Enzymes and Energy Transfer
There are three types of energy in the
universe.
Potential Energy (EP) : Energy
that is stored , either as energy of
position, or chemical energy
Ex; Energy stored in a stretched rubber
Band (position energy ) or in the food that
you eat (chemical energy)
2) Activation Energy (EA): Energy
required to begin a reaction
Ex: Pushing a wagon to start it down a hill,
the energy needed to start a chemical
(Striking a match)
reaction.
3) Kinetic Energy (EK) Energy of
movement and heat
Ex: A ball rolling down a hill
A match burning
(Movement)
(Heat)
EK=EP-EA
Kinetic Energy equals Potential
Energy minus Activation Energy
-Lowering EA to zero would make
EK = EP (100% efficiency)
-in other words, all the potential
energy (100%)would be converted.
Enzymes
Enzymes are complex
molecules made of protein
Enzymes work by lowering the
activation energy (EA) of
reactions
Kinetic Energy
Enzymes are very specific for the
molecules that they will work on.
-Similar to a Lock and Key,
only the correct key will fit
the lock.
The molecules that enzymes work
on are called the substrate.
SUBSTRATE
1) Substrate (maltose) and enzyme come
together
2) Substrate fits exactly in the enzyme, and bond
is over the active site of the enzyme
3) The enzyme puts a strain on the bond,
breaking it. 2 smaller glucose molecules result.
Substrate 1
Substrate 2
Active Sites on Enzyme
Enzyme
1) Substrate molecules
are attracted to the active
sites on the enzyme
Substrate 1
Substrate 2
Enzyme
2) Substrate molecules are
firmly held by the enzyme
at the active sites.
Molecules are oriented so
that bonding areas face
together.
Substrate 1
Substrate 2
Enzyme
3) Substrate molecules can
now bond easily, because
they are held in the proper
orientation.
New Substrate 1 New Substrate 2
Substrate 1
Enzyme
Substrate 2
4) Original substrate molecules
are released, making room for
two new molecules, and the
process is repeated over and
over.
Coenzymes:
-Molecules that help with the
enzymatic reaction. (Make the
reaction even more efficient)
-Coenzymes are often vitamins
or minerals
Types of Chemical Reactions
1)Exergonic (exothermic): Once
started, gives off energy (heat)
Ex: Fire, “heat pack”
Heat pack: Mg + H20 = Mg(OH)2
+ H2 + heat
2) Endergonic (endothermic):
Reaction uses energy, needs a
constant input of energy (heat)
Ex: Cold Pack
-barium hydroxide and
ammonium nitrate
Where does all that energy GO?
The source of energy for most
cellular endergonic reactions is ATP.
ATP: Adenosine Triphosphate
A
P
P
P
High Energy Bonds
A
A
P
P
P
P
Energy is given off
P
High in
potential energy
P
Lower in
potential energy
ATP Becomes ADP, plus a free
phosphate, plus free energy
The free energy is used to
Power other reactions within
the cell.
Examples:
Protein synthesis
DNA synthesis
The source of energy to make ATP
is cellular respiration.
Cellular Respiration: “Burning” of
sugar (glucose) to fuel cell reactions.
Aerobic vs. Anaerobic Respiration
Aerobic: Takes place in the presence
of oxygen
C6H12O6 + 6O2
6CO2+6H2O
Plus energy for 38 ATPs
Anaerobic: Takes place in the
absence of oxygen
C6H12O6
2CH3CHOHCOOH
(Lactic Acid)
Plus energy to create 4 ATPs
Fermentation: A form of anaerobic
respiration that produces CO2
and alcohol from sugar
C6H12O6
2C2H5OH + 2CO2
(Alcohol)
Plus energy for 4 ATPs