Enzymes and Energetics Notes PDF

ENZYMES AND ENERGETICS THE FLOW OF ENERGY IN LIVING THINGS 1. Life is a constant flow of energy. 2. Energy can take a lot of forms: mechanical, heat, electric, sound, light, radioactive radiation 3. It is measured most conveniently in terms of heat because all other forms can be convert...

ENZYMES AND ENERGETICS THE FLOW OF ENERGY IN LIVING THINGS 1. Life is a constant flow of energy. 2. Energy can take a lot of forms: mechanical, heat, electric, sound, light, radioactive radiation 3. It is measured most conveniently in terms of heat because all other forms can be converted to heat 4. KINETIC ENERGY-the energy of motion. Ex: water falling down a waterfall 5. POTENTIAL ENERGY-stored energy Ex: a boulder sitting on top of the hill KINETIC ENERGY POTENTIAL ENERGY 6. THERMODYNAMICS-the study of energy (the study of heat changes) 7. KILOCALORIE (kcal)-unit of heat energy 1 kcal=1000 cal a. 1 cal of heat is required to raise 1 gram of water 1 degree Celsius OXIDATION-REDUCTION 1. Energy flows into the biological world from the sun. 2. During a chemical reaction, energy stored in the bonds may be transferred to new bonds. 3. In some reactions, electrons actually pass from one atom to another. 4. OXIDATION-when atom loses an electron 5. REDUCTION-when an atom gains an electron LEO roars GER Loss of Electrons is Oxidation Gain of Electrons is Reduction 6. Oxidation and reduction reactions always happen together=REDOX REACTION 7. Redox reactions play a key role in the flow of energy through biological systems 8. When light hits an electron, it boosts it to a higher energy level. Added energy is stored as POTENTIAL ENERGY that the atom can release later LAWS OF THERMODYNAMICS 1. All activities needing energy from the buzzing of a bee to a nuclear blast involve changes in energy. 2. These reactions are governed by the Laws of Thermodynamics. 3. FIRST LAW OF THERMODYNAMICS-Energy can’t be created or destroyed. It can only change form. Ex: Lion eats prey and transfers potential energy stored in prey tissues to its own body. Energy enters the ecosystem via photosynthesis and changes form as it enters bodies and flows throughout the system. 4. SECOND LAW OF THERMODYNAMICS-Disorder in the universe is increasing = ENTROPY Organization requires energy. Disorder happens spontaneously. REACTION TYPES 1. When the products of the reaction contain more energy than the reactants in order to go, these reactions require an input of energy=ENDERGONIC 2. When the reactants of the reaction contain more energy than the products, this reaction occurs spontaneously, needing no energy input=EXERGONIC (spontaneously doesn’t mean instantaneously. It may go spontaneously but will go slowly) FREE ENERGY CHANGE ΔG 1. The universe is really “the system” (like a cell) plus the surroundings (other cells, organs, tissues, the environment, etc.) 2. GIBBS FREE ENERGY-the portion of a system’s energy that can perform work when temperature and pressure are uniform throughout the system (like a cell) ΔG = ΔH-TΔS ΔH=the change in the system’s ENTHALPY (in biological systems, equivalent to total energy) ΔS=the change in the systems ENTROPY (disorder) T= the temperature in K (Kelvin: K = °C + 273 3. Using chemical methods, we can calculate the ΔG for any reaction WHERE’S THE ENERGY? ANOTHER LOOK IN TERMS OF FREE ENERGY If ΔG is -, no energy needs to be put into If ΔG is +, energy needs to be put into the system to make a reaction go. the system to make a reaction go. ACTIVATION ENERGY 1. If all reactions that release free energy tend to go spontaneously, why haven’t they all happened? 2. Reason: most reactions still require energy to break existing bonds and get started 3. ACTIVATION ENERGY (Ea)-the “extra” energy needed to destabilize bonds to start a reaction 4. CATALYSIS-influencing the bonds in a way that lowers the Ea needed to start a reaction 5. CATALYST-substances that speed up a reaction without being used up in the reaction ENZYMES 1. Life is regulated by catalysts. 2. ENZYMES-proteins that act like catalysts in the body 3.. Enzymes have a three-dimensional shape that fit into SUBSTRATES-molecules that undergo a reaction HOW ENZYMES WORK 1. Enzymes have pockets called ACTIVE SITES. 2. Enzymes and the substrates they work on fit together there=”ENZYME-SUBSTRATE COMPLEX” 3. The binding of the enzyme to the substrate causes it to change shape slightly forming a better “fit”=INDUCED FIT. FACTORS AFFECTING ENZYME ACTIVITY 1. How well an enzyme catalyzes a reaction depends on the concentration of the enzyme and anything that can change its shape 2. Enzyme Concentration a. if more enzyme is added to a reaction, the rate of the reaction will increase because there’s more enzymes to react with substrate molecules 3. Substrate Concentration a. if more substrate is added to a reaction, the rate of the reaction will increase because there’s more substrate molecules for the enzyme molecules to interact with b. reaction rate levels off because enzymes are “saturated every enzyme molecule has a substrate molecule it’s interacting with FACTORS AFFECTING ENZYME ACTIVITY-continued 3. Temperature: a. The greater the temperature, the faster the reaction rate to a point called the TEMPERATURE OPTIMUM b. Reactions have a “best” temperature at which they run-where enzyme and substrate collisions are maximized c. when subjected to extreme heat enzymes denature (their H and ionic bonds break) and they don’t work d. when subject to extreme cold, the collisions between enzymes and substrates slow e. Humans: 35° C f. Bacteria that live in hot springs/geysers 70° C 4. pH a.Changes in pH remove or add H+ b. Disrupts the bonds and the interactions of ions in some of the charged amino acids that make them up c. The 2° and 3° structure is changed, enzyme denatures and doesn’t work d. Most enzymes have a pH optimum of 6-8 5. Inhibitors and Activators a. Enzyme activity is sensitive to the presence of substances that bind to the enzyme and change its shape b. Controlling an enzyme: 1. INHIBITION-a substance that binds to an enzyme and DECREASES its activity a. COMPETITIVE INHIBITORS-compete for the binding site of the substrate, thus blocking the active site. Reaction doesn’t go. b. Ex: penicillin-block the enzyme bacteria use to make their cell walls c. overcome by increasing the substrate concentration. Outcompetes inhibitor for enzyme active site FACTORS AFFECTING ENZYME ACTIVITY-continued 5. Inhibitors and Activators-continued b. NONCOMPETITIVE INHIBITORS-bind to the enzyme in a place other than the active site, changing its shape. Substrate can’t bind to the enzyme in its new shape=reaction doesn’t go. 1. ALLOSTERIC SITE-specific part of an enzyme where noncompetitive inhibitors bind. Serve as “on/off” switches. 2. ALLOSTERIC INHIBITOR-the molecule that binds to allosteric site and reduces enzyme activity Ex: anti-cancer drugs-inhibit enzymes involved in DNA synthesis -no DNA copying, no new cancer cells made 6. Enzyme Helpers 1. ACTIVATOR-chemical/molecule that binds to the allosteric site and keeps enzymes in their active mode, increasing enzyme activity a. COFACTORS-non-protein, small compounds and ions-INORGANIC Cofactors can be metal ions (zinc) or other substances: Mg, K, Ca, Zn, Fe, Cu Bind with enzyme molecule b. COENZYME- non-protein, organic compound-ORGANIC Bind temporarily or permanently to enzyme near the active site-prepare the active site for the enzyme Ex: vitamins BIOCHEMICAL PATHWAYS 1. Chemical reactions of life are organized in pathway 2. Most reactions in the body have several steps=BIOCHEMICAL PATHWAY 3. The product of one step is the reactant for the next step: A + B →C-->C + D→E→E + F-->G A—----->G 4. Efficiency-enzymes are grouped. If they are embedded in a membrane they are in sequential order. BIOCHEMICAL PATHWAY BIOCHEMICAL PATHWAYS-cont. 5. FEEDBACK INHIBITION- regulation and coordination of a biochemical pathway a. the product of one step is used in the next step of the pathway b. the final product is an inhibitor of an earlier step c. this product provides “feedback” and stops the whole reaction ATP: THE ENERGY CURRENCY OF LIFE/BIOLOGICAL PATHWAYS 1. ATP-ADENOSINE TRIPHOSPHATE-main energy molecule of all cells. 2. Structure: a. 5 carbon sugar b. adenine c. 3 phosphates (triphosphate group) 3. Bonds between phosphates are unstable and are easily broken 4. When the bonds are broken, energy is released/transferred 5. Cells use ATP to drive reactions that won’t go spontaneously (ENDERGONIC) 6. ATP is a good energy source but not a good energy storage molecule. The phosphate bonds are too unstable. Fats and carbs do that better. 7. Most cells usually only have a few seconds worth of ATP and have to continually produce it from ADP and phosphate. METABOLISM 1. sum total of all the reactions carried out in an organism a. ANABOLISM-making bonds b. CATABOLISM-breaking bonds METABOLISM OF FOOD ALL THE METABOLIC REACTIONS IN THE BODY