Name Period Chapter 8 An Introduction to Metabolism Concept 8 1 An organism s metabolism transforms matter and energy subject to the laws of thermodynamics 1 Define metabolism The totality of an organism s chemical reactions consisting of catabolic and anabolic pathways which manage the material and energy resources of the organism 2 There are two types of reactions in metabolic pathways anabolic and catabolic a Which reactions release energy catabolic b Which reactions consume energy anabolic c Which reactions build up larger molecules catabolic d Which reactions break down molecules catabolic e Which reactions are considered uphill anabolic f What type of reaction is photosynthesis catabolic g What type of reaction is cellular respiration catabolic h Which reactions require enzymes to catalyze reactions catabolic anabolic 3 Contrast kinetic energy with potential energy Kinetic energy is associated with the relative motion of objects whereas potential energy refers to an object not presently moving it is the energy that matter possesses because of its location or structure 4 Which type of energy does water behind a dam have A mole of glucose Water behind a dam has potential energy A mole of glucose also has potential energy though more specifically glucose has chemical energy a term used by biologists to refer to the potential energy available for release in a chemical reaction 5 What is meant by a spontaneous process A process that occurs without an overall input of energy a process that is energetically favorable Copyright 2011 Pearson Education Inc 1 Concept 8 2 The free energy change of a reaction tells us whether the reaction occurs spontaneously 6 What is free energy What is its symbol Free energy is the portion of a system s energy that can perform work when temperature and pressure are uniform throughout the system as in a living cell Free energy is symbolized by the letter G after Professor Willard Gibbs 7 For an exergonic reaction is G negative or positive An exergonic reaction proceeds with a net release of free energy Because the chemical mixture loses free energy G is negative for an exergonic reaction 8 Is cellular respiration an endergonic or an exergonic reaction What is G for this reaction Cellular respiration is an exergonic reaction The G for this reaction is G 686 kcal mol 2 870 kJ mol 9 Is photosynthesis endergonic or exergonic What is the energy source that drives it Photosynthesis is an endergonic reaction Plants get the required energy 686 kcal to make a mole of glucose from the environment by capturing light and converting its energy into chemical energy 10 To summarize if energy is released G must be what G must be negative Concept 8 3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions 11 List the three main kinds of work that a cell does Give an example of each a Chemical work the pushing of endergonic reactions that would not occur spontaneously such as the synthesis of polymers from monomers b Transport work the pumping of substances across membranes against the direction of spontaneous movement possible examples include the sodium potassium pump and proton pump c Mechanical work such as the beating of cilia the contraction of muscle cells and the movement of chromosomes during cellular reproduction 12 Here is a molecule of ATP Label it Use an arrow to show which bond is likely to break See page 149 of your text for the labeled figure a By what process will that bond break Hydrolysis Copyright 2011 Pearson Education Inc 2 b Explain the name ATP by listing all the molecules that make it up ATP contains the sugar ribose with the nitrogenous base adenine and a chain of three phosphate groups bonded to it forming adenosine triphosphate 13 When the terminal phosphate bond is broken a molecule of inorganic phosphate Pi is formed and energy is released For this reaction ATP ADP Pi G 7 3 kcal mol 30 5 kJ mol Is this reaction endergonic or exergonic Exergonic FYI An essay question on the 2009 AP Biology exam asked students to identify the molecules that make up ATP What are they again Sugar ribose with the nitrogenous base adenine and a chain of three phosphate groups 14 What is energy coupling In cellular metabolism the use of energy released from an exergonic reaction to drive an endergonic reaction 15 In many cellular reactions a phosphate group is transferred from ATP to some other molecule in order to make the second molecule less stable The second molecule is said to be phosphorylated intermediate 16 Look for this amazing bit of trivia on page 151 If you could not regenerate ATP by phosphorylating ADP how much ATP would you need to consume each day If ATP could not be regenerated by the phosphorylation of ADP humans would use up nearly their body weight in ATP each day Concept 8 4 Enzymes speed up metabolic reactions by lowering energy barriers 17 What is a catalyst A chemical agent that selectively increases the rate of a reaction without being consumed by the reaction 18 What is activation energy EA The amount of energy that reactants must absorb before a chemical reaction will start also called free energy of activation 19 Label the x axis of this graph Progress of the Reaction and the y axis Free Energy Label EA on this sketch both with and without an enzyme See page 152 of your text for the labeled figure Copyright 2011 Pearson Education Inc 3 a What effect does an enzyme have on EA An enzyme catalyzes a reaction by lowering EA barrier b Label G Is it positive or negative Negative c How is G affected by the enzyme It cannot make an endergonic reaction exergonic 20 Label this figure while you define each of the following terms See page 155 of your text for the labeled figure enzyme A macromolecule serving as a catalyst a chemical agent that increases the rate of a reaction without being consumed by the reaction Most enzymes are proteins substrate The reactant on which an enzyme works active site The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs products A material resulting from a chemical reaction 21 What is meant by induced fit How is it shown in the figure in question 20 Caused by entry of the substrate the change in shape of the active site of an enzyme so that it binds more snugly to the substrate In Figure 8 14 on page 154 when the substrate enters the active site it forms weak bonds with the enzyme inducing a change in the shape of the protein This