurs when during starvation, in regards to pyruvate?

A
  • Occurs in the liver
  • decrease in the PDC which converts Pyruvate to A.CoA
  • A.CoA is converted to ketons which is used for fuel
  • Increase in pyruvate carboxylate which converts pyruvate to OAA
41
Q

What is the fate of pyruvate pyruvate during during exercise

A
  • decrease in PDC
  • Pyruvate is converted to OAA and used for the CAC
42
Q

What are the most crucial factors the CAC responds to?

A
  • Energy state of the cell (ATP:ADP)
  • Redoc State of the cell
    (NADH: NAD+)
43
Q

Product inhibition of CA flux

A
  • nadh
  • succinyl-coa
  • citrate
44
Q

The activity of ETC controls…

A

the activity of the CAC

45
Q

What occurs if there is a decrease in ADP in the mitochandria?

A

= D activity of ATp synthase, In. proton gradient, De E- flow, DE reoxidation of NADH, and Increase NADH: NAD+

46
Q

What occurs if there is a increase in ADP in the mitochandria?

A

Increase ATP synthase activity, decreased proton gradient, increase electron flow, increase reoxidation of NADH and decreased NADH: NAD+

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