Cell Membrane MCQs

243 MCQs with clinical pearls · MBBS Biochemistry · Prof Jariya

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Topics covered (25)

Signal Transduction — 46 MCQs
Membrane Transport — 45 MCQs
Membrane Proteins — 17 MCQs
Membrane Lipids — 15 MCQs
Organelle Marker Enzymes — 14 MCQs
Phospholipid Translocators — 11 MCQs
Nuclear Receptors — 11 MCQs
Active Transport — Pump Classes — 10 MCQs
Membrane Potential and Pumps — 10 MCQs
Signal Transduction — Cholera and Pertussis — 9 MCQs
Tonicity and Intravenous Fluids — 9 MCQs
Steroid Hormone Signalling — 8 MCQs
Membrane Transport — Endocytosis — 6 MCQs
Membrane Asymmetry — 5 MCQs
Membrane Properties — 4 MCQs
Endocytosis — 4 MCQs
Membrane Structure — 3 MCQs
Membrane Proteins and Pumps — 3 MCQs
Membrane Cytoskeleton — 3 MCQs
GPI Anchors — Clinical — 2 MCQs
Membrane Toxins — 2 MCQs
Glucose Transporters — 2 MCQs
Cell Junctions — 2 MCQs
Signal Transduction — Nitroglycerin — 1 MCQs
Glucose Transport — 1 MCQs

Sample MCQs with clinical pearls

A healthy nerve cell keeps phosphatidyl choline and sphingomyelin in the outer leaflet through one-way traffic by:

A) Flippase

B) Floppase ✔

C) Phospholipase

D) Racemase

E) Scramblase

FLOPPASE moves phospholipids from the INNER to the OUTER leaflet, using ATP, keeping phosphatidylcholine and sphingomyelin - the choline lipids - on the outside. FLIPPASE does the reverse, pulling phosphatidylserine and phosphatidylethanolamine inward. SCRAMBLASE is ATP-INDEPENDENT, calcium-activated, and moves lipids both ways to abolish asymmetry. MEMORY: 'Flippase pulls in, floppase pushes out, scramblase mixes both.'

A healthy cell maintains phosphatidylcholine and sphingomyelin in the outer leaflet for structural asymmetry. Which enzyme is responsible?

A) Flippase

B) Floppase ✔

C) Phospholipase

D) Racemase

E) Scramblase

FLOPPASE maintains the OUTER leaflet, transporting phosphatidylcholine and sphingomyelin outward at the cost of ATP. Asymmetry is functional, not incidental: the outer leaflet carries the choline lipids and the glycocalyx sugars for recognition, while the inner leaflet holds phosphatidylserine and phosphatidylinositol, the latter supplying IP3 and DAG for signalling. MEMORY: 'Floppase keeps the choline lipids facing outward.'

An endometrial cell undergoes apoptosis during menstrual shedding. Which enzyme is inactivated by cytosolic calcium to facilitate apoptosis?

A) Flippase ✔

B) Floppase

C) Kinase

D) Phospholipase

E) Scramblase

FLIPPASE is the ATP-dependent translocase holding PHOSPHATIDYLSERINE on the inner leaflet. In apoptosis, rising cytosolic calcium INACTIVATES flippase while ACTIVATING scramblase, so PS flips outward and becomes the EAT-ME signal for macrophages. Falling ATP makes the change irreversible. MEMORY: 'Calcium switches flippase off and lets the death signal out.'

These are three of 243 MCQs in this section. Every question carries a clinical pearl explaining the reasoning.

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