Chemical Reactions

• Change substances into different ones by breaking and forming chemical bonds– Reactants are the substances changed during a

chemical reaction.– Products are the substances made by a chemical

reaction• Activation Energy: amount of energy needed

to start a reaction

ProductsReactants

How Do Enzymes Help?• 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 reduce energy needed (activation energy) to start a chemical reaction and increase reaction rate

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 bonded to enzyme, substrates bonds weakened• Substrates bonds break• Substrates re-bond to each other• New product is formed

Another Enzyme Structure

Review• 1) How do enzymes speed up chemical reactions?• 2) What are the molecules called that react with enzymes?• 3) Given the following chemical formula list the products

and reactants: 6O2 + C6H12O6 6CO2 + 6H2O• 4) What are the substances that are changed during a

chemical reaction called?• 5) What is another term for a catalyst? • 6) Why can’t the human body raise its temperature to allow

chemical reactions to happen quicker?• 7) Given Amylase and Amylose, which is the substrate?• 8) What do enzymes weaken between molecules?