BISC 130 - Chapter 5: The Plasma Membrane

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(FILL IN SOME MISSING NOTES)

• "Mosaic" because there are are many different components

  • Phospholipids

    • Form bilayer

  • Cholestrol

    • Stabilizes bilayer

  • Integral Membrane Proteins

    • Amino acids interact with the hydrophobic lipids to anchor the protein in the bilayer

    • They are positioned such that their hydrophobic parts are facing inward, interacting with the phospholipid tails

  • Glyco - means sugar

• Carbohydrates

  • Glycolipids

    • A combination of carbohydrates and lipids, in which carbs are attached to the heads of the lipids

  • Glycoproteins

    • A combination of proteins and carbohydrates, in which carbs are attached to the Integral Membrane Proteins.

• They create a hydrophilic coating that attracts water by facing outward, away from the inside of the cell.

• This model is "Fluid" because lipids and proteins aren't covalently attached to each other - they move laterally

• Passive Transport

  • The movement of materials that does not require any energy.

• Diffusion (First mode of passive transport)

  • Solutes - move from high to lower concentration

  • "Down" their concentration gradient - that's where it wants to naturally go, without any input.

• The plasma membrane is "selectively permeable".

  • Some atoms/molecules can move across it, but most can't.

  • Hydrophilic solutes wanting to cross/diffuse across the membrane can't do so.

• Facilitated Transport

  • Channel Proteins or Carrier Proteins allow for movement of solutes across the plasma membrane, down their concentration gradient.

  • Channel Proteins - A membrane protein that allows a substance to pass through its hollow, water-filled pore across the plasma membrane.

  • Carriers take the molecules, modify their shape, and then release them into the cell. They are usually slower than Channels.

• Channels are faster than carriers

• Channels and Carriers can be always open or be gated by specific mechanisms.

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• They are very specific for the atom or molecule they transport. Ex: Acquaporin

• Osmosis

  • The movement of water through a semipermeable membrane from an area of low-solute concentration to an area of higher solute concentration

• Due to acquaporins, the plasma membrane allows movement of water via osmosis in or out of the cell.

  • Movement depends on the amount of solutes in the surrounding solution.

• There are 3 types of solutions:

  1. Hypotonic Solution

     1. Where the surroundings have fewer solutes than the inside of the cell.

        1. Water moves into the cell - the cell swells, and can burst.

     2. Bad of animal cells, but good for plant cells

1. Hypertonic Solution

   1. Surroundings have more solutes than the inside of cell

      1. Water moves outside of cell - cell shrivels

   2. Bad for any cells.

1. Isotonic Solution

   1. Surroundings have the same amount of solutes as the inside of the cell

      1. No net movement of water

   2. Good for animal cells, bad for plant cells

• Active Transport

  • The movement of materials that requires energy

  • Moves materials against their concentration gradient - From low to high concentration.

  • Can be one or few atoms or molecules at a time OR:

• Bulk Transport

  • Active transport of large structures or quantities.

• 2 Types:

1. Endocytosis

   1. They enter in vesicles or vacuoles

1. Phagocytosis

   1. For large structures, Pinocytosis is for many small particles

2. Exocytosis

   1. A type of active transport that moves substances outside the cell. They exit from vesicles.

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