Cells and Movement Across Membranes

This section focuses on the similarities and differences between diffusion and osmosis, crucial concepts in WJEC GCSE Biology topics.

The explanation highlights that both diffusion and osmosis are passive processes involving the movement of particles from high to low concentration. However, osmosis specifically refers to the movement of water particles through a selectively permeable membrane, while diffusion can involve various particles and doesn't require a membrane.

Example: Diffusion occurs in alveoli where oxygen moves from the alveolar walls into the bloodstream through capillaries. Osmosis takes place in plant root hair cells, where water from the soil enters the cell.

The document also covers the effect of temperature on enzyme activity and effect of pH on enzyme activity, which are common topics in WJEC Biology past papers.

Definition: An enzyme is a protein catalyst that speeds up chemical reactions in living organisms.

As temperature increases, enzymes gain more kinetic energy, leading to more successful molecular collisions and faster reactions. However, excessive heat can denature the enzyme's active site, reducing or stopping product formation.

Highlight: Enzymes have an optimum temperature and pH at which they function most effectively.

The section concludes with a description of how plants take up nutrients from the soil, emphasizing the role of active transport and the energy (ATP) required for this process.