1. (c) The McGraw-Hill Companies, Inc.
Chapter 6
Biology
Sixth Edition
Raven/Johnson
(c) The McGraw-Hill Companies, Inc.

2. Membranes Allows a cell to interact with its environment
Delicate skin of proteins embedded in a thin sheet of lipid

3. Phospholipid Bilayer
Membranes are only two molecules (not atoms) thick
The lipid that makes up the membrane is a phospholipid

5. Hydrophilic polar heads lie on the outward-facing surfaces.
Hydrophobic nonpolar tails extend to the interior.
-a fluid consistency and a mosaic pattern of embedded proteins.

7. Components of the Cell Membrane
Lipid Bilayer
Transmembrane proteins
Network of supporting fibers
Exterior proteins and glycolipids

8. Figure 6.7

9. Non-Polar sections of protein force the molecule to stay within in the membrane.
Polar ends extend on either side of membrane

10. A single nonpolar segment is adequate to anchor a protein
Attach to the spectrin network of the cytoskeleton
Receive signals

11. Channel and carrier proteins have several non-polar helical segments
Allows passage of water soluble molecules or ions

12. Beta – pleated sheets form a large open tunnel
Allows water and other materials to pass through

13. Movement from an area of high concentration to an area of low concentration
Ion channels allow movement of ions by diffusion
Most channels are specific only for a certain type of ion

14. Carriers transport ions as well as other solutes
Physically binds with the solute
Movement is determined by the concentration gradient
3 characteristics of facilitated diffusion
1. It is specific
2. It is passive
3. It saturates

15. Water molecules move through specialized channels called aquaporins along a concentration gradient
Concentration of all solutes in a solution determines the osmotic concentration
Cell membrane is a differentially permeable membrane

17. Bulk Passage Into and Out of the Cell
Endocytosis – 3 types: Phagocytosis, Pinocytosis, and receptor-mediated endocytosis
- brings items into the cell
Exocytosis – discharges materials from the cell

18. Phagocytosis – particulate (solid) matter

19. Pinocytosis – material is liquid

20. Receptor-mediated endocytosis – specific molecules

21. Exocytosis – discharges material from the cell

22. Requires energy (ATP)
Involves a highly selective carrier protein
Moves substance against a concentration gradient

23. Works through a series of conformational changes – the first is energized by ATP
(active transport)
This process can occur up 100 times per second!

24. Moves protons against their gradient
Down gradient – high  low concentration (no energy required)
Up gradient – low  high concentration (energy required)

25. The Down gradient for Na+ is greater than the Up gradient for glucose
Protein here is a symport – both items move in same direction
Antiport – items move in opposite directions Na+/Ca++ (counter transport)

26. The End.