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 nucleotidesII. Types of Metabolic ReactionsIII. Metabolic Reactions and EnergyOutline of Current Lecture I. Metabolic Reactions and EnergyII. Reaction Rates Current LectureClarification 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 goo Energy added could come from energy released above or another sourceSpontaneous 1. acting in accordance with or resulting from a natural feeling, impulse, or tendency, without any constraint, effort, or premeditation2. having no apparent external cause or influence; occurring or produced by its own energy, force, etc. or through internal causes; self-acting3. growing naturally without being planted or tended; indigenous; wildThese 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 barrierEnzymes Lower Activation Energy- Enzymeso Proteins that are catalysts for reactions in biological systemso Catalysts increase the rates of chemical reactionso Speed up the process by increasing the activation energyo The whole enzyme will not be used up- Enzymes function by decreasing the activation energy for a specific chemical reactiono 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- Enzyme Propertieso 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 reactiono 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-yt-cl=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 energyo 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 Reactionso Factors affecting rates of enzyme-catalyzed reactions  Enzyme's catalytic rate: how fast reactants (substrates) are consumed andproducts generated- Some reactions generate many thousands of molecules per second- Others may take more than a minute to catalyze a single moleculeo Substrate concentration - ↑S will ↑ chance of ESbindingo Enzyme concentration - ↑E will ↑ES binding and↑max rate of S→Po Affinity of enzyme for substrateo Temperature and pHo If the enzyme concentration increases, thesubstrate concentration will increase. Thisincreases the maximum reaction of the product. Anincrease 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 enzymeRegulation of Enzyme Activity - Allosteric regulation- Covalent regulation- Feedback inhibition- Feedforward activationAllosteric Regulation - Each enzyme that can be regulated in this way has twobinding sites (STEP 1)o Active siteo Regulatory site- A modulator molecule binds to the regulatory siteo Changes shape and activity of the enzyme (STEP2)o Can increase or decrease activity- Generally alters the affinity of the enzyme for itssubstrate (STEP 3)- Diagram:o Green-with allosteric activatoro Pink- with allosteric inhibitoro In most cases, there is more than one protein change that occurso 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 requiresdifferent enzymes- Most common chemical group used in covalentmodulation = 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 bondo Green line- covalent bondo Blue enzyme on right- an enzyme with altered activity o Red