2.2 - Membrane Structure and Functions

• Fluid Mosaic Model - states that membrane proteins float freely throughout the phospholipid bilayer
• What’s the arrow pointing to?

  Hydrophobic Tail

  
• What’s the arrow pointing to?

  Hydrophilic head

  
• What is the arrow pointing at?

  integral protein (transport protein)

  
• What is the arrow pointing at?

  glycoprotein

  
• What is the arrow pointing at?

  lipid bilayer

  
• What is the arrow pointing at?

  microfilament of cytoskeleton

  
• What is the arrow pointing at?

  microtubule of cytoskeleton

  
• What is the arrow pointing at?

  glycolipid

  
• What is the arrow pointing at?

  outside cell

  outer cell

  
• What is the arrow pointing at?

  cytoplasm

  
• What is the arrow pointing at?

  cholesterol

  
• What is the arrow pointing at?

  peripheral proteins

  
• What is the arrow pointing at?

  carbohydrate groups

  
• What is the arrow pointing at?

  integral proteins

  
• Membranes contain a wide assortment of proteins
• Glycolipid - membrane lipid attached to carbohydrate group
• Glycoprotein - a membrane protein attached to carbohydrate group
• Glycoproteins and glycolipids are both involved in cell recognition and interaction.
• Integral Membrane Proteins

  • embedded in lipid bilayer
  • Has areas that interact with water/lipids
• Peripheral Membrane Proteins

  • on surface of membrane
  • do not interact with hydrophobic core of bilayer
• Phospholipids make up majority of cell membrane
• Hydrophobic tails and hydrophillic heads form bilayer in water (forms spontaneously)
• sterols (aka cholesterol)

  • help stop membranes from being too rigid in cold temps
  • hold membranes together at higher temps
• What are the five roles of membrane proteins?

  Transport, enzymatic activity, triggering signals, recognition, attachment
• Transport - transport substances across membranes (ones that cannot easily diffuse)

  • eg. may move larger amino acids across membrane
• Enzymatic Activity - help with cellular respiration/photosynthesis

  • ex. ATP Synthase used to create ATP
• Triggering Signals - bind to chemicals and cause changes w/n cell

  • e.g. hormons bind to membrane protein causing chem changes within cell
• Attachment - proteins can help anchor parts of cytoskeleton

  • e.g. proteins attach to microtubules
• Recognition - allows cells to recognize one another and invading and unknown pathogens (diseases)

  • e.g. neighbouring cells can recognize one another based on specific proteins