EnzymesCatalysts of Life

Review of Chemical ReactionsA chemical reaction is a process that

changes, or transforms, one set of chemicals into anotherReactants are elements or compounds that

enter into a chemical reactionProducts are the elements or compounds

produced by a chemical reactionChemical reactions usually require energy to

get startedActivation energy is the energy that is needed

to get a reaction started

What are enzymes?Enzymes are proteins

that hasten, or speed up, chemical reactionsA catalyst is a

substance that speeds up the rate of a chemical reaction

Enzymes are biological catalystsEnzymes speed up the

reactions that take place in cells

How do enzymes work?The molecule that an

enzyme binds with or acts upon is called the substrateThe spot on an enzyme

where the enzyme and substrate bind together is called the active site.

The active site is made of deep folds created by the folding of amino acid chains

Enzymes can be used over and over again after a reaction is complete

How do enzymes work?Enzymes have a

specific shapeSubstrates also have a

specific shapeIn order for an

enzyme and substrate to bind together and react, their shapes MUST fit together

This is called the lock-and-key model

How do enzymes work?If an enzyme shape does not match with a substrate,

there is no reactionAn enzyme’s shape can be changed if conditions are

not rightIf an enzyme’s shape is changed due to changing

conditions, then the enzyme has been denaturedNo reaction can occur if an enzyme’s shape is

denaturedFactors that affect enzyme shape

pH – too acidic or too basicTemperature – too hot or too coldEnzyme concentration – how many enzymes are there?

How do enzymes work?Web Link:http://www.lew-port.com/1071204111340279

3/lib/10712041113402793/Animations/Enzyme_activity.html

Other factors affecting enzymesCompetitive inhibitors are molecules that

are similar to the substrate’s shape Competitive inhibitors get stuck in the active

site and prevent the enzyme from binding with the substrate

Noncompetitive inhibitors are molecules that bind near, but not at, the active siteNoncompetitive inhibitors change the shape of

the active site and prevent the enzyme from binding with the substrate