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Chapter 8

Chapter 8. An Introduction to Metabolism. Remember These!. Identify forms of energy and energy transformations. Recognizes the laws of thermodynamics Recognize that organize live at the expense of free energy Relate Free-energy to metabolism

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Chapter 8

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  1. Chapter 8 An Introduction to Metabolism

  2. Remember These! • Identify forms of energy and energy transformations. • Recognizes the laws of thermodynamics • Recognize that organize live at the expense of free energy • Relate Free-energy to metabolism • Identify exergonic and endergonic reactions. Define catabolism and anabolism and relate them to metabolism • Explain the structure and hydrolysis of ATP • Recognize how ATP works and is coupled to metabolism • Recognize how ATP is regenerated

  3. Metabolism • Metabolism: • The totality of an organism’s chemical processes • From food to energy. • Concerned with managing the material and energy resources of a cell

  4. Metabolism • Organization of living life into Metabolic Pathways.

  5. Catabolism vs. Anabolism • Catabolic Pathways: • Release energy by breaking down complex molecules to simpler ones • Example: cellular respiration • Anabolic Pathways: • Consume energy to build complicated molecules from simpler ones • Example: Synthesis of a protein from AAs

  6. Bioenergetics • Bioenergetics: • The study of how organisms manage their energy resources • Energy = the capacity to do work • Kinetic energy: the energy of motion • Potential energy: stored energy

  7. Laws of Thermodynamics • 1st Law of Thermodynamics: • Energy can be transferred and transformed, but it can be neither created nor destroyed. • 2nd Law of Thermodynamics: • Every energy transfer or transformation increases the entropy of the universe.

  8. Energy • Spontaneous process: • A change that can occur without outside help • Free energy: • The portion of a system’s energy that can perform work when temperature is uniform throughout the system, as in a living cell • Called “free” because it is available to do work

  9. Exergonic vs. Endergonic Reactions • Exergonic Reactions • Proceed with a net release of free energy • “downhill” • Occur spontaneously • Example: cellular respiration • Endergonic Reactions • Reactions that absorb free energy from their surroundings • “uphill” • Do NOT occur spontaneously • Example: photosynthesis

  10. Exergonic vs. Endergonic Reactions

  11. ATP • All cellular work requires ATP! • Triphosphate tail is unstable • 3 phosphate groups attached to the ribose • Bonds between phosphate groups are unstable and are broken by hydrolysis • ADP + P is more stable than ATP • Therefore, this is a downhill (exergonic) reaction! • ATP has to be regenerated… • Cellular respiration!

  12. ATP

  13. Enzymes • Enzymes • Catalytic proteins • Catalyst = a chemical agent that changes the rate of a reaction without being consumed by the reaction

  14. Enzymes • Activation Energy • The energy required to break the bonds in the reactant molecules • Heat helps… but cannot be used in cells • Why not? • Enzymes can only speed up reactions that would eventually occur anyways

  15. Selectivity of Enzymes • Enzymes are VERY selective • Substrate = the reactant an enzyme acts on • Enzyme binds to the substrate(s) and converts the substrate(s) to the product(s) • Enzymes can distinguish its substrate from closely related compounds so each type of enzyme catalyzes a particular reaction

  16. Enzyme Structure • Active site: • The part of the enzyme that actually binds to the substrate • Induced Fit: • As a substrate enters the active site, it induces the enzyme to change its shape slightly so that the active site fits even more snugly around the substrate

  17. Enzymes

  18. Enzymes • How they speed up a reaction… • Put 2 substrates together (blind date) • Create a microenvironment conducive to a particular reaction (ie. Low pH)

  19. Enzyme Rate of Reaction • Rate of Reaction: • Partly a function of the initial concentration of a substrate • More substrate = more frequently access active sites of enzyme • There is a limit to this… • Sometimes all enzymes are “busy” • Enzyme is said to be “saturated” • Every enzyme has an optimal temperature and pH level

  20. Enzymes • Cofactors: • Nonprotein helpers required along with enzymes for catalytic activity • zinc, iron, copper, vitamins, etc.

  21. Enzymes • Enzyme Inhibitors: • Certain chemicals selectively inhibit the action of specific enzymes • Competitive inhibitors: • Mimics that compete with normal substrate molecules for admission into the active site • Noncompetitive inhibitors: • Impede enzymatic reactions by binding to a part of the enzyme away from the active site, thereby making the enzyme change its shape

  22. Enzymes • Allosteric site: • A specific receptor site on some part of the enzyme molecule remote from the active site to which the molecules that naturally regulate enzyme activity bind • Act as valves that control rates of key reactions in metabolic pathways • On/Off switch

  23. Enzymes • Cooperativity • One substrate molecule primes an enzyme to accept additional substrate molecules • Favorable conformational change in one subunit of an enzyme changes all the others too

  24. Enzymes • Feedback Inhibition: • A metabolic pathway is switched off by its end product, which acts as an inhibitor of an enzyme within the pathway • Thermostat

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