1. Mrs. Ireland has an elastic band wrapped around her finger ready to attack the next student that does not do their AP Biology homework. What type of energy does this elastic band represent? 2. What type of energy does ATP posses? 3. In a population of 500, 142 people have the trait for a disease known as the AP Biology homework slacker disease (A). What is the frequency of q allele and the hybrid trait? 3/3 Daily Catalyst Pg. 87 Enzymes Quiz #22 Enzymes on Wednesday Lab on Wednesday Test grade Unit Test #8 Energy on Friday Review day on Thursday Extra credit article due Tuesday (3/10) Test corrections due Tuesday (3/10) Tutoring after school, during fourth, and during lunch Schedule with Mrs. Ireland 3/3 Class Business Daily Catalyst Class Business Finish reviewing quiz #21 Intro to enzymes Exit ticket 3/3 Agenda Pg. 87 Enzymes Key Concepts An organisms metabolism transforms matter and energy, subject to the laws of thermodynamics The free-energy change of a reaction tells us whether the reaction occurs spontaneously Question #Reviewer 1Daquine 2Kordell 3Travia 4Daquine 5Yennifer 6Teresa 7Tiana 8Bristin 9Kiandria 10Taylor 11Anthony 12Quinshelle 13Tiffany 14Daniel 15John 16Annie Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriers Key Point #1: A catalyst- Is a chemical agent that speeds up a reaction without being consumed by the reaction Key Point #2: Enzymes- A protein catalyst ase They Lower the activation barrier How do enzymes speed up a reaction? The Activation Barrier Energy is needed to break and make bonds. This is what we call a reaction. Key Point #3: The activation energy, E A Is the initial amount of energy needed to start a reaction Heat or energy The energy profile for an exergonic reaction Free energy Progress of the reaction G < O EAEA A B C D Reactants A C D B Transition state A B CD Products I mentioned heat before as the energy source. Why is heat not always the best option in a cell? Key Point #4: Enzymes speed up reactions by lowering the activation energy. Same product is made Still exergonic or endergonic JUST FASTER! The effect of enzymes on reaction rate Progress of the reaction Products Course of reaction without enzyme Reactants Course of reaction with enzyme EAEA without enzyme E A with enzyme is lower G is unaffected by enzyme Free energy Figure 8.15 Substrate Specificity of Enzymes For enzymes to speed up a reaction, they need to bind to the substrate (reactant) Key Point #5: Enzyme binds to the substrate Forms the enzyme-substrate complex (ES complex) Can the substrate bind anywhere? Key Point #6: The active site Is the region on the enzyme where the substrate binds Lock and key Figure 8.16 Substate Active site Enzyme (a) Key Point #7 Induced fit of a substrate: Once bound, the active site changes shape so that the substrate fits even better. Figure 8.16 (b) Enzyme- substrate complex Reusable Key Point #8: Enzymes are not consumed in the reaction. They are reusable for the next reaction! The catalytic cycle of an enzyme Substrates Products Enzyme Enzyme-substrate complex 1 Substrates enter active site; enzyme changes shape so its active site embraces the substrates (induced fit). 2 Substrates held in active site by weak interactions, such as hydrogen bonds and ionic bonds. 3 Active site (and R groups of its amino acids) can lower E A and speed up a reaction by acting as a template for substrate orientation, stressing the substrates and stabilizing the transition state, providing a favorable microenvironment, participating directly in the catalytic reaction. 4 Substrates are Converted into Products. 5 Products are Released. 6 Active site Is available for two new substrate Mole. Figure 8.17 Key Point #9: The active site can lower an E A barrier by: Orienting substrates correctly Straining substrate bonds Providing a favorable microenvironment Covalently bonding to the substrate Key Point #10: Transition state:- The reactive (unstable) condition of the substrate Enzymes help the substrate reach the transition state by straining substrate bonds so they break easily. Enzyme activity Key Point #11: Enzyme activity also relies on the substrate concentration. Increase [substrate] = increase E-S complexes Eventually the solution will be saturated with substrates and more enzymes will be needed. Effects of Local Conditions on Enzyme Activity The activity of an enzyme Is affected by general environmental factors Effects of Temperature and pH Key Point #12: Each enzyme has an optimal temperature and pH in which it can function Figure 8.18 Optimal temperature for enzyme of thermophilic Rate of reaction Temperature (C) (a) Optimal temperature for two enzymes Optimal temperature for typical human enzyme (heat-tolerant) bacteria Has an optimal pH in which it can function Figure 8.18 Rate of reaction (b) Optimal pH for two enzymes Optimal pH for pepsin (stomach enzyme) Optimal pH for trypsin (intestinal enzyme) Example Cofactors Key Point #13: Enzyme assistance- Cofactors Are nonprotein enzyme helpers Coenzymes Vitamins 1. A very large population of randomly-mating laboratory mice contains 35% white mice. White coloring is caused by the double recessive genotype, "aa". Calculate allelic and genotypic frequencies for this population. 2. Describe the induced fit model of enzymes. 3. Use the word optimal in a sentence. 4. Label the following diagram: Daily Catalyst Pg. 88 Control of enzymes 1. A very large population of randomly-mating laboratory mice contains 35% white mice. White coloring is caused by the double recessive genotype, "aa". Calculate allelic and genotypic frequencies for this population. Answer: 35% are white mice, which = 0.35 and represents the frequency of the aa genotype (or q2). The square root of 0.35 is 0.59, which equals q. Since p = 1 - q then = Now that we know the frequency of each allele, we can calculate the frequency of the remaining genotypes in the population (AA and Aa individuals). AA = p2 = 0.41 x 0.41 = 0.17; Aa = 2pq = 2 (0.59) (0.41) = 0.48; and as before aa = q2 = 0.59 x 0.59 = If you add up all these genotype frequencies, they should equal 1. Daily Catalyst Pg. 88 Control of enzymes 2. Describe the induced fit model of enzymes. Once the substrate binds to the enzyme at the active site, the active site morphs to better form around the substrate to form a tighter bond. 3. Use the word optimal in a sentence. The optimal environment for taking the ACT on the 17 th of March is a silent location with a calculator that works. 4. Label the following diagram: A-substrate B-Active Site C-Enzyme D- Product Daily Catalyst Pg. 88 Control of enzymes Quiz #22 Enzymes TODAY Lab on Wednesday Test grade Unit Test #8 Energy on Friday Review day on Thursday Extra credit article due Tuesday (3/10) Test corrections due Tuesday (3/10) Tutoring after school, during fourth, and during lunch Schedule with Mrs. Ireland 3/4 Class Business Daily Catalyst Class Business Finish reviewing quiz #21 Intro to enzymes Exit ticket 3/4 Agenda Pg. 88 Control of Enzymes Cofactors- page 87 Key Point #13: Enzyme assistance- Cofactors Are nonprotein enzyme helpers Coenzymes Vitamins Pg. 88 Control of Enzymes Concept 8.5: Regulation of enzyme activity helps control metabolism A cells metabolic pathways must be tightly regulated Enzyme Inhibitors Key Point #1: Competitive inhibitors Bind to the active site of an enzyme, competing with the substrate The substrate cannot bind Figure 8.19 (b) Competitive inhibition A competitive inhibitor mimics the substrate, competing for the active site. Competitive inhibitor A substrate can bind normally to the active site of an enzyme. Substrate Active site Enzyme (a) Normal binding Enzyme Inhibitors Key Point #2: Noncompetitive inhibitors Bind to another part of an enzyme, changing the shape of the active site The substrate CANNOT bind Figure 8.19 A noncompetitive inhibitor binds to the enzyme away from the active site, altering the conformation of the enzyme so that its active site no longer functions. Noncompetitive inhibitor (c) Noncompetitive inhibition Allosteric Regulation of Enzymes Key Point #3: Allosteric regulation Is the term used to describe any case in which a proteins function at one site is affected by binding of a regulatory molecule at another site Regulatory molecules bind to specific sites (allosteric sites) and change the shape of the protein changing the shape of the active site Inhibit or stimulate the enzyme Allosteric Activation and Inhibition Many enzymes are allosterically regulated Enzymes change shape when regulatory molecules bind to specific sites, affecting function Stabilized inactive form Allosteric activater stabilizes active from Allosteric enyzme with four subunits Active site (one of four) Regulatory site (one of four) Active form Activator Stabilized active form Allosteric activater stabilizes active form Inhibitor Inactive form Non- functional active site (a) Allosteric activators and inhibitors. In the cell, activators and inhibitors dissociate when at low concentrations. The enzyme can then oscillate again. Oscillation Figure 8.20 Key Point #4: Cooperativity Is a form of allosteric regulation that can amplify enzyme activity Figure 8.20 Binding of one substrate molecule to active site of one subunit locks all subunits in active conformation. Substrate Inactive form Stabilized active form (b) Cooperativity: another type of allosteric activation. Note that the inactive form shown on the left oscillates back and forth with the active form when the active form is not stabilized by substrate. Key Point #5: Cooperativity example In hemoglobin (red blood cells), when the first oxygen binds to hemoglobin, it stabilizes hemoglobin and encourages other oxygen's to bind (4 O2s) Example in the TOOLBOX! Feedback Inhibition Key Point #6: In feedback inhibition The end product of a metabolic pathway shuts down the pathway Feedback inhibition Active site available Isoleucine used up by cell Feedback inhibition Isoleucine binds to allosteric site Active site of enzyme 1 no longer binds threonine; pathway is switched off Initial substrate (threonine) Threonine in active site Enzyme 1 (threonine deaminase) Intermediate A Intermediate B Intermediate C Intermediate D Enzyme 2 Enzyme 3 Enzyme 4 Enzyme 5 End product (isoleucine) Figure 8.21 Directions: With your partner, read the pre-lab reading and answer the pre-lab questions. Write 4 hypotheses based on the scenarios given to you. Check in with Mrs. Ireland before you move on! Noise: 2 (with partner) Time: until 12:50 James, Joe, and Paul (quiz at 8:30) Enzyme Lab