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.

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

Fluid-mosaic model of membrane structure Fig. 4.1

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

Membrane protein diversity Fig 4.2

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

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)

Passage of molecules into and out of cells Table 4.1

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”

Crossing the plasma membrane Fig. 4.3

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

Process of diffusion Fig. 4.4

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

Osmosis demonstration Fig. 4.6

Osmosis in animal and plant cells Fig 4.7

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

Facilitated transport and active transport Fig. 4.8 Fig. 4.9

The sodium-potassium pump Fig 4.10

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

Exocytosis Fig 4.11

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

Three methods of endocytosis Fig 4.12