(b) Explain cell membrane fluidity and asymmetry.
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Membranes are not static sheets of molecules locked rigidly in place. A membrane is held together primarily by hydrophobic interactions, which are much weaker than covalent bonds. Most lipids are randomly mobile in the plane of the membrane with an average migration rate of 22 µm (micrometers) per second. It is rare, however, for a molecule to flip-flop transversely across the membrane, switching from one phospholipid layer to the other; to do so, the hydrophilic part of the molecule would have to cross the hydrophobic core of the membrane. Temperature affects the fluidity of the membrane. A membrane remains fluid as temperature decreases, until finally, at some critical temperature, the membrane solidifies. The temperature at which a membrane solidifies depends on its fatty acid composition. A membrane rich in phospholipids with unsaturated hydrocarbon tails will remain fluid to a lower temperature because the kinks where the double bonds are located prevent the hydrocarbons from packing as closely together as saturated hydrocarbons. However, a cell can alter the lipid composition of its membranes to some extent as an adjustment to changing temperature. For instance, in many plants that tolerate extreme cold, such as winter wheat, the percentage of unsaturated phospholipids increases in autumn, an adaptation that keeps the membranes from solidifying during winter.
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Membranes are not static sheets of molecules locked rigidly in place. A membrane is held together primarily by hydrophobic interactions, which are much weaker than covalent bonds. Most lipids are randomly mobile in the plane of the membrane with an average migration rate of 22 µm (micrometers) per second. It is rare, however, for a molecule to flip-flop transversely across the membrane, switching from one phospholipid layer to the other; to do so, the hydrophilic part of the molecule would have to cross the hydrophobic core of the membrane. Temperature affects the fluidity of the membrane. A membrane remains fluid as temperature decreases, until finally, at some critical temperature, the membrane solidifies. The temperature at which a membrane solidifies depends on its fatty acid composition. A membrane rich in phospholipids with unsaturated hydrocarbon tails will remain fluid to a lower temperature because the kinks where the double bonds are located prevent the hydrocarbons from packing as closely together as saturated hydrocarbons. However, a cell can alter the lipid composition of its membranes to some extent as an adjustment to changing temperature. For instance, in many plants that tolerate extreme cold, such as winter wheat, the percentage of unsaturated phospholipids increases in autumn, an adaptation that keeps the membranes from solidifying during winter.
HOPE THIS ANSWER HELPS YOU
MARK AS BRAINLIEST ✌✌
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