2.4 Chemical Reactions

Enzymes

2.4 Chemical Reactions

KEY CONCEPTS:

Enzymes help chemical reactions to occur

2.4 Chemical Reactions

• Catalysts are substances that speed up chemical reactions.– Decrease Activation Energy– Increase Reaction Rate

2.4 Chemical Reactions

• Enzymes are catalysts in living things

– Enzymes are needed for almost all processes.

– Most enzymes are proteins– Enzymes are not used up in reactions!

2.4 Chemical Reactions

2.4 Chemical Reactions

• Disruptions in homeostasis can prevent enzymes from functioning.

– Enzymes function best in a small range of conditions

– Changes in temperature and pH can break apart enzymes and cause them to stop working

– An enzyme’s function depends on its structure

2.4 Chemical Reactions

• An enzyme’s structure allows only certain reactants to bind to the enzyme.

– The reactants in an enzyme-catalyzed reaction are called Substrates

– The substrates interact with the enzyme at the Active Site

2.4 Chemical Reactions

substrates (reactants)

enzyme

Substrates bind to anenzyme at certain places called active sites.

2.4 Chemical Reactions

2.4 Chemical Reactions

• The lock-and-key model helps illustrate how enzymes function.

– substrates brought together & combined into products

– Each enzyme only catalyzes one type of reaction

Substrates bind to anenzyme at certain places called active sites.

The enzyme bringssubstrates together and weakens their bonds.

The catalyzed reaction formsa product that is releasedfrom the enzyme.

2.4 Chemical Reactions

CHECK for Understanding!

• Energy of Reactants:

– A• Normal Activation Energy:

– B• Activation Energy w/ Enzyme:

– C• Energy of Products:

– D• Endothermic or Exothermic?

– Exothermic

2.4 Chemical Reactions

CHECK for Understanding!

• Reactant?– A

• Substrate?– A

• Enzyme?– B

• Products?– E