Basic structure of the cell

Figure 1. basic structure of cell and the difference between cytoplasm and cytosol

Composition of cell membrane

  • Lipids
  • Proteins
  • Carbohydrates

function of cell membrane

  • Serves as boundary of the cell.
  • Serve as markers that identify the cells.
  • Play significant role in transportation.
  • Cell recognition proteins-allow cell to recognize other cells.

Figure 2. cell membrane components

Lipid bilayers

Phospholipid

  •   Phosphatidylcholine
  •   Phosphatidylserine
  •   Phosphatidylethanolamine
  •   Phosphatidylinositol

Cholesterol

Sphingolipid

Lipid mobility

there are movements across the cell membrane, lateral movements, rotation and also Flip-flop. however, flip-flop is rare movement.

there are also two important features about the fluidity of cell membrane.

  • cholesterol in the cell membrane can reduce cell fluidity.
  • unsaturated hydrocarbon tails enhance the cell fluidity.

Figure 3. cell membrane fluidity

Membrane proteins

  • Integral (intrinsic) proteins
  • Peripheral (extrinsic) proteins

Most integral proteins span the entire membrane and are referred to as transmembrane proteins.

Integral membrane proteins are closely associated with the membrane lipids and cannot be extracted from the membrane without disrupting the lipid bilayer.

figure 4. membrane proteins

membrane carbohydrates

Carbohydrates are covalently linked to proteins (glycoproteins) or lipids (glycolipids) and also an important part of cell membranes, and function as adhesion and address loci for cells.

figure 4. cell membrane carbohydrates

 

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