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Biochemistry - 3 Questions
Which enzyme converts homocysteine to cystathionine? 1). Methionine synthase 2). Cystathionine ?-synthase 3). Homocysteine oxidase 4). Cysteine dioxygenase
Cystathionine ?-synthase requires vitamin B6 and converts homocysteine to cystathionine. Deficiency leads to homocystinuria.
Which amino acid serves as the precursor of niacin?1). Glycine2). Tyrosine3). Tryptophan4). Histidine
About 60 mg tryptophan produces 1 mg niacin.
Function of PTH?1. decreases plasma phosphate concentration (PTH:? serum Ca², serum PO)2. increases calcium absorption of bones3. decreases calcium reabsorption in kidneys4. none
Parathyroid hormone (PTH) acts on the kidneys to increase calcium reabsorption and decrease phosphate reabsorption, which lowers plasma phosphate concentration.
MCQ