1. Cholesterol is a membrane plasticizer or a membrane buffer. Explain what are the effects of...

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Biology

1. Cholesterol is a membrane plasticizer or a membrane buffer.Explain what are the effects of cholesterol at high and lowtemperatures.
2. What is the difference between integral and peripheralproteins?
3. Membrane lipids are distributed asymmetrically. Explain theconcept and the reason behind this asymmetrical distribution

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4.1 Ratings (718 Votes)

1 Cholesterolenhances membrane fluidity Lipid bilayers undergo ahighly cooperative phase transition with a defined TmBelow Tm the the acyl chains are tightly packed and the lipidsexist as a solidlike gel Above Tm the acyl chains are disordered and the lipids are in aliquidlike liquid crystal phase Rapid lateral diffusion of lipids and proteins occurs in theplane of the membranes above but not below TmLipid bilayers can be made more fluid higher Tm either bydecreasing fatty acyl chain length andor increasing the degree ofunsaturation Chain length and the presence of cisdouble bondscan greatly affect Tm and fluidity through affecting the extent ofvan der Waals packingMembrane fluidity is essential for the biological function ofmembranes Therefore organisms go to great lengths to maintain afluid membrane bilayer eg bacteria regulate acyl chainlengthBut simply increasing the degree of unsaturation can compromise theintegrity of the cell membrane Animals cells have another way ofincreasing membrane fluidityCholesterol Is a natural steroid About the same length as a C16 fatty acid therefore it reachesacross half of the bilayer Essential component of most mammalian membranes 20 of cellmembrane lipid Destroys the phase transition of pure lipid membranes therebykeeping the membranes fluid below the phase transition and morerigid above the phase transition Often referred to as a membraneplasticizerCholesterol another type of lipid that is embedded among thephospholipids of the membrane helps to minimize the effects oftemperature on fluidity At low temperatures cholesterol increasesfluidity by keeping phospholipids from See Answer

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