What is a chemical reaction?
chemical reaction - changes the bonds that join
atoms in compounds…occur nonstop in living cells
Reactant/s react
Product/s form
Example of an enzyme in use…
CO2 enters blood & reacts w/water to produce (soluble) carbonic
acid (H2CO3) which is carried by blood to lungs
In the lungs, the reaction is reversed and produces carbon dioxide
gas, which you exhale.
What is activation E?
Activation energy
The force needed to start a reaction
The difference between the E required to start the
reaction and the E of the reactants
Why do we need catalysts/enzymes?
Chemical reactions often depend on a catalyst.
A catalyst speeds up the rate of a reaction by
lowering a reaction’s activation energy.
Living organisms depend on organic catalysts called
enzymes
SPEED
• ENZYME may speed a reaction by 10 billion times
• 1500 years v. 5 seconds!
• A single enzyme my speed millions of rxns in 1 sec!
enzyme – specialized protein catalyst
active site – portion of enzyme that
touches the substrate
substrate - the substance being changed by an
Enzyme
lactose
substrate - the substance changed by an Enzyme
enzyme-substrate complex
product/s - changed substance
product/s - changed substance
enzymes are REUSEABLE
- after products are released, the UNCHANGED
enzyme is ready to bind with the next substrate.
Enzymes are SPECIFIC
- have an exact fit w/the
substrate
http://en.wikipedia.org/wiki/Enzyme
Due to specificity,
1 cell may have 4000 different types of enzymes
•Y?
Enzyme names
• Usually the substrate w/an –ase ending
• Ex: lactose/lactase
• Ex: amylose/amylase
• Ex: protein/protease
What would this enzyme be named?
lactose
Remember, enzymes are protein, like
egg whites…
http://www.youtube.com/watch?v=1kMfPC2grZI&feature=related
hair
Enzyme distortion
These factors can change the shape of an enzyme
•pH
Enzyme distortion
These factors can change the shape of an enzyme
•pH
•T
Enzyme distortion
These factors can change the shape of an enzyme
•pH
•T
•Medication
& other inhibitors
When the enzyme changes shape,
it no longer works
Regulation of Enzyme Activity
– Temperature, pH, and regulatory molecules are all
factors that can affect the activity of enzymes.
– Enzymes produced by human cells generally work
best at temperatures close to 37°C, the normal
temperature of the human body.
– Enzymes work best at certain pH values. For example,
the stomach enzyme pepsin, which begins protein
digestion, works best under acidic conditions.
– The activities of most enzymes are regulated by
molecules that carry chemical signals within cells,
switching enzymes “on” or “off” as needed.