Biochem Lec10 Citric Acid Cycle

Front 1

Where does the Citric acid cycle take place?

Back 1

Mitochondria

Front 2

What are the sources of Acetyl CoA to enter the Krebs cycle?

Back 2

-Amino acids

-Fatty acids

-Pyruvate from glycolysis

Front 3

What are the end products of Krebs cycle?

Back 3

1 Acetyl CoA --> 2 CO2, 3 NADH, 1 FADH2, 1 GTP/ATP

Front 4

Why is it called the Citric Acid Cycle and what are it's other two names?

Back 4

named after CITRATE - the product of the 1st rxn

-Krebs cycle

-Tricarboxylic acid cycle (TCA)

Front 5

What is the fate of oxaloacetate in the Krebs cycle?

Back 5

consumed in 1st step but regenerated in last step

Front 6

Are the carbon atoms from the 2 resulting CO2 from Acetyl CoA in the Krebs cycle?

Back 6

NO

Front 7

How does pyruvate get into the mitochondria?

Back 7

A transport protein imports pyruvate along with H+ ions

Front 8

What are the different fates of Pyruvate?

Back 8

-reduced to Lactate

-converted to oxaloacetate

-transaminated to Alanine

-converted to acetyl-CoA and CO2

Front 9

Where is Acetyl CoA utilized?

Back 9

-Fatty acid synthesis

-cholesterol synthesis

-acetycholine synthesis

-KREBS cycle - more energy production

Front 10

What enzyme converts Pyruvate to Acetyl CoA and what are other byproducts.

Back 10

Pyruvate Dehydrogenase - by oxidative decarboxylation

+1 NADH, CO2

Front 11

What is the enzyme of the 1st rxn of Krebs, what kind of enzyme, and the products/reactants.

Back 11

Citrate synthase - condensation

Acetyl CoA + oxaloacetate + H2O --> Citrate + CoASH + H*

rate determing - very exergonic - rate determining

Front 12

What regulates the 1st rxn of the Krebs cycle?

Back 12

competitively inhibited by: Succinyl-CoA, Citrate, NADH

-Substrate availability

-product inhibition

-competitive feedback inhibition

Front 13

What is the enzyme of the 2st rxn of Krebs, what kind of enzyme, and the products/reactants.

Back 13

Aconitase - isomerization

Citrate <--cis-Aconitate--> Isocitrate

reversible

Front 14

What is the enzyme of the 3rd rxn of Krebs, what kind of enzyme, and the products/reactants.

Back 14

Isocitrate Dehydrogenase - oxidative decarboxylation

isocitrate + NAD* + Mn++/Mg++ --> alpha-ketoglutarate + NADH + CO2 (1st one)

not reversible

Front 15

What stimulates/inhibits Isocitrate dehydrogenase?

Back 15

-stimulated by Ca++ ions

-Allosterically Activated by ADP

-Inhibited by NADH (product)

-Allosterically Inhibited - ATP

Front 16

What is the enzyme of the 4th rxn of Krebs, what kind of enzyme, and the products/reactants.

Back 16

alpha-ketogluterate - oxidative decarboxylation

alpha-ketogluterate + CoASH + NAD* --> Succinyl-CoA + NADH + CO2 (2nd one)

not reversible

Front 17

What stimulates/inhibits alpha-ketogluterate dehydrogenase?

Back 17

-stimulated by Ca++ ions

-inhibited by products NADH and Succinyl-CoA (also inhibits 1st step)

Front 18

What is the enzyme of the 5th rxn of Krebs, what kind of enzyme, and the products/reactants.

Back 18

Succinyl-CoA Synthetase - cleaving

Succinyl-CoA + GDP + Pi <--> Succinate + GTP

reversible (is exergonic but just barely)

Front 19

What is the enzyme that will convert GTP to ATP?

Back 19

diphosphate kinase

Front 20

What is the enzyme of the 6th rxn of Krebs, what kind of enzyme, and the products/reactants.

Back 20

Succinate dehydrogenase - oxidation/reduction

Succinate + FAD <--> Fumerate + FADH2

reversible

Front 21

What is the enzyme of the 7th rxn of Krebs, what kind of enzyme, and the products/reactants.

Back 21

Fumerase - hydration

Fumerate + H2O <--> L-Malate

reversible (exergonic but just barely)

Front 22

What inhibits succinate dehydrogenase?

Back 22

Highly inhibited by MALATE

Front 23

What is the enzyme of the 8th rxn of Krebs, what kind of enzyme, and the products/reactants.

Back 23

Malate Dehydrogenase - redox

L-Malate + NAD* <--> Oxaloacetate + NADH

reversible

oxaloacetate regenerated here

Front 24

What regulates Malate dehydrogenase?

Back 24

dependant on NAD*

Front 25

What happens to the NADH and FADH2 produced from the Krebs cycle?

Back 25

They are put into the electron-transport chain to synthesize ATP

Front 26

Why do you only get 2 ATP from FADH2?

Back 26

It enters the electron transport chain at a different step than NADH

Front 27

What are the 3 rate-determining enzymes of Krebs?

Back 27

-citrate synthase #1

-isocitrate dehydrogenase #3

-alpha-ketoglutarate dehydrogenase #4

Front 28

What are the 3 mechanisms that regulate enzymes in Krebs?

Back 28

-substrate availability

-product inhibition

-competitive feedback inhibition (by intermediates further along the cycle)