MDS PREP
Features of Vitamin C deficiency is due to defect of which enzyme
1. Lysyl hydroxylase
2. Lysyl oxidase
3. Procollagen peptidase
4. None of the above
Biochemistry
Answer: 1
Vitamin C deficiency is due to defect of Lysyl hydroxylase
The essential. sulphur containing amino acid is:
1. Methionine 2. Cystetne
3. Cystine 4. Valine
Biochemistry
Answer: 1
Methionine is sulphur containing AminoAcid
Glutamate-pyruvate trans-aminase is predominantly present In:
1. Skeletal muscle
2. Cardiac muscle
3. Brain
4. Liver
Biochemistry
Answer: 4
Glutamate-pyruvate trans-aminase is predominantly present In Liver
The principal role of Vitamin E in the prevention of oxidative damage is to
1. oxidize metals to their less reactive state.
2. potentiate the action of superoxide dismutase.
3. reduce Vitamin C to its active oxidation state.
4. terminate free radical chain reactions in lipid bilayers.
Biochemistry
Answer: 2
The principal role of Vitamin E in the prevention of oxidative damage is to potentiate the action of superoxide dismutase
The biochemical defect in Osteogenesis Imperfecta, type II is:
1. a mutation in the alpha 1 chain of Type I collagen.
2. a deficiency in collagenase.
3. a deficiency in lysyl oxidase.
4. a deficiency in lysyl hydroxylase.
Biochemistry
Answer: 4
The biochemical defect in Osteogenesis Imperfecta, type II is a deficiency in lysyl hydroxylase.
An enzyme increases the rate of a biochemical reaction by
1. decreasing substrate concentration.
2. decreasing activation energy.
3. increasing Km.
4. increasing Keq.
Biochemistry
Answer: 2
Enzymes are biological catalysts that increase the rate of chemical reactions
by lowering the activation energy required for the reaction to occur.
Hyperuricemia in Lesch-Nyhan syndrome is due to a defect in which of the following pathways?
1) Purine biosynthesis
2) Pyrimidine biosynthesis
3) Purine salvage
4) Pyrimidine salvage
Biochemistry Answer: 3
Uric acid is a purine derivative, increased by purine salvage reactions that convert purines, purine ribonucleosides, and purine deoxyribonucleoside to mononucleotides (incorrect answer 4).
Such salvage reactions require much less energy than de novo synthesis (incorrect answers 1, 2). The liver is the major site of purine nucleotide biosynthesis and provides excess purines for other tissues that cannot synthesize purines.
A defect in hypoxanthine-guanine phosphoribosyl transferase, one of the enzymes of purine salvage, is responsible for purine overproduction and subsequent hyperuricemia observed in Lesch-Nyhan syndrome.
After fasting for 24 hours, the major source of glucose for the whole body is
1. amino acids from muscle protein degradation.
2. ketone bodies from muscle triglycerides.
3. glycogen stored in the muscle.
4. creatine phosphate
Biochemistry Answer: 4
Creatine Phosphate is the major source of glucose for the whole body during starvation