Carbohydrate Chemistry and Metabolism MCQs

184 MCQs with clinical pearls · MBBS Biochemistry · Prof Jariya

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Topics covered (24)

Carbohydrate Digestion and Absorption — 22 MCQs
Gastrointestinal Secretions — 18 MCQs
Carbohydrate Classification — 16 MCQs
Glycosaminoglycans — 12 MCQs
Mucopolysaccharidoses — 10 MCQs
Fructose Metabolism — 10 MCQs
Galactose Metabolism — 10 MCQs
Gluconeogenesis — 9 MCQs
Diabetes Mellitus — 8 MCQs
Proteoglycans — 7 MCQs
Fed and Fasting State — 7 MCQs
Blood Glucose Regulation — 6 MCQs
Glycolysis Regulation — 6 MCQs
Glycolysis — 6 MCQs
Glycogen Metabolism — 6 MCQs
TCA Cycle — 6 MCQs
Polyol Pathway — 5 MCQs
Disaccharides — 4 MCQs
Polysaccharides — 4 MCQs
Glycogen Storage Diseases — 4 MCQs
Von Gierke Disease — 3 MCQs
HMP Shunt — 3 MCQs
Minor Pathways of Glucose — 1 MCQs
Pyruvate Kinase Deficiency — 1 MCQs

Sample MCQs with clinical pearls

Mutarotation is a property of reducing sugars. Which of the following best describes mutarotation?

A) Aldose to ketose conversion

B) Enantiomer formation

C) Interconversion of alpha and beta anomers ✔

D) Isomerisation at non-anomeric carbon

E) Rotation of polarisation plane only

MUTAROTATION = spontaneous INTERCONVERSION between ALPHA and BETA ANOMERS of a reducing sugar in solution, passing through the open-chain form. Alpha-D-glucose (specific rotation +112°) ⇌ open chain ⇌ beta-D-glucose (specific rotation +18.7°) → equilibrium mixture (specific rotation +52.7°). ANOMERS differ only at the anomeric carbon (C1 in aldoses): alpha = OH axial (below ring in Haworth), beta = OH equatorial (above ring). EPIMERISM = differing at any non-anomeric carbon. 📹 [VIDEO LINK]

Glucose and galactose have the same molecular formula (C₆H₁₂O₆) but differ only in the configuration at carbon-4. They are therefore classified as which of the following?

A) Anomers

B) Diastereomers

C) Enantiomers

D) Epimers ✔

E) Isomers

EPIMERS = two sugars that differ in configuration at ONE specific non-anomeric carbon. Glucose and galactose = C4 EPIMERS (differ only at C4). Glucose and mannose = C2 EPIMERS. Compare: ANOMERS = differ at the anomeric carbon (C1) only. ENANTIOMERS = mirror images (D vs L — all carbons inverted). Clinical: GALACTOSAEMIA — GALT enzyme deficiency → galactose-1-phosphate accumulates → liver damage, cataracts, intellectual disability. [Diagram: Haworth projections of glucose and galactose side by side. Glucose: ring structure with OH at C4 pointing DOWN (equatorial). Galactose: identical except OH at C4 pointing UP (axial). Red circle highlighting C4 in both. Arrow between them labelled: C4 EPIMERS — differ ONLY at C4. Interconversion by UDP-galactose-4-epimerase. Clinical box: Galactosaemia = deficient GALT → galactose toxic → cataracts + liver damage + intellectual disability.] 📹 [VIDEO LINK]

Glucuronic acid is converted to iduronic acid in proteoglycan synthesis by the action of which of the following enzymes?

A) Epimerase ✔

B) Isomerase

C) Kinase

D) Mutase

E) Racemase

EPIMERASE converts glucuronic acid → IDURONIC ACID by inverting the configuration at C5 → occurs in the GOLGI during proteoglycan processing. Iduronic acid is found in: heparin, heparan sulfate, and DERMATAN SULFATE. Distinction: EPIMERASE (changes configuration at one carbon), ISOMERASE (converts aldose ↔ ketose), MUTASE (moves phosphate group), RACEMASE (inverts all stereocentres). 📹 [VIDEO LINK]

These are three of 184 MCQs in this section. Every question carries a clinical pearl explaining the reasoning.

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