Download Enzymes

Chemical Reactions
• Energy stored in chemical bonds
– When bonds broken = Energy released (heat &
light)
• Activation Energy: amount of energy needed to
start a reaction
Exothermic Reactions
• Exo = exit; thermic = heat
• Defined: Release more energy than it absorbs
– Light & heat
• Ex: Cellular Respiration
– Process that creates energy for cells
– Chemical energy released for cells…
– Heat energy released for warmth
Endothermic Reactions
• Endo = within; thermic heat
• Defined: Absorb more energy than it releases
• Ex: Photosynthesis
– Sunlight is absorbed by plants…to create
energy as glucose
Enzymes
• Activation energy
usually comes from an
increase in temp
– Slow process
• Catalyst: substance
that decreases the
activation energy
needed to start a
chemical reaction
– Speeds up reaction
• Enzymes are catalysts
in living organisms.
Controlled Settings
• Human body ~98.6°F
– Can’t raise body temp to
start reactions.
• Internal reactions
would be too slow to
sustain life without a
catalyst
• Ex: Saliva
– Breaks down starch
1,000,000x faster with
amylase
Enzyme Structure
• Enzyme shape allows specific reactants to bind together
– Reactants = substrate
– Ex: Amylase & starch: Starch is the substrate because it
binds to amylase
• Substrates binds to activation sites on the enzyme (key fitting
into a lock)
• Once binded to enzyme, substrates bonds weakened
• Substrates bonds break
• Substrates form new bonds (product)
Recap
• 1) How do enzymes speed up chemical reactions?
• 2) What is released when chemical bonds are broken?
• 3) Why is photosynthesis an example of an endothermic
reaction?
• 4) Why is cellular respiration an example of an exothermic
reaction?
• 5) Besides enzymes, what else is often a catalyst that
speeds up reactions?
• 6) What are the molecules called that react with enzymes?
• 7) What do enzymes weaken between molecules?