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6.4.3. Functions of the plasma membrane

Functions of the components of the plasma membrane

  • Functions of lipids  in the plasma membrane:
    • They regulate resistance and fluidity. The fluidity depends on the length and degree of saturation of the fatty acids of the phospholipids. The more saturated and long, the lower the fluidity. The cholesterol is involved in the movement of phospholipids, decreasing the flow.
    • They regulate permeability. Water-soluble molecules cannot pass through the membrane due to their hydrophobic interior.
  • Functions of the proteins  of the plasma membrane:
    • Transportation. It allows the passage of molecules that cannot cross the lipid bilayer.
    • Communication. They receive and transmit chemical signals to other cells.
    • Enzymatic. They are involved in various chemical reactions, such as in the respiratory chain.
  • Functions of oligosaccharides  of the plasma membrane:

Main functions of the plasma membrane

The most important functions of the plasma membrane are:

  • Limit the cell, separating the cytoplasm and organelles from the external environment.
  • Keeping the internal cellular environment stable, controlling the passage of substances between the extra and intracellular medium, which is why it has selective permeability.
  • It maintains the cell shape, anchoring the cytoskeletal filaments or the components of the extracellular matrix .
  • Exchange of signals between the external environment and the cellular environment.
  • Allows cell recognition and identification.
  • Cell division: the membrane is involved in the control and development of cell division or cytokinesis.
  • Cellular immunity: some molecules with antigenic properties are located in the membrane, related, for example, to rejection in tissue or organ transplants from other individuals.
  • Endocytosis and exocytosis: the membrane is related to the uptake of large particles (endocytosis) and the secretion of substances to the outside (exocytosis).

Membrane receptors

Some hormones are secreted by the hypothalamus or pituitary gland, they travel throughout the body but only produce a response in some cells of the body. Only some cells have specific receptors for hormones or other chemical messengers on their membrane. These receptors are glycolipids or glycoproteins located on the outer side of the plasma membrane.