2. 2.5 Enzymes
Chemical Reaction = one or more
substances are changed into new
substances by the breaking and/or
forming of chemical bonds
ex. cracker in the mouth:
polysaccharide
monosaccharide
3. 2.5 Enzymes
How do you know if a reaction has occurred?
When one or more of the following has
occurred:
1. Formation of precipitate (a new solid
compound forms from two solutions)
2. Change in color
3. Production of gas
4. Change in temperature
Endothermic Rxn – takes in heat (gets
cold)
4. 2.5 Enzymes
Reactions are shown as balanced equations
Which means, each side has the same elements
and the same number of elements on each side
2H2 + O2 2H2O
Reactants Products
Checking for balanced equations...
compare reactants and products:
Reactants
2H2 = 4 Hydrogens
O2 = 2 Oxygens
Products
5. 2.5 Enzymes
• How do you speed up a chemical reaction?
– Temperature
– Catalyst
6. 2.5 Enzymes
A catalyst lowers activation energy.
• Catalysts are substances that speed up chemical
reactions.
– decrease activation energy
– increase reaction rate (this is the speed of the rxn)
7. 2.5 Enzymes
Enzymes allow chemical reactions to occur under tightly
controlled conditions.
• Enzymes are catalysts for chemical rxns in living things.
– Enzymes are needed for almost all processes.
– Most enzymes are proteins.
8. 2.5 Enzymes
• Disruptions in homeostasis can prevent enzymes from
functioning. Need stable conditions.
– Enzymes function best in a small range of conditions.
– Changes in temperature and pH can break
hydrogen bonds. This affects enzyme function.
– An enzyme’s function depends on its structure.
– Large changes in temp. and pH change shape
(structure) called denature
9. 2.5 Enzymes
• An enzyme’s structure allows only certain reactants to
bind to the enzyme. Shape determines function!
– substrates
– active site
substrates
(reactants)
enzyme
Substrates bind to an
enzyme at certain places
called active sites.
10. 2.5 Enzymes
• The lock-and-key model helps illustrate how enzymes
function.
– substrates brought together
– bonds in substrates weakened
Substrates bind to an
enzyme at certain places
called active sites.
The enzyme brings
substrates together and
weakens their bonds.
The catalyzed reaction forms
a product that is released
from the enzyme.
11. 2.5 Enzymes
Some Enzymes and their substrates
Enzyme
• Catalase
• DNA Polymerase
• RNA Polymeras
• Maltase
• Lactase
• Sucrase
• Amylase
Substrate
• Hydrogen peroxide
• DNA
• RNA
• Maltose
• Lactose
• Sucrose
• Starch
