Plasma Membrane

• The main components of the plasma membrane are phospholipids, arranged into a film called the phospholipid bilayer consisting of two layers of phospholipids facing tail to tail
• Phospholipids consist of a phosphate head and 2x fatty acid tails:

  • Head: made of a glycerol + phosphate group (ion), negatively charged (polar) and hydrophilic (water loving)
  • Tail: long chains of carbon and hydrogen, uncharged (nonpolar) and hydrophobic (water fearing)
• Properties of phospholipids:

  • Head: negatively charged (polar) and hydrophilic (water loving)
  • Tail: uncharged (nonpolar) and hydrophobic (water fearing)
• Phospholipids are amphipathic molecules with hydrophobic and hydrophilic parts, making the plasma membrane incredibly stable
• The fluid mosaic model describes the true nature of the phospholipid bilayer, where the "fluid" part refers to the membrane's flexibility and the "mosaic" part comes from the embedded structures like proteins, carbohydrates, and cholesterols
• Proteins in the plasma membrane have various functions:

  • Transport: controls what comes in and out of the cell
  • Catalysts: speed up chemical reactions
  • Communication: receive signals or recognize cells and molecules
  • Adhesion: stick to other cells
• Carbohydrates in the plasma membrane aid in cell communication, signaling, and recognition of self and non-self molecules
• Cholesterol, a lipid steroid, regulates the fluidity of the membrane by keeping phospholipids stuck together at higher temperatures and fluid at low temperatures
• glycolipid a phospholipid bound to a carbohydrate
• glycoprotein a protein bound to a carbohydrate