Cell Physiology: Diffusion, Osmosis and Active Transport

Syllabus tag: KCSE | Biology | Form 1 | Topic 4 Cell Physiology

Lesson objectives

By the end of this topic, you should be able to:

• Define diffusion, osmosis and active transport.
• State the factors affecting each process.
• Describe the effects of different solutions on plant and animal cells.
• State the roles of these processes in living organisms.

Summary

Substances cross the cell membrane in three ways. Diffusion is the movement of particles from high to low concentration. Osmosis is the diffusion of water through a semi-permeable membrane. Both are passive and need no energy. Active transport moves substances against the concentration gradient and therefore requires energy from respiration.