Engaging Enzymes
Accelerated Biology 2009
2
Flow of energy through life
Life is built on chemical reactions
3
Chemical reactions of life
Metabolism
forming bonds between molecules
dehydration synthesis
breaking bonds between molecules
hydrolysis
4
Spontaneous reactions?
If reactions are “downhill”, why don’t
they just happen spontaneously?
because covalent bonds are stable
Why don’t organic
molecules
(carbohydrates,
proteins & fats) just
spontaneously digest
into their monomers
5
Activation energy
Breaking down large molecules
requires an initial input of energy
activation energy
macromolecules are stable
requires energy to break bonds
energy
cellulose
CO2 + H2O + heat
6
Activation energy
the amount of
energy needed to
destabilize the
bonds of a
molecule
moves the
reaction over an
“energy hill”
7
Reducing Activation Energy
Catalysts
reduce the amount of energy needed to
start a reaction
Pheew… that
takes a lot
less energy!
8
Catalysts
So what does a cell do to reduce
activation energy?
GET HELP! Chemical help in the form
of ENZYMES
ΔG
9
Enzymes
Act as biological catalysts
Help to run chemical reactions
increase rate of reaction without
being consumed (used up) in the
process
reduce activation energy
Required for most biological reactions
Specific enzyme for each reaction
thousands of different enzymes in
cells
10
Enzymes & substrates
SUBSTRATE
Reactant molecule which binds to enzyme
Temporary enzyme-substrate complex
Enzymes are SUBSTRATE SPECIFIC
PRODUCT
Molecule or molecules that result from this reaction
11
Enzymes & substrates
Enzyme + substrates →
products
Enzymes usually named
for their substrate…but
add an -ASE
sucrase
enzyme breaks
down sucrose
binds to sucrose
& breaks disaccharide
into fructose & glucose
DNA polymerase
enzyme builds DNA
adds nucleotides to
a growing DNA strand
12
Lock and Key model
Simplistic model of enzyme action
3-D structure of enzyme
fits substrate
Active site
enzyme’s cata