2-4 CHEMICAL REACTIONS AND
ENZYMESObjectives:
1) Explain how chemical reactions affect chemical bonds in
compounds.
2) Explain why enzymes are important to living things.
WARM UP Chemical reaction demo
INTRODUCTION Everything that happens in an
organism is based on chemical reactions
CHEMICAL REACTIONS
Chemical reaction: a process that changes one set of chemicals into another set of chemicals Reactants: the elements or compounds that enter into a
chemical reaction Products: the elements or compounds produced by a
chemical reaction Chemical reactions always involve the breaking of
bonds in reactants and the formation of new bonds in products
https://www.youtube.com/watch?v=OwM_P_4CmXE
ENERGY IN REACTIONS Elephant’s toothpaste demo Energy is released or absorbed
whenever chemical bonds form or are broken Involve changes in energy
ENERGY CHANGES Energy changes are
one of the most important factors in determining whether a chemical reaction will occur
Chemical reactions that release energy often
occur spontaneously Absorb energy will not
occur without a source of energy
Borax and glue demo
ENERGY CHANGES
Energy can be released in the form of heat, light, or sound
Organisms need to carry out reactions that require energy Every organism must have a source of energy to carry out
chemical reactions Plantssunlight Animalseating food and drink
ACTIVATION ENERGY Activation
energy: the energy that is needed to get a reaction started
http://phet.colorado.edu/en/simulation/reversible-reactions
ENZYMES Catalyst: a
substance that speeds up the rate of a chemical reaction Work by lowering a
reaction’s activation energy
Enzymes: proteins that act as biological catalysts Speed up chemical
reactions that take place in cells
ENZYMES CONT’D Enzymes are very specific
Generally catalyzing only one chemical reaction
Part of an enzyme’s name is usually derived from the reaction it catalyzes
ENZYME ACTION
Reactants must collide with enough energy so that existing bonds will be formed If there’s not enough energy, they will be
unchanged after the collision
THE ENZYME-SUBSTRATE COMPLEX Substrates: the
reactants of enzyme-catalyzed reactions
Active site: the substrates bind to a site on the enzyme
The substrates and active site have complementary shapes (like puzzle pieces)
THE ENZYME-SUBSTRATE COMPLEX CONT’D
Forms the enzyme-substrate complex
Remain together until reaction is finished
Then the products are released
The enzyme moves to start the process again
REGULATION OF ENZYME ACTIVITY Enzymes can be
affected by any variable that influences a chemical reactionpH valuesTemperature
REGULATION OF ENZYME ACTIVITY CONT’D Cells regulate
activities of enzymes Cell proteins turn
enzymes “on” and “off” Enzymes are essential
in Regulating chemical
pathways Making materials that
cells need Releasing energy Transferring information
2-4 EXIT TICKET Answer the
following questions.
Use complete sentences.
You may NOT use your book. You MAY use your notes.
This is a quiz grade.
1) Explain how chemical reactions affect chemical bonds in compounds.
2) Explain why enzymes are important to living things.