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.