Oxidation of Pyruvate and TCA Cycle

Question 1

Oxidation of pyruvate and the TCA cycle account for complete oxidation of glucose to what?

Answer 1

CO2 and H2O

Question 2

Pyruvate formed in the cytosol is transported into the mitochondrion by a ____ ____

Answer 2

proton symporter

Question 3

Inside the mitochondrion, pyruvate is oxidatively decarboxylated to acetyl-CoA by ____ ____ multienzyme complex

Answer 3

pyruvate dehydrogenase (PDH)

note: 3 enzymes, 5 coenzymes, regulatory proteins

Question 4

Pyruvate is covalently bound to ___ associated with first enzyme of the pyruvate dehydrogenase

Answer 4

TPP

Question 5

Dihydrolipoyl transacetylase catalyzes the transfer of acetyl group to CoA-SH, which leaves the lipoic acid in the ____, ____ form

Answer 5

reduced; sulfhydryl

Question 6

The oxidized form of _____ is regenerated by dihydrolipoyl dehydrogenase

Answer 6

lipoamide

Question 7

Activity of the PDH complex is affected by _____/_____

Answer 7

phosphorylation/dephosphorylation

note: inactive when phosphorylated

Question 8

Where does the TCA cycle take place in the cell?

Answer 8

matrix of mitochondria

Question 9

In regards to the TCA cycle, oxidation of acetylCoA produces reduced ____ and ____

Answer 9

NADH; FADH2

Question 10

In regards to the TCA cycle, deoxidation of NADH and FADH2 through the ____ ____ chain, reduces O2 to H2O

Answer 10

electron transport

Question 11

What are other roles of citrate?

Answer 11

source of other synthetic pathways (FAs)
regulation of other reactions (PFK-1)
source of reducing equivalents

Question 12

The isomerization of citrate to isocetrate by aconitase is ___, with the migration of the -OH from the central carbon of citrate being always adjacent to the carbon which is derived from the -CH2- of OAA

Answer 12

sterospecific

Question 13

Which enzyme produces the first NADH and CO2 of the TCA cycle

Answer 13

Isocitrate DH

Question 14

What is the rate limiting step of the TCA cycle?

Answer 14

isocitrate to alpha-ketoglutarate

enzyme: isocitrate DH

Question 15

alpha-ketoglutarate dehydrogenase has 3 catalytic subunits E1, E2, and E3. Give the requirements of this enzyme, and mention if it is regulated by phosphorylation.

Answer 15

requires: TPP, lipoid acid, CoASH, FAD, NAD+

NOT regulated by phosphorylation

Question 16

Which enzyme produces the second NADH and CO2 of the TCA cycle?

Answer 16

alpha-ketoglutarate DH

Question 17

What is the only substrate level phosphorylation of the TCA cycle?

Answer 17

Succinyl CoA synthetase/succinate thiokinase

Question 18

Which enzyme of the TCA cycle produces FADH2 (third reducing equivalent

Answer 18

succinate DH

Question 19

Which enzyme of the TCA cycle produces the fourth (and final) reducing equivalent, NADH?

Answer 19

malate DH

Question 20

What determines the rate of the TCA cycle?

Answer 20

rate of ATP utilization

Question 21

Citrate synthase is inhibited by ____-___

Answer 21

succinyl-CoA

Question 22

Isocitrate DH is stimulated by ____, inhibited by ____

Answer 22

ADP; ATP

Question 23

alpha-ketoglutarate is inhibited by _____-___, ___ and ____

Answer 23

succinyl-CoA; NADH; GTP

Question 24

What is the grand total of aerobic oxidation of one mole of glucose (total ATP)?

Answer 24

38