Energy and Metabolism Chapter 8

1. Energy and MetabolismChapter 8

2. Energy

3. Energy

4. Energy

5. Metabolism • All the chemical reactions carried out by the cell

6. Metabolism • Catabolic reactions: • Break down large molecules into smaller substances • Exergonic: • Releases energy

7. Metabolism • Anabolic reactions: • Synthesis of large molecules from smaller substances • Endergonic: • Requires energy

8. Metabolism • Biochemical pathways: • Reactions in a cell • Occur in sequence • Product of one reaction • Becomes substrate in the next • Pathways are highly regulated and coordinated • Feedback inhibition: • End product of a reaction blocks the pathway from producing more.

9. Energy

10. Energy • Bioenergetics: • Analysis of how energy powers activities of living systems • Growth, order, reproduction, responsiveness & regulation

11. Energy • Energy: • The capacity to do work • Kinetic energy: • Energy of motion • Potential energy: • Energy of position or stored energy

12. Energy • Kinetic energy: • Potential energy:

13. Energy • Thermodynamics: • Study of energy “heat changes” • Most work done by living organisms • Transformation of PE to KE

14. Energy • Sun main source of energy • Energy from sun • Combine smaller molecules to make larger molecules • Energy is stored in the chemical bond

15. Energy • Redox(oxidation-reduction) reactions: • Transfer of an electron or electrons • Play a key role in the flow of energy in biological systems • An electron is passed from one atom to another energy is passed

16. Law of thermodynamics • Laws of thermodynamics govern all energy changes in the universe. • First law of thermodynamics: • Energy cannot be created or destroyed • Change from one form to another. (potential to kinetic) • Total amount of energy stays the same

17. First law • In living organisms: • Eating transfers energy from the bonds in food to organism • PE is transferred to KE

18. First Law • Heat: • Random motion of molecules • Heat can be lost in the system during conversions • Sun replaces energy lost as heat

19. Second law • Second law of thermodynamics: • Transformation of PE to heat (random motion of molecules). • Entropy (disorder) in the universe is increasing

20. Second law • Energy transformations tend to proceed spontaneously • Convert matter from a more ordered state to a less ordered or more stable state.

21. Second law • Entropy(s): • Disorder in a system • Enthalpy (H): • Heat content • Free energy(G): • Amount of energy available to do work in any system. • Amount of energy available to break and then make other chemical bonds

22. Second law • G=Gibbs free energy • G = H - TS (T=Kelvin temp) • G is positive • Products have more energy than reactants • Due to more energy in the bonds or less randomness • Endergonic reaction

23. Endergonic reaction

24. Second law • G is negative • Products have less energy than reactants • H is lower (bond energy) or S is greater- more randomness • Exergonic: • Reaction that releases energy

25. Exergonic reaction

26. Exergonic reactions

27. Activation Energy • Energy needed to initiate a reaction • All reactions require activation energy. • Reactions with higher AE tend to move forward more slowly

28. Enzymes • Catalyst in living organisms • Large three-dimensional globular protein • Ribozymes: • RNA catalysts are specific & speed up reactions

30. Enzymes • Substrate: • Molecule that is going to undergo the reaction • Active sites: • Specific spots on the enzyme that substrates binds • Enzyme-substrate complex: • Enzymes are bound to substrates with a precise fit. • Induced fit: • When the substrate causes the enzyme to adjust to make a better fit • E+S ES E + P

32. Substrates enter active site; enzyme changes shape such that its active site enfolds the substrates (induced fit). 1 2 Substrates held in active site by weak interactions, such as hydrogen bonds and ionic bonds. Fig. 8-17 Substrates Enzyme-substrate complex Active site can lower EA and speed up a reaction. 3 6 Active site is available for two new substrate molecules. Enzyme 5 Products are released. 4 Substrates are converted to products. Products

33. Enzymes • Only small amounts are necessary • Can be recycled • Specific • Speeds up the reactions • Different types of cells have different enzymes • Determine the course of chemical reactions in the cell

34. Enzyme examples • Lipase, protease • Carbonic anhydrase • CO2 + H2O H2CO3 • Lactate dehydrogenase • Lactate to pyruvate • Pyruvate dehydrogenase • Enzyme that starts the Kreb cycle

35. Enzymes • Factors that affect the rate of enzyme • 1. Concentration of enzyme & substrate • 2. Factors that affect 3-D shape of the enzyme • Temperature, pH, salt concentration and regulatory molecules

36. Enzymes • Inhibitor: • Binds the enzyme • Prevents it from working • Occurs at the end of a pathway to stop the reactions • Two types of inhibitors • Competitive • Noncompetitive

37. Fig. 8-19 Substrate Active site Competitive inhibitor Enzyme Noncompetitive inhibitor (c) Noncompetitive inhibition (b) Competitive inhibition (a) Normal binding

38. Enzymes • Allosteric site: • On/off switch for the enzyme • Usually at different location than the active site • Allosteric inhibitor: • Binds at the allosteric site • Stops the enzyme activity • Activators: • Binds & increases the activity

40. Enzymes • Cofactor: • Assists enzyme function such as Zn, Mg, Cu • Coenzymes: • Cofactors that are not proteins but are organic molecules • Help transfer electrons & energy associated with the electrons • Vitamins are coenzymes • NAD+ important coenzyme

41. Energy

42. ATP • ATP powers the energy requiring processes in the cell • 1. Chemical work (making polymers) • 2. Transporting substances • 3. Mechanical work • Muscle movement, cilia

43. ATP • Structure of ATP • Ribose sugar • Adenine • 3 phosphate attached in a row

44. ATP

45. ATP • ATP • ADP • Losses a inorganic phosphate • Hydrolysis • 7.3kcal/mole of energy is released.