Unit 1 Atomic structure and the periodic table Unit 2 Eukaryotic and prokaryotic cells Unit 3 Particle explanations of density and pressure Unit 4 DNA and the genome Unit 6 Health and disease Unit 7 Measuring and calculating motion Unit 8 Biological molecules and enzymes Unit 9 Structure and bonding Unit 10 Transport and exchange surfaces in humans Unit 11 Electric fields and circuit calculations Unit 12 Coordination and control: the human nervous system Unit 13 Separating substances Unit 14 Coordination and control: hormones and the human endocrine system Unit 15 Measuring waves Unit 17 Calculations involving masses Unit 18 Inheritance, genotype and phenotype Unit 19 Energy of moving objects Unit 20 Cell division: mitosis and meiosis Unit 22 Stem cells and differentiation Unit 23 Energy of moving particles Unit 24 Fossil evidence, selective breeding and explaining evolution Unit 25 Chemistry of carbon Unit 26 Living organisms and their environments Unit 27 Circuit components