Membranes

• Colorimetry: used to measure the concentration of a solution.
• What model is used to describe cell membranes?

  Fluid mosaic model
• Cholesterol is responsible for regulating the fluidity of the cell membrane by getting in between phospholipid molecules and making the membrane more rigid
• The membrane consists of a phospholipid bilayer with a hydrophilic head and hydrophobic tail
• Factors affecting membrane structure:

  temperature -> phospholipids have more kinetic energy and move around more which increases membrane permeability

  polarity of solvent: polar solvent can form hydrogen bonds with the hydrophilic heads of the phospholipids membrane and cause the structure to break down
• Different types of lipids found in the cell membrane:

  • phospholipids
  • cholesterol - regulates membrane fluidity
  • glycolipids - Antigens or cell marker
• Different type of proteins found in the cell membrane:

  • surface proteins - provide mechanical support
  • Glycoproteins - recognition sites for foreign cells or chemicals
  • Transport proteins - Transport proteins that transport substances across the membrane
• different type of transport proteins:

  channel proteins - transport ions

  carrier proteins - transports large substances using ATP

  co-transport proteins - transports 2 molecules at once
• facilitated diffusion is the movement of molecules across a membrane from a region of high concentration to a region of low concentration using transport proteins
• diffusion is the movement of particles from an area of high concentration to an area of low concentration
• Exocytosis is when materials are released out of the cell through fusion of vesicles with the plasma membrane.
• active transport is the movement of molecules against their concentration gradient, requiring energy (ATP)
• Adaptations for simple and facilitated diffusion:

  • large surface area to volume ratio
  • Maintaining a steep concentration gradient
  • short diffusion distance
  • Large number of transport proteins (facilitated diffusion)