KIN 292 1st Edition Lecture 5 These are the notes from Professor Starnes lecture of Clinical Human Physiology These come from the slideshows provided by the professor and include extra notes and explanations Highlighted or bolded information are things that I believe to be information that is important to look over multiple times The notes in red are my personal additions and quotes of Professor Starnes from the class lecture Outline of Last Lecture I Finishing nucleotides II Types of Metabolic Reactions III Metabolic Reactions and Energy Outline of Current Lecture I Metabolic Reactions and Energy II Reaction Rates Current Lecture Clarification from Last Lecture Reactants possess more energy than products this statement needs some clarification When true reactions proceeds spontaneously When false it will not o There will be more energy in the reactions than in the products Exergonic reactions proceed spontaneously because it obeys the 2nd Law of Thermodynamics Entropy Endergonic reactions do not proceed spontaneously It needs an added energy source in order to go o Energy added could come from energy released above or another source Spontaneous 1 acting in accordance with or resulting from a natural feeling impulse or tendency without any constraint effort or premeditation 2 having no apparent external cause or influence occurring or produced by its own energy force etc or through internal causes self acting 3 growing naturally without being planted or tended indigenous wild These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute If you lower the activation energy it s easier for the reaction to occur If it is raised then it will not be as easy for the reaction to occur So how can this spontaneous occurrence be controlled By altering the activation energy barrier Enzymes Lower Activation Energy Enzymes o Proteins that are catalysts for reactions in biological systems o Catalysts increase the rates of chemical reactions o Speed up the process by increasing the activation energy o The whole enzyme will not be used up Enzymes function by decreasing the activation energy for a specific chemical reaction o Enzymes bind to a reactant substrate enzyme substrate ES product enzyme Oxidation of glucose in bomb calorimeter A and your body B In the body we use the glucose when we need it so that we don t use all of it up at once o Enzyme Properties Enzymes are specific for one set of substrates or a group of similar substrates 2 Models of Substrate Specificity Lock and Key model and Induced fit model next o Enzymes are not changed in the reaction The enzymes won t be damaged during the change They will change the reactant to a product o Enzymes are not consumed in the reaction o Almost all Enzymes are identified by the suffix ase Notes from the Youtube videos o https www youtube com watch x yt ts 1421782837 v E r3omrnxw x ytcl 84359240 Enzymes are proteins catalyzed by metabolic reactions that turn a substrate into a product Lock and Key Model when the enzyme binds with substrates due to their complementary shape A good example for this is like when a spaceship is docking into a space station The substrate must fit well with the active site in order for the reaction to occur Induced Fit model the enzyme changes shape to accommodate the substrate Enzymes enable metabolic processes to proceed rapidly at room temperature by providing an alternative reaction pathway or a lower activation energy o http www youtube com watch v PILzvT3spCQ Competitive enzyme inhibition when an enzyme encounters a blocker which mimics the substrate and binds to the active site So when the substrate comes along no reaction occurs because the substrate cannot attach Non competitive enzyme inhibition the binding of a blocker in a place on the enzyme that is not the active site This causes a change in the shape of the enzyme which changes the shape of the active site Therefore no reaction occurs Enzyme Catalyzed Reactions o Factors affecting rates of enzyme catalyzed reactions Enzyme s catalytic rate how fast reactants substrates are consumed and products generated Some reactions generate many thousands of molecules per second Others may take more than a minute to catalyze a single molecule o Substrate concentration S will chance of ES binding o Enzyme concentration E will ES binding and max rate of S P o Affinity of enzyme for substrate o Temperature and pH o If the enzyme concentration increases the substrate concentration will increase This increases the maximum reaction of the product An increase in temperature increases the reaction rate as well An increase in maximum capacity will also increase the reaction rate o When an enzyme is saturated it cannot go faster once it gets to a certain concentration o A maximum reaction rate is set for an enzyme Regulation of Enzyme Activity Allosteric regulation Covalent regulation Feedback inhibition Feedforward activation Allosteric Regulation Each enzyme that can be regulated in this way has two binding sites STEP 1 o Active site o Regulatory site A modulator molecule binds to the regulatory site o Changes shape and activity of the enzyme STEP 2 o Can increase or decrease activity Generally alters the affinity of the enzyme for its substrate STEP 3 Diagram o Green with allosteric activator o Pink with allosteric inhibitor o In most cases there is more than one protein change that occurs o The regulatory site will change the shape but not completely Only just enough to block it off mostly If it were completely blocked off it would kill the enzyme BLUE ARROW IS POINTING TO THE ALLOSTERIC REGULATOR Covalent Regulation Enzyme exists in two states active high catalytic rate and inactive low catalytic rate Changing state requires formation of a covalent bond between a protein enzyme and a chemical group Formation and breaking of a covalent bond requires different enzymes Most common chemical group used in covalent modulation phosphate group Diagram o Enzyme A purple catalyzes formation of covalent bond between chemical group and enzyme molecule o Enzyme B dark blue catalyzes breakage of covalent bond o Green line covalent bond o Blue enzyme on right an enzyme with altered activity o Red triangle chemical group o Blue enzyme on the left includes its active site Covalent Regulation by Phosphorylation Protein kinase o enzyme Pi enzyme P protein kinase Phosphate o enzyme P enzyme Pi