Topic 1: Molecules, diet, transport and health - Edexcel A-Level Biology B overview

Topic 1 of Edexcel A-Level Biology B (specification 9BN0, the Salters-Nuffield course) is titled Molecules, diet, transport and health. It is introduced through the context of a heart attack and builds the biochemistry and transport foundations used throughout the course. This page maps the four dot-point areas and how they are examined.

The four dot-point areas

Biological molecules

The structure and bonding of carbohydrates (monosaccharides, disaccharides and polysaccharides), lipids (triglycerides and phospholipids) and proteins, and how condensation and hydrolysis build and break them.

The heart and circulation

The structure of the mammalian heart, the cardiac cycle and pressure changes, and the structure of arteries, veins and capillaries in the double circulatory system.

Cardiovascular disease and diet

How atherosclerosis develops, the roles of cholesterol, lipoproteins and blood pressure as risk factors, and how diet, lifestyle and treatments reduce risk.

Gas exchange and cell transport

The fluid mosaic membrane, diffusion, osmosis and active transport, the properties of water, and the features of efficient exchange surfaces.

How Topic 1 is examined

Topic 1 appears across all three papers, with the molecules and circulation content prominent in Paper 1 and revisited in the synoptic Paper 3. Expect precise recall of bonds and processes, data questions on diet and disease, and structure-to-function reasoning. Several core practicals, such as investigating membrane permeability, draw on this topic.

How to study Topic 1

1. Learn the bonds. Glycosidic, ester and peptide bonds, and condensation versus hydrolysis, recur throughout the course.
2. Link structure to function. Practise explaining why glycogen branches, why the left ventricle wall is thick and why capillaries are thin.
3. Handle risk data. Distinguish correlation from cause when evaluating diet and CVD studies.
4. Master water potential. Describe osmosis in terms of water potential, not concentration.

Work through the dot points

Each dot point has a focused answer page with worked exam questions and cross-links: biological molecules; the heart and circulation; cardiovascular disease and diet; and gas exchange and cell transport.

For the official specification

Pearson publishes the full specification (9BN0), past papers and mark schemes at qualifications.pearson.com. Always revise from the current specification and Edexcel's own past papers.