Chemical Reactions and Enzymes

Objectives Identify the parts of a chemical reaction. Relate energy changes to chemical reactions. interpret energy diagrams Summarize the importance of enzymes in living things. enzymes (definition) “lock and key” model effect of temp. and pH on enzyme activity effect of concentration on enzyme activity

Chemical Reactions Definition Chemical bonds are broken and/or formed. process by which atoms or groups of atoms in substances are reorganized into different substances Chemical bonds are broken and/or formed.

Chemical Equations Reactants Products Read the following: “yields” C6H12O6 + 6O2 --> 6H20 + 6CO2 glucose oxygen water carbon dioxide “yields”

Energy of Reactions Energy Activation Energy (Ea) Energy Change ( H) needed to start chemical reactions Activation Energy (Ea) minimum amount of energy needed for reactants to form products Energy Change ( H) (Energy of Reactants - Energy of Products) Exothermic (- H) energy of products lower than energy of reactants Endothermic (+ H) energy of products higher than energy of reactants

Energy Diagram Exothermic Reaction Peak represents the amount of energy that must be added to the system to make the reaction go

Energy Diagram Endothermic

___________ HELP CHEMICAL REACTIONS _______________ Catalysts ___________ HELP CHEMICAL REACTIONS _______________ CATALYSTS HAPPEN FASTER Catalysts work by ____________ the ___________________________to get a chemical reaction started. DECREASING ACTIVATION ENERGY required NOTE: does not increase the amount of product does not get used up in the reaction

Enzymes Enzymes types of proteins act as biological catalysts speed up the rate of reaction in biological processes (by lowering activation energy) most are specific to one reaction

Enzymes Naming Enzymes Examples: many end in _____ beginning of the name tells what it does Examples: DNA Polymerase “polymerizes” joins monomers to make DNA Protease breaks down proteins ATP synthase synthesizes ATP

Energy Diagram

Enzymes Substrate Active Site reactants that bind to the enzyme Active Site location where the substrate binds on the enzyme Enzymes combine with the substrate in the active site to form the enzyme-substrate complex

Enzymes Lock & Key Model: Enzymes exhibit specificity: substrate and active site -> complimentary shapes (puzzle pieces that fit together) Enzymes exhibit specificity: enzymes only fit with a particular substrate due to the shape of the active site

3) Enzyme-Substrate Complex Enzyme Demonstration 5) Product Released; enzyme free to react again 1) Substrate 2) Fits into active site 4) Reaction takes place 3) Enzyme-Substrate Complex

Enzymes Factors that affect enzyme activity pH temperature concentration (amt.) of substrate concentration (amt.) of enzyme

Enzymes Optimal pH (dependent on enzyme) Too low -> decreased rate of reaction Too high -> enzyme denatures (breaks apart)

Denatured Proteins When a protein loses its shape (its tertiary (3-D) structure) Cause: -high temperature (like on the stove) -pH extremes (like in your stomach) Effect: -Losses its ability to function -Properties can change (become insoluble, change color) Happens when a protein loses its structural integrity, its tertiary (3-D) structure is destroyed

Denatured Proteins changes shape ACTIVE SITE CAN’T BIND Denaturing an enzyme _______ the _______ of the ______________ so enzyme ______________ to ____________ shape ACTIVE SITE CAN’T BIND SUBSTRATE As a result, the reaction occurs at a reduced rate or stops all together.

Denatured Proteins As a result, the reaction occurs at a reduced rate or stops all together.

Enzymes Optimal Temp. Temp , Activity Temp too high-> protein denatures (breaks apart)

Enzymes Predict what would happen if… (1) you added more enzyme to the reaction? (2) you added more substrate to the reaction? what if you added more enzyme to the reaction? what if you added more substrate to the reaction?

WHITEBOARDS! How does the amount of the substrate and the amount of enzyme affect the rate of reaction?

Lab: Understanding Enzymes Objectives: Understand the function of enzymes in the human body. Observe the function of several commercially important enzymes. Predict the effect of enzyme concentration, temperature, and pH on enzyme activity rate. Understand the structure of enzymes & how denaturation occurs. Graph enzyme activity rates and different enzyme concentrations.

Enzyme Inhibitors Competitive Inhibition Non-Competitive Inhibition plug up active site-->substrate can’t bind Non-Competitive Inhibition bind to enzyme (not in active site) --> change shape of active site

Enzyme Inhibitors May be Examples Permanent - covalent bond Reversible - hydrogen bond Examples Nerve gas Penicillin Cyanide Aspirin AZT

Online Tutorials for additional information & visuals http://resources.emb.gov.hk/biology/english/virtual_lab/flash/enzyme_lab.html http://www.bbc.co.uk/education/asguru/biology/02biologicalmolecules/01proteins/11enzymes/index.shtml http://www.tvdsb.on.ca/westmin/science/sbi3a1/digest/enzymes.htm Note: Not required.

Can you… …identify the parts of a chemical reaction? …relate energy changes to chemical reactions? interpret energy diagrams? …summarize the importance of enzymes in living things? enzymes (definition)? “lock and key” model? effect of temp. and pH on enzyme activity?