Citric Acid Cycle

Question 1

What is the citric acid cycle?

Answer 1

Breakdown of fuel molecules into carbon dioxide and water

Question 2

Carbon molecules in cycle:

Answer 2

C2 + C4 = C6

C6 -> C5 -> C4

Question 3

What’s produced in the cycle?

Answer 3

2x CO2

1x GTP

3xNADH

1x FADH2

Question 4

What eventually happens to the FADH2 produced in the cycle?

Answer 4

Hydrogen combines with oxygen and forms water

This process is coupled to ATP synthesis

Question 5

What does FAD stand for?

Answer 5

Flavin Adenine Dinucleotide

Question 6

What is FAD formed from?

Answer 6

Vitamin riboflavin

Question 7

Deficiency of riboflavin:

Answer 7

Lesions of mucous membranes

Question 8

Where does citric acid cycle take place?

Answer 8

Mitochondrial MATRIX

Question 9

How is pyruvate broken down to form C2?

Answer 9

Pyruvate broken down into Acetyl CoA by pyruvate dehydrogenase

NAD+ is converted to NADH and CO2 is released

Acetyl CoA is broken down into Acyl unit (2 carbon)

Question 10

What is CoA?

Answer 10

Nucleotide

Contains vitamin B5

Question 11

What must happen first in the cycle in regards to acyl group (C2)?

Answer 11

Condensation with oxaloacetate (C4)

Citrate is formed (C6)

Question 12

What then happens to citrate in cycle?

Answer 12

Dehydrogenation

NADH and CO2 formed

C5 formed

Question 13

What must happen to C5 in cycle?

Answer 13

Dehydrogenation

NADH and CO2 formed

CoA is needed to form C4

Question 14

What then happens to C4?

Answer 14

1. GTP formed and CoA is released
2. FADH2 is formed
3. NADH is formed
4. Oxaloacetate is formed - cycle starts again

Question 15

Where does oxidative phosphorylation take place?

Answer 15

Macromolecular assemblies in inner mitochondrial membrane

Question 16

What essentially is oxidative phophorylation?

Answer 16

H+ and electrons are taken from fuel molecules by NAD+

They are passed down chain of electron-carrying molecules until passed to oxygen

Question 17

Respiratory chain:

Answer 17

Electron transport chain

Question 18

How many complexes in Respiratory chain?

Answer 18

4 large complexes linked by electron shuttles

Question 19

What feeds electrons into respiratory chain?

Answer 19

NADH and FADH2

Question 20

What’s complex 1 in respiratory chain?

Answer 20

NADH-Q reductase

Question 21

Where does complex 1 send electrons?

Answer 21

To Q which then sends electrons to complex 3

Question 22

What’s complex 2 in respiratory chain?

Answer 22

FADH2 in flavoproteins

Question 23

Where do electrons from FADH2 go to?

Answer 23

To Q which then sends electrons to complex 3

Question 24

What’s complex 3?

Answer 24

Cytochrome reductase

Question 25

Where do electrons from complex 3 go to?

Answer 25

To Cyt C and then passed onto complex 4

Question 26

What’s complex 4?

Answer 26

Cytochrome oxidase

Question 27

Where do electrons on complex 4 go to?

Answer 27

Combine with oxygen

Question 28

What does Q stand for?

Answer 28

Ubiquinone

Question 29

Respiratory chain order:

Answer 29

NADH —> NADH-Q reductase —> Q —> Cytochrome reductase FADH2 —> Cytochrome Cytochrome Reductase —> Cyt c —> oxidase ——-> O2

Question 30

Inhibitors of respiratory chain:

Answer 30

Rotenone - insecticide Antimycin A - Antibiotic Carbon monoxide and cyanide

Question 31

What’s important about electrons being passed from one complex to another in the chain?

Answer 31

Energy is released and used more efficiently

Question 32

What does the respiratory chain generate?

Answer 32

H+ ion (pH) gradient across inner mitochondrial membrane due to movement of electrons

Question 33

What’s the electrochemical gradient across inner mitochondrial membrane used for?

Answer 33

To drive ATP synthesis by ATP synthase

Question 34

How is ATP synthase different to sodium-potassium ATPase pump?

Answer 34

Work in opposite directions Na/K pump uses ATP to generate ion gradient ATP synthase uses ion gradient to generate ATP

Question 35

How much ATP does oxidation of NADH produce?

Answer 35

2.5

Question 36

How much ATP does oxidation of FADH2 produce?

Answer 36

1.5

Question 37

Overall net yield from citric acid cycle:

Answer 37

4 ATP 2 NADH - cytoplasm (breakdown of pyruvate) 8 NADH - mitochondria 2 FADH2 Note: cycle happens twice per glucose

Question 38

Overall net yield from glycolysis:

Answer 38

2 ATP | 2 NADH

Question 39

Overall yield of ATP from breakdown of glucose?

Answer 39

32 ``` 4 ATP 25 ATP (from 10 NADH x 2.5) 3 ATP (from 2 FADH2 x 1.5) ```