TCA cycle

Question 1

How many reactions are involved in the TCA cycle?

Answer 1

8

Question 2

What occurs during pyruvate oxidation?

Answer 2

Pyruvate is oxidised to acetate, with the formation of NADH and the release of CO2. Acetate is combined with coenzyme A, yielding CoA

Question 3

What occurs in the first step of the TCA cycle?

Answer 3

The two carbon acetyl group and four-carbon oxaloacetate combine, forming six-carbon citrate

Question 4

What occurs in the second step of the TCA cycle?

Answer 4

Citrate is rearranged to form its isomer, isocitrate

Question 5

What happens in the third step of the TCA cycle?

Answer 5

Isocitrate is oxidised to a-ketoglutarate, yielding NADH and CO2

Question 6

What happens in the fourth step of the TCA cycle?

Answer 6

Alpha-ketoglutarate is oxidised to succinylcholine CoA with the formation of NADH and CO2; this step is almost identical to pyruvate oxidation

Question 7

What happens in the 5th step of the TCA cycle?

Answer 7

Succinyl CoA releases coenzyme A, becoming succinate; the energy thus released converts GDP to GTP, which in turn converts ADP to ATP

Question 8

What happens in the sixth step of the TCA cycle?

Answer 8

Succinate is oxidised to fumarate, with the formation of FADH2

Question 9

What happens in the seventh step of the TCA cycle?

Answer 9

Fumarate and water react, forming malate

Question 10

What happen sin the eighth step of the TCA cycle?

Answer 10

Malate is oxidised to oxaloacetate, with the formation of NADH. Oxaloacetate can now react with acetyl CoA to reenter the cycle

Question 11

What is the mnemonic used for remembering the steps in the TCA cycle?

Answer 11

A- Acetyl CoA
Clown- Citrate
In- Isocitrate
Kilamanjaro- a-Ketoglutarate
Sings- Succinyl CoA
Songs- Succinate
For- Fumarate
Money- Malate
Only- Oxaloacetate

Question 12

State the products from the reaction - Acetyl CoA + Oxaloacetate

Answer 12

Citrate + CoA Citrate synthase

Question 13

State the enzyme produced from citrate

Answer 13

Isocitrate Aconitase

Question 14

State the enzymes produced from Isocitrate + NAD+

Answer 14

a-ketoglutarate + NADH + CO2 Isocitrate dehydrogenase

Question 15

Where are all enzymes of the TCA cycle located apart from succinate dehydrogenase and where is that enzyme located?

Answer 15

Mitochondrial matrix

Integrated in the inner mitochondrial membrane

Question 16

State the products from succinate + FAD

Answer 16

Fumarate + FADH2

Question 17

What does each turn of the TCA cycle onvolve the uptake and releasde of?

Answer 17

Uptake of two carbon atoms in the form of acetyl-CoA and the release of two carbon atoms as CO2

Question 18

What does each turn in the TCA cycle involve the transfer of?

Answer 18

Transfer of 3 pairs of electrons to NAD+ to form NADH + H+, and the transfer of 1 paor of electrons to reduce FAD to FADH2

Question 19

One substrate level phosphorylation reaction results in what?

Answer 19

The formation of GTP from GDP and Pi

Question 20

What does high ATP, NADH and acetyl-CoA mean?

Answer 20

Plenty of energy

Question 21

What does high ADP and NAD+ mean?

Answer 21

Lack of energy

Question 22

What does high succinylcholine-CoA and acetyl-CoA mean?

Answer 22

Plenty of precursor molecules for biosynthetic reactions

Question 23

State the products of the TCA cycle

Answer 23

From each acetyl-CoA, the TCA cycle generates:
3x NADH + H+
1X FADH2
1X GTP
2X CO2

Question 24

What is the TCA cycle used for?

Answer 24

Can be used to complete oxidation derived from gylcolysis or to convert other carbon sources