Nucleotides Metabolism

Question 1

The two forms of Carbamoyl Phosphate synthetase

Answer 1

CPS 1

CPS 2

Question 2

Differentiate carbamoyl phosphate synthetase 1 and 2

Answer 2

CPS1 - located in mitochondria only in liver

     - uses ammonia as nitrogen source 
     - regulated by N-acetylglutamate
     - involved in urea cycle and synthesis of arginine

CPS2 - located in cytosol in all tissues

      - uses glutamine as nitrogen source
     - regulated by UMP (UDP, UTP, dUTP, CTP) 
     - involved in synthesis of pyrimidines

Question 3

What happens when ureal cycle is blocked?

Answer 3

Carbamoyl phosphate accumulates and spills over into cytosol. Triggers synthesis of pyrimidines = breakdown = buildup of orotic acid = orotic aciduria

Question 4

Excess uric acid precipitates into

Answer 4

Monosodium urate (MSU) and Calcium Pyrophosphate Dihydrate (CPPD) crystals

Question 5

Which substance accumulates in soft tissues in tophi?

Answer 5

Sodium urate

Question 6

Normal urate levels

Answer 6

3-7 mg/dL

Question 7

Probenecid blocks what transport proteins and in which part of the kidney are they found?

Answer 7

URAT (urate) transporters in the proximal tubules of the kidneys

Question 8

Allopurinol is oxidized into

Answer 8

alloxanthine

Question 9

Allopurinol is a structural analog of

Answer 9

hypoxanthine

Question 10

Major cause of severe combined immunodeficiency syndrome and its inheritance pattern

Answer 10

Mutation of gamma chain of T lymphocytes and interleukin-2 receptors
X-linked recessive