1. Membrane Dynamics Cell membrane structures and functions
Membranes form fluid body compartments
Membranes as barriers and gatekeepers
How products move across membranes
i.e., methods of transport
Distribution of water and solutes in cells & the body
Chemical and electrical imbalances
Membrane permeability and changes

2. Microscopic Observation of Cells

3. Electron Micrograph

4. Cell organelles

5. The Cell Membrane Fluid Mosaic Model Phospholipids Integral Proteins
Peripheral Proteins
Glycocalyx
Glycoproteins
MHC
Glycolipids
Cholesterol

7. Membrane Structure 7

8. Cell Membrane Structure: Fluid Mosaic Model
Thickness ~ 8nm
Cell Membrane Structure: Fluid Mosaic Model
PLs
Cholesterol
Proteins: peripheral (associated) or integral

9. Integral Membrane Proteins9

10. Membrane Bound Receptors10

12. Passive Transport Active Transport = Diffusion (Def?) – 3 types:
Simple diffusion
Facilitated diffusion (= mediated transport)
Osmosis
Active Transport
Always protein-mediated – 3 types:
Co-transport
Vesicular transport
Receptor mediated transport

13. Diffusion Process (Passive)
Uses energy of concentration gradient
Net movement until state of equilibrium is reached (no more conc. gradient)
Direct correlation to temperature
Indirect correlation to molecule size
Lipophilic molecules can diffuse through the phospholipid bilayer

14. Diffusion through Membranes
Oxygen, carbon dioxide, fatty acids, and steroid hormones are examples of nonpolar molecules that diffuse rapidly through the lipid portions of membranes.
Remember that lipophilic (lipid-loving) substances move through easily.
Polar molecules and hydrophilic (water-loving) do not diffuse readily through the membranes.

15. Simple Diffusion

16. Simple Diffusion

17. Open and Closed Ion Channels17

19. Facilitated Diffusion
Some molecules are too polar or too large to pass through the lipid bilayer.
Carrier proteins change shape after the molecules bind then envelopes the molecule and releases it
The binding site is moved from one side of the membrane to the other by a change in the confirmation of the carrier protein.

20. http://highered. mcgraw-hill

21. Osmosis The net diffusion of water across a membrane
Through channel proteins called aquaporins

23. Tonicity
Physiological term describing how cell volume changes if cell placed in the solution
Always comparative. Has no units.
Isotonic sol’n = No change in cell
Hypertonic sol’n = cell shrinks
Hypotonic = cell expands
Depends not just on osmolarity but on nature of solutes and permeability of membrane

24. Red Blood Cells in Isotonic and Hypotonic Solutions24

26. Tonic solutions Isotonic, hypotonic, and hypertonic solutions:
Isotonic solutions have the same concentration of nonpenetrating solutes as normal extracellular fluid.
Hypotonic solutions have a lower concentration of nonpenetrating solutes as normal extracellular fluid.
Hypertonic solutions have a higher concentration of nonpenetrating solutes as normal extracellular fluid.

27. Active Transport Movement from low conc. to high conc. ATP needed
Creates state of disequilibrium
1o (direct) active transport
ATPases or “pumps”
Uniport and Antiport
2o (indirect) active transport
Symport and antiport

28. Na+/K+ ATPase

29. Primary Active-Transporters
The Na+/K+-ATPase primary active transporter is found in every cell and helps establish and maintain the membrane potential of the cell.
In addition to the Na+/K+-ATPase transporter, the major primary active-transport proteins found in most cells are:
(1) Ca2+-ATPase
(2) H+-ATPase
(3) H+/K+-ATPase

32. Secondary Active Transport

33. Cotransport Symport Antiport Molecules are carried in same direction
Examples: Glucose and Na+
Antiport
Molecules are carried in opposite direction
Examples: Na+/K+ pump

34. Vesicular Transport Movement of macromolecules across cell membrane:
Phagocytosis (specialized cells only)
Macrophage or Phagocytes
2. Pinocytosis
“Cell drinking”
3. Receptor mediated endocytosis
Down Regulation
4. Exocytosis

36. Endocytosis & Exocytosis

37. Endocytosis Movement of molecules into the cell via vesicles.
There are three general types of endocytosis that may occur in a cell:
1. Phagocytosis
2. Pinocytosis
3. Receptor-mediated endocytosis

38. Phagocytosis

39. Phagocytosis Requires energy
Cell engulfs particle into vesicle via pseudopodia formation
E.g.: some WBCs engulfs bacteria
Vesicles formed are much larger than those formed by endocytosis
Phagosome fuses with lysosomes  ?

41. Pinocytosis

42. Receptor Mediated Endocytosis
No. 1 uptake method
in most cells
Receptors and substance is internalized into a coated pit-clathrin
Down Regulation

43. Exocytosis Intracellular vesicle fuses with membrane 
Requires energy (ATP) and Ca2+
Examples: large lipophobic molecule secretion; receptor insertion; waste removal

44. Clinical Case Study
A 22-year-old woman was competing in her first marathon. She was in good health, but was completely inexperienced in long-distance runs. In the hour before the race, she drank two 20-ounce bottles of water in anticipation of the water loss she expected to experience due to perspiration during the race. The race took place on an unseasonably cool day in April. As she ran, she took a drink at each water station. At the 20-mile mark she was feeling extremely fatigued and her leg muscles began cramping. Thinking she was losing too much fluid, she drank additional water. At 23 miles she began to feel confused and disoriented and developed a headache. She finished yet another bottle of water even though she was not thirsty. Twenty minutes later, she collapsed, lost consciousness, and was taken to a local hospital. Her blood Na+ levels had decreased to 115 mM and she was diagnosed with exercise-associated hyponatremia. What was the effect of excessive water consumption on the osmolarity of this woman’s extracellular fluids? How would this affect ion gradients and cell volumes in areas such as her brain and skeletal muscles?

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