CAIE IGCSE Biology 3.1 Diffusion

Practise defining diffusion as net movement down a concentration gradient, showing its direction in cells and predicting how surface area, distance and temperature affect rate.

Exam points

define diffusion as net particle movement down a concentration gradient due to random motion
distinguish diffusion from osmosis and active transport using particle type, membrane and energy evidence
predict how surface area, temperature, gradient and diffusion distance alter the rate of movement

Covered syllabus points

3.1.1—Diffusion 3.1.2—Energy for diffusion comes 3.1.3—Diffusion through cell membranes 3.1.4—Importance of diffusion 3.1.5—Factors that influence diffusion

[Maximum number: 4]

Fig. 1.1 shows the movement of particles through an epithelial cell in the small intestine.

Fig. 1.1

(a)

In Fig. 1.1, arrow P represents the diffusion of oxygen molecules.

[ 3 ]

(i)

Describe what is meant by the term diffusion.

[ 2 ]

(ii)

State the type of energy needed for diffusion.

[ 1 ]

(b)

Carbon dioxide molecules also move by diffusion.

[ 1 ]

(i)

On Fig. 1.1, draw an arrow to show the direction of diffusion of carbon dioxide molecules.

[ 1 ]

[Maximum number: 1]

How do carbon dioxide and oxygen move into and out of a mesophyll cell?

active transport

diffusion

respiration

transpiration

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Covered syllabus points

3.1 Diffusion question 1

Question (a)

Question (i)

Question (ii)

Question (b)

Question (i)

3.1 Diffusion question 2