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Metabolism Cell Energetics Cell do three main kinds of work Mechanical – move themselves Transport – move something else Chemical – convert stuff to other stuff Work requires energy Where does the energy come from and how do cells use it? Cell Energetics Energy is ______ Metabolism 2 types of metabolism Two forms of energy How do cells use the 2 forms 2 Laws of Thermodynamics Entropy 2 types of reactions Cell Energetics Metabolism = total of all the chemical reactions taking place in an organism Metabolism Anabolism = ‘build up’ processes; ‘consume’ (store) energy by assembling macromolecules Photosynthesis Catabolism = ‘break down’ reactions; release energy by breaking down (lyse) molecules Digestion Energy Energy – the ability to do work Potential = capacity to do work (move something); due to position or stored (chemical energy; glucose, glycogen) Kinetic = motion Equilibrium = energy runs out Kinetic and potential energy What does the types of energy have to do with biology? Thermodynamics 1st Law – energy cannot be created nor destroyed Energy can be transformed 2nd Law – ‘Law of Entropy’ whenever energy is transformed, some of it becomes ‘unusable’ Entropy - amount of usable energy decreases each time it is used ‘Lost’ as heat Energy is running down, universe is tending towards disorder Biological Order and Disorder Organisms are open systems Use energy to maintain order and organization Trade organization for heat (increase entropy in the environment) Metabolism: Reactions Two types of reactions: Exergonic, endergonic Exergonic reaction - release of free energy Less stable, more work Fire, respiration Metabolism: Reactions Endergonic reaction - energy is absorbed/stored Photosynthesis Chemical Reactions Equilibrium is eventually reached in closed systems Reduced free energy No work is done You’re dead! What cells do.. Review What are the 2 forms of energy? _____ is the ability to do work Energy is lost in chemical reactions as __ A reaction that stores/absorbs energy is said to be _____ A reaction that releases energy is _____ The total of all chemical reactions in an organism is called ____ Coupled Reactions Living systems use coupled reactions Endergonic reactions are linked (coupled) with exergonic reactions Energy from an exergonic reaction (respiration) is stored in chemical bonds Coupled Reactions ATP – Adenosine triphosphate Cyclical Catabolic pathways drive the regeneration of ATP from ADP and phosphate Controlled by enzymes Uses of Energy Mechanical - moving of cilia/flagella, muscle, cytoplasm, chromosomes (mitosis), mousetrap Transport - H+ ‘pump’, receptors Chemical – polymerization Bioluminescence • Enzymes control metabolism – If enzymes are present, reactions take place, if not, they don’t. Enzymes speed up reactions by lowering activation energy Enzymes Biological catalysts Accelerate a reaction without being changed Proteins (700) Catabolic or anabolic reactions Enzymes All chemical reactions require activation energy Activation energy (EA) - the initial amount of energy needed to start a chemical reaction Transition state = reactants have absorbed energy Have become unstable Reaction takes place Enzymes Some reactions occur spontaneously due to heat from the environment (rust) Cellular T needs to remain low Metabolism is too slow at low T Starch to glucose Enzymes used to reduce activation energy (metabolism at lower T) Enzymes Substrate = substance enzyme acts on Active site = area on the enzyme where substrate binds Verryyy specific Groove, pocket = 3d shape Enzymes Lock and key mechanism Induced Fit = enzyme may change shape to allow better reaction on substrate Factors That Affect Enzyme Activity Temperature pH Inorganic salts – Disrupt H bonds, ionic bonds, hydrophobic interactions Cofactors Inhibitors Temperature and pH affect enzyme activity Cofactors Cofactors - nonprotein enzyme helpers Metals – Fe, Zn, Cu Coenzymes - organic cofactors Vitamins Enzymes Inhibitors = substances that inhibit the actions of enzymes (2 kinds:) Competitive inhibitors Noncompetitive inhibitors Competitive inhibitors resemble substrate, block active site Neurotoxin, Disulfiram Enzymes Noncompetitive inhibitors - causes enzyme to change shape Destroys conformation (active site) DDT, nerve gas (DSF) May be allosteric regulation Allosteric Regulation of Enzymes Allosteric regulation - a protein’s function at one site is affected by binding of a regulatory molecule at another site Receptor site located away from the active site (quatenary structure) Allosteric site has to be activated, (may be inhibited) Allosteric activator Allosteric inhibitor Enzymes Cooperativity - one substrate molecule can activate all other subunits of an enzyme Induced fit Only requires a small concentration of substrate to activate enzyme Enzyme Activity Helps Control Metabolism A cell’s metabolic pathways must be tightly regulated DNA codes for proteins (enzymes) Amount of enzyme can determine rate of reaction Feedback Inhibition - end product of the pathway inhibits the pathway Regulation Metabolic pathways – series of enzymes creates small steps to a final product Controlling the enzymes (activity or production) controls the pathway and product(s) Feedback Inhibition Final product of the pathway shuts off the pathway Feedback inhibition prevents cells from wasting resources “don’t need gas if you don’t have a car.” Isoleucine – allosteric inhibitor