Chemical Reactions & Chemical Reactions & EnzymesEnzymes

- Means to write that information down.- Means to write that information down.

Chemical Reactions and EnzymesChemical Reactions and Enzymes

As we have seen living things are made of As we have seen living things are made of chemical compounds, but more importantly chemical compounds, but more importantly chemistry isn’t just what life is made of, chemistry isn’t just what life is made of, chemistry is also what life does.chemistry is also what life does.

Chemical ReactionsChemical Reactions Chemical reaction Chemical reaction – is a process that changes – is a process that changes

one set of chemicals into another set of one set of chemicals into another set of chemicals.chemicals.

The elements or compounds that enter into a The elements or compounds that enter into a chemical reaction are the chemical reaction are the reactantsreactants..

The elements or compounds produced by a The elements or compounds produced by a chemical reaction are known as chemical reaction are known as productsproducts..

Energy in ReactionsEnergy in Reactions Energy is neither created nor destroyed, Energy is neither created nor destroyed,

therefore energy is released or absorbed therefore energy is released or absorbed whenever chemical bonds form or are broken.whenever chemical bonds form or are broken.

Chemical reactions that release energy often Chemical reactions that release energy often occur spontaneously. occur spontaneously. Chemical reactions Chemical reactions that absorb energy will not without a that absorb energy will not without a source of energy.source of energy.

Activation EnergyActivation Energy Do all reactions occur spontaneously?Do all reactions occur spontaneously? If this were true what would happen to your If this were true what would happen to your

textbooks?textbooks? Will wood burn only if you light it with a match.Will wood burn only if you light it with a match.

Chemists call the energy that is needed to get a Chemists call the energy that is needed to get a reaction started the reaction started the activation energyactivation energy

Fig 2–19 (p. 50) shows, Fig 2–19 (p. 50) shows, activation energyactivation energy is a factor in is a factor in whether the overall chemical reaction releases energy whether the overall chemical reaction releases energy or absorbs energy.or absorbs energy.

EnzymesEnzymes Some chemical reactions that make life Some chemical reactions that make life

possible are too slow or have activation possible are too slow or have activation energies that are too high to make them energies that are too high to make them practical for life.practical for life.

These reactions require These reactions require catalystscatalysts or substances or substances that speed up the rate of a chemical reaction.that speed up the rate of a chemical reaction.

CatalystsCatalysts work by lowering a reaction’s work by lowering a reaction’s activation energy.activation energy.

Two paths will take you to the same end Two paths will take you to the same end location. Which one will take less energy to location. Which one will take less energy to

get there and will happen faster?get there and will happen faster?

Activation EnergyActivation Energy What significance do these energy changes have to do with living things?What significance do these energy changes have to do with living things?In order to stay alive, organisms need to carry out reactions that require In order to stay alive, organisms need to carry out reactions that require

energy.energy.

EnzymesEnzymes

EnzymesEnzymes – are special proteins that act as – are special proteins that act as biological catalysts.biological catalysts.

Enzymes speed up chemical reactions that Enzymes speed up chemical reactions that take place in cells.take place in cells.

Enzymes are very specific, generally Enzymes are very specific, generally catalyzing only one chemical reactioncatalyzing only one chemical reaction..

EnzymesEnzymes

For a chemical reaction to occur, the For a chemical reaction to occur, the reactants must collide with enough energy so reactants must collide with enough energy so that existing bonds will be broken and new that existing bonds will be broken and new bonds will be formed.bonds will be formed.

Enzymes provide a place where reactants Enzymes provide a place where reactants can be brought together to react.can be brought together to react.

The reactants of enzyme – catalyzed The reactants of enzyme – catalyzed reactions are known asreactions are known as substratessubstrates..

The Enzyme/Substrate ComplexThe Enzyme/Substrate Complex Each protein (enzyme) has a specific shape, Each protein (enzyme) has a specific shape,

the substrate binds to the active site on the the substrate binds to the active site on the protein to help speed up the reaction.protein to help speed up the reaction.

AKA “lock and key”AKA “lock and key”

Enzymes - In Summary

Digestive Enzyme Basics

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