HUMAN PHYSIOLOGY
DIGESTION AND ABSORPTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Molecules that are small enough to fit through the holes
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Nothing enters through the cell membrane
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Everything can fit
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Any size food can fit through the cell membrane
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Detailed explanation-1: -Cell membranes are an example of semi-permeable membranes. Cell membranes allow small molecules such as oxygen, water carbon dioxide, and oxygen to pass through but do not allow larger molecules like glucose, sucrose, proteins, and starch to enter the cell directly.
Detailed explanation-2: -The simplest mechanism by which molecules can cross the plasma membrane is passive diffusion. During passive diffusion, a molecule simply dissolves in the phospholipid bilayer, diffuses across it, and then dissolves in the aqueous solution at the other side of the membrane.
Detailed explanation-3: -Small hydrophobic molecules and gases like oxygen and carbon dioxide cross membranes rapidly. Small polar molecules, such as water and ethanol, can also pass through membranes, but they do so more slowly.
Detailed explanation-4: -Cell membranes allow small molecules such as oxygen, water carbon dioxide and glucose to pass through, but do not allow larger molecules like sucrose, proteins and starch to enter the cell directly.
Detailed explanation-5: -Channel proteins form pores, or tiny holes, in the membrane. This allows water molecules and small ions to pass through the membrane without coming into contact with the hydrophobic tails of the lipid molecules in the interior of the membrane.