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HOW ENZYMES FUNCTION

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HOW ENZYMES FUNCTION. 5.14 Activation Energy. Activation energy ( E A ): Energy available to break bonds and form new ones Although there is a lot of potential energy in biological molecules, such as carbohydrates, it is not released spontaneously. Reaction without enzyme. E A without - PowerPoint PPT Presentation
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HOW ENZYMES FUNCTION
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Page 1: HOW ENZYMES FUNCTION

HOW ENZYMES FUNCTION

Page 2: HOW ENZYMES FUNCTION

5.14 Activation Energy

• Activation energy (EA): Energy available to break bonds and form new ones

• Although there is a lot of potential energy in biological molecules, such as carbohydrates, it is not released spontaneously

Page 3: HOW ENZYMES FUNCTION

Reactionwithoutenzyme

EA with enzyme

Ener

gy Reactants

Reaction withenzyme

EA withoutenzyme

Netchangein energy(the same)

ProductsProgress of the reaction

Page 4: HOW ENZYMES FUNCTION

• Purpose: to lower the Energy of Activation Ea

• Enzymes are proteins and specific in shape

• If shape changes the enzyme will not function b/c substrate is specific for active site

5.14 Enzymes- Purpose

Page 5: HOW ENZYMES FUNCTION

5.15 Enzymes- Specific Structure

• Enzymes have unique three-dimensional shapes

– As a result of its shape, the enzyme has an active site where the enzyme interacts with the enzyme’s substrate

– Consequently, the substrate’s chemistry is altered to form the product of the enzyme reaction

Page 6: HOW ENZYMES FUNCTION

Substrate

Active site

Enzyme Enzyme-substratecomplex

Page 7: HOW ENZYMES FUNCTION

Enzyme availablewith empty activesite

Active site

1

Enzyme(sucrase)

Page 8: HOW ENZYMES FUNCTION

Enzyme availablewith empty activesite

Active site

1

Enzyme(sucrase)

Substrate bindsto enzyme withinduced fit

2

Substrate(sucrose)

Page 9: HOW ENZYMES FUNCTION

Enzyme availablewith empty activesite

Active site

1

Enzyme(sucrase)

Substrate bindsto enzyme withinduced fit

2

Substrate(sucrose)

Substrate isconverted toproducts

3

Page 10: HOW ENZYMES FUNCTION

Enzyme availablewith empty activesite

Active site

1

Enzyme(sucrase)

Substrate bindsto enzyme withinduced fit

2

Substrate(sucrose)

Substrate isconverted toproducts

3Products arereleased

4

Fructose

Glucose

Page 11: HOW ENZYMES FUNCTION

5.15 Enzymes- Environmental Conditions

• Enzymes require certain environmental conditions

– Temperature is very important– human enzymes function best at 37ºC, or body temperature– High temperature will denature (change the shape of)

human enzymes

– Enzymes also require a pH – around neutral for best results

Page 12: HOW ENZYMES FUNCTION

5.15 Enzymes- Environmental Conditions

Page 13: HOW ENZYMES FUNCTION

5.15 Enzymes- Cofactors

• Some enzymes require non-protein helpers

– Cofactors are inorganic, such as zinc, iron, or copper

– Coenzymes are organic molecules and are often vitamins

Page 14: HOW ENZYMES FUNCTION

5.16 Enzymes- Inhibitors

• Competitive inhibitors bind to the active site of an enzyme, competing with the substrate

• Noncompetitive inhibitors bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

• Examples of inhibitors include toxins, poisons, pesticides, and antibiotics

• BOTH type inhibit enzyme activity!

Page 15: HOW ENZYMES FUNCTION

Substrate

Enzyme

Active site

Normal binding of substrate

Competitiveinhibitor

Enzyme inhibition

Noncompetitiveinhibitor

Page 16: HOW ENZYMES FUNCTION

5.16 Enzyme Inhibitors

• Is inhibition reversible?

Page 17: HOW ENZYMES FUNCTION

Covalent bonds form between Enzyme and Inhibitor!

Page 18: HOW ENZYMES FUNCTION

5.16 Enzyme Inhibitors

• Enzyme inhibitors are important in regulating cell metabolism

• Feedback inhibition: when the product of a reaction can serve as an inhibitor of one enzyme in the same reaction

– The more product formed, the greater the inhibition = regulation of the reaction

Page 19: HOW ENZYMES FUNCTION

5.16 Enzyme Inhibitors

• What would happen if they did not produce feedback inhibitors??

Page 20: HOW ENZYMES FUNCTION

5.16 Enzyme Inhibitors

• There would be chaos in the cell!

• Too many chemical reactions!


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