PLASMA MEMBRANE

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PLASMA MEMBRANE
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Plasma Membrane

• Boundary that separates the living cell from its
  non-living surroundings.

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Plasma Membrane

• Controls traffic into and out of the cell with
  phospholipids and transport proteins.
• 8 nm thick
• Selectively permeable

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Selective Permeability

• The property of biological membranes which allows
  some substances to cross more easily than others.

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Fluid Mosaic

• 1972 - Singer and Nicolson called the membrane a
  Fluid Mosaic Model.

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Fluid Mosaic

• Mosaic different proteins embedded in the
  phospholipids.
• Fluid proteins and phospholipids can move freely
  in the membrane.

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Fluid Mosaic - cont.

• Components of a phospholipid bilayer.
• 1. phospholipids
• 2. proteins
• 3. glycolipids

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Fluid Mosaic - cont.

• 4. glycoproteins
• 5. carbohydrates
• 6. cholesterol

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Phospholipids

• Phosphate Head
• Glycerol, Phosphate, Choline
• Face outwards
• Hydrophilic (water loving)

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Phospholipids

• Lipid Tails
• Face inwards
• Hydrophobic (water hating)

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Phospholipid

• Kink is from unsaturated fatty acids

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Cholesterol

• Provides rigidity to the membrane.
• Temperature buffer

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Glycoproteins and Glycolipids

• Glyco- carbohydrate
• Used in cell to cell recognition.

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Membrane Proteins

• Can be
• Integral (embedded)
• Transmembrane- span the entire membrane

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Membrane Proteins

• Peripheral (attached)
• Cytoskeleton
• Attachment to other cells.

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Integral Proteins

• Types
• Transport (carrier and channel)
• Enzymatic
• Signal Transduction
• Cell-Cell Recognition
• Intercellular Joining
• Attachment to Cytoskeleton

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Side Trip

• AP- Notes- Chapter 7- Diffusion.ppt

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Transport Across Membranes

• Diffusion/Osmosis
• Very small molecules
• Some nonpolar
• Facilitated Diffusion
• Needs Proteins (channel or carrier)

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Transport Across Membranes

• Channel Proteins act as a gate

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Aquaporins

• Example of channel protein
• Recently discovered
• Allow water to pass through membrane

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Transport Across Membranes

• Carrier Proteins bind to a substance
• More controlled

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Transport Across Membranes

• Active Transport
• Uses carrier proteins
• Requires ENERGY

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Sodium- Potassium Pump

• Uses ATP
• Pumps 3 Na out of cell and 2 K into cell
• Against their gradients

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Sodium- Potassium Pump

• Maintains negative cells
• Important for Muscles and Nerves
• Glucose transporter needs Na to function

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Co-Transport

• One substance cannot enter a cell unless it
  hitchhikes with another substance.
• The hitchhiked substance must be actively pumped

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Endocytosis

• Big things IN (Bulk Transport)
• Pinocytosis- cell drinking
• Phagocytosis- cell eating
• Receptor Mediated- specific
• Creates vacuole inside cell

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Exocytosis

• Big things OUT