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Chapter 8 notes

Chapter 8 notes. An Introduction to Metabolism. Concept 8.1. Metabolism : the totality of an organism’s chemical reactions A metabolic pathway begins with a specific molecule and is altered into a product - each step is catalyzed by an enzyme. Concept 8.1.

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Chapter 8 notes

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  1. Chapter 8 notes An Introduction to Metabolism

  2. Concept 8.1 Metabolism: the totality of an organism’s chemical reactions A metabolic pathwaybegins with a specific molecule and is altered into a product - each step is catalyzed by an enzyme

  3. Concept 8.1 Catabolic pathway: release energy in the breaking down of complex molecules into simpler compounds - ex. glucose  CO2 + H2O Anabolic pathway: consume energy to build complicated molecules from simpler ones - ex. amino acids  proteins

  4. Concept 8.1 Energy: the capacity to do work Reactions are either exergonic (energy outward) or endergonic (energy inward)

  5. Concept 8.2 Exergonicreactionsproceed with a net release of energy - occur spontaneously Endergonicreactionsabsorb free energy from their surroundings - nonspontaneous

  6. Concept 8.2

  7. Concept 8.2 Cells do three kinds of work: - mechanical work (ex. contraction of a muscle cell) - transport work (ex. pumping of substances across a memebrance) - chemical work (ex. synthesis of polymers from monomers)

  8. Concept 8.3 Energy coupling: the use of an exergonic process to drive an endergonicone. ATP (adenosine triphosphate) is the energy source used in most reactions. - contains a ribose (sugar), adenine (base), and 3 phosphate molecules

  9. Concept 8.3

  10. Concept 8.3 Energy is released from ATP when the terminal phosphate bond is broken ATP  ADP + Pi + Energy - work is accomplished by phosphorylation - the transferring of the Pi to another molecule (ex. channel protein)

  11. Concept 8.3 ATP is regenerated in the cell by phosphorylating ADP through an exergonicreaction in the cell - in a muscle cell 10 million ATP areconsumed and regenerated per second per cell

  12. Concept 8.3

  13. Concept 8.4 Spontaneous reactions may occur at very slow rates - sucrose  glucose + fructose - if an enzyme is added, the same reaction can be completed in seconds . Catalyst : a chemical agent that speeds up reaction w/out being consumed

  14. Concept 8.4 Enzyme : a biological catalyst Activation energy , the energy needed to begin a reaction, prevents many reactions from occurring quickly Heat is used to speed up reactions because it increases the speed of reactant molecules (they collide more often).

  15. Concept 8.4 In biological systems heat alone would not work - too much heat denatures proteins and kills cells An enzyme (catalyst) lowers the amount of activation energy needed - enzymes are very selective

  16. Concept 8.4

  17. Concept 8.4 The reactant an enzyme binds to is called the substrate - binds to the active site of the enzyme - the enzyme converts the substrate to product - the product is released Enzyme animation

  18. Concept 8.4 Up to a point, the rate of an enzymatic reaction will increase with temperature - eventually it will drop because of thermal agitation and protein denaturing

  19. Concept 8.4 Most human enzymes function best at 35 - 40 oC. - some bacteria that live in hot springs have proteins that work best at 70 oC. Most human enzymes also work best at 6-8 pH . - pepsin in the stomach work best at pH of 2.

  20. Concept 8.4

  21. Concept 8.4 Certain chemicals can selectively inhibit the activity of specific enzymes Competitive inhibitors: reduce enzyme activity by blocking the substrate from binding to the active site - can be overcome by increasing the substrate

  22. Concept 8.4 Noncompetitive inhibitors: impede the reaction by attaching to another part of the enzyme, thus changing its shape - ex. toxins and poisons

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