Chemical Reactions and Enzymes BIOCHEMISTRY UNIT SEPTEMBER 23, 2015

Chemical Reactions  Definition: a process that changes one set of chemicals into another.  Mass and energy are conserved.  Speed of a chemical reaction.  Slow (rust on a bicycle).  Fast (atomic bomb).

Chemical Reactions H 2 O + CO 2 C 6 H 12 O 6 + O 2 Reactants: go into the chemical reaction. Products: made by the chemical reaction. ***Chemical reactions involve changes in the chemical bonds that join atoms in compounds. ***Chemical reactions also involve changes in energy.

ENERGY in REACTIONS  Chemical reactions that release energy occur SPONTANEOUSLY.  Energy may be released as heat, light or sound.  Chemical reactions that absorb energy need an ENERGY SOURCE.  Plants get energy from sunlight to perform chemical reactions.  Animals get energy from consuming other organisms to perform chemical reactions.

Energy ABSORBED! Products have more energy. Energy RELEASED! Reactants have more energy.

Activation Energy Definition: the energy needed to get a reaction started. *** Not all reactions that release energy occur spontaneously.

Lowering Activation Energy  Catalyst: substance that speeds up the rate of a reaction.  ENZYMES: proteins that act as catalysts  Speed up chemical reactions that take place in cells.  Lower the activation energy needed to start a reaction.

How Enzymes Work  Enzymes are very specific!  Each enzyme binds to a specific substrate (the reactant of a reaction).  Substrate binds/fits in the active site of the enzyme.  Lock and key!  Enzymes are named for the substrate they bind to with –ase added to the end.  Example: amylase is the enzyme that breaks down starch called amylose.

Anabolic – Make ‘em

Catalytic – Break ‘em