AS 1: Molecules and Cells

What AS 1 covers

• Water, carbohydrates and lipids
• Proteins and protein structure
• Enzymes and rates of enzyme-controlled reactions
• Cell structure and organelles (including microscopy)
• The cell membrane and transport across membranes
• Mitosis and meiosis
• Nucleic acids, DNA replication and protein synthesis
• Viruses and the immune response

Assessment: Written paper — structured questions plus an extended-response question carrying quality of written communication (QWC) credit. The definitive content statements are published by CCEA at ccea.org.uk.

Where marks get lost

• Describing osmosis without using water potential (Ψ) and the correct 'less negative to more negative' direction.
• Confusing the induced-fit model with lock-and-key when explaining enzyme specificity.
• Losing marks on protein synthesis by muddling transcription and translation sequence.

Question styles to drill

• Enzyme rate graphs: describe the trend with figures, then explain it with collision and denaturation ideas.
• Membrane transport comparisons (diffusion, facilitated diffusion, active transport, osmosis) in a single linked answer.
• 6-mark QWC answers on the immune response — antigen, antibody, plasma cell, memory cell, secondary response.

Other CCEA AS units

• AS 2 · Organisms and Biodiversity
• AS 3 · Practical Skills in AS Biology