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1 CHAPTER ENERGY AND LIVING CELLS “Life Requires Free Energy” ( Bozeman biology) G= Free energy is the available(useable) energy to do work in the system Q. So during an exothermic reaction does the G go up or down? Q. As you move up a food chain does G go up or down? Gibbs Free Energy Equation ΔG= ΔH – TΔS ΔH= change in enthalpy(total energy) ΔS = change in entropy (randomness) C6H12O6 + 6O2 ----- 6CO2 + 6H20 Will a reaction be spontaneous or not? -ΔH + ΔH Spontaneous at ΔG= ΔH – TΔS + ΔS Spontaneous always high temps only at Never - ΔS Spontaneous Low temps only spontaneous +ΔH gained enthalpy as reaction proceeded -ΔS means we have decreased entropy -ΔH means we have lost enthalpy(heat) (exergonic) 2 Everything in the universe moves to a state of more randomness or increasing disorder This is called ENTROPY (S) For equations when there are more particles in the products than reactants, the amount of entropy of the system has increases C6H12O6 + 6O2 ----- 6CO2 + 6H20 + energy What is this reaction? ( 2nd Law of Thermodynamics) : Everything moves to a state of more disorder. In every energy exchange some useable(Free) energy is lost as heat. -Living organisms seem to run counter to this law. However they are always using energy to maintain a balance. Their life spans are finite and when they die become much more disordered 3 KEY CONCEPTS : 1. Energy enters the earth when green plants use solar energy to photosynthesize to build food from CO2 + H20 Sun + CO2 + H20 -- Glucose + O2 2. Energy is released to be used during respiration as glucose is broken down to carbon dioxide and water. 3. Organisms use energy to combat the universal tendency toward entropy ( disorder) ENERGY TRANSFORMATIONS: What is energy? The capacity to do work. The capacity to cause change or motion. Energy can be transformed , that is it can be changed from one form to another. 4 LAWS OF THERMODYNAMICS 1ST Law of Thermodynamics: Energy can be neither created or destroyed but transformed from one type to another. ( You can’t win) 2nd Law of Thermodynamics: ( Entropy) In every energy transaction some energy is lost in the form of heat ( You can’t even break even) ( Entropy: The degree of disorder) ( ex. Diffusion) KINETIC ENERGY: Energy due to motion POTENTIAL ENERGY: Stored energy due to position. ( chemical bonds) 5 CHEMICAL REACTIONS AND ENERGY - Free energy: useable energy - Exergonic rxns - Release of energy Decrease in free energy - Endergonic rxns – Absorption of energy Increase in free energy Activation Energy: The amount of energy needed to get a rxn to run to completion. Free Energy This is endergonic rxn products Reactants exergonic rxn products Time EQUILIBRIUM : The point at which no net rxn is occurring Forward and backward rxns are equal 6 2glucose ---- 1 sucrose PHOTOSYNTHESIS AND RESPIRATION Where does energy for cells come from? Energy to run most cellular processes comes from organic food molecules that contain chemical potential energy in the bonds. Breaking the bonds releases the energy. Organic molecules made from Photosynthesis Solar energy --- Chemical potential energy (CH2O)n = carbs Raw materials are low energy molecules CO2 + water converted to high energy molecules 7 All Photosynthetic or chemosynthetic organisms are called (AUTOTROPHS) (AUTO- SELF) ( TROPH- FOOD) Ex. Plants, Algae, some protists ( euglena) Archaea (chemosyn.) HETEROTROPHS: ( Hetero- other) - All organisms that must obtain (organic) food from other organisms . - Ex. Animals, some protists CELLULAR RESPIRATION: Process of breaking down food molecules to energy for use by the cell. (CH2O)n + O2 ------- CO2 + H2O + energy( ATP) PHOTOSYNTHESIS : CO2 + H2O + E ----- (CH2O)n + O2 PHOTOSYNTHESIS CELL RESPIRATION release 8 OXIDATION – REDUCTION RXNS: Reactions that require the transfer of one or more efrom one ion to another. Oxidized: The molecule that loses eReduced: The molecule that gains eLeo goes Ger LoseElectronOxidized GainElectronReduced Simplest case. The oxidation of iron +2 -2 Fe + O2 -------- FeO As a general rule : ( O2 is an oxidizer) Oxygen is reduced and thus gains or accepts e- from another substance ( Oxygen is an oxidizing agent) In respiration, Oxygen oxidizes sugars and thus sugar reduce oxygen. (CH2O)n + O2 ------- CO2 + H2O + energy( ATP) 9 Respiration is the oxidation of small organic molecules Photosynthesis is the reduction of carbondioxide ENERGY INTERMEDIATES: Cells need many endergonic rxns which go “uphill” in terms of energy . How are these rxns powered? 1. Enzymes lower activation energy 2. The rxns are coupled w/ exergonic rxns The exergonic rxns. Must release more useful energy than the endergonic ones require(2nd law OTD) However releasing too much excess energy is. 1. Wasteful 2. Damaging to the cells enzymes 3 dim. Struct. ( denaturation) A large burst of heat destroys enzymes . 10 Therefore :Rxns that release a lot of heat , suc as oxid. – reduct. Do so in small steps. The conversion of lactate to pyruvate is catalyzed by lactate dehydrogenase. In this reaction lactate loses two electrons (becomes oxidized) and is converted to pyruvate. NAD+ gains two electrons (is reduced) and is converted to NADH. ENERGY INTERMEDIATES At various steps energy releases are stored as “Energy Intermediates” . These intermediates transfer middle sized amounts of energy. ATP and GTP ATP---- ADP ----AMP GTP ---- GDP ---- GMP 11 GTP is an energy intermediate for the production of ribosomes ATP is an energy intermediate for Sodium-Potassium pumps Making of proteins, Photosynthesis Energy is released when phosphate bonds are broken 2 high energy bonds ATPases : break down and build up atp 7kcals/ n of energy for each bond in ATP Guanosine triphosphate 12 Adenosine triphosphate See picture pg 106 old b. ENERGY INTERMEDIATES: ATP and GTP ATP is made up of 1. Nitrogenous base( adenine) 2. Ribose 3. 3 phosphate groups When Phosphate of ATP split off….. 13 ATPase ATP + H2O -- ADP + Pi + 7Kcal/n Note: ADP = Adenosine diphosphate ATPase ADP + H2O -- AMP + Pi + 7Kcal/n Note: AMP = adenosine monophosphate ELECTRON TRANSPORT SYSTEM: Function: is to separate hydrogen atoms into electrons and protons and carry the e- away. ( final electron acceptor is oxygen O2) - All H+ is left on the inside of the membrane therefore setting up a H+ gradient. ATPases: Enzymes that act on ATP to make or break the phosphate bonds. How ATP is Made: 14 1. Using large amounts of energy released by organic molecules ( ex. Glucose) when they transfer a phosphate group to ADP . 2. Most ATP is made using a membrane potential Pg 107 fig 6-10 old pg 118 new The energy to put the ATP together comes from hydrogen ions (H+) moving across membranes . 1. Hydrogen molecule inside the cell is stripped of e- by membrane 2. H+ is expelled to inside by electreon transport system 3. Channel proteins permit H+ to move down the conc. gradient 4. ATP synthetase attaches phosphate to ADP or AMP using the Kinetic energy of the moving hydrogen ion. 5. This process is called chemiosmosis or chemiosmotic ATP synthesis. Phosphorylation 15 WHERE DOES CHEMIOSMOSIS OCCUR IN THE CELL? 1. Bacterial cells: plasma membrane 2. Eukaryotes: a. Mitochondria: inner membrane b. Chloroplasts : inner membrane A Oxygen must be replenished, otherwise electron transport cannot proceed. Each carrier, once reduced, would have to stay that way because there would be no place for the electrons to go. The need to deliver oxygen to the electron transport system is why we have respiratory and circulatory systems. Oxygen is necessary to "drain" electrons from the system, 16 otherwise all of the carriers would remain reduced and electron transport would have to stop. Embedded in the inner membrane among the structures of the electron transport system are structures called the ATP synthase complex. The complex consists of a proton channel and catalytic sites for the synthesis of ATP from ADP and phosphate. When ADP and phosphate are available, they bind the catalytic sites on the ATP synthase. When this happens, the channel opens, and protons can come whooshing back in. The energy released is used to couple the phosphate to ADP, to make ATP. 17 18 An Ion gradient has potential energy and can be used to power chemical 19 20 21 22 INTERPRETING CLADOGRAMS : Taxon 1 Taxon 2 Taxon 3 Taxon 4 C B A Terminology : Clade: includes the common ancestral population (node) plus all its descendents Node A ( clade would include taxon 1-4) Node: corresponds to a hypothetical ancestor. It is found at the beginning of a group or taxon. Terminal node: the end of the taxonomic group Monophyletic group: One branch would make up a monophyletic group Polyphyletic group: more than one branch would be Shared ancestor: The common ancestor is found at the first node and is called the root Outgroup: group that doesn’t include any of the traits of the other groups 23 When drawing cladograms you never leave an empty terminal node. It should always end with a taxon . ( otherwise it will be marked as incorrect) 1. Taxon 1 is more closely related to Taxon 2 than to taxon 4. 2. Common ancestor b would include which taxon? 3. The universal ancestor for taxon 1,2,3,4 would be?