Download Enzymes

Chapter 9 Enzymes
Metabolism –The sum of all the chemical reactions that take place within an organism.
e.g. growth, movement etc. Metabolism maintains a balanced internal state in an
organism (homeostasis).
Sources of Energy
a) Solar Energy – Energy from the Sun. Primary source of energy for life, plants carry
out photosynthesis using this sunlight energy to make chemical energy (stored as
food).
b) Cellular Energy – Is energy stored in the bonds of biomolecules e.g. carbohydrates
and lipids. Each organism breaks down biomolecules in respiration and this releases
energy which is either used by the cell or released as heat.
Enzymes
Enzymes are catalysts made of protein. They are proteins that speed up a reaction with
being used up in the reaction.
A catalyst is a substance that speeds up a reaction, without itself being used up in the
reaction.
Enzymes are often called biological catalysts.
Enzymes speed up a chemical reaction and allows the reaction to take place at
normal cell temperatures.
Enzymes are made up of chains of amino acids and then folded into a 3 dimensional shape. The
3-D shape means that enzymes will only react with a substance that has a shape that matches a
particular enzyme.
Anything that changes the shape of an enzyme e.g. pH or temperature
reduces its efficiency.
Features of Enzymes
1. Enzymes are made of protein.
2. Enzymes need the correct shape to
fit their substrate
3. Enzyme reactions are reversible
(an enzyme can cause a reaction to proceed in
either direction).
Examples of enzyme catalysed reactions
The Role of Enzymes
Enzymes are necessary in plants and animals to control metabolic reactions.
a) Catabolic Enzymes – enzymes that break down large molecules into smaller
molecules e.g. Amylase. It converts starch to maltose in the mouth and duodenum.
b) Anabolic Enzymes – Enzymes that convert simpler molecules into more complex
molecules. E.g. DNA ligase enzyme is used in genetic engineering to join two
pieces of DNA together.
Factors Affecting Enzyme Activity
A denatured enzyme has lost its shape and can no longer function.
Enzymes work best under ideal conditions e.g. a particular temperature and pH.
Any change in these conditions will affect the rate of reaction.
1. Temperature
At very low temperatures e.g. O C enzymes do
not work. As the temperature increases the rate
of enzyme reaction increases.
Human enzymes work best at 37C. Most plant enzymes
work best at 20-30C. Above a certain temperature
enzymes begin to lose their 3-D shape and the rate
of reaction decreases and the enzyme becomes
Denatured.
2. pH
pH scale runs from 0 to 14. Enzymes
Are sensitive to changes in pH. Most enzymes
work best at pH 6-8, outside this pH range
The activity of the enzyme falls rapidly
Immobilised Enzymes
Bio-processing involves the use of enzyme
controlled reactions to produce a product.
e.g. Traditionally bioprocessing involves the use of microorganisms e.g. yeast or bacteria to produce foodstuffs eg.
Cheese, yoghurt, bread etc.
In recent times bioprocessing has been used to develop
products like antibiotics, vaccines etc.
A bioreactor is a vessel or container in which living
cells or their products are used to make a product.
Enzymes are immobilised (fixed into place) in a
bioprocessing reaction because using free enzyme is
very wasteful.
Uses of Immobilised Enzymes
1. Fizzy drinks are often sweetened with a sugar called
fructose (sweeter but more expensive than glucose) . An
enzyme called glucose isomerase is used to convert glucose
to fructose.
2. Penicillin acylase is very expensive enzyme used to alter
the structure of the antibiotic penicillin to make new
antibiotics. It is used in an immobilised form.
3. Lactase is an expensive enzyme which is used to convert
lactose sugar into two sweeter sugars (glucose and
galactose) which are used in making toffee and caramel.
Enzyme Experiments
In each experiment one factor (pH, temperature, enzyme concentration,
substrate concentration) is varied (changed)
Activity 10: To prepare an enzyme immobilisation and examine its application
The drops of liquid coming out of the separating
funnel are tested with clinistix (sticks to test for
glucose). The stick will turn from purple to pink if
glucose is present.
Result: The free yeast/water in the control solution
will form a cloudy product and the immobilised
yeast enzyme will form a clear product. The
glucose product will form faster in the free
yeast/water reaction.