Enzymes

1. Enzymes Honors Biology Mrs. Mawhiney

2. Flow of energy through life • Life is built on chemical reactions • transforming energy from one form to another organic moleculesATP & organic molecules sun organic moleculesATP & organic molecules solar energyATP& organic molecules

3. Enzymes • Biological catalysts • proteins (& RNA) • facilitate chemical reactions • increase rate of reaction without being consumed • reduce activation energy • don’t change free energy (G) released or required • required for most biological reactions • highly specific • thousands of different enzymes in cells • control reactionsof life

4. Enzymes • Enzymes are catalysts. They increase the speed of a chemical reaction without themselves undergoing any permanent chemical change. • Enzymes are neither used up in the reaction, nor do they appear as reaction products. 4

5. Enzyme Specificity • The action of an enzyme depends primarily on the structure of the protein that constitutes the enzyme. • The part of the enzyme structure that acts on the substrate is called the active site. • The active site is a groove or pocket in the enzyme structure where the substrate can bind. 5

6. Enzyme Mechanics • An enzyme-substrate complex forms when the enzyme’s active site binds with the substrate like a key fitting a lock.  • The shape of the enzyme must match the shape of the substrate. • Enzymes are therefore very specific; they will only function correctly if the shape of the substrate matches the active site. 6

7. Enzymes vocabulary substrate • reactant which binds to enzyme • enzyme-substrate complex: temporary association product • end result of reaction active site • enzyme’s catalytic site; substrate fits into active site active site products substrate enzyme

8. Induced Fit Theory 8

9. Induced Fit Theory • The substrate molecule normally does not fit exactly in the active site. • This induces a change in the enzymes conformation (shape) to make a closer fit. • In reactions that involve breaking bonds, the inexact fit puts stress on certain bonds of the substrate. • This lowers the amount of energy needed to break them. 9

10. Properties of enzymes • Reaction specific • each enzyme works with a specific substrate • Not consumed in reaction • single enzyme molecule can catalyze thousands or more reactions per second • enzymes unaffected by the reaction • Affected by cellular conditions • any condition that affects protein structure • temperature, pH, salinity

11. energy Activation energy • Breaking down large molecules requires an initial input of energy • activation energy • large biomolecules are stable • must absorb energy to break bonds cellulose CO2 + H2O + heat

12. Reducing Activation energy • Catalysts • reducing the amount of energy to start a reaction Pheeew…that takes a lotless energy! uncatalyzed reaction catalyzed reaction NEW activation energy reactant product

13. Catalysts • So what’s a cell got to do to reduce activation energy? • get help! … chemical help… ENZYMES Call in the ENZYMES! G

14. Enzymes Without Enzyme With Enzyme Free Energy Free energy of activation Reactants Products Progress of the reaction 14

15. Factors that Affect Enzymes

16. Factors Affecting Enzyme Function • Enzyme concentration • Substrate concentration • Temperature • pH • Salinity catalase