Chapter 19

Where is glycolysis done in the cell? Citric acid cycle?

Cytosol

Mitochondria: most done in matrix

Describe precursor step in citric acid cycle:

1. reactants/products

2. enzyme

3. redox reaction? reduced/oxidized

4. What was released?

5. Control step?

1. Pyruvate + NAD+ + CoA-SH → Acetyl-CoA

2. pyruvate dehydrogenase

3. NAD is reduced to NADH. Pyruvate is oxidized to acetyl-CoA

4. 1 NADH and 1 CO2 (each molecule)

5. control

Describe step 1: formation of citrate

1. reactants/products

2. enzyme

3. redox reaction? reduced/oxidized

4. What was released?

5. Control step?

1. Oxaloacetate + acetyl CoA → citrate + CoA-SH

2. citrate synthase

3. N/A

4. N/A

5. Control

Describe step 2: isomerization of citrate

1. reactants/products

2. enzyme

3. redox reaction? reduced/oxidized

4. What was released?

5. Control step?

1. citrate → isocitrate

2. aconitase

3. N/A

4. N/A

5. Not control

Describe step 3: formation of α-ketoglutarate and CO2 - First Oxidation

1. reactants/products

2. enzyme

3. redox reaction? reduced/oxidized

4. What was released?

5. Control step?

1. isocitrate → α-ketoglutarate + CO2

2. isocitrate degydrogenase

3. NAD is reduced to NADH. Isocitrate is oxidized to α-ketogluterate

4. 1 NADH and 1 CO2 (each molecule)

5. Control

Describe step 4: formation of succinyl CoA and CO2

1. reactants/products

2. enzyme

3. redox reaction? reduced/oxidized

4. What was released?

5. Control step?

1. α-ketogluterate + CoA-SH + NAD+ → succinyl-CoA

2. α-ketogluterate dehydrogenase complex

3. NAD is reduced to NADH. α-ketogluterate is oxidized to succinyl-CoA *uses redox energy to attach CoA

4. 1 CO2 (each molecule)

5. Control

Describe step 5: formation of succinate

1. reactants/products

2. enzyme

3. redox reaction? reduced/oxidized

4. What was released?

5. Control step?

1. succinyl CoA → succinate

2. succinyl CoA synthetase

3. N/A

4. CoA and 1 GTP (each molecule)

5. not control

Describe step 6: formation of fumerate

1. reactants/products

2. enzyme

3. redox reaction? reduced/oxidized

4. What was released?

5. Control step?

1. succinate → fumarate

2. succinate dehydrogenase * takes place in inner mitochondria membrane

3. FAD is reduced to FADH2. Succinate is oxidized to fumerate

4. 1 FADH2 (each molecule)

5. not control

Describe step 7: formation of L-malate

1. reactants/products

2. enzyme

3. redox reaction? reduced/oxidized

4. What was released?

5. Control step?

1. fumerate + H2O → L-malate

2. fumerase

3. N/A

4. N/A

5. not control

Describe step 8: regeneration of oxaloacetate

1. reactants/products

2. enzyme

3. redox reaction? reduced/oxidized

4. What was released?

5. Control step?

1. L-malate + NAD+ → oxaloacetate + NADH

2. malate dehydrogenase

3. NAD is reduced to NADH. Malate is oxidized to oxaloacetate

4. 1 NADH (each molecule)

5. not control

What are the control steps in citric acid cycle?

• precursor

• 1

• 3

• 4

What citric acid cycle steps release CO2?

• precursor, 3, 4

Calculate the amount of ATP in the citric acid cycle

Which steps of the citric acid cycle are redox reactions?

steps 3, 4, 6, 8

Which steps of the citric acid cycle produce NADH?

steps 3, 4, 8

Which steps of the citric acid cycle produce FADH2?

step 6

Which steps of the citric acid cycle produce GTP?

step 5

If fructose 6 phosphate is fed into glycolysis, how much energy would be producted under aerobic conditions?

33 ATP

How does ATP affect citric acid cycle?

increased levels of ATP turn off control steps: precursor, 1, 3, 4

How does NADH affect citric acid cycle?

increased levels of NADH turn off control steps

What are the negative and positive allosteric receptiors

Negative:ATP, NADH

Positive: ADP + NAD+

What is the ATP/ADP and NADH/NAD+ ratio for cells in a resting state? *EXAM

High ATP, low ATP = ATP ratio is high

High NADH, low NAD+ = NADH ratio is high

What is the ATP/ADP and NADH/NAD+ ratio for cells in an active state? *EXAM

Low ATP, high ATP = ATP ratio is low

Low NADH, high NAD+ = NADH ratio is low

Glyoxylate cycle

• Where it occurs

• Main purpose

• plant and bacteria

• gains carbohydrate from acetyl CoA

If valine is fed into the citric acid cycle as succinyl CoA, how much ATP would be made?

5 ATP

Describe oxaloacetate (beginning reactant for citric acid cycle)

only comes from carbohydrates for animals

• uses enzyme pyruvate carboxylase and CO2 to make oxaloacetate

acetyl CoA gets oxaloacetate in plants and bacteria

Oxaloacetate is apart of which step(s) of the citric acid cycle?

step 1 and 8

Which control enzyme is responsible for activating pyruvate dehydrogenase?

pyruvate dehydrogenase phosphatase

What are the control enzymes of the citric acid cycle?

citrate synthase

isocitrate dehydrogenase

α- keglutarate dehydrogenase

For the control enzymes, which of the following are allosteric inhibitors?

NADH and ATP

When glutamine is degraded it enters the citric acid cycle as the product of step 3, how much ATP would result from glutamate?

7.5 ATP