This document summarizes key concepts about the movement of substances across the plasma membrane: 1) The plasma membrane is made up of a phospholipid bilayer (X) and embedded proteins (Y). Substances can pass through the membrane via passive transport methods like diffusion and osmosis, or active transport powered by ATP. 2) Oxygen and glucose enter cells via passive transport, while calcium ions require active transport involving membrane proteins. 3) Passive transport requires no energy while active transport is an energy-requiring process powered by ATP.

1. Chapter 3: Movement of Substances Across the Plasma Membrane
Section A
1. Diagram shows the structure of plasma membrane based on the fluid mosaic model.
a) Name the parts of the plasma membrane labeled X and Y. [2m]
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b) (i) Describe the structure of X and the functions of its parts. [2m]
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(ii) State the function of Y [1m]
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c) Substances can move across the plasma membrane by passive transport and active
transport.
(i) Explain two ways by which passive transport can take place [2m]
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(ii) Explain how active transport occurs [2m]
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d) How do oxygen, glucose and calcium ions are transported across the plasma
membrane? [3m]
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e) State two differences between passive transport and active transport. [2m]
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2. Section B (Open response)
2. The movement of substances across the plasma membrane of the root hair cells
enables the plant to obtain the substances it needs.
a) Explain how
(i) Water in the soil enters the roots of the plant [2m]
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(ii) Calcium in the soil enters the roots of the plant [2m]
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The concentration of solution surrounding the cell will influence the function of
the cell. Solutions that are isotonic, hypotonic and hypertonic can affect both plant
cells and animal cells
b) (i) What is the meaning of isotonic, hypotonic and hypertonic? [3m]
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(ii) Write a report on the effects of these three solutions on erythrocyte cells. [9m]
(iii)Describe how erythrocyte cells are prevented from being destroyed in the blood.
[4m]
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