MODULE 14

• Plasma membrsbe is a thin semi-permeable membrane that surrounds the cytoplasm of a cell.
• Plasma membrane protect the integrity of the interior of the cell by allowing certain substances into the cell, while keeping other substances out (selectively permeable)
• Plasma membrane serves as a base of attachment for the cytoskeleton in some organisms and the cell wall in others.
• In endocytosis, lipids and proteins are removed from the cell membrane as substances are internalized.
• Plasma membrane serves to help support the cell and help maintain its shape.
• Plasma membrane regulate cell growth through the balance of endocytosis and exocytosis.
• In exocytosis, vesicles containing lipids and proteins fuse with the cell membrane increasing cell size.
• Animal cells, plant cells, prokaryotic cells, and fungal cells have plasma membranes.
• Internal organelles are also encased by membranes
• CELL MEMBRANE LIPIDS

  • Phospholipids
  • Cholesterol
  • Glycolipids
• Phospholipids are lipid bilayer which is semi-permeable, allowing only certain molecules to diffuse across the membrane.
• Cholesterol molecules are selectively dispersed between membrane phospholipids.
• Cholesterol helps to keep the cell membranes from becoming stiff by preventing phospholipids from being too closely packed together.
• Cholesterol is not found in the membranes of plant cells.
• Glycolipids are located on cell membrane surfaces and have a carbohydrate sugar chain attached to them.
• Glycolipids help the cell to recognize other cells of the body.
• CELL MEMBRANE PROTEINS

  • Peripheral membrane proteins
  • Integral membrane proteins
  • Structural proteins
  • Receptor proteins
  • Glycoproteins
• Peripheral membrane proteins are exterior to and connected to the membrane by interactions with other proteins.
• Integral membrane proteins are transmembrane proteins. These transmembrane proteins are exposed on both sides of the membrane.
• Structural proteins help to give the cell support and shape
• Receptor proteins help cells communicate with their external environment through the use of hormones, neurotransmitters, and other signaling molecules.
• Transport proteins, such as globular proteins, transport molecules across cell membranes through facilitated diffusion.
• Glycoproteins have a carbohydrate chain attached to them.
• Glycoproteins are embedded in the cell membrane and help in cell-to-cell communications and molecule transport across the membrane.
• Glycoproteins are embedded in the cell membrane and help in cell-to-cell communications and molecule transport across the membrane.