Protein/AA Metabolism

Question 1

What are ketogenic amino acids?

Name some

Answer 1

Amino acids that can be used to produce acetyl CoA
Leucine
Lysine

Question 2

Name some amino acids which are both gluco and ketogenic

Answer 2

PITTT mnemonic 
Phenylalanine
Isoleucine
Threonine
Tyrosine
Tryptophan

Question 3

What are glucogenic amino acids? Name some

Answer 3

Amino acids that can be converted to produce glucose (and other TCA cycle intermediates)
Glycine
Alanine
Valine
Serine
Glutamate

Question 4

Name some places where we have nitrogen in our bodies

Answer 4

Proteins
DNA/RNA nucleotides
Creatine
Some hormones/neurotransmitters

Question 5

What are the essential amino acids

Answer 5

Isoleucine (if), Lysine (learned), Threonine (this), Histidine (huge), Leucine (list), Methionine (may), Phenylalanine (prove), Tryptophan (truly), Valine (useful)

Question 6

What is the eventual final product(s) of amino acid metabolism? amino group and carbon skeleton.

Answer 6

Ammonia 
Urea
Glutamine 
Carbon skeleton-
 Used to produce other amino acids (keto and glucogenic)

Question 7

Why is tyrosine important?

Answer 7

Used to make

• thyroglobulin TF thyroid hormones
• melanin
• catecholamines (nor/adrenaline)

Question 8

What is tyrosine synthesised from? TF how could a deficiency in tyrosine come about?

Answer 8

Phenylalanine
In Phenylketonuria (PKU) they need to remove phenylalanine from their diet TF may not have enough to produce tyrosine

Question 9

How could PKU lead to hypothyroidism?

Answer 9

PKU requires removal of phenylalanine from the diet
Phenylalanine (PA) is needed to synthesise tyrosine
TF lack of PA would result in lack of tyrosine
Tyrosine is needed to synthesise thyroid hormones
TF lack of tyrosine- hypothyroidism

Question 10

Why do we remove the amino group in the metabolism of amino acids?

Answer 10

To release the carbon skeleton to allow it to be used for synthesis/production of other amino acids

Question 11

Why is Cysteine important?

Answer 11

Used to make-

• glutathione
• hydrogen sulphide

Question 12

Why is tryptophan important?

Answer 12

Used to make-
Serotonin
Melatonin

Question 13

What two ways are used to remove nitrogen? Describe briefly

Answer 13

Transamination- transfer amino group to a keto acid

Deamination- liberated as free ammonia

Question 14

What keto acid is most commonly used in transamination?

Answer 14

α-ketoglutarate

Question 15

Which keto acid is used as an exception/less often in transamination?

Answer 15

Oxaloacetate

Question 16

Which enzyme is used in the most common transamination? Name enzyme and amino acids

Answer 16

Alanine amino transferase

Alanine–> glutamate

Question 17

Alongside glutamate, which keto acid is produced in a transamination reaction?

Answer 17

Pyruvate

Question 18

Write the reaction for the most common form of transamination.

Answer 18

Alanine + α-ketoglutarate–> pyruvate + glutamate

Question 19

In the less common/exception transamination, what enzyme is used?

Answer 19

Aspartate aminotransferase

Question 20

Write the equation for the less common/exception transamination

Answer 20

Glutamate + oxaloacetate–> keto acid + aspartate

Question 21

When using aspartate aminotransferase (AST), which amino acid is used and produced?

Answer 21

Glutamate

Aspartate

Question 22

What enzymes are tested for in a liver function test?

What can their abnormal reading show?

Answer 22

AST- aspartate aminotransferase
ALT- alanine aminotransferase
Raised levels–> viral hepatitis
autoimmune liver disease
toxic injury

Question 23

What do ALT and AST stand for?

Answer 23

Alanine and aspartate aminotransferase

Question 24

Instead of an NH2 group, what is present on a keto acid?

Answer 24

=O

Question 25

Other names for ALT and AST?

Answer 25

Glutamate pyruvate transaminase

Glutamate oxaloacetate transaminase

Question 26

Why are high levels of ammonia toxic?

Answer 26

CNS is very sensitive to high levels
Affects glutamate dehydrogenase
Less production of α-ketoglutarate 
TF TCA cycle slows 
TF less energy

Question 27

What happens in deamination?

List some enzymes that do it

Answer 27

Liberates NH2 as free ammonia
Glutaminase
Glutamate dehydrogenase
Amino acid oxidases

Question 28

What equation does the Glutaminase enzyme catalyse?

Answer 28

Glutamine–> glutamate + NH3

Question 29

What is the substrate and product for the reaction catalysed by Glutamate dehydrogenase?

Answer 29

Glutamate- substrate

α-ketoglutarate- product

Question 30

What is the equation that occurs naturally with ammonia in (p)pH?

Answer 30

NH3 + H2O–> NH4+ + OH-

Question 31

What three ways are ammonia removed from the body?

Answer 31

Directly in the urine
Combines with Glutamine to form Glutamate
Converted to urea

Question 32

Properties of urea (3)

Where do the NH2 groups in urea come from?

Answer 32

Water soluble
Non-toxic
Chemically inert
Ammonia
Aspartate

Question 33

What is refeeding syndrome?

Answer 33

The urea cycle involves 5 enzyme
Their activity is inducible and controlled by protein levels
Low protein lowers their number
TF after prolonged starvation, numbers decrease
TF when they reintroduce protein they don’t have enough enzymes to cope TF build up of ammonia

Question 34

Why do you need to reintroduce food to starving patients slowly?

Answer 34

To allow time for their enzyme levels to rise

Question 35

Which form of proteins are found in nature?

Answer 35

L-form (IE left hand form, the other is D)