IGCSE Revision- Biology
Chapter 5- Enzymes
5.1 Biological catalysts
- Many chemical reactions can be speeded up by substances called catalysts.
Catalysts alter the rate of reactions, without being changed itself
- Almost every metabolic reaction is controlled by catalysts called enzymes
- A different enzyme is needed for each kind of nutrient. For example, starch is
digested to a sugar called maltose by an enzyme called amylase. Proteins are
digested into amino acids by protease
- Another enzyme which speeds up the breakdown of a substance is called
catalase. Catalase works inside all the cells in living organisms. It breaks down
hydrogen peroxide to water and oxygen. This is important because hydrogen
peroxide is produced by many of the chemical reactions which take place inside
cells. Hydrogen peroxide is very dangerous and must be broken down
immediately
- Not all enzymes are for breaking things down. Many enzymes help make larger
molecules out of smaller ones. For example, enzymes help link together amino
acids to make proteins
NAMING ENZYMES
- Enzymes are named after the reaction they catalyse
- Their names often end in -ase
- For example: protease, lipase, carbohydrase
- Sometimes enzymes are given more specific names than this. A carbohydrase
that breaks down maltose is called maltase, and a carbohydrase that breaks
down sucrose is called sucrase
- The substance that an enzyme changes is called substrate
HOW ENZYMES WORK
- Each enzyme has a very specific shape. The enzyme molecule has a dent in it,
called the active site
- The enzyme works by allowing a molecule of its substrate to fit into the active
site, where the substrate and the enzyme bind together. For this to happen, the fit
has to be perfect. We say that the shape of the enzyme and the shape of the
substrate are complementary to one another
- When the substrate is changed it is called the product
- The enzyme catalase is the fastest enzyme known.mone catalase molecule can
break down almost 44 million hydrogen peroxide molecules in one second
- Enzyme- substrate complex: The short-lived structure formed as the substrate
binds temporarily to the active site of an enzyme
- Specificity: Of enzymes, only able to act on a specific substrate
Chapter 5- Enzymes
5.1 Biological catalysts
- Many chemical reactions can be speeded up by substances called catalysts.
Catalysts alter the rate of reactions, without being changed itself
- Almost every metabolic reaction is controlled by catalysts called enzymes
- A different enzyme is needed for each kind of nutrient. For example, starch is
digested to a sugar called maltose by an enzyme called amylase. Proteins are
digested into amino acids by protease
- Another enzyme which speeds up the breakdown of a substance is called
catalase. Catalase works inside all the cells in living organisms. It breaks down
hydrogen peroxide to water and oxygen. This is important because hydrogen
peroxide is produced by many of the chemical reactions which take place inside
cells. Hydrogen peroxide is very dangerous and must be broken down
immediately
- Not all enzymes are for breaking things down. Many enzymes help make larger
molecules out of smaller ones. For example, enzymes help link together amino
acids to make proteins
NAMING ENZYMES
- Enzymes are named after the reaction they catalyse
- Their names often end in -ase
- For example: protease, lipase, carbohydrase
- Sometimes enzymes are given more specific names than this. A carbohydrase
that breaks down maltose is called maltase, and a carbohydrase that breaks
down sucrose is called sucrase
- The substance that an enzyme changes is called substrate
HOW ENZYMES WORK
- Each enzyme has a very specific shape. The enzyme molecule has a dent in it,
called the active site
- The enzyme works by allowing a molecule of its substrate to fit into the active
site, where the substrate and the enzyme bind together. For this to happen, the fit
has to be perfect. We say that the shape of the enzyme and the shape of the
substrate are complementary to one another
- When the substrate is changed it is called the product
- The enzyme catalase is the fastest enzyme known.mone catalase molecule can
break down almost 44 million hydrogen peroxide molecules in one second
- Enzyme- substrate complex: The short-lived structure formed as the substrate
binds temporarily to the active site of an enzyme
- Specificity: Of enzymes, only able to act on a specific substrate
