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Block 1 — Biochemistry MCQs
UHS · 918 MCQs with clinical pearls · Prof Jariya
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Sections in this uhs
- Signal Transduction — 46 MCQs
- Membrane Transport — 45 MCQs
- Protein Structure — 32 MCQs
- Cell Organelles — Clinical Correlations — 28 MCQs
- Amino Acid Classification — 23 MCQs
- Nucleotide Derivatives — 19 MCQs
- Collagen — 18 MCQs
- Membrane Proteins — 17 MCQs
- Iron Metabolism — 17 MCQs
- Prion Disease — 16 MCQs
- Cofactors and Coenzymes — 16 MCQs
- Membrane Lipids — 15 MCQs
- Hereditary Spherocytosis — 15 MCQs
- Collagen Disorders — 15 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.'
918 MCQs are arranged to the learning outcomes of this uhs.
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