Chemical  Reactions

Warm Up… page 20/21 •  What are the Macromolecules found in our food? •  Which one is the MAIN SOURCE of energy? •  How is energy released? Agenda •  Flowers •  Macromolecule Notes •  Chemical Reaction Notes •  Study Guide… page 17 •  Endo/Exo Sticks

Think  About  it •  When you hear the term “Chemical

Reaction,” what comes to mind?

Chemical  Reactions •  Chemical reactions

change substances into different substances

•  HOW? •  By breaking and

forming chemical bonds.

•  An exothermic reaction releases more energy than it absorbs. o  These reactions are usually “breaking down” something,

like cellular respiration does. o  These reactions give off excess energy, usually in the form

of heat or light.

•  An endothermic reaction absorbs more energy than it releases. o  These reactions are usually “making” something, like

photosynthesis does. o  Sometimes these reactions will feel cold.

•  Question: Do you think the glow that a firefly gives off is an example of an exothermic or an endothermic reaction?

Biochemical  Reactions •  Biochemical reactions allow organisms

to grow, develop, and adapt. •  Biochemical reactions are affected by

o Temperature o pH o Enzymes

Factors  that  Affect  Reaction  Rates:  Temperature  and  pH

•  Temperature usually affects the rate of a chemical reaction o Increase temperature = increase rate of

reaction o Decrease temperature = decrease rate of

reaction •  In most organisms pH must be kept within a

very narrow range in order for a reaction to occur. Because a small change in pH can highly disrupt cell processes.

Factors  that  Affect  Reaction  Rates:  What  is  a  catalyst?

•  A catalyst is a substance that changes the rate of a chemical reaction o Aka: speeds up a

chemical reaction o Enzymes are

proteins which serve as catalysts in living organisms.

•  Catalysts (enzymes) are not consumed or changed during a chemical reaction! o  So, catalysts can be used over and over again

•  Enzymes are very specific •  Each enzyme can only catalyze one

chemical reaction

Structure •  The structure of enzymes can be altered by

temperature and pH o  Therefore, each enzyme/catalyst is customized

for and works best at a specific temperature and pH

•  If an enzyme’s structure is altered by a high temperature or an extreme pH, it becomes denatured o Denatured = enzyme no longer functions

Enzyme  Lab

After? •  Review tomorrow •  Test Friday