Inquiry into Life Eleventh Edition Sylvia S Mader

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

4. 1 Plasma membrane structure and function • Membrane structure – Fluid-mosaic model – Phospholipid bilayer • Hydrophobic tails face inward • Hydrophilic heads face surfaces – Proteins • Integral proteins-embedded • Peripheral proteins-inner surface – Glycoproteins, glycolipids, cholesterol 2

Fluid-mosaic model of membrane structure • Fig. 4. 1 3

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 4

Membrane protein diversity • Fig 4. 2 5

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 6

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 (carriermediated) 7

Passage of molecules into and out of cells • Table 4. 1 8

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” 9

Crossing the plasma membrane • Fig. 4. 3 10

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 11

Process of diffusion • Fig. 4. 4 12

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 13

Osmosis demonstration • Fig. 4. 6 14

Osmosis in animal and plant cells • Fig 4. 7 15

4. 4 Transport by carrier proteins • 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 16

Facilitated transport and active transport • Fig. 4. 8 • Fig. 4. 9 17

The sodium-potassium pump • Fig 4. 10 18

4. 5 Exocytosis and endocytosis • Exocytosis – Vesicles containing cell products fuse with plasma membrane – Products are released and vesicle membrane becomes part of the plasma membrane 19

Exocytosis • Fig 4. 11 20

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 21

Three methods of endocytosis • Fig 4. 12 22