Q) Describe the roles of phospholipids, cholesterol and glycolipids in the cell membrane
Main points | |
Key idea: | Phospholipids |
· Roles : (i) main component of cell membr, (ii) determine permeability of membr toward diff substances · Ref to each mol having 1 polar head, 2 non-polar hydrocarbon tails + its orientation to form bilayer struc · Ref to polar heads of phospholipids pointing towards aq medium while hydrocarbon tails form hydrophobic core · Ions or polar mol unable to diffuse a/x hydrophobic core of bilayer struc via simple diffusion · Ref to special transmembrane proteins (e.g. carriers or channel proteins) embedded w/n membr to regulate transport of these substances a/x membr | |
Key idea: | Cholesterol |
· Roles : (i) Regulate fluidity of membr + ref to changes in fluidity under diff temp · Details : - when temp increases, cholesterol decreases fluidity by interacting w hydrocarbon chains of phospholipids which are prevented fr moving too far fr each other. - when temp decreases, cholesterol increases fluidity of membr by disrupting close packing of phospholipids which prevents membr fr solidifying · (ii) Provide mechanical stability to membr, so it does not break easily · (iii) As impt component of myelin sheath + ref to reducing uncontrolled leakage of ions a/x membr of neurones, for efficient nerve transmission t | |
Key idea: | Glycolipids |
· Only on ext surf of cell membr · Roles : (i) cell recognition + adhesion roles ; (ii) stabilizes membr struc due to orientation of carbo chains toward ext aq envt, H bonds form b/w carbo chains + water mol (iii) In some white blood cells, glycolipids may serve to detect pathogens + signal for their destruction | |
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) | |
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