1. Inquiry into Life Eleventh Edition Sylvia S. Mader
Chapter 4
Lecture Outline
Prepared by: Wendy Vermillion Columbus State Community College
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 4.1 Plasma membrane structure and function
Fluid-mosaic model
Phospholipid bilayer
Hydrophobic tails face inward
Hydrophilic heads face surfaces
Proteins
Integral proteins-embedded
Peripheral proteins-inner surface
Glycoproteins, glycolipids, cholesterol

3. Fluid-mosaic model of membrane structure
Fig. 4.1

4. Membrane structure and function, cont’d.
Functions of membrane proteins
Channel proteins
Form channels for substances can move across membrane
Receptor proteins
Bind to substances in the environment and trigger cell responses
Carrier proteins
Transport specific substances across cell membrane
Enzymes
Catalyze chemical reactions for cell metabolism

5. Membrane protein diversity
Fig 4.2

6. Membrane structure and function, cont’d.
Carbohydrate chains
Bound to outer surface of cell recognition proteins
Form a “sugar coat”-glycocalyx
Diversity of carbohydrate chains produces individual “fingerprint”
Recognition of self vs. nonself
Immune responses
Summary
Membrane consists of a fluid, dynamic phospholipid bilayer
Embedded proteins form a mosaic pattern
Provide structural integrity and perform many functions
Carbohydrate chains project from outer surface

7. 4.2 Permeability of plasma membrane
Plasma membrane is selectively permeable
Some substances pass through freely while others do not
Passive transport-no cellular energy required
Kinetic energy drives passive mechanisms
Movement is always from high concentration to low
Diffusion, facilitated diffusion (carrier-mediated)

8. Passage of molecules into and out of cells
Table 4.1

9. Permeability of plasma membrane, cont’d.
Active transport mechanisms-require ATP, can transport against a concentration gradient
Active transport
Requires a carrier protein
Transports molecules from low concentration to high
Exocytosis-vesicle mediated transport
Transports cell products and wastes out of the cell by vesicle formation
Endocytosis-vesicle mediated transport
Transports substances into the cell by vesicle formation
Pinocytosis-”cell drinking”
Phagocytosis-”cell eating”

10. Crossing the plasma membrane
Fig. 4.3

11. 4.3 Diffusion and osmosis Diffusion
Movement of molecules from an area of high concentration to an area of low concentration
Random kinetic energy drives diffusion
Lipid soluble molecules, gases, and some small water soluble molecules may diffuse freely across cell membrane

12. Process of diffusion
Fig. 4.4

13. 4.3 Diffusion and osmosis, cont’d.
Osmosis-diffusion of water across a semi permeable membrane
Osmotic pressure-force that causes water to move in a direction
Osmotic pressure is due to the number of nondiffusable particles in solution
Hypotonic solutions-cause cells to swell and burst
Hypertonic solutions-cause cells to shrink, or crenate
Isotonic solutions-no change

14. Osmosis demonstration
Fig. 4.6

15. Osmosis in animal and plant cells
Fig 4.7

16. 4.4 Transport by carrier proteins
Carrier proteins are specific for the molecules they transport
Facilitated transport
Passive mechanism
Transports from high concentration to low
Active transport
Requires cellular energy
Transports against the concentration gradient

17. Facilitated transport and active transport
Fig. 4.8
Fig. 4.9

18. The sodium-potassium pump
Fig 4.10

19. 4.5 Exocytosis and endocytosis
Vesicles containing cell products fuse with plasma membrane
Products are released and vesicle membrane becomes part of the plasma membrane

20. Exocytosis
Fig 4.11

21. Exocytosis and endocytosis, cont’d.
Endocytosis-an area of cell membrane invaginates and surrounds a substance, then pinches off to form a vesicle
Phagocytosis-material taken in is large; ex: bacteria, cell debris
Pinocytosis-material is liquid or small
Receptor-mediated-specific type of pinocytosis which occurs in response to receptor stimulation

22. Three methods of endocytosis
Fig 4.12