The aim of this sub-topic is to provide a basis of knowledge and understanding which can be developed further in the Biotechnology topic. Pupils should know that cells produce enzymes and that many cellular processes depend upon the activity of enzymes. This activity can be affected by changes in factors such as temperature and pH. Pupils should understand the specific relationship between an enzyme and its substrate. This sub-topic forms a suitable vehicle for developing those skills related to practical abilities and problem solving.