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Chapter 8

Chapter 8. An Introduction to Metabolism. Metabolism. The totality of an organism’s chemical reactions http://www.elmhurst.edu/~ chm/vchembook/images/590metabolism.gif. 2 types of reactions in metabolic pathways. Anabolic and catabolic Which reactions release energy?

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Chapter 8

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  1. Chapter 8 An Introduction to Metabolism

  2. Metabolism • The totality of an organism’s chemical reactions • http://www.elmhurst.edu/~chm/vchembook/images/590metabolism.gif

  3. 2 types of reactions in metabolic pathways • Anabolic and catabolic • Which reactions release energy? • Which reactions consume energy? • Which reactions break down molecules? • Which reactions build up larger molecules? • Which reactions are considered “uphill”? • What type of reaction is photosynthesis? • What type of reaction is cellular respiration?

  4. Forms of Energy • Contrast kinetic energy with potential energy. • Which type of energy does water behind a dam have? A mole of glucose? • http://upload.wikimedia.org/wikipedia/commons/thumb/5/57/Hydroelectric_dam.svg/1280px-Hydroelectric_dam.svg.png • http://thumbs.dreamstime.com/z/glucose-molecule-11063520.jpg

  5. The free-energy of a reaction tells us whether the reaction occurs spontaneously • What is free energy? What is its symbol? • Endothermic - absorbs heat, H > 0 • Exothermic - releases heat,H < 0 • Reactions can also be classified according to the change in the free energy of the reaction: • Endergonic - NON-SPONTANEOUS, G > 0 • Exergonic - SPONTANEOUS, G < 0

  6. Cellular Respiration vs Photosynthesis • Is cellular respiration an endergonic or an exergonic reaction? What is ∆G for this reaction? • Is photosynthesis endergonic or exergonic? What is the energy source that drives it? • \

  7. ATP powers cellular work by coupling exergonic reactions to endergonic reactions • List the three main kinds of work that a cell does. Give an example of each. • 1. Chemical work • 2. Transport work • 3. Mechanical work

  8. ATP – Adenosine Triphosphate W Which bond is likely to break?

  9. ATP • By what process will that bond break? • When the terminal phosphate is broken, a molecule of inorganic phosphate Pi is formed, and energy is ___________? • For this reaction ATP  ADP + Pi, ∆G = ?

  10. How ATP Performs Work • What is energy coupling? See Fig. 8.10 • 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 ____________.

  11. Enzymes speed up metabolic reactions by lowering energy barriers • http://www.indiana.edu/~oso/animations/SN2%2BE.html • What is a catalyst? • What is activation energy? See Fig. 8.14

  12. Review of energy profile of an exergonic reaction • What effect does an enzyme have on EA? • Is ∆G positive or negative? • How is ∆G affected by the enzyme?

  13. Catalysis in the Enzyme’s Active Site • http://bio1151.nicerweb.com/Locked/media/ch08/08_17CatalyticCycle.jpg • What is meant by induced fit? • Explain how protein structure is involved in enzyme specificity. • Enzymes use a variety of mechanisms to lower activation energy. Describe four of these mechanisms.

  14. 4 Mechanisms • 1. acting as a template for substrate orientation • 2. stressing the substrates and stabilizing the transition state • 3. providing a favorable microenvironment • 4. participating directly in the catalytic reaction

  15. Effects of Local Conditions on Enzyme Activity • Many factors can affect the rate of enzyme action. Explain each factor listed below. • A. Initial concentration of substrate • B. pH • C. Temperature • Why can extremes of pH or very high temperatures affect enzyme activity? • Name a human enzyme that functions well in pH 2. Where is it found?

  16. Effects of Local Conditions on Enzyme Activity • Distinguish between cofactors and coenzymes. Give examples of each. • Compare and contrast competitive inhibitors and noncompetitive inhibitors. • http://bcs.whfreeman.com/thelifewire/content/chp06/0602001.html

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