Foundations of Biology 1
Foundations of Biology 1
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Date Created: 10/15/14
Chapter 8 Energy and Enzymes Coupling Reaction 0 Exergonic Reaction releases energy and Endergonic reaction requires energy both happen at the same time 0 If there s an endergonic reaction taking place it is relying on energy released from the exergonic reaction Biochemical changes involve energy 0 Sucrose C12H12011 H20 9 Glucose C6H1206 Fructose C6H1206 0 In biological systems the sum total of all chemical reactions occurring at a given time Metabolism 0 There are two types 1 Anabolism build up endergonic require input of energy to make a product 9 Anabolic steroids the synthesis of complex molecules in living organisms from simpler ones together with the storage of energy constructive metabolism 2 Catabolism breakdown exergonic release of energy the breakdown of complex molecules in living organisms to form simpler ones together with the release of energy destructive metabolism Endergonic Reaction 0 Ball and Hill model graph 0 Ball at the bottom is the reactant R 0 The red arrow represents the energy required to form the product 0 Red ball more towards the top is the product 0 Often products are more complex Exergonic Reaction Energy released Taking a higher energy reactant and releasing energy into a lower energy product The products are seen as more simple in these reactions Energy transformations in a waterfall 1 Potential energy Waiting on top of the waterfall a lot of energy housed 2 Kinetic Energy As it falls through the waterfall you have kinetic energy getting released 3 Other forms of energy Mechanical energy is released and you have lower potential energy Conclusion Energy is neither created nor destroyed Energy transformation in an atom The more you get away from the nucleus the more potential energy that electron has because of the electromagnetic forces that bring the electron in to the nucleus and increasing the speed of the electron Valence electrons bond by using energy As you get towards the nucleus kinetic energy increases and the amount of potential energy decreases Laws of Thermodynamics 15 law Energy is neither created nor destroyed The cube size has not changed after energy transformation has taken place 2nd Law Disorder entropy tends to increase Energy before 9 Usable energy after free energy and unusable energy Multiple Reactions and the 2quot law In any system total energy usable energy unusable energy Another way of saying the 15 law Cells don t get to the point where unusable energy is 100 or else metabolism wouldn t happen Enthalpy H total energy Free Energy G usable energy Entropy S Unusable energy Gibbs freeenergy H G TS T is absolute temperature Disorder increases from increasing temperatures Or G H TS Gibbs freeenergy changg Change in energy can be measured in calories or joules 1 calorie 4184 Change in free energy Delta G in a reaction is the difference in free energy of the products and the reactants Delta G Delta H T X Delta S Is Delta G lt0 free energy is released exergonic spontaneous if Delta Ggt 0 free energy is consumed endergonic nonspontaneous if Delta G 0 chemical reaction is at equilibrium Implications of the Second Law of Thermodynamics Disorder tends to increase because of energy transformations Living organism must have a constant supply of energy to maintain order Active Review Glucose Galactose 9 Lactose Water Is this a condensation or hydrolysis reaction Answer Condensation Reaction What are the Reactants What are the Products Answer Reactants Glucose and Galactose Products Lactose and Water Is this an anabolic or catabolic reaction Answer Anabolic reaction Is energy required or released Answer Energy is required Review Question 1 Which of the following best describes the two graphs below Answer Graphs C because Exergonic Reaction Delta G is negative Endergonic Reaction Delta G is positive Review Question 2 Which of the following reactions is an example of an exergonic reaction Answer C6H1206 602 9 6CO2 6H2O because There are simpler products Coupling Reactions Energy released from one reaction drives another 2 Mechanisms 0 Transfer of electrons for cellular respiration Transfer of Phosphate Group Redox Reactions reductionoxidation reactions 0 Electrons in Glucose and being transferred and pooled towards Oxygen because of Electronegativity differences 0 Carbon is losing the electrons and therefore carbon is oxidized 0 Reduced element where Oxygen is holding the electrons closer to itself and therefore it is reduced 0 OIL Oxidation Is Loss of Electrons 0 Keep track of if an element has lost or gained electrons 0 If atom gains electrons you consider that atom to be reduced ATP 0 P O Phosphoanhydride Bond Oxygen is unstable 0 Where the energy is and given out for reactions to happen 0 Nitrogenous Base 0 Adenine 0 Ribose as Sugar 0 Ribose Adenine 9 Adenosine 0 Whether how many phosphate groups you have attached to the 5carbon is what determines if you have a monophosphate AMP diphosphate ADP or triphosphate ATP 0 ATP H20 9 ADP Pi inorganic phosphate Free Energy 0 Exergonic 9 Delta G 73 kcalmol 0 PO4 negatively charged 0 Negative charge repelling in the phosphate makes it having more energy in ATP 0 If phosphate group was more neutral it would function less as a highly energized molecule you are taking away from ATP s value 0 When you put 3 phosphate groups together it is ready to release energy in the system NADNADH is an electron carrier Nicotinamide adenine dinucleotide NAD H proton is snatched away from NADH forming NAD NADH is a high energy molecule used by cells to generate ATP Ribose Adenine Nicotininade group Nicotinamide group is ready to be used as the electron carrier 0 When you have the oxidation to NADH 9 NAD electron is Hydrogen we are losing that Hydrogen NADH is being oxidized Oxidation of NADH 9 NAD is highly exergonic 0 Highly Exergonic 524 kcal Would this reaction occur Spontaneously Delta G Is this an endergonic or exergonic reaction 0 Answer Exergonic Reaction Delta G is negative Spontaneous Reaction 0 Glucose and fructose are isomers Same formula but different arrangement of atoms 0 Enzymes 0 Proteins 0 Catalysts Orient Reactants Lower Activation Energy Change in free energy during chemical reaction 0 Activation Energy Amount of energy required for the bonds to interact with one another from the reactant to climb to the transition state before the product can be made which is the most unstable form of the reaction 0 We then reach our peak of the most activation energy which then drops down into the product 0 Delta G Difference between reactants and products and the amount of free energy Enzymes lower the activation energy 0 Even if an enzyme is placed in the reaction Delta G doesn t change but the Activation energy decreases 0 Does an enzyme changes any of the free energies in the chemical reaction Answer No because the free energy of the reactants and products doesn t change only the activation energy Regulation of metabolism occurs by regulation of enzymes Metabolic pathways are represented by the equation 4 different enzymes are required to convert intermediary s to the final products Need to maintain homeostasis in the presence of all this metabolism how 1 Amount of enzyme is regulated by the cell too much enzyme or too little enzyme disrupts homeostasis 2 Activity of Enzyme a Inhibition To alter the function of an enzyme in order to maintain regulation b Allosteric Changing shapes Changes making the enzyme in other shape in order to regulate its function c Feedback mechanisms d The Environment Tertiary Structure is what allows for these 4 mechanism to take play within a metabolic pathway R groups that are present allow for multiple enzyme regulation activity to take place Catalytic Mechanisms of Enzymes Inducing strains Bonds in substrate are pulled instability which makes the reaction easier to take place Substrate Enzymes target in the reaction orientation If proximity goes up the likelihood of bonding increases Interacting chemical groups R groups on amino acids protein can be involved These three mechanisms are not sequential they are concurrent or they can happen simultaneously Green represents enzyme and red represents the substrate Some enzymes require proteins Cofactors are inorganic ions that bind to certain enzymes A coenzyme is a carboncontaining molecule that is required for the action of one or more enzymes It is usually relatively small compared with the enzymes to which it temporarily binds and it adds or removes chemical groups from the substrate A coenzyme is like a substrate in that it does not permanently bind to the enzymes it binds to the active site changes chemically during the reaction and then separates from the enzyme to participate in other reactions A coenzyme differs from a substrate in that it can participate in many different reactions with different enzymes Prosthetic groups are distinctive nonamino acid atoms or molecular groupings that are permanently bound to their enzymes Cofactors Iron2 or 3 Copper or 2 and Zinc 2 these three are inorganic ions Iron and Copper help with oxidationreduction Zinc helps bind NAD Coenzymes Biotin Coenzyme A NAD FAD ATP Biotin carries COO Coenzyme A carries CO CH3 NAD and FAD carries electrons and ATP providesextracts energy Prosthetic Groups Heme Flavin and Retinal Heme binds ions 02 and electrons contains iron cofactors Flavin binds electrons and Retinal converts light energy You can have these partners interacting with one another For example Heme binds with Iron which is a cofactor Enzyme Inhibitors Irreversible DIPF Malathion reacts with serine residues Covalent boding Reversible 1 NonCompetitive 2 Competitive Diagram represents irreversible inhibition sphere represents the Whole enzyme What s important is that it is a covalent bond which is one reason that it is irreversible binding since covalent bonds are stable Competitive inhibitors how they function Competes for active site Structurally similar to substrate Non covalent bindings therefore helps to be reversible If you decrease the concentration of the competitive inhibitor Ci then enzyme activity increases Brackets represent concentration Increase the competitive inhibitor with a ratio of 1001 the reaction may not happen at all N onCompetitive inhibitors how they function Does not bind to the active site Results in change of enzyme shape Example of Allosteric Change Allosteric modulationregulation It is a reversible or a double headed arrow process Inactive Active gt1 Allosteric site is possible It is possible to have more than 1 allosteric site It can be covalent or noncovalent Covalent modification Phosphorylation PO4 An enzyme is required to take place Phobic becomes phillic through exposing active sites your enzyme is activated because of exposing the active site to the environment Changing from a phobic state go through allosteric changes and convert to phillic In general you need another enzyme to phosphorylate an enzyme Protein Kinase Automatically think phosphorylation Allosteric ModulationRegulation Non covalent bonding Involves in activation which opens the site of an enzyme Kinetics of an enzymatic reaction Line for a catalytic reaction is presented which means an enzyme must be present As substrate concentration increases it takes the time for the product formation to form and then the line starts to turn horizontal You have reached saturation which means every enzyme at every time point is occupied 100 from substrate Adding more enzymes helps with the rate Feedback Inhibition Starting with Threonine Intermediate product is Ketobutyrate End product is Isoleucine Enzyme 1 is required in order for the starting material to be converted to intermediate product 1 Intermediate Product 2 3 4 and 5 and then your end product Anytime you see a horizontal line and a perpendicular line to it it inhibits or blocks that particular product The final product is inhibiting enzyme 1 Conclusion End product blocks enzyme E1 synthesis therefore an increase in isoleucine blocks intermediate product production which means levels of ketobutyrate decreases As you increase the amount of product produced the more you able to regulate the enzyme Effect of pH on enzyme activity Environment Stomach pH 122 Small intestine pH 65 The stomach doesn t do that much digestion compared to the small intestine As your food is delivered from stomach to small intestine and through the bicarbonate you can neutralize your acidic environment and regulate enzyme activity Pepsin is functional in the stomach and Chymotrypsin and Arginase are functional in the small intestine Pepsins peek reaction is at a pH of 2 Effect of Temperature of enzyme Activity In general an increase in temperature results in an increase in enzyme activity because of more collisions of moeclule There is enough kinetic energy to overcome Activation Energy as you increase temperature If you really increase the temperature past the optimal temperature what the actually results is strain and denaturation of proteins Isozymes Multiple forms of same enzymatic function If you have multiple forms of enzymes Different primary structures and they have the same function Do Physical conditions affect enzyme function
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