Membrane Structure and Function, 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. Facilitates: adhesion between cells b. Reception of: signal molecules c. 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. Membrane has consistency of olive oil
2. The more unsaturated fatty acids, the more fluid
3. Phospholipids can move sideways, allows membrane to be pliable
4. 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. CARRIER PROTEINS: selectively interact with a specific molecule so it can cross the membrane. Some use energy (ATP).
3. CELL RECOGNITION PROTEINS: glycoproteins allow the body's immune system to distinguish between foreign invaders and body cells
4. RECEPTOR PROTEINS: shaped so that a specific molecule can bind to it
5. ENZYMATIC PROTEINS: carry out specific metabolic reactions
6. AQUAPORINS: specialized