Protein Metabolism

Question 1

What are major nitrogen containing compounds?

Answer 1

Amino acids
Proteins
Purines + Pyrimidines
Creatine phosphate

Question 2

What is creatinine?

Answer 2

Breakdown product of creatine and creatine phosphate

Question 3

What creatinine be used for?

Answer 3

Provides estimate of muscle mass

Indicator of renal function

Question 4

What is the normal state of nitrogen balance?

Answer 4

Nitrogen equilibrium - intake = output

Question 5

What can cause positive N balance?

Answer 5

Intake > output

Growth
Pregnancy

Question 6

What can cause negative N balance?

Answer 6

Intake < output

Trauma
Infection
Malnutrition

Question 7

What are the types of amino acid?

Answer 7

Glucogenic

Ketogenic

Question 8

What happens to glucogenic amino acids?

Answer 8

Used in gluconeogenesis

Question 9

What happens to ketogenic amino acids?

Answer 9

Used to make ketone bodies

Question 10

What can cause an increase in protein synthesis?

Answer 10

Insulin

Growth hormone

Question 11

What can cause an increase in protein degradation?

Answer 11

Glucocorticoids

Question 12

What is the structure of amino acids?

Answer 12

Amino group - CH (R) - carboxyl group

Variable R group

Question 13

How is nitrogen removed from amino acids?

Answer 13

Transamination

Deamination

Question 14

What happens in transamination?

Answer 14

Amino acid 1 + keto acid 2 amino acid 2 + keto acid 1

Use an aminotransferase

Question 15

What keto/amino acid do most aminotransferases use?

Answer 15

α-ketoglutarate -> glutamate

Question 16

What keto/amino acid does aspartate aminotransferase use?

Answer 16

Oxaloacetate -> aspartate

Question 17

Where is the coenzyme for aminotransferases derived from?

Answer 17

Vitamin B6

Question 18

What are the key aminotransferases?

Answer 18

Alanine aminotransferase (ALT)
Aspartate aminotransferase (AST)

Question 19

What does ALT convert?

Answer 19

Alanine to glutamate

Question 20

What does AST convert?

Answer 20

Glutamate to aspartate

Question 21

What happens in deamination?

Answer 21

Liberates amino group as a free ammonia

Question 22

Where does deamination occur?

Answer 22

Liver

Kidney

Question 23

How is ammonia excreted?

Answer 23

Converted to urea and excreted in urine

Question 24

What is the process of producing urea called?

Answer 24

Urea cycle

Question 25

Where does the urea cycle take place?

Answer 25

Liver

Question 26

What are the symptoms of ammonia toxicity?

Answer 26

Vomiting Lethargy Irritability Mental retardation

Question 27

How is ammonia transported?

Answer 27

Combines with glutamate to form glutamine - broken down again by glutaminase Liver - ammonia enters urea cycle Kidney - ammonia excreted in urine

Question 28

How are amine groups transported?

Answer 28

Transferred to glutamate by transamination Pyruvate transaminated by glutamate to form alanine Alanine transported in blood to liver Alanine converted back to pyruvate Amino group fed into urea cycle

Question 29

What is phenylketonuria(PKU)?

Answer 29

Deficiency of phenylalanine hydroxylase

Question 30

What is the inheritance pattern of PKU?

Answer 30

Autosomal recessive

Question 31

What happens in PKU?

Answer 31

Accumulation of phenylalanine in tissue, plasma and urine Phenylketones in urine

Question 32

How is PKU managed?

Answer 32

Low phenylalanine diet | Diet enriched with tyrosine

Question 33

What are the homocysteinurias?

Answer 33

Problems breaking down methionine Most common = defect in cystathionine B-synthase