Protein And Amino Acid Metabolism

Question 1

Ketogenic amino acids

Answer 1

Lysine

Leucine

Question 2

Glucogenic amino acids

Answer 2

Alanine

Cysteine

Question 3

Ketogenic and glucogenic amino acids

Answer 3

Tryptophan

Threonine

Question 4

Catabolism of amino acid

Answer 4

1. Removal of amino group
2. Amino group converted to urea and excreted in urine
3. C skeleton converted to intermediates

Question 5

9 Essential amino acids

Answer 5

Phenylanine
Valine
Threonine

Tryptophan
Isoleucine
Methionine

Histidine
Lysine
Leucine

Question 6

Where does deamination take place

Answer 6

Liver and kidney

Question 7

Tyrosine derived compounds

Answer 7

Catecholamines - noradrenaline and adrenaline

Melanin

Thyroid hormones

Question 8

Cysteine derived compounds

Answer 8

Hydrogen sulphide - signalling molecule

Glutathione

Question 9

Tryptophan derived compounds

Answer 9

Nicotinamide
Melatonin
Serotonin

Question 10

Histidine driver compounds

Answer 10

Histamine

Question 11

Glutamate derived compounds

Answer 11

GABA

Question 12

Arginine derived compounds

Answer 12

Nitric oxide

Question 13

Serine derived compounds

Answer 13

Sphingosine

Question 14

Glycine

Answer 14

Purines
Glutathione
Haem
Creatine

Question 15

Liver function test

Answer 15

ALT - alanine aminotransferase
AST - aspartate aminotransferase

Alanine + alpha ketoglutarate —> glutamate + Pyruvate

Glutamate + oxaloacetate —> aspartate + alpha ketogluterate

Question 16

Deamination

Answer 16

Liberate amine group as free ammonia NH3

at physical pH NH4+

Question 17

Deamination enzymes

Answer 17

Amino acid oxidases
Glutaminase
Glutamate dehydrogenase

Question 18

Urea CO(NH2)2

Answer 18

High nitrogen content 
Inert (non toxic) 
Ammonia converted to urea 
Excreted In urine via kidney 
Osmotic role

Question 19

Urea cycle

Answer 19

Occurs in liver - half - cytosol and half mitochondria

Aspartate and glutamate feed into urea cycle easily

Question 20

Urea cycle defects

Answer 20

Effects: hyperammonaemia
Accumulation of urea cycle intermediates

Symptoms:
Vomiting 
Lethargy
Mental retardation 
Seizures 
Coma 

Management: low protein diet
Replace amino acids with ketoacids

Question 21

Glutamine synthase

Answer 21

Ammonia + glutamate —> glutamine + H3PO4+

Glutamine transported to live and kidney

Question 22

Glutaminase

Answer 22

Glutamine —> glutamate + ammonia

Question 23

Glutamate dehydrogenase

Answer 23

Glutamate —> alpha ketoglutarate + ammonia

Question 24

Heel prick test

Answer 24

Sickle cell anaemia
Cystic fibrosis
Congenital hypothyroidism

Question 25

Inborn errors of amino acid metabolism

Answer 25

Phenylketonuria 
Maple syrup urine disease 
Glutamic aciduria 
Homocystinuria 
Isovaleric acidaemia

Question 26

PKU

Answer 26

Deficiency in phenylalanine hydroxylase

Symptoms: 
severe intellectual disability 
Developmental delay 
Microcephaly 
Seizures 
Hypopigmentation 

Treatment: 
low phenylalanine diet 
Enriched tyrosine diet 
Avoid artificial sweeteners 
Avoid protein rich diet

Question 27

Homocystinuria

Answer 27

Defect in methionine breakdown
Excess homocystine excrete in urine

Defect in cystathione beta synthase (most common)

Treatment:

Low methionine diet
Avoid milk, meat, eggs, cheese , fish , nuts

Give cysteine, vitamin B6, betaken, B12 and folate