| Movement into and out of Cells | Human Nutrition |
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Diffusion stops at equilibrium because there is no concentration gradient, so there is no net movement of particles
Why does diffusion stop when equilibrium is reached?
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Pepsin works in acidic pH of stomach; small intestine is alkaline, so pepsin is inactive.
Why does pepsin only work in the stomach and not in the small intestine?
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RBC lacks a cell wall; plant cell has a rigid cell wall.
Explain why a red blood cell placed in distilled water bursts, but a plant cell does not?
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Lipase needs bile to emulsify fats, increasing surface area for digestion.
Explain why lipase cannot digest fats efficiently without bile?
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Why does active transport stop immediately when respiration is inhibited in a cell?
Respiration stops, so ATP is unavailable.
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Proteins are digested into amino acids, because they are small enough to be absorbed directly.
During digestion, why does starch need to be broken down into maltose then glucose before being absorbed, but proteins are absorbed as amino acids?
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The solution has equal or slightly lower water potential than the cell.
A plant cell becomes flaccid instead of plasmolysed in a certain solution. What does this indicate about the solution’s water potential?
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Large intestine absorbs water by osmosis, forming solid faeces and preventing dehydration.
How does the large intestine help conserve water in the body?
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Cell wall rigidity or elasticity differs, so protoplast shrinks differently.
OR Initial water potential or vacuole size may vary, affecting the extent of plasmolysis.
Two plant cells, X and Y, are placed in the same hypertonic solution. After 30 minutes, cell X is fully plasmolysed, while cell Y is only partially plasmolysed, even though both cells are of the same type and size. Explain two possible reasons for this difference. Give one reason
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