Dr. Hope

Vault of Medicine ♡|| Tutor || Mentor || MB;Bs in view

MBBS • Anatomy • Physiology • Pathology • Biochemistry • Pharmacology

[Dr. Hope @HopeNweke_1]

A researcher studies a cell that is unable to synthesise new DNA strands effectively. Which enzyme normally synthesises the new DNA strand by adding nucleotides to its growing end?

A. DNA polymerase
B. RNA polymerase
C. DNA ligase
D. Helicase

[Dr. Hope @HopeNweke_1]

A patient ingests a substance that inhibits cytochrome c oxidase, also known as Complex IV of the electron transport chain. Which process is directly inhibited?

A. Transfer of electrons to oxygen

B. Conversion of glucose to pyruvate

C. Conversion of glycogen to glucose-1-phosphate

D. Synthesis of fatty acids

[Dr. Hope @HopeNweke_1]

A newborn develops jaundice because of increased unconjugated bilirubin. Which organ normally conjugates bilirubin to increase its water solubility?

A. Kidney
B. Liver
C. Spleen
D. Pancreas

[Dr. Hope @HopeNweke_1]

A pregnant woman has a folate deficiency. Her developing fetus is at increased risk of neural tube defects. Folate is particularly important in which process?

A. One-carbon transfer reactions required for nucleotide synthesis

B. Direct hydrolysis of triglycerides

C. β-oxidation of long-chain fatty acids

D. Formation of acetyl-CoA

[Dr. Hope @HopeNweke_1]

A man with chronic alcohol misuse presents with confusion, unsteady gait, and abnormal eye movements. Deficiency of which vitamin is associated with this presentation?

A. Vitamin B1 (thiamine)
B. Vitamin B2 (riboflavin)
C. Vitamin B6 (pyridoxine)
D. Vitamin B12 (cobalamin)

[Dr. Hope @HopeNweke_1]

A patient presents with bleeding gums, easy bruising, and delayed wound healing. Which biochemical process is impaired by vitamin C deficiency?

A. Hydroxylation of proline and lysine during collagen synthesis

B. Conversion of glucose to glycogen

C. Synthesis of haem from porphyrins

D. Oxidative decarboxylation of pyruvate directly by vitamin C

[Dr. Hope @HopeNweke_1]

A 60-year-old patient presents with megaloblastic anaemia, numbness, and impaired vibration sense. Which biochemical reaction requires vitamin B12?

A. Conversion of pyruvate to lactate

B. Conversion of methylmalonyl-CoA to succinyl-CoA

C. Conversion of glucose to glucose-6-phosphate

D. Conversion of acety

[Dr. Hope @HopeNweke_1]

A malnourished patient develops dermatitis, diarrhoea, and cognitive changes. Deficiency of which vitamin is responsible for pellagra?

A. Niacin (vitamin B3)
B. Riboflavin (vitamin B2)
C. Folate (vitamin B9)
D. Vitamin K

[Dr. Hope @HopeNweke_1]

A newborn develops abnormal bleeding. Investigations reveal reduced activity of several vitamin K-dependent clotting factors. Which biochemical modification is impaired?

A. Hydroxylation of proline residues
B. γ-Carboxylation of glutamate residues
C. Methylation of DNA bases
D. Phosphorylation of tyrosine residues

[Dr. Hope @HopeNweke_1]

A 19-year-old patient with type 1 diabetes presents with abdominal pain, vomiting, dehydration, and deep, rapid breathing. Blood tests reveal hyperglycaemia, metabolic acidosis, and elevated ketone bodies. Which organ is primarily responsible for producing the excess ketone bodies?

A. Brain
B. Liver
C. Skeletal muscle
D. Pancreas

[Dr. Hope @HopeNweke_1]

A patient on a severely restricted diet develops scaly skin and poor wound healing. The nutritional deficiency may involve essential fatty acids. Which fatty acid is essential in humans?

A. Palmitic acid
B. Oleic acid
C. Linoleic acid
D. Stearic acid

[Dr. Hope @HopeNweke_1]

A 20-year-old man has very high LDL cholesterol and tendon xanthomas. His condition is caused by a mutation that reduces the function of LDL receptors. Which process is primarily impaired?

A. Cellular uptake of LDL cholesterol

B. Synthesis of bile salts from cholesterol

C. Breakdown of triglycerides in the intestine

D. Synthesis of ketone bodies

[Dr. Hope @HopeNweke_1]

A child presents with hypoketotic hypoglycaemia after prolonged fasting. Investigations suggest medium-chain acyl-CoA dehydrogenase deficiency (MCAD). Which metabolic process is directly impaired?

A. Fatty acid β-oxidation

B. Glycogen synthesis

C. Cholesterol synthesis

D. Protein translation

[Dr. Hope @HopeNweke_1]

A patient has elevated plasma triglycerides because of deficient lipoprotein lipase activity. Which process is most directly impaired?

A. Conversion of cholesterol to bile acids

B. Hydrolysis of triglycerides in circulating chylomicrons and VLDL

C. Uptake of glucose by skeletal muscle

D. Synthesis of albumin by the liver

[Dr. Hope @HopeNweke_1]

A 55-year-old man presents with severe chest pain. Laboratory investigations reveal elevated cardiac troponin levels and increased CK-MB. Which process best explains the rise in these markers?

A. Increased synthesis of enzymes by healthy cardiac cells

B. Release of intracellular proteins following cardiac muscle injury

C. Reduced renal production of cardiac enzymes

D. Increased protein absorption from the intestine

[Dr. Hope @HopeNweke_1]

A researcher studies an enzyme in the presence of a competitive inhibitor. Which change is expected?

A. Increased Km with unchanged Vmax
B. Decreased Km with unchanged Vmax
C. Unchanged Km with decreased Vmax
D. Decreased Km and decreased Vmax

[Dr. Hope @HopeNweke_1]

A child with a metabolic disorder has impaired conversion of phenylalanine to tyrosine. Phenylalanine hydroxylase normally requires which cofactor?

A. Tetrahydrobiopterin
B. Biotin
C. Pyridoxal phosphate
D. Thiamine pyrophosphate

[Dr. Hope @HopeNweke_1]

A 42-year-old woman presents with jaundice. Laboratory investigations show a markedly elevated alanine aminotransferase (ALT) and aspartate aminotransferase (AST). These findings most strongly suggest:

A. Hepatocellular injury
B. Isolated bone disease
C. Iron deficiency anaemia
D. Primary thyroid dysfunction

[Dr. Hope @HopeNweke_1]

A patient has a genetic disorder caused by a deficiency of glucose-6-phosphate dehydrogenase (G6PD). Following an oxidative stressor, the patient develops haemolytic anaemia. Which substance is inadequately regenerated because of the enzyme deficiency?

A. ATP
B. Reduced glutathione
C. Acetyl-CoA
D. Urea

[Dr. Hope @HopeNweke_1]

A newborn infant develops developmental problems, and screening reveals elevated phenylalanine levels in the blood. Which enzyme is most commonly deficient in this condition?

A. Tyrosinase

B. Phenylalanine hydroxylase

C. Homogentisate oxidase

D. Branched-chain α-ketoacid dehydrogenase