Lesson Overview
Chemical Reactions and Enzymes
Chemical
Reactions and
Enzymes
Lesson Overview
Chemical Reactions and Enzymes
Number 1
What is a chemical reaction?
A process that changes, or transforms, one set of chemicals
into another by changing the chemical bonds that join
atoms in compounds.
Lesson Overview
Chemical Reactions and Enzymes
Number 2
What is conserved during chemical transformations?
MASS
ENERGY
Lesson Overview
Chemical Reactions and Enzymes
Number 3
Compare / contrast reactants and products.
Both are parts of a chemical reaction and both can be
elements or compounds
Reactants are the elements or compounds that enter into a
chemical reaction
Products are the elements or compounds produced by a
chemical reaction
Lesson Overview
Chemical Reactions and Enzymes
Number 4
Reactants and products of the following…
2 Na + 2 HCl 2 NaCl + H2
REACTANTS
PRODUCTS
Lesson Overview
Chemical Reactions and Enzymes
Number 5
What is changed in a chemical reaction?
The chemical bonds that join atoms in compounds are
changed in a chemical reaction
Bonds can be either created or broken
Lesson Overview
Chemical Reactions and Enzymes
Number 6
Why is the melting of ice not a chemical reaction?
New chemical bonds are not formed
The bonds between hydrogen and oxygen are not changed
Lesson Overview
Chemical Reactions and Enzymes
Number 7
Chemical reaction in your bloodstream
As CO2 enters the blood, it reacts with water to produce
carbonic acid (H2CO3), which is highly soluble
This reaction enables the blood to carry the carbon dioxide to
the lungs
In the lungs, the reaction is reversed and produces carbon
dioxide gas, which you exhale
Lesson Overview
Chemical Reactions and Enzymes
Number 8
How do plants get the energy needed to stay alive?
Plants trap and store the energy from sunlight in energy-rich
compounds
Lesson Overview
Chemical Reactions and Enzymes
Number 9
How do animals get the energy needed to stay alive?
Animals consume plants or other animals to get their energy
Lesson Overview
Chemical Reactions and Enzymes
Number 10
What is activation energy?
The energy that is needed to get a reaction started
It is the difference between the required energy and the
energy of the reactants
Lesson Overview
Chemical Reactions and Enzymes
Number 11
Label the following…
C
A
B
A = Reactants
B = Activation Energy
C = Products
This is an energy-absorbing reaction (endothermic reaction)
Lesson Overview
Chemical Reactions and Enzymes
Number 11
Label the following…
A
B
C
A = Reactants
B = Activation Energy
C = Products
This is an energy-releasing reaction (exothermic)
Lesson Overview
Chemical Reactions and Enzymes
Number 12
What is a catalyst? Why are catalysts important?
A substance that speeds up the rate of a chemical reaction
Catalysts work by lowering the activation energy
Catalysts are important because some reactions that make
life possible are too slow or have activation energies that
are too high
Lesson Overview
Chemical Reactions and Enzymes
Number 13
What are enzymes?
Proteins that act as biological catalysts
Enzymes speed up chemical reactions that take place in cells
Lesson Overview
Chemical Reactions and Enzymes
Number 14
Steps of an enzyme-catalyzed reaction
1. The substrates bind to the
enzyme on the active site
2. The substrates are
converted into products
3. The products are released
4. The enyzme is ready for
another reaction
The enzyme brings the
substrate together which
means less energy is
required
Lesson Overview
Chemical Reactions and Enzymes
Number 15
Why is the enzyme-substrate complex compared to a lock and key?
The active site and the substrates have complementary
shapes
The fit is very precise, much like a lock that can only be
opened by one key
Lesson Overview
Chemical Reactions and Enzymes
Number 16
What are some variables that can affect enzymes?
Temperature, pH, and regulatory molecules are all factors that
can affect the activity of enzymes.
Enzymes work best at certain temperatures.
Enzymes produced by human cells generally work best at
temperatures close to 37 degrees Celcius, the normal
temperature of the human body.
Enzymes work best at certain pH values.
For example, the stomach enzyme pepsin, which begins protein
digestion, works best under acidic conditions.
The activities of most enzymes are regulated by molecules that carry
chemical signals within cells, switching enzymes “on” or “off” as
needed.