Chapter 8 Overall Flow of Energy glucose ATP Concept 8 1 Sunlight Green Plant Cell Photosynthesis Glucose Metabolism of Metabolism totality of organism s chemical reactions Metabolism is an emergent property of life Metabolic Pathways Begins with a specific molecule and ends with product A specific enzyme catalyzes each stage Catabolic Pathways Release energy by breaking down complex molecules into simpler compounds Ex Cellular respiration the breakdown of glucose in the presence Anabolic Pathways consume energy to build complex molecules from Ex The synthesis of protein from amino acids is an example of Bioenergetics Study of how organisms manage their energy sources of oxygen simpler ones anabolism Forms of Energy Energy Capacity to cause change Potential Energy energy due to location or structure Kinetic Energy Energy due to motion Laws of energy transformation Thermodynamics is the study of energy transformation Organisms are open systems First law of thermodynamics Energy is a constant Energy can be transferred or transformed byt not created or destroyed Also known as the principle of conversation of energy Second Law of thermodynamics During transfer some is unusable and is lost as heat Every energy transfer of transformation increases the entropy of the universe quickly or slowly Energy G change in free change Delta G Living organisms convert organized forms of energy to eat Spontaneous processes occur with out energy input they can happen For a process to occur without energy input they must increase entropy in the universe Biological order and disorder Cells create ordered structures from less ordered materials Organisms also replace ordered forms of matter and energy with less Evolution of more complex organisms does not violate the 2nd law of Entropy may decrease in an organism but total entropy will increase in the In order to decrease entropy in an organism that organism needs to create more complex structures which require energy heat is lost ordered forms thermodynamics universe Concept 8 2 require input of energy Free Energy Biologists want to know which reactions occur spontaneously and which Must determine energy changes that occur in chemical reactions Energy that can do work holding temperature and pressure constant Spontaneous reactions can be harnessed to preform work Delta G Delta H Temperature Delta S Delta G Gf Gi Non Spontaneous Endothermic If Gf Gi Then Delta G 0 Spontaneous Exothermic If Gf Gi Then Delta G 0 Free Energy and Metabolism processes The concept of free energy can be applied to the chemistry of life s Exergonic reaction Releases energy spontaneous Endergonic Reaction Absorbs energy non spontaneous Reaction is not spontaneous and requires energy endergonic Maltose Synthesis Maltose Breakdown Reaction is spontaneous and releases energy exergonic General rule of reaction Breaking of molecules apart by hydrolysis causes 1 Delta G 2 Spontaneous and exergonic Forming molecules through dehydration reactions 1 Delta G 2 Non spontaneous and endergonic Reactions in closed systems eventually reach equilibrium and then do no Equilibrium and Metabolism work Life Metabolism is never t equilibrium Cells are not at equilibrium Concept 8 3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions A cell does three kinds of work 1 Chemical 2 Transport 3 Mechanical Most energy coupling in cells is mediated by ATP Structure and Hydrolysis of ATP Adenosine triphosphate is the cell s energy shuttle ATP is Ribose Sugar Adenine Nitrogen Base and 3 phosphate groups Bonds between phosphate groups of ATP s tails can be broken through hydrolysis ATP drives endergonic reactions by phosphorylation transferring phosphate group to other molecules Recipient is called a phosphorylated intermediate Allows for coupling of exergonic and endergonic reactions Bonds between phosphate groups contain high potential energy from a repulsion of charge between oxygens on the phosphate group How the Hydrolysis of ATP preforms work Overall the couple reactions are exergonic 3 types of cellular work are powered by hydrolysis of ATP Glucose Glucose ATP Maltose ADP PO4 The phosphorylated intermediate is more reactive less stable than the original phosphorylated molecule The Regeneration of ATP ATP is a renewable resource that is regenerated by addition of a phosphate group to adenosine di phosphate Potential energy is stored in this bond ATP drives most cellular work ATP ADP Phosphate group ATP cycle is a revolving door through which energy passes during transfer from catabolic to anabolic pathways Metabolic Pathways Metabolic pathway begins with a specific molecule and ends with a product required Each step is catalyzed by a specific enzyme 2 questions about cell reactions Will a reaction occur spontaneously or will extra energy be What is the speed of the reaction Concept 8 4 Enzymes speed up metabolic reactions by lowering energy barriers A catalyst is a chemical agent that speeds up reactions without being consumed Enzyme as a catalytic protein Hydrolysis of sucrose by the enzyme Sucrase is an example of an enzyme catalyzed reaction Sucrase can also drive the reaction in the opposite direction Activation Energy barrier forming of bonds Every chemical reaction between molecules involves the breaking and Initial energy needed to start a chemical reaction is called free energy of activation or Activation Energy or EA Activation energy is often supplied in the form of thermal energy When the molecules gain enough energy and become unstable they enter the transition state Enzymes and Energy Barrier Enzymes catalyze reactions by lowering the activation energy barrier Instead of using high temperature which would denature proteins Enzymes do not affect the change inn free energy Delta G instead they hasten reactions that would occur eventually Enzyme cannot change an endergonic reaction into an exergonic and kill cells one toward equilibrium Can catalyze reaction in both ways but always toward Delta G and Enzyme substrate is its molecule that it can catalyze Substrate Specification Enzymes Enzyme binds with substrate called enzyme substrate complex Active site is the region on the enzyme where the substrate binds R groups of amino acids in active site binds to specific chemical groups on the substrate Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reaction Specific enzymes will work
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