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SingaporeBiology

Movement of Substances

4 dot points across 4 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How can a cell move substances against the concentration gradient?

Define active transport and explain its role using energy, with examples in cells
A focused answer to the O-Level Biology outcome on active transport. The definition, why it needs energy from respiration, how it differs from diffusion, and examples such as mineral uptake in roots and glucose uptake in the gut.
7 min answer →

How do substances move into and out of cells without using energy?

Define diffusion and explain its importance in living organisms and the factors affecting its rate
A focused answer to the O-Level Biology outcome on diffusion. The definition, why it matters for gas exchange and absorption, the factors that change its rate, and how to explain them in an exam.
8 min answer →

How does water move into and out of plant and animal cells?

Define osmosis and explain its effects on plant and animal cells in solutions of different concentration
A focused answer to the O-Level Biology outcome on osmosis. The definition, the meaning of a partially permeable membrane, and the effects on plant cells (turgid, flaccid, plasmolysed) and animal cells (swell or shrink).
8 min answer →

Why do large organisms need special surfaces for exchange while tiny ones do not?

Explain how surface area to volume ratio affects the exchange of substances in organisms
A focused answer to the O-Level Biology outcome on surface area to volume ratio. Why the ratio falls as size rises, why small organisms exchange across their surface, and why large organisms need specialised exchange surfaces.
8 min answer →