Chemical Reaction – process that changes one set of chemicals into another set of chemicalsThe breaking bonds in reactant and the formation of

new bonds in products!

Reactants – elements or compounds that enter into a chemical reactionbonds are brokenenergy is released

Products – the elements or compounds produced by a chemical reactionbonds are formedenergy is absorbed

Example of a Chemical ReactionIn blood: CO2 + H2O → H2CO3 to lungs

Reactants Products H2CO3 → CO2 + H2O --breathe out

Energy ChangesChemical reactions that release energy are

spontaneous

Chemical reactions that absorb energy will not occur without an input of energy

Organisms need to carry out reactions that need energy to stay alive.plants get energy from sunlightanimals get energy from digested food

Energy and chemical reactionsMost chemical reactions require energy to

begin - the energy required to start a chemical

reaction is called activation energy.

What are enzymes?Enzymes are proteins which reduce

activation energy allowing chemical reactions to occur in living things

Enzymes reduce activation energy

Enzymes Act as Biological CatalystsCatalysts are inorganic molecules that speed up

chemical reactionsEnzymes speed up reactions in living things

-enzymes are not changed by the reaction they speed up

- one molecule of enzyme can catalyze (start) many

reactions

Active SiteEnzymes have an area called an active site. - the active site is where the chemical

reaction occurs

The Shape of the Enzyme Determines FunctionThe active site of the enzyme fits with only

one type of molecule known as the substrate.Substrate is the molecule that the enzyme

acts on.The fact that the active site can only accept

one type of substrate is known as enzyme specificity

Enzyme ReactionsWritten as : Enzyme + Substrate ES Enzyme + Product - ES refers to the enzyme substrate complex, the time

when the substrate joins with the active site.

Example

Catalase + 2H2O2 ES Catalase + 2H2O + O2

enzyme substrate enzyme enzyme product product substrate complex

Facts: •Enzymes are specific to the reaction that they catalyze•Enzymes are NOT used up in the chemical reaction•Enzymes can build molecules

Activation Energy Graph (pg51)

Two Ideas About Enzyme Action

Lock & Key Model Induced Fit Model

Lock & Key ModelSubstrate fits into the active site like a key

into a lockThe enzyme puts stress on the bond which reduces the amount of energy needed to break apart the substrateThe products of the reaction leave and make the enzyme available for more substrate

Induced Fit ModelSubstrate doesn’t quite

fit into the active siteSubstrate causes

(induces) the enzyme to

change shape – allows the substrate to fit into the active site

Enzyme stresses bonds

on substrate

Enzymes can build molecules

Substrate molecules can only bond one way.

Substrate moleculesfit into the active site in the best position to bond Once in the active site, the molecules of

substrate join

Enzyme InhibitorsInhibitors control the rate of enzyme activity - if there is too much of an enzyme’s product,

inhibitors can slow or even stop an enzyme’s activity

Two types of Inhibition - Competitive - Non

Competitive

Competitive InhibitionThe inhibitor is a molecule that can occupy part

of the active siteWhile the inhibitor is in the active site,

substrate can’t bind with the enzyme – inhibitors compete with the substrate for the active site

inhibitor competes with substrate inhibitor blocks the active site

Noncompetitive InhibitionThe inhibitor binds with the enzyme at a site away

from the active site.Inhibitor causes enzyme to change shape – prevents substrate from entering the active site

Inhibitor binds with enzyme Enzyme changes shape keeps substrate from active site

Feedback Inhibition Enzymes are often part of

a series of reactions called a biochemical pathway

- the product of one enzyme acts as the substrate for another enzyme

-the final product – acts as an inhibitor for the first enzyme in the pathway

- this stops the pathway and the production of the end-product stops as well

Co-Enzymes and Co-factorsCo-enzymes and Co-factors are molecules

that help certain enzymes to catalyze a reaction

- co-enzymes and co-factors often act as carriers of electrons, atoms or functional groups needed to complete a reaction.

Co-Enzymes and Co-Factors - while they bind to an enzyme’s active site, and

participate in the reaction, they are not changed by the reaction and aren’t considered substrates.

- Co-enzymes are organic molecules and include: NAD, NADP, FAD, vitamin B 1, vitamin B 6, and vitamin B 12

- Co-factors are inorganic molecules and include dietary minerals like zinc, iron, copper & potassium

Denatured Enzymes• Enzymes are proteins and if they are exposed to extremes of temp or pH, they will lose their shape

• if an enzyme is denatured, substrate can’t enter the active site

extreme temp

or

pH

Common EnzymesAmylase - breaks down starchCatalase – breaks down H2O2

DNA polymerase – joins DNA nucleotides to build DNA

Lipase – break apart fatsLactase – breaks apart lactose – milk sugarProtease- breaks apart protein molecules

-What does –ase in a molecules’ name imply?