Amino Acids

Question 1

Where does AA degradation & catabolism occur?

Answer 1

The hepatocytes of the liver

Question 2

Any AA not required as a building block for protein synthesis must undergo….

Answer 2

Degradation

Question 3

AA are catabolised for?

Answer 3

For energy release (by ultimately entering Krebs) & excretion (as NH3 - ammonia) into urea cycle

Question 4

What are the 2 main catabolism processes?

Answer 4

Transamination

Oxidative deamination

Question 5

What is transamination?

What happens in it?

Answer 5

Alpha ketoglutarate readily accepts an amine group from alanine
Forms glutamate + pyruvate

Question 6

What is the pyruvate used in?

Answer 6

Gluconeogenesis
Aerobic resp (produced In glycolysis)

Question 7

What is the enzyme used in transamination?

Answer 7

Alanine aminotransferase

Question 8

Equation for transamination?

Answer 8

Alpha ketoglutarate + alanine —(ALT)—-> glutamate + pyruvate

Question 9

What happens in oxidative deamination?

Answer 9

Glutamate hydrolysed to reform alpha ketoglutarate + NH3 (a way of removing ammonia from body)
Toxic NH3 removed to enter urea cycle

Question 10

What coenzyme is involved in oxidative deamination?

Answer 10

NAD+ (forwards reaction)

NADH (backwards reaction)

Question 11

Which enzyme is used in oxidative deamination?

Answer 11

Glutamate dehydrogenase

Question 12

What is the equation for oxidative deamination?

Answer 12

Glutamate + H2O—(glutamate dehydrogenase)—> alpha ketoglutarate + NH3

Question 13

What is the most abundant amino acid?

Answer 13

Glutamate

Question 14

These reactions are ….

Answer 14

Reversible

Question 15

What is nitrogen balance?

Answer 15

N in/N out, heavily dependent on AA/protein intake

Question 16

What is a negative nitrogen balance and what is it caused by?

Answer 16

Catabolic

Nin

Question 17

What is a positive nitrogen balance and what is it caused by?

Answer 17

Anabolic
Nin>Nout
Caused by pregnancy

Question 18

Urea cycle

All enzymes involved are found where?

Answer 18

In the liver in either the mitochondria or cytosol of hepatocytes

Question 19

What is the acronym to remember the urea cycle?

Answer 19

Cit arg orn

Question 20

What happens in the urea cycle?

Answer 20

Citrulline binds with NH3 to form arginine

Arginine is cleaved by arginase generating urea and ornithine

Ornithine binds with NH3 and CO2 to regenerate citrulline

Question 21

What is the only product of the urea cycle?

Answer 21

Urea

Question 22

One turn of the cycle consumes?

Answer 22

3 ATP equivalents

4 high energy nucleotides (PO4-)

Question 23

Deficiencies of any of the enzymes involved is associated with …….
Absence of any of them is …..

Answer 23

Higher levels of ammonia in the blood

Not compatible with life

Question 24

NH3 Is ….

Answer 24

Neurotoxic

Question 25

Why are high levels of ammonia neurotoxic?

Answer 25

Ammonia can cross the blood brain barrier very easily
Once inside it is converted to glutamate under the action of the glutamate dehydrogenase enzyme
Leads to depletion in alpha ketoglutarate
Falls so does oxaloacetate resulting in the Krebs cycle stopping
Impairs aerobic resp
Results in irreparable cell damage & neural cell death