Homeostasis and C ell Transport

1. Homeostasis and Cell Transport Reviewing for the next quiz coming up this week on Wednesday and Thursday

2. Function and Structure of the plasma membrane • Passive membrane:

3. Function and Structure of the plasma membrane (pm) • The main function of the pm is to control what enter and what exists a cell, that is, to keep certain substances inside and other substances outside • The pm is comprised of a phospho-lipid bilayer. • Pm has 2 basic components: a head (phospho) and a pair of tails (fatty acids chains)

4. Function and Structure of the plasma membrane (pm) part 2 • One component is water-soluble (hydrophilic [water-loving] • The second component hydrophobic [water-hating molecule] • Look at the model placed on the desk in front of the class: identify these two components • One layer has its head facing the water on the outside the cell

5. Function and Structure of the plasma membrane (pm) part 3 • The 2nd layer has its water-loving heads facing the interior of the cell. • All water-hating tails are in the center of the bilayer where their exposure to water is minimal. • Through this bilayer, a cell maintains a continuous barrier between its internal environment and the outside world

6. Movement of molecules across the plasma membrane • Passive transport: Passive transport requires no energy from the cell. Examples include the diffusion of oxygen and carbon dioxide, osmosis of water, and facilitated diffusion. • In diffusion, molecules move along a concentration gradient • Concentration gradient = more molecules of a certain type of molecules found in one area than in another area

7. Movement of molecules across the plasma membrane (part 2) • Diffusion also occurs across a pm due to a concentration gradient • Water is one of the molecules small enough to cross the plasma membrane through diffusion • Osmosis = diffusion of water molecules across a membrane. • Water will flow from high concentration to low concentration

8. Hyper-Hypo-Iso --- tonic solutions • Hypertonic solutions are those in which more solute (and hence lower water potential) is present. • Hypotonic solutions are those with less solute (again read as higher water potential).  • Isotonic solutions have equal (iso-) concentrations of substances. Water potentials are thus equal, although there will still be equal amounts of water movement in and out of the cell, the net flow is zero.

9. Water relations and cell shape in blood cells

10. Water relations in plant cells

11. Types of passive transport

12. Active Transport • Active transport requires the cell to spend energy, usually in the form of ATP. Examples include transport of large molecules (non-lipid soluble) and the sodium-potassium pump

13. Types of active transport.

14. Vesicle-mediated transport • Vesicles and vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell. • Exocytosis is the term applied when transport is out of the cell. • Endocytosis is the case when a molecule causes the cell membrane to bulge inward, forming a vesicle.

15. Vesicle-mediated transport (part 2) • Phagocytosis is the type of endocytosis where an entire cell is engulfed. • Pinocytosis is when the external fluid is engulfed. (come up with a better definition): Examples include the transport of insulin and cholesterol into animal cells.

16. Endocytosis and exocytosis

17. Terms • Active transport • ATP • diffusion • endocytosis • exocytosis • homeostasis

18. Terms (part 2) • hypertonic • hypotonic • isotonic • osmosis • passive transport • hydrophilic • hydrophobic

19. Terms (part 3) • phagocytosis • phosphate group • phospholipid • sodium-potassium pump • vacuoles • vesicles

20. Ready for your quiz • Go to the wiki: http://martellye.wikispaces.com • Look for the file: The plasma membrane and Cellular transport. • There are four quizzes for you to practice and get ready for the quiz: pages 19-25 • No excuse for a grade < 90%