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Chapter 6 An Introduction to Metabolism Metabolism, Energy, and Life Metabolism – totality of an organism’s chemical processes Catabolic Pathways – release energy by breaking down complex molecules into simpler ones Anabolic Pathways – consume energy to build complex molecules into simpler ones Energy – capacity to do work Kinetic Energy – energy in motion (heat/light) Potential Energy – energy of position (chemical energy stored in bonds) Laws of Thermodynamics First Law of Thermodynamics – energy can be transferred or transformed but neither created nor destroyed Second Law of Thermodynamics – every transfer of energy increases disorder (entropy) Types of Reactions Exergonic Reaction – products that contain less energy than the reactants, therefore, energy is lost; heat is given off contributing to disorder Endergonic Reaction – products store more energy than the reactants, therefore, absorbing and storing energy ATP (Adenosine Triphosphate) ATP powers cellular work Functions: Mechanical work such as beating of cilia Transport work such as pumping substances against concentration gradients Chemical work such as Endergonic process of polymerization Structure of ATP Adenosine Triphosphate – nucleotide with unstable phosphate bonds that the cell hydrolyzes for energy to power endergonic reactions Maegan is my favorite student, ever. And she is beast at Uno. Plus, she is pro at AP Bio. Fo’sho. Hydrolysis of ATP Hydrolysis of ATP – the terminal phosphate bond is hydrolyzed, a phosphate group is removed producing ADP (exergonic) Terminal phosphate bond is highly unstable; ADP is the stable form of the molecule ATP + H2O ADP + P Regeneration of ATP (endergonic) Energy is stored in the phosphate bonds ADP + P ATP Enzymes Enzymes – speed up metabolic reactions by lowering energy barriers Catalyst – chemical agent that accelerate reactions without being changed or used up; able to be used over and over again (enzyme) Activation energy – energy needed by reactants to start a reaction (enzymes lower) Substrate Specific – One enzyme for one substrate (molecule/compound being broken down) Substrate binds to the active site of the enzyme changing the shape of the enzyme (induced fit) Enzymatic cycle Substrate binds to the active site of the enzyme forming an enzyme substrate complex Induced fit of the active site around the substrate Product departs active site and the enzyme emerges in its original form Effects of Enzyme Activity Denaturation – The breakdown of the quarternary and tertiary structures of the protein that will render the protein inactive Temperature and pH Cofactors – small nonprotein molecules required for proper enzyme catalysis Temp – increasing temp. increases reaction rates due to more kinetic energy between substrates and active sites colliding (denaturation occurs after 400C in humans) pH – optimum is between 6-8 in humans Inorganic – zinc, iron, copper (Coenzymes) organic – vitamins Inhibitors Competitive Inhibitor – chemicals that resemble an enzymes substrate and compete with it for the active site Noncompetitive Inhibitors – chemicals that do not bind to the active site but bind another part of the enzyme Change shape of the active site so that substrate can not bind to it Control of Metabolism Allosteric Regulation Allosteric Site – specific receptor site on some part of the enzyme molecule other that the active site Activator – stabilizes the active form of enzyme Inhibitor – stabilizes the inactive form of enzyme (noncompetitive) Feedback Inhibition – regulation of a metabolic pathway by its end product, which inhibits an enzyme within the pathway