Cell Transport

Cell Transport

Cell Membrane
1. Made of Phospolipids
  1. Phosphate head- Polar and it attracted to water (Hydrophilic)
  2. Two fatty acid tails - nonpolar and repels water (Hydrophobic)
2. Proteins
  1. Identify cell type
  2. Help substances through
  3. Recognize and bind to substances outside cell
Cell Transport
1. Semi Permeable/Selectively permeable - only certain substances can pass through
2. The barrier allows only small, non-polar substances to pass through.
3. Concentration
  1. Amount of substances
  2. When the concentration is the same
    1. The state of the cell is at an equilibrium
  3. When the concentration is NOT the same
    1. A concentration gradient exists
    2. Results in a movement of molecules from a place of higher concentration to a place of lower concentration
4. Two Types
  1. Passive Transport
    1. Energy input NOT required
  2. Active Transport
    1. Energy input required
Passive Transport
1. Energy is not required
  1. High to Low concentration
  2. Down concentration gradient
2. 3 Types
  1. Simple Diffusion
    1. Small non polar molecules can easily pass through lipid bilayer
      1. Examples: In: Oxygen Out: Carbon dioxide
  2. Facilitated Diffusion
    1. Particles move with the help of membrane proteins
  3. Osmosis
    1. Diffusion of water through a cell membrane allowing the cell to maintain water balance
    2. The direction in which the water moves depends on the concentration of the cell environment
      1. From high concentration to low concentration
    3. Solutions have 2 parts: Solvent and Solute
      1. Solvent: Water
      2. Solute: sugar, salt, etc
    4. Preventing Water Movement
      1. Hypertonic
        Water moves out if the solution is hypertonic
        Has a higher concentration of solute than the cytoplasm
        Cell loses water and shrinks
      2. Hypotonic
        Water moves in if the solution is hypotonic
        Has a lower concentration of solute than the cytoplasm
        Cell loses water and shrinks
      3. Isotonic
        No net change if the solution is Isotonic
        Has the same concentration
        Water moves in and out of the cell at an equal rate
        Cell is at an equilibrium and stays the same size
Active Transport
1. Energy is required
  1. Need ATP (Adenosine Triphosphate)
2. Low to high concentration
  1. Against Concentration gradient
3. 3 Types
  1. Ion Pumps
    1. Carrier proteins use energy to move substances
    2. Sodium - Potassium pump prevents Na ions from building up in the cell maintaining homeostasis
      1. Moves out 3 sodium and brings in 2 potassium
  2. Endocytosis
    1. Into the cell
    2. Cell membrane forms a pouch
      1. Pouch closes and pinches off to form vesicle inside the cell
  3. Exocytosis
    1. Out the cell
    2. Vesicles inside the cell fuse to the cell membrane and then release

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