27. Energy II: Acetyl CoA, Mitochondria, Oxygen

Question 1

Describe aerobic respiration? (4pts)

Answer 1

1. Occurs only in the presence of oxygen
2. Yields more ATP
3. Takes place in the mitochondria
4. Requires the TCA cycle and oxidative phosphorylation.

Question 2

Explain the steps in the TCA cycle? (4pts)

Answer 2

1. Glucose (6C) is converted to 2 molecules of Pyruvate (3C)
2. Pyruvate is then metabolised to Acetyl coA.
3. Acetyl CoA combines with Oxaloacetate (4C) to form the 6 Carbon Citrate.
4. The 6 Carbon molecule then undergoes a series of reactions which lead back to the formation of Oxalocetate.

For each glucose:

1. 6NADH produced
2. 2 FADH2 produced
3. 2 GTP produced
4. 4 C02 produced

Question 3

Describe the TCA cycle? (2pts)

Answer 3

1. Takes place in the mitochondrial matrix

2. TCA cycle is the source of building blocks for most important bio-molecules.

Question 4

Describe the conversion of Pryuvate to Acetyl CoA?

Answer 4

Pyruvate (3 Carbon compound) is converted to Acetyl CoA (2 Carbon compound) and C02 via the enzyme pyruvate dehydrogenase.

Question 5

Describe Pryuvate dehydrogenase phosphate? (3pts)

Answer 5

1. In the muscle pyruvate dehydrogenase phosphate is stimulated by calcium ions.
2. In liver adrenaline increases calcium ions through the activation of adregenic receptors and IP3.
3. In liver and adipose tissue insulin stimulates the phosphatase which funnels glucose to fatty acid synthesis.

Question 5

Describe Pryuvate dehydrogenase phosphate? (3pts)

Answer 5

1. In the muscle pyruvate dehydrogenase phosphate is stimulated by calcium ions.
2. In liver adrenaline increases calcium ions through the activation of adregenic receptors and IP3.
3. In liver and adipose tissue insulin stimulates the phosphatase which funnels glucose to fatty acid synthesis.

Question 6

Name the regulators of the TCA cycle? (4pts)

Answer 6

1. Pyruvate dehydrogenase
2. Citrate synthase
3. Isocitrate dehydrogenase
4. a-Keto glutarate dehydrogenase

Question 7

Describe Pyruvate dehydrogenase? (2pts)

Answer 7

1. inhibited by NADH, ATP, acetyle CoA

2. Stimulated by ADP and pyruvate

Question 8

Describe Citrate synthase?

Answer 8

negatively regulated by its product citrate

Question 9

Describe Isocitrate dehydrogenase? (2pts)

Answer 9

1. Inhibited by ATP and NADH

2. Simulated by ADP

Question 10

Describe a-keto glutarate dehydorgenase?

Answer 10

1. inhibited by NADH, ATP and Succinyl COA

Question 11

What happens when ADP use is increased?

Answer 11

When ADP use is increased the levels of ATP increases which stimulates the cycle.

Question 12

Describe Beriberi? (5pts)

Answer 12

1. Vitamin b1 deficiency (deficiency in thiamine)
2. Common when rice is a staple
3. Characterised by cardiac and neurological symptoms
4. Thiamine is a prosthetic group for pryuvtae and -ketoglutarate dehydorgenase.
5. Neurological problems are common as glucose is the primary source of energy.

Question 13

Describe the electron transport chain? (4pts)

Answer 13

1. FADH and NADH produced by the TSA cycle donate hydrogen atoms which are split into a electron and a proton.
2. The electrons pass through a series of enzymes called cytochromes in the electron transport chain.
3. As electrons pass down the electron transport chain protons are pumped from the matrix to the inter mitochondrial space which forms a proton gradient.
4. The gradient is dissipated by the passage of protons through ATP synthase.
5. ATP synthase is a molecular engine and as the protons pass through the molecules ATP is formed.

• this process relies on the fact that the inner mitochondrial membrane is very impermeable.

Question 14

What is white fat?

Answer 14

Fat majority filled with lipids

Question 15

What is brown fat? (2pts)

Answer 15

1. Has a large number of mitochondria present. This gives it a brown colour.
2. Infants have brown fat on their neck and shoulders and this is used to generate heat as they have not yet developed the shivering reflex.

Question 16

Describe the difference between a normal mitochondria and a mitochondria of brown fat?

Answer 16

A normal mitochondria has an impermeable inner mitochondrial membrane. The gradient is formed which is then dissipated and it forms ATP. Brown fat on the other hand expressed an uncoupling protein which diverts the flow of protons away from the generation of ATP and generates heat.

Question 17

Describe the OXPHOS diseases? (5pts)

Answer 17

1. Common degenerative diseases
2. Caused by mutations in genes encoding proteins of the electron transport chain
3. Symptoms include fatigue, epilepsy and dementia,
4. Dependant on the mutation, symptoms may be evident near birth or to early adulthood.
5. Metabolic consequences can be congenital lactic acidosis.