Practice MCQS — Biochemistry

A 45-year-old woman with limited sun exposure presents with bone pain and muscle weakness. Laboratory findings reveal low serum calcium and phosphate levels. Which vitamin deficiency is most likely responsible for her condition?

• Vitamin A

• Vitamin C

• Vitamin D

• Vitamin K

A 60-year-old man complains of numbness and tingling in his extremities. His labs show macrocytic anemia. Which vitamin deficiency best explains his neurological symptoms?

• Vitamin B1 (Thiamine)

• Vitamin B6 (Pyridoxine)

• Vitamin B12 (Cobalamin)

• Folate

A patient on long-term antibiotic therapy presents with easy bruising and bleeding gums. Prothrombin time (PT) is prolonged. Which vitamin deficiency is most likely the cause?

• Vitamin C

• Vitamin E

• Vitamin K

• Vitamin D

A 25-year-old sailor develops bleeding gums, poor wound healing, and petechiae after several months at sea without fresh fruits. Which biochemical process is impaired due to this vitamin deficiency?

• Fat absorption

• Collagen synthesis

• Heme synthesis

• DNA repair

A chronic alcoholic presents with confusion, ataxia, and ophthalmoplegia. Deficiency of which vitamin is responsible for this clinical picture?

• Vitamin B1 (Thiamine)

• Vitamin B2 (Riboflavin)

• Vitamin B6 (Pyridoxine)

• Niacin

A marathon runner collapses after consuming excessive water during the race. Serum sodium is 122 mEq/L. Which of the following is the most likely physiological consequence of this condition?

• Cellular dehydration

• Cerebral edema

• Hypocalcemia

• Hypokalemia

A patient with chronic kidney disease presents with muscle weakness and ECG changes showing peaked T waves. Which electrolyte imbalance is responsible for these findings?

• Hyponatremia

• Hyperkalemia

• Hypokalemia

• Hypocalcemia

A post-thyroidectomy patient complains of tingling around the mouth and muscle spasms. Chvostek’s sign is positive. Which electrolyte imbalance explains her symptoms?

• Hypokalemia

• Hypocalcemia

• Hypernatremia

• Hypermagnesemia

A malnourished alcoholic patient presents with tremors, muscle weakness, and ventricular arrhythmias. Serum magnesium is low. Which physiological function is most affected by magnesium deficiency?

• Lipid digestion

• Neuromuscular excitability regulation

• Bone mineralization

• Bile acid synthesis

A patient with iron deficiency anemia is advised to take her supplements with orange juice. What is the role of vitamin C in this recommendation?

• Inhibits iron absorption

• Converts ferric iron to ferrous form

• Promotes iron excretion

• Neutralizes stomach acid