A&P Ch. 3 PPT Quinn (2) PDF

Energy, Chemical Reactions, and Cellular Respiration  Today’s Objectives 1. Examine the extent that energy drives reactions within the body  Energy, Chemical Reactions, and Cellular Respiration 1. All living organisms require energy 2. We need energy to: – p...

Energy, Chemical Reactions, and Cellular Respiration  Today’s Objectives 1. Examine the extent that energy drives reactions within the body  Energy, Chemical Reactions, and Cellular Respiration 1. All living organisms require energy 2. We need energy to: – power muscle – pump blood – absorb nutrients – exchange respiratory gases – synthesize new molecules – establish cellular ion concentrations 3. Glucose broken down through metabolic pathways – Forms ATP, the “energy currency” of cells  Energy: States of Energy 1. Energy: the capacity to do work – Invisible except for the effects it has on matter 2. Energy exists in two states – Potential energy = stored energy (energy of position) – Kinetic energy = energy of motion 3. Energy can be converted from one state to another – E.g., water at the top of a dam has potential energy – When water falls over the dam it has kinetic energy this energy can be harnessed to do work  Energy: States of Energy 1. Potential energy and the plasma membrane – Concentration gradient across the plasma membrane of the cell – Sodium ion concentration greater outside the cell – Has potential energy (analogous to water at the top of a dam) – Has kinetic energy when sodium ion moves from area of high concentration to area of lesser concentration energy can be harnessed to do work Potential energy Na+ ions in high concentration have potential energy. Na+ Inside cell Outside cell Potential energy Na+ ions in high concentration have potential energy. Na+ Inside cell Outside cell Potential energy Na+ ions in high concentration have potential energy. Na+ Inside cell Outside cell Na+ Na+ moving to area of low concentration have kinetic energy. Kinetic energy  Energy: Forms of Energy Chemical Energy (A Form of Potential Energy) 1. Chemical energy: energy stored in a molecule’s chemical bonds – Most important form of energy in the body – Used for movement, molecule synthesis, establishing concentration gradients – Present in all chemical bonds released when bonds are broken during reactions  Energy: Forms of Energy Chemical Energy (A Form of Potential Energy) 2. Molecules function in chemical energy storage – Triglycerides long-term energy storage in adipose tissue – Glucose glycogen stores in liver and muscle – ATP stored in all cells produced continuously and used immediately – Protein can be used as a fuel molecule but has more important functions  Energy: Forms of Energy Kinetic Energy Forms 1. Electric energy: movement of charged particles – E.g., electricity or the movement of ions across the plasma membrane of a neuron 2. Mechanical energy: exhibited by objects in motion – E.g., muscle contraction for walking 3. Sound energy: molecule compression caused by a vibrating object – E.g., sound waves causing vibration of the eardrum in the ear  (a) Potential and Kinetic Energy Fig. 3.3left-2 The Two States of Energy Potential Energy: The energy of position Kinetic Energy: The energy of motion Na+ Na+ Na+ Na+ Na+ Na+ ions exhibit kinetic A perched eagle has Na+ energy as they Na+ ions have potential energy. move down the potential energy due concentration to concentration gradient. gradient difference between the outside and Na+ Na+ inside of Na+ Na+ the cell. When the eagle flies, it converts its potential energy to kinetic energy. Fig. 3.3b (left) Mechanical Energy: Movement of a structure or a substance Example: The pumping action of the heart to circulate blood is a form of mechanical energy.  Sound Energy: Movement of Fig. 3.3b (middle) compressed molecules through a medium initiated by a vibrating object Example: Sound waves vibrating the tympanic membrane of the ear stimulate sensory receptors for hearing.  Energy: Forms of Energy Kinetic Energy Forms (continued) 1. Radiant energy: energy of electromagnetic waves – Vary in wavelength and frequency – Higher frequencies with greater radiant energy – Forms with frequency higher than visible light able to penetrate the body and mutate DNA cells protect themselves with the dark pigment melanin – Visible light detected by retinal cells of the eye Radiant Energy: Movement of Fig. 3.3b (right) electromagnetic waves that travel in the universe and vary in wavelength and frequency Example: Visible light, a form of radiant energy, is focused on the retina of the eye for vision.  Increasing frequency (energy) Increasing wavelength.001 nm 1 nm 10 nm.01 cm 1 cm 1 m 100 m Gamma UV Infrared Radio X-rays rays light light waves High electromagnetic energy Visible light Range capable of entering the Range perceived by the body and damaging DNA, retina of the eye causing mutations 400 nm 740 nm Light Point of mutation in DNA molecule Eye  Energy: Forms of Energy Kinetic Energy Forms (continued) 1. Heat: kinetic energy of random motion – Usually not available to do work – Measured as the temperature of a substance 22  Energy: Laws of Thermodynamics 1. Energy can change forms. For example: – a burning candle converting chemical energy to light and heat energy – retinal cells converting light energy into electrical energy of a nerve impulse – chemical energy in food converted to another chemical form, then into mechanical energy 2. Thermodynamics: study of energy transformations  Energy: Laws of Thermodynamics 1. First law of thermodynamics – Energy can neither be created nor destroyed; it can only change in form. 2. Second law of thermodynamics – When energy is transformed, some energy is lost to heat. the amount of usable energy decreased – E.g., moving around to warm up on a cold day as chemical energy converts to mechanical energy, heat produced  (c) Laws of Energy Conversion of energy from one form to another First Law of in the human body produces Thermodynamics Sound heat and helps to maintain homeostasis. Energy cannot be created or destroyed, it can Electrical only be converted from one form to another. Chemical Mechanical Second Law of Thermodynamics Heat Every time energy is (nonusable transformed from energy) one form to another, some Radiant of that energy is converted to heat.  ALE Let’s Graph It! 1. Write on your notes – Two graphs Over the course of time (of a reaction or the life of “energy”), depict what happens to the amount of available energy (gas in the tank) Over the course of time, show the cumulative amount of heat generated (heat given off)  Chemical Reactions: Chemical Equations 1. Metabolism – Collective term for all chemical reactions in the body 2. Chemical reactions – Occur when chemical bonds in existing molecular structures are broken – New bonds formed – Summary of changes written as a chemical equation  Chemical Reactions: Chemical Equations 1. Components of chemical equations – Reactants, the substances present prior to start of a chemical reaction written on left side of equation – Products, the substances formed by the reaction written on right side of equation A + B C – A and B reactants; C the product – Arrow indicating direction – In a balanced equation, number of elements equal on both sides of the reaction  Decomposition reaction: A large molecule is broken down into smaller chemical structures; AB A+B CH2OH CH2OH CH2OH CH2OH H2O H O H O H H O H O H H H OH H O H OH OH H + H OH HO CH2OH HO OH HO CH2OH H OH OH H H OH OH H Sucrose Glucose Fructose (a)  Chemical Reactions: Classification of Chemical Reactions 1. Classified based on three criteria: – changes in chemical structure, changes in chemical energy, and whether the reaction is irreversible or reversible Classification Based on Changes in Chemical Structure 1. Catabolism – Collective term for all decomposition reactions (breakdown) 2. Anabolism – Collective term for all synthesis reactions (build up) 3. Metabolism – Collective term for all chemical reactions in the body Page 76  Chemical Reactions: Classification of Chemical Reactions Classification Based on Changes in Chemical Energy 1. Exergonic reactions – Reactants with more energy within their chemical bonds than products – Energy released with net decrease in potential energy – E.g., decomposition reactions 2. Endergonic reactions – Reactants with less energy within their chemical bonds than products – Energy supplied with a net increase in potential energy – E.g., synthesis reactions  ALE Let’s Graph It! 1. Draw in your notes: – Two graphs Over the course of a reaction, graph the quantity of energy supplied/released relative to the number of products gained – Exergonic (releasing/breaking down) – Endergonic (taking in/build up) 33  Energy supplied Products Energy supplied (e.g., proteins) Energy Reactants Reactants supplied (e.g., Glucose + O2) (e.g., amino acids) 0 0 Energy released Energy released Products Energy (e.g., CO2 + H2O) released Course of reaction Course of reaction (a) Exergonic reaction (b) Endergonic reaction  Chemical Reactions: Classification of Chemical Reactions Classification Based on Changes in Chemical Energy (continued) 1. ATP cycling – The continuous formation and breakdown of ATP – ATP formed from energy released in exergonic reactions fuel molecules from food oxidized energy in their bonds transferred to ADP and free phosphate to form ATP – ATP oxidized released energy used for energy-requiring processes – Only a few second worth of ATP present at a time formation of ATP occurs continuously to provide energy  ATP (a) ATP formation Triphosphate Adenine Adenine (b) Splitting ATP (Endergonic reaction) group (Exergonic reaction) P P P High-energy bond Ribose Energy Energy supplied released ADP P Diphosphate Adenine P Phosphate (Pi) group P P Ribose  Chemical Reactions: Classification of Chemical Reactions Classification Based on Reaction Reversibility 1. Irreversible reaction – Net loss of reactants and a net gain in products over time A +B AB 2. Reversible reaction – No net change in concentration of reactants and products reactants become products and products become reactants at equal rate A+B AB  Chemical Reactions: Reaction Rates and Activation Energy 1. Activation energy (Ea) – Energy required to break existing chemical bonds – A primary factor determining reaction rate 2. Overcoming the activation energy – In a lab, increasing temperature provides energy to break bonds – Significant temperature increase in a cell would denature proteins protein catalysts used instead  Enzymes: Function of Enzymes 1. Enzymes – Always end in -ase – Are catalysts that accelerate normal chemical activities – Decrease the activation energy of cellular reactions – Only facilitate reactions that would already occur – Increase the rate of product formation 2. Chemical reactions – Are termed uncatalyzed reactions if no enzyme present – Are termed catalyzed reactions if enzyme present  Enzymes: Function of Enzymes – Exergonic reaction Energy supplied – Substrates with higher Activation energy of potential energy than reaction without enzyme total potential energy of Activation energy of reaction with enzyme products – Activation energy Reactant (sucrose) required to initiate the Energy released O reaction – More glucose and Products (glucose and fructose) fructose formed in a Uncatalyzed period of time with Catalyzed enzyme Course of reaction  Enzymes: Structure and Location 1. Most enzymes globular proteins – Unique three-dimensional structure 2. Active site – Region of enzyme accommodating the reaction substrate – Temporarily forms enzyme-substrate complex – Specificity of shape permits only a single substrate to bind helps catalyze only one specific reaction  Enzymes: Structure and Location Active site Active site’s specificity of Substrate shape: – permits only a single substrate to bind – helps catalyze only one specific reaction Enzyme Enzyme-substrate complex  Enzymes: Mechanism of Enzyme Action 1. Enzyme catalysis: 1) substrate enters active site, forming enzyme-substrate complex 2) enzyme changes shape slightly, resulting in even closer fit (induced-fit) 3) change in enzyme shape stresses chemical bonds, permitting new bonds to be formed 4) products are released; enzyme may repeat process  Decomposition reaction: Lactose digested to glucose and galactose Lactose 1 The substrate binds 2 The enzyme changes 3 The bond is Galactose to the enzyme, forming shape, resulting in an broken between an enzyme-substrate induced fit between glucose and Glucose O complex. substrate and enzyme. O galactose. O Substrate: Lactose 4 Products: Glucose and galactose are released, and the Enzyme-substrate complex enzyme is free to bind other substrates. Enzyme: Lactase (a)  Synthes is reaction: Glucose molecules synthesized into a glycogen molecule Glucose 1 The glucose substrate 2 The enzyme changes 3 Bonds are broken and a new binds to the enzyme, shape, resulting in an bond is formed between forming an induced fit between the new glucose molecule enzyme-substrate substrate and enzyme. and the growing glycogen complex. molecule. Substrate: Glucose monomers 4 Product: Glycogen is released, and the enzyme is free to bind Enzyme: Glycogen other substrates. synthetase (b)  Enzymes: Enzymes and Reaction Rates Effect of Temperature 1. Three-dimensional shape of enzymes dependent on temperature – Human enzymes function best at optimal temperature normal to slightly elevated body temperature (95-104° F) – Moderate fever results in more efficient enzyme activity – Severe increases in temperature cause protein denaturation with loss of function  Temperature 3-D shape of Optimum temperature for maximum protein is more protein flexibility of intact human rigid at cooler enzyme (35°–40°C). temperatures. Enzyme denatures as weak Rate of reaction intramolecular interactions are broken at higher temperatures. 30 40 50 60 Temperature °C (b)  Enzymes: Enzymes and Reaction Rates Effect of pH 1. Enzymes function best at optimal pH – Between pH of 6 and 8 for most enzymes – Changes in H+ disrupting electrostatic interactions – Enzyme loss of shape, denaturation – Optimal pH may differ e.g., enzymes working in the lower pH of the stomach  pH Optimum pH for most human enzymes (6–8). Enzyme denatures. Enzyme denatures. Rate of reaction H+ H+ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Acidic Neutral Basic pH (c)  Enzymes Clinical View: Lactose Intolerance 1. Caused by a deficiency in lactase – Required to break the bond in lactose into glucose and galactose 2. Symptoms of abdominal upset 3. Treated with lactase enzymes or avoidance of milk