1. Mader: Biology 8 th Ed. Metabolism: Energy and Enzymes Chapter 6

2. Mader: Biology 8 th Ed. Outline Forms of Energy Laws of Thermodynamics Metabolic Reactions ATP Metabolic Pathways Energy of Activation Enzymes Photosynthesis Cellular Respiration

3. Mader: Biology 8 th Ed. Forms of Energy Kinetic - Energy of motion. – Mechanical Potential - Stored energy. – Chemical

4. Mader: Biology 8 th Ed. Laws of Thermodynamics First law (law of conservation of energy) states: – Energy cannot be created or destroyed, but it can be changed from one form to another. Second law states: – Energy cannot be changed from one form to another without a loss of usable energy.

5. Mader: Biology 8 th Ed. Cells and Entropy Second law can also be explained as every energy transformation makes the universe less organized and more disordered. – Entropy  Second law means that every cellular process increases the total entropy of the universe.

6. Mader: Biology 8 th Ed. Cells and Entropy

7. Mader: Biology 8 th Ed. Metabolic Reactions Metabolism - Sum of cellular chemical reactions. – Reactants and products Free energy is the amount of energy available to perform work. – Exergonic Reactions - Reactants have more free energy than products. – Endergonic Reactions - Products have more free energy than reactants.

8. Mader: Biology 8 th Ed. ATP Adenosine triphosphate (ATP) is constantly being generated from Adenosine diphosphate (ADP). – Composed of adenine and ribose (adenosine) and three phosphate groups.

9. Mader: Biology 8 th Ed. ATP Cycle

10. Mader: Biology 8 th Ed. Coupled Reactions In coupled reactions, the energy released by an exergonic reaction drives an endergonic reaction.

11. Mader: Biology 8 th Ed. Coupled Reactions

12. Mader: Biology 8 th Ed. Function of ATP Chemical Work - Energy needed to synthesize macromolecules. Transport Work - Energy needed to pump substances across plasma membrane. Mechanical Work - Energy needed to contract muscles, beat flagella, etc.

13. Mader: Biology 8 th Ed. Metabolic Pathways Reactions are usually part of a series of linked reactions. – Begin with a particular reactant and terminate with an end product. Enzymes are protein molecules that function as organic catalysts to speed a chemical reaction.

14. Mader: Biology 8 th Ed. Energy of Activation The energy that must be added to cause molecules to react with one another is called the energy of activation. – Enzymes lower energy of activation by bringing the substrates into contact with one another.

15. Mader: Biology 8 th Ed. Energy of Activation

16. Mader: Biology 8 th Ed. Enzyme-Substrate Complex

17. Mader: Biology 8 th Ed. Enzyme-Substrate Complex In most instances, only the active site complexes with the substrates. – Active site undergoes a change in shape to accommodate the substrates.  Induced fit model

18. Mader: Biology 8 th Ed. Enzyme Speed Generally, enzyme activity increases as substrate concentration increases. – More collisions between substrate molecules and the enzyme. As temperature rises, enzyme activity increases. – Warmer temperatures cause more effective collisions between enzyme and substrate.

19. Mader: Biology 8 th Ed. Enzyme Speed – If temperature rises beyond a certain point, the enzyme becomes denatured and the enzyme activity levels out. Enzymes also have an optimal pH.

20. Mader: Biology 8 th Ed. Enzyme Concentration Cells regulate which enzymes are present and/or active. – Enzyme Cofactors  Vitamins  Phosphorylation  Enzyme Inhibition  Feedback Inhibition

21. Mader: Biology 8 th Ed. Feedback Inhibition

22. Mader: Biology 8 th Ed. Feedback Inhibition Most metabolic pathways are regulated by another type of feedback inhibition. – End product of the pathway binds to an allosteric site.  Binding shuts down the pathway, and no more product is produced.

23. Mader: Biology 8 th Ed. Oxidation-Reduction In redox reactions, electrons pass from one molecule to another. – Oxidation is the loss of electrons. – Reduction is the gain of electrons. Oxidation and reduction always take place at the same time as one molecule accepts the electrons given up by another molecule.

24. Mader: Biology 8 th Ed. Photosynthesis Carbon dioxide + water + solar energy yields glucose and oxygen. 6 CO 2 + 6 H 2 O + energy  C 6 H 12 O 6 + 6 O 2 Chloroplasts capture solar energy and convert it via electron transport chain to ATP. Coenzyme active during photosynthesis. NADP + + 2e - + H +  NADPH

25. Mader: Biology 8 th Ed. Cellular Respiration Glucose + oxygen yields carbon dioxide + water + energy. C 6 H 12 O 6 + 6 O 2  6 CO 2 + 6 H 2 O + energy Most oxidations involve a coenzyme: NAD + + 2e - + H +  NADH

26. Mader: Biology 8 th Ed. Electron Transport System A series of membrane-bound carriers that pass electrons from one carrier to another. – High-energy electrons delivered, and low- energy electrons leave.

27. Mader: Biology 8 th Ed. ATP Production Chemiosmosis: Production of ATP due to a hydrogen ion gradient across a membrane.

28. Mader: Biology 8 th Ed. Review Forms of Energy Laws of Thermodynamics Metabolic Reactions ATP Metabolic Pathways Energy of Activation Enzymes Photosynthesis Cellular Respiration

29. Mader: Biology 8 th Ed.