Chapter 5: The Working Cell

1. Chapter 5: The Working Cell

2. All chemical reactions involve the transfer of energy • Metabolism – All chemical reactions of a cell • Energy has two forms: • Potential Energy – stored energy (i.e. chemical bonds) • Kinetic Energy – energy of movement

3. Potential and Kinetic Energy (5-1)

4. Laws of Energy • Conservation of energy • Energy cannot be created; only changed • Total energy in a closed system remains constant • Entropy • Available energy is lost when changes occurs • All processes cause increases in disorder as energy is lost

5. Fig. 5-2

6. Energy is carried by molecules • A.T.P. Adenosine TriPhosphate • Energy molecule found in all living organisms • Adenine Base with three Phosphate groups • Breaking the phosphate-phosphate bond releases stored energy to be used by to the cell

7. ATP is rechargeable (Fig. 5-9)

8. ATP in action

9. ATP Synthase • Turns ADP + Pi into ATP • Energy comes from H+ that are pumped across a membrane then move through a channel in ATP synthase

10. Reactions Require Energy • Activation Energy increases the kinetic energy of molecules • More movement increases the likelihood of collisions. • Enzymes lower the activation energy of a reaction

11. Enzymes are Protein Catalysts • Catalysts are not used up in the reaction • Each enzyme performs a specific reaction. • Enzymes end in “ase” (ex: catalase)

12. How do enzymes work? • Reactants (Substrate) bind to enzyme’s active site • “Induced Fit” Hypothesis

13. Induced Fit (5.9)

14. Multiple enzymes create metabolicpathways which can produce a variety of products (NIB)

15. Enzyme Regulation • Enzymes can be inhibited by molecules blocking the active site • Allosteric regulation: secondary site regulates enzyme • Enzymes can be inhibited by negative feedback

16. Enzyme control (5.10)

17. If an enzyme changes, substrates are unable to bind. • The enzyme is denatured • Increased Heat • Change pH • Enzymes perform within a narrow temperature and pH range.

18. Diffusion • Molecules move randomly through a fluid because of their kinetic energy. • Net movement is from areas of high concentration to areas of low concentration • This high -> low movement occurs until the concentration is equal throughout (equilibrium).

19. Membrane proteins (5.11)

20. Transport Across Membranes • Diffusion - movement of molecules from high concentration to low concentration. • Equilibrium is reached and the concentration on both sides remain constant • In cells transport can be • Simple – move straight through membrane • Facilitated – passes through channel or carrier proteins

22. Diffusion Through a Membrane

23. Osmosis • Diffusion of free water across membrane • Moves from low concentration of salts to high concentration – think slugs • Osmosis controlled to maintain cell size and shape

24. Free water molecules diffuse through a membrane

25. Isotonicsolution • Salt concentration is the same inside and outside of a cell. • Net movement of water is zero.

26. Hypertonic solution • Salt concentration is higher outside the cell. • Net movement of water is out of the cell.

27. Hypotonic solution • Salt concentration is lower outside the cell. • Net movement of water is into the cell.

28. Active Transport (5.16) • Maintains high concentration. • Requires energy (ATP) to move molecules.

29. Endocytosis • Cell membrane engulfs molecules/ microorganisms • Vesicles carry material where they are broken down

30. Exocytosis –5.18 Vesicles release molecules

31. Receptor Proteins Play a Role in Cell Communication

32. Exam 1 • 50 questions - multiple choice • Bring Scantron • Number 2 pencil • Extra credit assignments – 10 points • Sample questions