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9.1 Membrane Structure β Test 1
Q1. The width of a lipid bilayer is 30 Γ
. If a protein permeates it as a right-handed Ξ±-helix (rise 1.5 Γ
per residue, 3.6 residues per turn), the number of Ξ±-helical turns spanning the bilayer is approximately:β 5.6
Q2. For an Ξ±-helix spanning a 30 Γ
bilayer (1.5 Γ
rise per residue), the number of amino-acid residues required is approximately:β 20
Q3. Which detergent is commonly used to release integral proteins from membranes?β Triton X-100
Q4. Which of the following is NOT an integral membrane protein?β Spectrin
Q5. The flip-flop (transverse) movement of lipids in membranes is studied using which spectroscopic technique?β ESR (electron spin resonance)
Q6. Match Column A (membrane feature) with Column B (lipid):β I-1, II-4, III-2, IV-3
Q7. Which spectroscopic technique is used to study lateral lipid movement in membranes?β ESR / fluorescence (FRAP)
Q8. Which statement about the lipid-to-protein mass ratio in membranes is WRONG?β The ratio is always exactly equal in all membranes
Q9. The mitochondrial membrane is matched with which lipid?β Cardiolipin
Q10. Which is a correct way that proteins are anchored to membranes?β GPI anchor on the extracellular face
Q11. According to the SingerβNicolson fluid mosaic model, membrane proteins are best described as:β Globular proteins dispersed in and through a fluid lipid bilayer
Q12. Membrane asymmetry (different lipids on the two leaflets) is actively maintained by:β Flippases, floppases and scramblases
Q13. Increasing the proportion of unsaturated fatty-acyl chains in a membrane will:β Decrease the phase-transition temperature and increase fluidity
Q14. At temperatures above the transition temperature, cholesterol in an animal cell membrane tends to:β Decrease fluidity (orders the bilayer)
Q15. Lipid rafts are best described as:β Dynamic microdomains enriched in cholesterol and sphingolipids
Q16. A defect in the chloride channel protein CFTR, an integral membrane transport protein, causes which membrane-associated disease?β Cystic fibrosis
Q17. Hydropathy plots of a membrane protein sequence are used to predict:β The number and location of transmembrane segments
Q18. Which technique demonstrated rapid lateral mixing of membrane proteins (the classic FryeβEdidin experiment)?β Cell fusion with fluorescently labelled surface antigens
Q19. Glycolipids and glycoproteins of the plasma membrane are found:β Only on the extracellular (outer) leaflet
Q20. A peripheral membrane protein can typically be removed from the membrane by:β High salt concentration or pH change