ENZYMES
Enzymes are proteins.
Enzymes are biological catalyst.
o Catalyst speed up reactions.
o These reactions would take place anyway… the enzymes just speed them up!
Enzymes speed up the rate of chemical reactions by lowering the activation energy (amount of
energy needed to start a reaction).
EA=activation energy
Increase rate
Decrease energy
CHARACTERISTICS of Enzymes –
1. Enzymes do not make anything happen that couldn’t happen on its own, just makes it happen
faster.
2. Enzymes are not used up in reactions. They can be used over and over again!
3. Enzymes are only needed in small amounts.
4. Each enzyme is highly selective about its substrate.
5. Enzymes chemically recognize, bind and modify substrates.
How ENZYMES Work??
1. Enzymes have a specific shape.
2. Part of the enzyme matches the shape of the molecule to be reacted called the substrate.
3. The part of the enzyme that binds to the substrate is the active site.
4. When the substrate and enzyme bind temporarily, an enzyme-substrate complex is formed.
5. The activation energy needed for the reaction to occur is reduced.
6. After the reaction is complete, the substrate has formed a new product and the enzyme is
released to be reused.
ENZYME ACTION – can occur two ways:
1. Lock and Key model – substrate molecules
already have the right shape to fit an enzyme.
2. Induced Fit model – interaction between the
enzyme and substrate induces or changes the
shape of the molecules to produce a suitable fit.
ENZYME
REACTANTS
PRODUCTS
FACTORS AFFECTING ENZYME ACTIVITY –
1. Temperature – Enzymes function optimally at certain temperatures.
o High temps – inactive or denature enzyme
o Warm temps – increase speed
o Cold temps – work slowly or not at all
2. pH – Enzymes are sensitive to changes in acidity.
o Too acidic or too basic will slow or denature enzymes
3. Concentration of Enzymes or Substrates – When concentration increases, reaction is
faster. When concentration decreases, reaction is slower.
4. Enzyme activators - Co-enzymes – Some vitamins and minerals in small quantities work with
enzymes to speed up reactions.
5. Enzyme inhibitors – stops the action of enzymes by blocking active site or changing shape of
enzyme