They're grouped like this according to the number of sugar units found in their molecule. Find out how they're put together. In this part of the programme, AS Biology expert Mary Jones helps untangle things. One of the most important roles proteins play is as enzymes. Biologist Susan Greenfield describes the lock and key model of how enzymes work.
Cells are the basic building blocks of life.
Find out how AS Biology expert Mary Jones defines the difference between a prokaryotic cell and an eukaryotic cell. Find out more about cell structures and why specialist Paul Nurse thinks a cell is like a motorcycle. Investigating cell structure Cells can be investigated either microscopically or biochemically. Often both techniques are used to complement each other. Watch how scientists do it for real.