Lecture 30: TCA Cycle Overview Flashcards Preview

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1

TCA Cycle

-nearly universal central catabolic pathway
-compounds from carbohydrates, fats, and proteins are oxidized to CO2
-most of the energy from oxidation is converted to reduced electron carriers NADH and FADH2

2

Where do these reactions occur for the entry of acetyl-CoA?

eukaryotes-Mitochondrial Matrix
Bacteria-Cytosol

3

What is the energy gain from one acetyl-CoA being oxidized?

3 NADH
1 FADH2
1 ATP (GTP)

4

What is the result of the TCA cycle?

Release of 2 CO2

5

Mitochondrion

Has two bilayer membranes:
-outer membrane
-inner membrane

6

Outer membrane

-porous
-easy equilibration of material from the cytoplasm across this membrane to the intermembrane space

7

Inner membrane

-75% protein by weight
-completely closed
-transporters are needed for movement of molecules

8

Where does the TCA cycle occur?

takes place inside the inner membrane of the mitochondrion
-reduced electron carriers accumulate in here (NADH and FADH2)

9

What reactions are metabollically irreversible in TCA cycle

1, 3, and 4

10

Pyruvate Dehydrogenase Reaction

entry of pyruvate into TCA cycle
-enzyme: Pyruvate Dehydrogenase Complex-> contains 3 types subunits

11

E1 of the pyruvate dehydrogenase complex and what coenzyme is involved

pyruvate dehydrogenase
-TDP (aka TPP)

12

E2 of the pyruvate dehydrogenase complex and what coenzyme is involved?

dihydrolipoamide acetyltransferase
-lipoyllysine

13

E3 of the pyruvate dehydrogenase complex and what coenzyme is involved?

dihydrolipoamide dehydrogenase
-FAD

14

What is the purpose of the coenzymes utilized in the pyruvate dehydrogenase complex?

take care of covalently attaching to pyruvate, transfer of H-CoA, and oxidation

15

Rxn 1 of TCA cycle extra info

acetyl-CoA
-is a high energy compound
-used as a substrate which contributes to the Large standard free energy decrease
-making this reaction irreversible

16

Rxn 2 of TCA cycle extra info

despite the +free energy value, the cell goes to the right because isocitrate is used immediately in the next reaction. so its concentration is kept very low

17

Aconitase

contains
- iron sulfur coenzyme center and the Fe2+ of the iron-sulfur participates in binding and catalysis

18

Succinate Dehydrogenase

-enzyme found in inner side of the inner mitochondrial membrane