In this topic we are learning to: z Explain the role of energy and its changes in living organisms. z Describe the role of enzymes in controlling chemical reactions in cells. z Explain how organisms achieve homeostasis.
Metabolism
Thousands of chemical reactions must take place within living things to give them the energy they need to grow, reproduce and respond to their environment.
Together, all of the chemical reactions that take place in the cells of organisms are known as metabolism.
Enzymes
In Chemical World we learn that chemicals that control the rate of a reaction are called catalysts. An enzyme is a biological catalyst that speeds up the chemical reactions in cells.
There are thousands of different enzymes. Each enzyme controls a specific step in a chemical reaction.
z The substance an enzyme acts on is called a substrate. z The enzyme acts on the substrate and changes it into a product.
For example, the enzyme maltase acts on the substrate maltose and changes it into the product glucose.
Product (glucose) Substrate (maltose) Key Words
Metabolism Enzyme Substrate Product
Homeostasis
3.1
Fig. 3.1.1
An enzyme changing maltose to glucose
Enzyme (maltase) ‘Enzyme’
Eduard Buchner, a German scientist, discovered that when he added an extract from yeast to sugar, the sugar turned into alcohol. As a result, he coined the term ‘enzyme’ from the Greek words en meaning ‘in’ and zyme meaning ‘yeast’.
Can you think of any commercial uses for changing sugar into alcohol? 47 47 Enzyme (maltase)
