8.2 Cell Membrane Structure, Study notes of Cellular and Molecular Biology

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8.2 Cell Membrane

Structure

Cell Walls

Cell wall - provides support and protection for the cell

• rigid, inflexible
• located outside the cell membrane Prokaryotes, plants, algae, fungi, and many prokaryotes have cell walls. Animal cells do not.

Cell Membranes

made of phospholipid bilayer providing a flexible structure that forms a barrier between the cell and its surroundings.

The Properties of Lipids

fatty acid portions of phospholipids are hydrophobic, or “water-hating.” Phosphate end of the molecule is hydrophilic, or “water-loving.”

The Fluid Mosaic Model

cell membranes contain protein molecules embedded in the lipid bilayer. Carbohydrate molecules are attached to many of these proteins.

The Fluid Mosaic Model

Because the embedded proteins can “float” among the lipids, and because many different molecules compose the membrane, the cell membrane is called a “fluid mosaic.”

The Fluid Mosaic Model

Cell membranes are semipermeable or selectively permeable, meaning some substances can pass across them and others cannot.