🧬 KSSM · Form 4 · Age 16

Movement of Substances Across Plasma Membrane

67 exam-format practice questions · Biology, Form 4 · Free to start

Lesson overview

This lesson explores how cells maintain homeostasis through the selective permeability of the plasma membrane. Students will study passive transport mechanisms including simple diffusion, facilitated diffusion, and osmosis, understanding how substances move down their concentration gradients without energy input. The syllabus also covers active transport, where cells use ATP to move molecules against the gradient via carrier proteins. Additionally, learners will examine bulk transport processes such as endocytosis and exocytosis for moving large particles or fluids across the cell boundary. These concepts are fundamental for understanding nutrient absorption in the small intestine and water regulation in plant roots, forming the basis of cellular physiology in the Malaysian secondary school curriculum. Many students confuse osmosis with diffusion, often forgetting that osmosis specifically involves water movement across a selectively permeable membrane rather than general solute movement. Another common error is misidentifying isotonic solutions or failing to explain why active transport requires metabolic energy while passive does not. Mastering these distinctions helps students accurately interpret experimental data on tissue mass changes and predict cellular responses to different environmental conditions. This deep understanding is crucial for answering structured essay questions in the SPM examination and provides a solid foundation for advanced topics like nerve impulse transmission and kidney function in Form 5 biology studies.

Try these questions

Q1. Which of the following best explains why a plant wilts when placed in a highly concentrated salt solution?

A.Salt ions actively enter the plant cells, causing them to burst.

B.Water moves out of the plant cells by osmosis, causing the cells to become flaccid.

C.The salt solution prevents transpiration, leading to water loss.

D.The cell wall collapses due to the high external pressure.

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Q2. A student immersions a potato cylinder in a solution and observes that it becomes flaccid. Which of the following is the most likely condition of the solution?

A.The solution is hypotonic relative to the potato cells.

B.The solution is isotonic relative to the potato cells.

C.The solution is hypertonic relative to the potato cells.

D.The solution has a lower solute concentration than the potato cells.

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Q3. A student places a red blood cell into a hypertonic solution. Which of the following describes the net movement of water and the resulting effect on the cell?

A.Water moves into the cell; the cell swells and bursts.

B.Water moves out of the cell; the cell shrinks and becomes crenated.

C.Water moves into and out of the cell at equal rates; no change in cell shape.

D.Water moves out of the cell; the cell swells and bursts.

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