Membrane Structure and Function AP Biology, Exams of Nursing

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Chapter 5:

Membrane Structure and

Function

AP Biology

Fluid Mosaic Model Video https://www.youtube.com/watch?v=ipa1vmQ7H_4&t=61s

Fluid Mosaic Model

1. Singer and Nicolson (1972) introduced this model
2. Embedded proteins are scattered throughout membrane in an irregular pattern

Phospholipids: have two regions: Amphipathic- have both hydrophilic and hydrophobic regions Phospholipids spontaneously form a bilayer in an aqueous environment.

1. Heads: polar (hydrophilic) and directed outwards
2. Tails: nonpolar (hydrophobic) and directed to the interior

Glycolipids & Glycoproteins

1. Carbohydrate side-chains attached to either phospholipids or proteins
2. Function: a. b. c. Facilitates: adhesion between cells Reception of: signal molecules Cell-to-cell recognition

Asymmetrical: The outside of the cell membrane’s phospholipid bilayer looks different than the inside To the outside: glycolipids/ proteins To the inside: cytoskeleton

Specific Function: Fluidity 1 2 3 4

. Membrane has consistency of olive oil . The more unsaturated fatty acids, the more fluid . Phospholipids can move sideways, allows membrane to be pliable . Some proteins are held in place by cytoskeletal filaments but most drift in the fluid bilayer

Specific Function: Proteins Plasma and organelle membranes have unique proteins Membrane proteins determine most of the membrane's functions

1. CHANNEL PROTEINS: allows a particular molecule to cross the plasma membrane freely = NO energy needed. a. Channel proteins are always specific 2 3

. CARRIER PROTEINS: selectively interact with a specific molecule so it can cross the membrane. Some use energy (ATP). . CELL RECOGNITION PROTEINS: glycoproteins allow the body's immune system to distinguish between foreign invaders and body cells

1. RECEPTOR PROTEINS: shaped so that a specific molecule can bind to it
2. ENZYMATIC PROTEINS: carry out specific metabolic reactions
3. AQUAPORINS: specialized