Topic 4 The Cell Surface

Cells are separated from the external world by a thin, fragile structure called the ________ that is only 5 to 10 nm wide.

Encloses the content of the entire cell

Provide cell with an extensive framework or scaffolding within which component can be ordered for effective interaction.

Prevent the unrestricted exchange of molecules from one side to the other. (Provide means of communication)

Contains the machinery for physical transporting substances from one side of the membrane to another.

Signal transduction (receptors)

• mediates interactions bet. a cell and its neighbors
• allows cells to recognize and signal one another, to adhere when appropriate, and to exchange materials and information.

one type of energy is converted to another type

The Fluid Mosaic Model proposed in 1972 by

serves primarily as a structural backbone of the membrane; provides the fluid structure of the membrane and provides the barrier that prevents random movements of watersoluble materials into and out of the cell.

carry out most of the specific functions

They are always found on the exterior surface of cells and are bound either to proteins (forming glycoproteins) or to lipids (forming glycolipids)

All are ______ (contain both hydrophilic and hydrophobic regions)

• Provides the basic structure for all cell membranes.
• Contains a wide diversity of lipids

• Lipids are water-insoluble biomolecules that are highly soluble in organic solvents such as chloroform.
• Lipids have a variety of biological roles: they serve as fuel molecules, highly concentrated energy stores, signal molecules, and components of membranes.

There are three main types of membrane lipids:

Most membrane lipids contain a phosphate group, which makes them _______.

Because most membrane phospholipidsare built on a glycerol backbone, they are called

________ are hydrophobic, unbranched hydrocarbons approximately 16 to 22 carbons in length.

are described as omega-3 fatty acids because their last double bond is situated three carbons from the omega (CH 3 ) end of the fatty acyl chain.

• Less abundant class of membrane lipids
• Are also amphipathic
• Are derivatives of sphingosine, an amino alcohol that contains a long hydrocarbon chain

If the carbohydrate is a simple sugar, the glycolipid is called a ______ ; if it is a small cluster of sugars that includes sialic acid, the glycolipid is called a ______

• In some animal cells, it makes up to 50% of the lipid molecules.
• It is absent from the plasma membranes of most plant and all bacterial cells.