1.13 Detoxification of ammonia

Question 1

Sources of urea in the body

Answer 1

• Oxidative deamination
• Biogenic amine degradation
• Absorption from GI tract

Question 2

Why is urea dangerous?

Answer 2

It can cross the blood-brain barrier → CNS affected

Question 3

How does urea alter the TCA cycle?

Answer 3

It removes α-ketoglutarate from the TCA cycle → Ø Energy produced

Question 4

Give the reaction producing Carbamoyl phosphate

Answer 4

Question 5

Give the steps of the urea cycle

Answer 5

1. Ornithine
2. Citrulline
3. Argininosuccinate
4. Arginine
5. Ornithine + 1 Urea

Question 6

Give the pathway of Ornithine → Argininosuccinate

Answer 6

Question 7

Give the pathway of Argininosuccinate → Ornithine + Urea

Answer 7

Question 8

Give the pathway showing the fate of fumarate

Answer 8

Question 9

The urea cycle can eliminate …NH₃ per cycle

Answer 9

2

Question 10

Location of the urea cycle

Answer 10

Liver (Cytoplasm + Mitochondria)

Question 11

Give the energy balance of the urea cycle

Answer 11

Question 12

Give the regulation of the urea cycle

Answer 12

Question 13

Draw the urea cycle in ruminants

Answer 13

Question 14

List the alternative urea detoxification pathways

Answer 14

1. Glutamine synthesis
2. Asparagine synthesis
3. L-glutamate synthesis
4. Purine synthesis

Question 15

Draw the glutamine synthesis pathway

Answer 15

Question 16

Draw asparagine synthesis

Answer 16

Question 17

Draw L-glutamate synthesis

Answer 17