Cell Membrane Structure Quiz

Cell Membrane Structure

• The cell membrane (plasma membrane) is a vital structure for transport mechanisms and separates the living cell from its surroundings.
• To perform these roles, the cell membrane needs lipids, which make a semi-permeable barrier between the cell and its environment, proteins, involved in cross-membrane transport and cell communication, and carbohydrates attach to the proteins or lipids, enabling cells to recognize each other.

Structural Components of the Cell Membrane

• Lipids: Form the primary structure of the membrane, acting as a semi-permeable barrier to prevent water-soluble molecules from entering or exiting the cell.

• Proteins: Embedded within the lipid bilayer. These proteins assist in transport of specific molecules across the membrane, support structural integrity, and act as recognition sites for other cells.

• Carbohydrates: Attached to proteins (glycoproteins) or lipids (glycolipids) on the outer surface of the membrane. They play a vital role in cell-cell recognition and communication.

• In 1935, the Davson-Danielli model of the membrane proposed that the membrane consisted of a phospholipid bilayer sandwiched between two protein layers.

• In 1972, Singer and Nicolson proposed the fluid mosaic model. This model describes the membrane as a mosaic of proteins dispersed within a phospholipid bilayer; only the hydrophilic regions of the proteins are exposed to water.

Membrane Fluidity

• Membrane fluidity is influenced by temperature, the configuration of the unsaturated fatty acid tails, and the presence of cholesterol.
• Unsaturated fatty acids increase fluidity.
• Cholesterol reduces fluidity at high temperatures but maintains fluidity at lower temperatures.