Cambridge AS & A Level Biology 9700 – Topic Summaries
A free overview of the topics in Cambridge International AS & A Level Biology (9700). Topics 1–11 are the AS content and topics 12–19 are the extra A Level content.
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1. Cell structure
Microscopes differ in magnification and resolution. Eukaryotic cells contain organelles such as the nucleus, mitochondria, ER, Golgi and chloroplasts, each with a role; prokaryotic cells are smaller and simpler, and viruses are non-cellular.
Key terms: magnification, resolution, organelle, prokaryote, eukaryote, virus
2. Biological molecules
Carbohydrates, lipids and proteins are built from monomers joined by condensation and broken by hydrolysis. Their structures, such as glycosidic, ester and peptide bonds and the levels of protein structure, explain their roles, and water’s properties support life.
Key terms: condensation, hydrolysis, glycosidic bond, triglyceride, peptide bond, protein structure
3. Enzymes
Enzymes are proteins that lower activation energy. Their activity depends on temperature, pH, substrate and enzyme concentration, and inhibitors; Vmax and Km describe enzyme efficiency.
Key terms: active site, induced fit, activation energy, competitive inhibition, Vmax, Km
4. Cell membranes and transport
The fluid mosaic membrane controls what enters and leaves cells by diffusion, facilitated diffusion, osmosis, active transport and bulk transport.
Key terms: fluid mosaic model, diffusion, osmosis, water potential, active transport, endocytosis
5. The mitotic cell cycle
Chromosomes are copied and shared equally in mitosis for growth and repair. Telomeres and stem cells matter for cell division, and uncontrolled division leads to cancer.
Key terms: chromosome, mitosis, cell cycle, telomere, stem cell, tumour
6. Nucleic acids and protein synthesis
DNA replicates semi-conservatively, and genes are transcribed to mRNA and translated into polypeptides using the genetic code. Mutations change base sequences.
Key terms: nucleotide, semi-conservative replication, transcription, translation, codon, mutation
7. Transport in plants
Xylem carries water and minerals by transpiration pull; phloem carries sucrose by mass flow. Leaf and stem structure support these processes.
Key terms: xylem, phloem, transpiration, cohesion–tension, translocation, mass flow
8. Transport in mammals
The heart pumps blood through arteries, capillaries and veins. Haemoglobin carries oxygen, and the oxygen dissociation curve and Bohr shift explain delivery to tissues.
Key terms: cardiac cycle, blood vessel, tissue fluid, haemoglobin, dissociation curve, Bohr shift
9. Gas exchange
Lungs provide a large, thin, moist surface for gas exchange, with airways protected by cilia and mucus.
Key terms: alveoli, trachea, ciliated epithelium, surfactant, gas exchange surface
10. Infectious diseases
Diseases such as cholera, malaria, TB and HIV/AIDS are caused by pathogens and spread in different ways. Antibiotics treat bacterial infections, but resistance is increasing.
Key terms: pathogen, transmission, antibiotic, antibiotic resistance, vector
11. Immunity
Phagocytes and lymphocytes defend the body. B cells make antibodies and T cells coordinate and kill; vaccination gives long-term immunity.
Key terms: phagocyte, antigen, antibody, B lymphocyte, T lymphocyte, memory cell, vaccination
12. Energy and respiration
ATP is made by glycolysis, the link reaction, Krebs cycle and oxidative phosphorylation; anaerobic respiration yields less ATP.
Key terms: ATP, glycolysis, Krebs cycle, electron transport chain, respiratory quotient
13. Photosynthesis
Light-dependent reactions make ATP and reduced NADP, used in the Calvin cycle to fix carbon; limiting factors control the rate.
Key terms: chlorophyll, photophosphorylation, Calvin cycle, RuBisCO, limiting factor
14. Homeostasis
Negative feedback keeps internal conditions stable. The kidney controls water and urea, insulin and glucagon control blood glucose, and plants control stomata.
Key terms: negative feedback, nephron, ADH, insulin, glucagon, stomata
15. Control and coordination
Nerve impulses travel as action potentials across synapses, muscles contract by sliding filaments, and hormones coordinate slower responses in animals and plants.
Key terms: neurone, action potential, synapse, sliding filament, auxin
16. Inheritance
Meiosis produces variation. Monohybrid and dihybrid crosses, linkage, epistasis and chi-squared tests explain and test inheritance patterns, and gene expression is controlled.
Key terms: meiosis, allele, dihybrid cross, linkage, epistasis, chi-squared
17. Selection and evolution
Variation, natural and artificial selection and isolation drive evolution and speciation; the Hardy–Weinberg principle tests allele frequencies.
Key terms: natural selection, genetic drift, Hardy–Weinberg, speciation, artificial selection
18. Classification, biodiversity and conservation
Organisms are classified into domains and kingdoms. Biodiversity is measured and protected by conservation methods.
Key terms: domain, kingdom, species diversity, Simpson’s index, conservation
19. Genetic technology
Recombinant DNA, PCR, gel electrophoresis and genome sequencing are used in medicine and agriculture, with ethical questions.
Key terms: recombinant DNA, PCR, electrophoresis, gene therapy, GM crop
These summaries are written by Dabour Hub from the published course outline. Full notes, diagrams, quizzes and question banks are available to registered students.
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