CAIE IGCSE Biology 3.1 Diffusion Questions

Practise defining diffusion as random kinetic movement down a concentration gradient, tracing it across membranes and exchange surfaces, and predicting its rate factors.

Exam points

Define diffusion as the net movement of particles down a concentration gradient caused by random kinetic motion, and show the direction of movement for gases or solutes.
Apply diffusion across cell membranes and exchange surfaces, distinguishing it from osmosis and active transport and using membrane-permeability evidence.
Explain why diffusion is important for gas exchange and cell supply or waste removal, tracing pathways through stomata, air spaces, alveoli or cell membranes.
Predict how surface area, temperature, concentration gradient and diffusion distance affect rate, including interpretation of linked experiment graphs.

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: 1]

Diffusion may be defined as the net movement of particles from a region of their ...... $1 \ldots \ldots$ concentration, to a region of their ...... $2 \ldots . .$ . contration where movement is 3..... a concentration gradient.

Which words complete gaps 1,2 and 3 ?

higher

lower

down

higher

lower

higher

down

lower

higher

[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

Question 1

Question 2

Question (a)

Question (i)

Question (ii)

Question (b)

Question (i)

Question 3