Energy In Reactions
• Energy is released or
absorbed whenever
chemical bonds are
formed or broken.
• Because chemical
reactions involve
breaking and forming
of bonds, they involve
changes in energy.
Catalyst
• A catalyst is a
substance that
speeds up the rate of
a chemical reaction.
• Catalyst work by
lowering reaction’s
activation energy.
Notice that without the enzyme it takes a lot more
energy for the reaction to occur. By lowering the
activation energy you speed up the reaction.
Enzymes
• Enzymes are proteins that act as biological
catalysts.
• Cells use enzymes to speed up chemical
reactions that take place in cells.
• Enzyme speed up reactions by lowering the
activation energies.
• Because a particular enzyme catalyzes only one
reaction, there are thousands of different
enzymes in a cell catalyzing thousands of
different chemical reactions
Note:
Enzymes
end in
ase
Catalase
Amalase
Enzymes
• Enzymes provide a
site where reactants
can be brought
together to react.
• Such a site reduces
the energy needed for
a reaction to occur.
All enzymes have an active site,
where substrates are attracted to.
• Enzymes are used over and over again.
Substrate
• The substance
changed or acted
upon by an enzyme is
the substrate.
The Enzyme Substrate complex
• When enzymes function
the active site interacts
with the substrate.
• The active site shape
matches the substrates
shape.
• Once the substrate and
active site meet a change
in shape of the active site
causes a stress that
changes the substrate
and produces an end
product.
Which one will fit ?
• http://www.lewport.wnyric.org/jwanamaker/
animations/Enzyme%20activity.html
The factors that affect enzyme
activity are
• pH
• Temperature
• Amount of substrate
Affects of temperature on an
enzyme
• If temp to high or to
low the enzyme will
not fit. No reaction
will occur.
How pH affects an enzyme
• If the pH is to high or
low the enzyme will
not work, because its
shape will change.
pH
• All enzymes have an
optimum pH that they
function best at.
• If the pH is to low or
to high the enzyme
will work slow
because the change
in pH changes the
shape of the enzyme
making it harder for
the substrate to fit in.
Analyze the graph at what ph does
Chymotrypsin function best?
Temperature
• Enzymes function best at
an optimum temperature
depending on the type of
enzyme it is.
• As the temperature rises
the enzyme and substrate
molecules move quicker
causing more collisions to
occur, there for creating
more products.
• If you make the
temperature to high you
will destroy the protein
(denature) it.
What is the optimal temp for this
enzyme
Amount Of Substrate Present
• At low substrate
concentrations, collisions
between enzymes and
substrate molecules are
rare and reactions are
slow.
• As the amount of
substrates increase so
does the collisions
between enzymes and
substrates.
• This continues until the
enzymes are saturated.