Chemical
Reactions
Chemical Reactions and Enzymes
chemical reaction: process that
changes one set of compounds
(reactants) into another set of
compounds (products)
A. example:
wood + oxygen  carbon dioxide + water + energy
Reactants
Products
Reactants:
• The elements or compounds
present at the beginning of a
chemical reaction
Products:
• The elements or compounds
produced at the end of a
chemical reaction
Chemical reactions:
• Always involve changes in the
chemical bonds that joins
atoms in compounds.
How many molecules are in a chemical
formula/equation? Photosynthesis:
Put a box around the products and circle reactants
carbon dioxide + water  glucose + oxygen
Reactants
Products
chemical equation:
CO2
+ H2O  C6H12O6 + O2
Reactants
Products
6CO2
• This Molecule is called….
• Carbon Dioxide
• Number of molecules….
•6
• Number of Carbon atoms….
•6
• Number of Oxygen atoms…
• 12
6H2O
a) This Molecule is called….
• Water
• Number of molecules….
•6
• Number of Hydrogen atoms….
• 12
• Number of Oxygen atoms…
•6
Glucose: C6H12O6
b) Glucose or Sugar:
• Number of molecules….
•1
• Number of Carbon Atoms…
•6
• Number of Hydrogen atoms….
• 12
• Number of Oxygen atoms…
•6
6O2
c) Oxygen….
• Number of molecules….
•6
• Number of Oxygen atoms…
• 12
• How many TOTAL ATOMS of
each element are present on
the REACTANTS side of the
reaction:
• Carbon: ___________
6
• Oxygen: _____________
18
• Hydrogen: ____________
12
• How many TOTAL ATOMS of
each element are present on
the PRODUCTS side of the
reaction:
• Carbon: ___________
6
• Oxygen: _____________
18
• Hydrogen: ____________
12
• If you did your math correctly in
step d. and e. you have observed
a fundamental scientific principle
called THE CONSERVATION OF
MATTER.
• Using the information you gained
in part d. and e. explain what the
conservation of matter is using
the sentence starter provided:
• The principle of the conservation
of matter is demonstrated by the
chemical reaction above because:
C. Conservation of matter: During a
chemical reaction, atoms are not
created or destroyed – just
rearranged. Therefore, chemical
equations must be balanced so there
is the same number of atoms on both
sides of the equation.
balancedequation:
chemical equation
chemical
CO22 ++ H

C
H
O
+
O
6CO
6H
O

C
H
O
+
6O
2O
6
12
6
2 2
2
6 12 6
Apply what you’ve LEARNED
a.) 2 H2O2  2H2O +
O2
• # of reactant molecules: 2
• # of product molecules: 3
• What are the molecules:
• Hydrogen Peroxide
• Water
• Oxygen
Apply what you’ve LEARNED
b.) 2 H2O2  2H2O +
O2
• # of reactant atoms: 8
• (4 H and 4 O)
• # of product atoms: 8
• (4H, 2O, 2O)
Apply what you’ve LEARNED
c.) 2 H2O2  2H2O +
O2
• # of reactant elements: 2
• # of product elements: 2
• What are the elements:
• Hydrogen
• Oxygen
II. Energy in Reactions:
• Energy is absorbed or released
whenever chemical bonds form
or are broken.
Chemical reactions that
Release energy….
• Often Occur Spontaneously
(without warning)
• Example: Explosion gun powder or
fireworks
Chemical reactions that
Absorb energy….
• Will not occur without a source
of energy.
• Example: Instant Ice Packs or
Photosynthesis.
• The speed of a reaction
depends on whether is absorbs
or releases energy.
Chemical Reactions and Enzymes
III. Label the graph:
Activation
energy
Products
Activation
Energy
Reactants
Energy Absorbing
Reactants
Products
Energy Releasing
A. All reactions require some energy
to start: activation energy.
Example: if some reactions that
release energy did not require
activation energy, what could
happen to the pages of your text
book as you sit here reading?
They could spontaneously combust
into flames.
B. catalyst: substance that speeds up a
chemical reaction by lowering the
activation energy
Catalysts found in living things are
called enzymes
C. Enzymes
•provide a site where the reactants of
a chemical reaction can be brought
together
•are not used up or changed during
the chemical reaction
•active site: part of the enzyme where the
reactants bind (stick)
•reactants: molecules at beginning of a
chemical reaction. Called the substrate
when they encounter an enzyme.
•substrate only fits into the active site of
the correct enzyme (like a key and lock)
Labeled diagram:
Enzyme
Active Site
Reactants
III. How does an enzyme work?
A. substrate binds to the enzyme
Enzyme
Substrate
Active Site
Reactants
III. How does an enzyme work?
A. substrate binds to the enzyme
Enzyme
Substrate
Active Site
III. How does an enzyme work?
B. reactants converted to product
Enzyme
Product
Active Site
III. How does an enzyme work?
C. products are released – enzyme is
free to bind new substrate
Enzyme
Product
Active Site
IV. Enzymes
only work in specific
conditions
A. temperature: heat=destroy enzyme,
cold= slow enzyme down
B. pH: changes the shape of the enzyme
and its active site
C. coenzymes: make enzymes work better
D. inhibitor molecules: block substrate
from entering active site
pH Change:
Enzyme
Product
Active Site
No Product
Made
Inhibitor Molecules:
Enzyme
Product
Active Site
Enzyme: Peroxidase in liver cells
Reactants: Hydrogen peroxide
Enzyme
Reactants
Hydrogen
Peroxide
Active Site
Enzyme: Peroxidase in liver cells
Reactants: Hydrogen peroxide
Enzyme
Reactants=Substrate
Active Site
Enzyme: Peroxidase in liver cells
Products: Water and Oxygen
Enzyme
Product
O2
H2O
Active Site
Enzyme: Peroxidase in liver cells
Products: Water and Oxygen
Enzyme
More
Hydrogen Peroxide
Active Site
O2
H2O
Product
Macromolecules
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids
Carbohydrates
• Made of Sugar
• Main Source of energy
• Examples: Sugar
Lipids
• 1 Glycerol & 3 Fatty
Acids
• Stores energy
• Examples: Fats,
Cholesterol
Protein
• Amino Acids
• Makes up structures in
body
• Examples: Hair,
muscles, skin, bones,
etc.
Nucleic Acids
• Nucleotides
• Store genetic material
• Examples: DNA, RNA
Chemical Reactions and Enzymes
D. Practice: balance the following
equations
2) _2 Cu + _1 S  1_ Cu2S
1) 4_ Na + _1 O2  _2 Na2O
3) _1 CuO + _1 H2  1_ Cu + _1 H2O