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Block 5 — Biochemistry MCQs
UHS · 771 MCQs with clinical pearls · Prof Jariya
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Sections in this uhs
- Hormone Signal Transduction — 31 MCQs
- Infertility — 30 MCQs
- Signal Transduction — 28 MCQs
- Transcription — 23 MCQs
- Contraception — 23 MCQs
- Calcium and Vitamin D — 22 MCQs
- Thyroid Hormones — 22 MCQs
- Translation — 20 MCQs
- Genetic Terminology — 20 MCQs
- Recombinant DNA Techniques — 19 MCQs
- DNA Damage and Repair — 17 MCQs
- Inheritance Patterns and Pedigrees — 17 MCQs
- Mutations — 16 MCQs
- Cortisol — 15 MCQs
Sample MCQs with clinical pearls
A 7-year-old child develops runny nose and nasal congestion after contact with a classmate. The responsible virus attaches to nasal epithelial cells via ICAM-1. ICAM-1 belongs to which protein superfamily?
A) Cadherin family
B) Ficolin family
C) Immunoglobulin superfamily ✔
D) Integrin family
E) Selectin family
RHINOVIRUS, the commonest cause of the common cold, enters cells by binding ICAM-1, a member of the IMMUNOGLOBULIN SUPERFAMILY of adhesion molecules. These share the immunoglobulin fold and mediate calcium-INDEPENDENT adhesion, unlike the cadherins. ICAM-1 normally binds leucocyte integrins during firm adhesion in inflammation - so the virus exploits a receptor built for immune traffic. MEMORY: 'The cold virus uses the cell's own adhesion molecule as a door.'
Light strikes a rod photoreceptor and activates rhodopsin. Rhodopsin belongs to which receptor class?
A) Enzyme-linked receptor
B) G protein-coupled receptor ✔
C) Ligand-gated ion channel
D) Nuclear receptor
E) Receptor tyrosine kinase
RHODOPSIN is a G PROTEIN-COUPLED RECEPTOR with the classic seven-transmembrane structure, and is remarkable in that its ligand, 11-CIS-RETINAL, is covalently bound within the protein. Light does not deliver a new ligand but ISOMERISES the retinal to all-trans, changing the receptor's conformation. Rhodopsin was the first GPCR whose structure was solved. MEMORY: 'Rhodopsin carries its own ligand and light is the switch.'
During phototransduction in a rod cell, which G protein is specifically activated by light-stimulated rhodopsin?
A) G12
B) Gi
C) Gq
D) Gs
E) Gt ✔
TRANSDUCIN (Gt) is the rod photoreceptor G protein. Activated rhodopsin catalyses GDP-GTP exchange on transducin, whose alpha subunit activates cGMP PHOSPHODIESTERASE. cGMP falls, cGMP-gated sodium channels CLOSE and the cell hyperpolarises. Amplification is enormous - one photon can block the entry of a million sodium ions. MEMORY: 'Light to rhodopsin to transducin to phosphodiesterase.'
771 MCQs are arranged to the learning outcomes of this uhs.
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