CAIE IGCSE Biology 3.3 Active Transport

Practise recognising active transport from movement against a concentration gradient, then explain the roles of membrane carriers and energy released by respiration.

Exam points

recognise movement from lower to higher concentration across a membrane as against the gradient
state that active transport uses energy released by respiration and occurs in living cells
apply the process to mineral-ion uptake by root hairs and other carrier-mediated membrane transport

Covered syllabus points

3.3.1—Active transport as the movement 3.3.2—Importance of active transport 3.3.3—Protein carriers move molecules or

[Maximum number: 3]

Fig. 1.1 shows several villi from the ileum, which is part of the small intestine.

Fig. 1.2 shows the tip of a villus in more detail.

Fig. 1.2

The epithelial cells of the villi absorb nutrients by diffusion and active transport.

Describe how active transport differs from diffusion.

[Maximum number: 3]

Wetlands are important ecosystems. Researchers studied the feeding relationships between the organisms in an area of wetland on the coast of Texas.

Fig. 1.1 shows part of the food web that they studied.

Fig. 1.1

Describe how nitrate ions enter the roots of plants shown by arrow C on Fig. 1.2.

[Maximum number: 2]

Fig. 3.1 is a diagram of the junction between two neurones in a healthy person.
Fig. 3.2 is a diagram of the junction between the same two neurones in a person who has Parkinson's disease. This disease affects the nervous system.

Fig. 3.1

Fig. 3.2

Cell membranes also contain protein carriers. Describe the role of protein carriers.

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Covered syllabus points

3.3 Active transport question 1

3.3 Active transport question 2

3.3 Active transport question 3