Free Biology study notes
Step-by-step answers to common Biology questions, with worked examples, common mistakes and exam tips.
Free Biology study notes
8 notes
How does photosynthesis work?
Photosynthesis is the process plants use to make glucose. In the chloroplasts, chlorophyll absorbs light energy, which is used to convert carbon dioxide and water into…
Explain how a vaccination can prevent an illness.
A vaccine contains a dead, inactive or weakened form of a pathogen, or parts of it, carrying its antigens. White blood cells (lymphocytes) respond by making specific…
What is the difference between mitosis and meiosis?
Mitosis produces two genetically identical diploid cells and is used for growth and repair. Meiosis produces four genetically different haploid cells (gametes such as…
How does the heart pump blood around the body?
The heart is a muscular pump with four chambers. The right side pumps deoxygenated blood to the lungs, where it picks up oxygen. The left side pumps oxygenated blood to…
What is the difference between diffusion and osmosis?
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration. Osmosis is a special case: the diffusion of water…
How do enzymes work?
Enzymes are proteins that act as biological catalysts: they speed up reactions without being used up. Each enzyme has an active site with a specific shape that only fits…
What is the structure of DNA?
DNA is a double helix: two strands twisted around each other. Each strand is a chain of nucleotides, and each nucleotide has a sugar, a phosphate and one of four bases…
What is a food chain and how does energy flow through it?
A food chain shows what eats what in a habitat. It starts with a producer, usually a green plant that makes food by photosynthesis, followed by consumers. The arrows…