Amino acid metabolism

Question 1

What can’t happen when there is excess amino acids?

Answer 1

• They can’t be stores
• They aren’t secreted

Question 2

What happens when there are excess amino acids in the body?

Tell me the amount in g/day that are used?

Answer 2

Question 3

Whats the final destination for the AA in pool?

Answer 3

• protein synthesis
• direct use/ minor modification
• Breakdown and redeployment

Question 4

AA can be used as neurotransmitters. Name some neurotransmitters

Answer 4

• glutamate
• aspartate
• glycine

Question 5

What neurotransmitters are the following AA turned into?

• Glutamate
• Tyrosine
• Tryptophan
• Arginine

Answer 5

• glutamate –> GABA
• Tyrosine –> Dopamine, noradrenaline, adrenaline
• Tryptophan –> Serotonin
• Arginine –> NO

Question 6

What hormones do the following AA produce

• Tyrosine
• Tryptophan

Answer 6

Tyrosine –> Thyroxine

Tryptophan –> melatonin

Question 7

Draw the process of how a carbon skeleton is formed from an amino acid?

What can the carbon skeleton be used for?

Answer 7

Question 8

Draw the reaction, including intermediates, of how most AA form urea?

What is the name of the processes?

Answer 8

• Transferring amino group from the AA onto something else like alpha-ketoglutarate to then form glutamate
• Kidney then converts ammonia –> urea
• Can reuse alpha ketoglutarate

Question 9

Draw the overall process of transamination and the enzyme used?

Answer 9

Question 10

Is there energy use in the process of transamination?

Answer 10

No

Question 11

What does it mean if the enzyme AST is present in the blood?

Answer 11

Then it indicates liver damage

Question 12

What does aminotransferase use to do the amino group transfer

Answer 12

Aminotransferases use a Vit B6-derived prosthetic group called Pyridoxal phosphate (PLP) to do the amino group transfer

• ping-pong mechanism where the substrates don’t meet
• Reaction can go in either direction

Question 13

How are amino groups funnelled into Glu removed?

Answer 13

deamination

Question 14

Whats the process of deamination?

Answer 14

Question 15

Whats the process of urea synthesis ?

Answer 15

Question 16

Draw the urea cycle and the structures

Answer 16

Question 17

Draw the overall formation of urea and the overall energy cost

Answer 17

Question 18

What do extrahepatic tissues do?

Give an example

Answer 18

Catabolise AA to NH3, but can’t make urea

e.g. BCAA (branch chain AA) catabolism for energy in muscles

Question 19

Complete the following reactions

• alpha-KG + NH3 –>
• Glu + NH3 –>

Answer 19

• Alpha-KG + NH3 –> Glu
• Glu + NH3 –> Gln (export of 2 amino into the blood)

Question 20

In the kidney, what can Gln be deaminated back to

Answer 20

Glu to release NH3 into the urine for acid neutralisation

Question 21

What can carbon skeletons all end up as according to the starting amino acid ?

Answer 21

Question 22

How is sulphur disposed of?

Answer 22

Question 23

What are the transamination reactions for Cys and Cysteinesulphnate?

How is SO2 and H2S removed?

Answer 23

Question 24

What does synthesising de novo mean?

Answer 24

De novo synthesis refers to the synthesis of complex molecules from simple molecules such as sugars or amino acids, as opposed to recycling after partial degradation

Question 25

list the amino acids that can’t be synthesised de novo?

Answer 25

FHIKLMTVW

Question 26

How can other AA be made?

Answer 26

From essential AA

TCA cycle

Question 27

Can purines and pyrimidines be synthesised de novo?

Answer 27

yes

Question 28

What does catabolism produce?

Answer 28

Toxic ammonia and a carbon skeleton

Question 29

What is ammonia converted to?

Answer 29

urea and excreted

Question 30

What processes are carbon skeletons used in?

Answer 30

other synthetic pathways or via pyruvate and TCA cycle for ATP production