Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe UNIT THREE LECTURE 14 this II Metabolism certain product I Energy enters as sunlight and leaves as heat Nutrients cycle through our ecosystem A Organisms and their environment interact in these ways 1 Matter and energy are the commodities of the interaction 2 Ecosystems are dynamic a matter nutrients in the case cycles b energy flows 3 Energy conversion b chemical bonds go into kinetic energy c This is life a light goes into chemical bonds plants are important when it comes to A Metabolic pathway defined steps that happen to a single molecule resulting in a B Metabolism the whole balance of materials and energy it is the totality of an organism s chemical reaction 1 catabolism large molecules being broken down to smaller ones 2 anabolism building larger molecules from simpler ones C Energy the capacity to cause change Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe 1 Kinetic energy is the energy of motion a Thermal energy is the energy from the motion of atoms due to heat 2 Potential energy is the energy due to the location of the structure within the a chemical energy is the potential energy due to the chemical 3 enthalpy H is the measure of the total energy in a system D Thermodynamics is the study of energy transformations 1 isolated systems are approximations we use to describe perfect systems This is one in which no heat is exchanged 2 open systems systems where energy can be transferred humans are open 3 First law of thermodynamics energy can be transformed or transferred but cannot be created or destroyed think of law of conservation of energy 4 Second law of thermodynamics every energy transfer favors an increase in entropy disorder In order for a process to be spontaneous it must increase the entropy of a A spontaneous reaction is a reaction that occurs without energetic input A Gibbs Free Energy the part of a systems energy that is free to perform work Also a measure of the systems stability unstable systems have lots of free energy atmosphere arrangement of atoms systems the system II Free Energy Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe Equation for Gibbs Free Energy is G H T S G Gibbs free energy if the reaction is spontaneous if it is never spontaneous H enthalpy or total energy T Temperature in Kelvin S entropy disorder B Equilibrium this is the state at which the forward and reverse reactions are occurring at the same rate equilibrium 1 A spontaneous process can only do work when it is moving towards C Endergonic endothermic describes a reaction that absorbs free energy therefore a positive G these types of reactions need energy to proceed D Exergonic exothermic describes a reaction that releases free energy has a negative G these processes are spontaneous reactions E Cells are NEVER in equilibrium F Systems in equilibrium have the lowest G and can do no work G Exothermic spontaneous reactions still need an input of energy to make them go III Enzymes lower energy barriers A an enzyme is a macromolecule that is also a catalyst 1 most of the time they are proteins 2 RNA molecules can also be catalytic ie ribosomes B energy of activation Ea this is the energy that is required to prime a chemical reaction Ea determines the rate of a reaction C enzymes lower the Ea barrier Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe D Substrates are reactants 1 the substrate binds the enzyme and chemistry makes the product Enzyme substrate enzyme and substrate combined enzyme product 2 Active sites are the part of the enzyme where the substrate binds The active site can change shape to help put the substrate molecule in a better position in order to help lower its Ea This is called the induced fit model E Enzymes lower the Ea through several mechanisms 1 it is a template to orient the substrate 2 it distorts the bonds 3 the active site enhances chemistry 4 some cofactors can help lower the Ea such as a inorganic metal ions b coenzymes 5 Enzymes can be slowed down stopped or sped up by interactions with other molecules in the cell such as proteins nucleic acids small molecules 6 Enzymes can be localized in cells to facilitate their function like ATP synthase in the membranes of the mitochondria IV Regulating enzymes regulates metabolism A allosteric regulation activity at one site is affected by binding a regulatory molecule at another place 1 many times the shape of the protein determines if the protein is active or inactive and that shape can be affected by small molecules or other proteins Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe a activators increase activity b inhibitors decrease activity 2 the concentration of regulators changes with the cellular environment 1 substrate binding activates activity in other subunits C Feedback inhibition a metabolic pathway is turned off by a downstream product 1 competitive inhibition substrate analogs block the real substrate 2 noncompetitive inhibitors block the activity far from the active site B Cooperativity D inhibitors Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe LECTURE 15 The cell needs to be able to do work they do this through energy coupling which joins an exergonic with an endergonic process to make the endergonic process move forward This occurs A Chemical work making reactions that would otherwise not occur go forward in I ATP reaction B Transport work active transport C Mechanical work beating of cilia A Adenosine Triphosphate through hydrolysis 1 Adenine ribose triphosphate whose bonds are labile easily changed 2 phosphate bonds are high energy because the G is large This is why the removal of phosphates from ATP is used to fuel most work in the cell B ATP performs work by 1 releasing energy to the cell thru ATP hydrolysis 2 the transfer of a phosphate group called phosphorylation enzymes perform this a phosphate is transferred to a more labile position b changes the shape of the molecule c when the phosphate gets transferred to its target the post translationally modified protein is called the phosphorylated intermediate 3 Coupling energy released by ATP hydrolysis to other endothermic reactions Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe 4 ADP Pi ATP a ADP turns back over needing 7 3 kcal mol to regenerate ATP This comes from catabolic pathways or photosynthesis in plants b an enzyme called ATP synthase performs this reaction II Catabolic pathways oxidize organic fuels A Three pathways processes 1 Fermentation sugar is degraded in the absence of oxygen 2
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