Chemical
reactions
Chemical reactions
 Add
the baking soda to one corner of the
bag and add vinegar to the other end of
the bag. MAKE SURE THEY ARE SEPARATE.
 Mix
the substances and watch the
reaction
 what
physical changes did you observe?
 Sodium
bicarbonate + vinegar  water + carbon
dioxide
 Reactants? Enter into a chemical reaction
 products? What are formed from the chemical
reaction
 http://www.youtube.com/watch?v=ezsur0L0L1c
 Chemical
change always involves
change in the bonds that join the atoms.
 http://www.youtube.com/watch?v=H6ZDi
RIvc2E
 In order for a chemical reaction to
happen, there needs to be enough
energy to break existing bonds so new
bonds can be formed.
Activation energy
 The
energy needed to get a reaction
started is activation energy.
 Chemical reactions need energy to react.
 Red rover
Energy
releasing
Like burning a
match!
Label the graph!!
?
?
?
?
?
Enzymes
 Chemical
reactions are made possible in our bodies
but the activation energy is so high, they need the
help of enzymes
 Enzymes- Proteins that speed up a chemical reaction
by lowering the activation energy.
 Catalyst- An inorganic enzyme. (can work in more
extreme conditions)
Enzymes
Enzymes are protein molecules, and so are made up of amino acids. Most
enzymes contain between 100 and 1,000 amino acids.
These amino acids are joined together in a long chain, which is folded to
produce a unique 3D structure.
Enzymes work by binding to a specific component due to its shape.
Enzymes are very specific about which reactions they catalyze. Only
molecules with exactly the right shape will bind to the enzyme and react.
These are the reactant, or substrate, molecules.
The part of the enzyme to which the
reactant binds is called the active site.
This is a very specific shape and the
most important part of the enzyme.
What happens at the active site?
In the same way that a key fits into a lock, so a substrate is thought to fit into
an enzyme’s active site. The enzyme is the lock, and the reactant is the key.
↔
+
enzyme
+
reactant
↔
↔
enzyme-reactant
complex
+
↔
enzyme
+
products




Enzymes are NOT used up in this process, after
they combine with the necessary substrate
(reactant) in the reaction.
When the enzyme and substrate combine,
the substrate is changed to a different
chemical called the product.
when the substrate and the active site on an
enzyme combine, a product is created.
The product is then released so a new
substrate can bind.
Induced Fit Model
 Enzyme
changes shape to fit the substrate.
 The induced fit model has been compared
to a hand-in-glove model, wherein it may
be difficult to insert the first finger into the
proper place, but once done, the other
fingers go in easily because the glove is now
properly aligned.
 http://www.cengage.com/chemistry/discipl
ine_content/media/gob_now/dswmedia/se
ager/CI_Seager_22_2.html
Factors that affect the rate of a reaction include:
 temperature
 substrate concentration
 pH
 surface area
 enzyme concentration
 pressure.
All enzymes work best at only one particular temperature and pH: this is
called the optimum.
Different enzymes have different optimum temperatures and pH values.
If the temperature and pH changes sufficiently beyond an enzyme’s optimum, the
shape of the enzyme irreversibly changes.
This affects the shape of the active site and means that the enzyme will no
longer work.
When this happens the enzyme is denatured.
heat
pH
normal
denatured
Review
 What
is an enzyme?
 What are the 2 common ways enzymes
are denatured?
 An enzyme is similar to a __________ but it
is biological.