Amino Acids, Proteins, and Enzymes Enzymes Enzyme Action Factors Affecting Enzyme Action Enzyme Inhibition

Enzymes Catalysts for biological reactions Most are proteins Catalyst: Substance that speeds up a chemical reaction without being used in the process Most are proteins Lower the activation energy Minimum energy required to start a reaction Increase the rate of reaction

Enzyme Action and the Hydrolysis of Sucrose Enzyme Sucrase breaks down a molecule of sucrose into glucose and fructose http://highered.mcgraw-hill.com/classware/ala.do?isbn=0072965819&alaid=ala_1032271&showSelfStudyTree=true

What do enzyme names tell us? Enzyme names usually end in –ase Identifies a reacting substance sucrase – breaks down sucrose lipase - breaks down lipids Describes function of enzyme oxidase – catalyzes oxidation hydrolase – catalyzes hydrolysis Common names of digestion enzymes still use –in ex. pepsin, trypsin What do you think lactase does? …Manon???

Important Enzyme Terms Substrate: Reactant(s) an enzyme is acting on ex. what is the substrate sucrase acts on? Active Site: The location on the enzyme where the substrate binds Enzyme-Substrate Complex: An enzyme with its substrate attached to the active site

2 Models for Enzyme Action Lock and Key Model Induced Fit Model

Enzyme Action: Lock and Key Model An enzyme binds a substrate in a region called the active site Only certain substrates can fit the active site Amino acid R groups in the active site help substrate bind Enzyme-substrate complex forms Substrate reacts to form product Product is released

Lock and Key Model

Lock and Key Model

Lock and Key Model + + E + S ES complex E + P P S S P

Enzyme Action: Induced Fit Model Enzyme structure flexible, not rigid Enzyme and active site adjust shape to bind substrate Increases range of substrate specificity Shape changes also improve catalysis during reaction

Enzyme Action: Induced Fit Model E + S ES complex E + P P S S S P

Learning Check The active site is (1) the enzyme (2) a section of the enzyme (3) the substrate B. In the induced fit model, the shape of the enzyme when substrate binds (1) Stays the same (2) adapts to the shape of the substrate

Solution E2 The active site is (2) a section of the enzyme B. In the induced fit model, the shape of the enzyme when substrate binds (2) adapts to the shape of the substrate

Practice Questions Complete the 2 practice questions at the end of the worksheet with a partner

Factors Affecting Enzyme Action: Temperature Little activity at low temperature Rate increases with temperature Most active at optimum temperatures (usually 37°C in humans) Activity lost with denaturation at high temperatures

Factors Affecting Enzyme Action Optimum temperature Reaction Rate Low High Temperature

Factors Affecting Enzyme Action: Substrate Concentration Increasing substrate concentration increases the rate of reaction (enzyme concentration is constant) Maximum activity reached when all of enzyme combines with substrate

Factors Affecting Enzyme Action Maximum activity Reaction Rate substrate concentration

Factors Affecting Enzyme Action: pH Maximum activity at optimum pH The pH affects the R group of the amino acid Changing the pH changes the charge on R groups which changes the tertiary structure of the enzyme Different enzymes have a different optimal pH Pepsin works best at a pH of 2 (found in the stomach) Trypsin works best at a pH of 8 (found in small intestine) Most lose activity in low or high pH

Factors Affecting Enzyme Action Reaction Rate Optimum pH 3 5 7 9 11 pH

Learning Check E3 Sucrase has an optimum temperature of 37°C and an optimum pH of 6.2. Determine the effect of the following on its rate of reaction (1) no change (2) increase (3) decrease A. Increasing the concentration of sucrose B. Changing the pH to 4 C. Running the reaction at 70°C

Solution E3 Sucrase has an optimum temperature of 37°C and an optimum pH of 6.2. Determine the effect of the following on its rate of reaction (1) no change (2) increase (3) decrease A. 2, 1 Increasing the concentration of sucrose B. 3 Changing the pH to 4 C. 3 Running the reaction at 70°C

Potato Lab How do these factors relate to the lab we are doing today? What is the enzyme in this lab? What is the substrate in this lab? Which factors affecting enzyme action are we manipulating?

Time to Plan! As a group you need to design the procedure for the second half of the lab When your group has agreed on the procedure share it with me for approval Once it is approved everyone needs to write the procedure into their lab handout All written procedures, observations, and questions need to be completed in your own words

Safety Precautions What safety precautions do you think are necessary for this lab? Materials: 3% Hydrogen Peroxide (purchased at the drug store, used as a disinfectant for cuts) Potato blended with water

Enzyme Inhibition Inhibitors cause a loss of catalytic activity Change the protein structure of an enzyme May be competitive or noncompetitive Some effects are irreversible

Competitive Inhibition A competitive inhibitor Has a structure similar to substrate Occupies active site Competes with substrate for active site Has effect reversed by increasing substrate concentration

Noncompetitive Inhibition A noncompetitive inhibitor Does not have a structure like substrate Binds to the enzyme but not active site Changes the shape of enzyme and active site Substrate cannot fit altered active site No reaction occurs Effect is not reversed by adding substrate

Learning Check E4 Identify each statement as describing an inhibitor that is (1) Competitive (2) Noncompetitive A. Increasing substrate reverses inhibition B. Binds to enzyme, not active site Structure is similar to substrate D. Inhibition is not reversed with substrate

Solution E4 Identify each statement as describing an inhibitor that is (1) Competitive (2) Noncompetitive A. 1 Increasing substrate reverses inhibition B. 2 Binds to enzyme, not active site C. 1 Structure is similar to substrate D. 2 Inhibition is not reversed with substrate

Allosteric Regulation

Allosteric Regulation Allosteric Regulation: A method used by cells to control enzyme activity Allosteric Sites: A receptor site that is located some distance from the active site Binds substances that inhibit or stimulate an enzyme’s activity Activator: Binding to allosteric site on enzyme stabilizing the protein conformation keeping the active site available for the substrate Allosteric Inhibitor: Binding to allosteric site on enzyme stabilizing the protein conformation keeping the active site UNavailable for the substrate …Does this sound familiar???

Applications of Enzymes Used in laundry detergents! Combincation of Proteases, Lipases, and Amylases Lactase for lactose intolerant people! Can be eaten in a pill Milk/dairy products can be pre-treated Meat Tenderizer Protease can be added to tough cuts of meat to make the meat more tender Contact Lens Solution Proteases and lipases added to get rid of dirt

Homework: Use of Enzymes- Reading Answer the questions on the question sheet using the information in the reading

Homework: Complete your portfolio for Unit 1

Unit Test: Biochemistry There are review questions on the website I will also post the review questions created by your peers Will be next Saturday at the start of class Will cover all the material we have discussed in the biochemistry unit (including questions from your lab!) If you are unclear about any of these concepts please email me!