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Enzymes
Standard 1b
Cell Standards
• 1) The fundamental life processes of plants and
animals depend on a variety of chemical
reactions that occur in specialized areas of the
organism’s cells. As a basis for understanding
this concept:
▫ b) Students know enzymes are proteins that catalyze
biochemical reactions without altering the reaction
equilibrium and the activities of enzymes depend on
the temperature, ionic conditions, and the pH of the
surroundings.
Overview
• Enzymes are protein catalysts made by
living organisms.
▫ Catalysts speed up chemical reactions
▫ Without enzymes food would look exactly the
same at the “other end.”
Structure
• Enzymes are proteins
(long chains of amino
acids held together by
peptide bonds)
• They fold into specific
3D shapes determined
by the amino acid
sequence
• Enzymes contain one or more active sites
▫ Active site: where one or more substrates
bind.
▫ Substrate: a molecule that reacts, with the
help of an enzyme, to produce new product
molecules
• The enzyme must be the perfect shape or
it won’t work!
Action of Enzymes
1. Enzymes bind to
specific substrates.
2. The substrate fits
into the active site
of the enzyme like
a lock and key.
3. The enzyme carries
out a reaction to
make or break bonds
in the substrate.
▫
▫
lining up molecules
so they can react
(matchmaker!)
putting pressure on
bonds to break up
molecules
(homewrecker!)
• 4. The reaction produces a product or
products.
• Enzymes are not used up during the
reaction. One enzyme can cause millions of
reactions.
Activation Energy
• Activation energy: the energy
required to start a chemical reaction
Activation Energy
Example:
• Enzymes lower
the activation
energy necessary
for the reaction
to happen.
Demonstration of an enzyme in action
Half the steak was placed into the fresh
pineapple
After three hours sitting at room
temperature
Factors affecting Enzyme activity
• Enzymes are denatured (stop working)
when conditions are not right.
• 1. Temperature
• 2. pH (acid & base)
• 3. Substrate
concentration(amount)
▫ Few molecules =
slow reaction
▫ Many molecules =
fast reaction