Cell Transport

Cell Transport

1. Cell Membrane

   • Made of Phospolipids
     • Phosphate head- Polar and it attracted to water (Hydrophilic)
     • Two fatty acid tails - nonpolar and repels water (Hydrophobic)
   • Proteins
     • Identify cell type
     • Help substances through
     • Recognize and bind to substances outside cell

2. Cell Transport

   • Semi Permeable/Selectively permeable - only certain substances can pass through
   • The barrier allows only small, non-polar substances to pass through.
   • Concentration
     • Amount of substances
     • When the concentration is the same
       • The state of the cell is at an equilibrium
     • When the concentration is NOT the same
       • A concentration gradient exists
       • Results in a movement of molecules from a place of higher concentration to a place of lower concentration
   • Two Types
     • Passive Transport
       • Energy input NOT required
     • Active Transport
       • Energy input required

3. Passive Transport

   • Energy is not required
     • High to Low concentration
     • Down concentration gradient
   • 3 Types
     • Simple Diffusion
       • Small non polar molecules can easily pass through lipid bilayer
         • Examples: In: Oxygen Out: Carbon dioxide
     • Facilitated Diffusion
       • Particles move with the help of membrane proteins
     • Osmosis
       • Diffusion of water through a cell membrane allowing the cell to maintain water balance
       • The direction in which the water moves depends on the concentration of the cell environment
         • From high concentration to low concentration
       • Solutions have 2 parts: Solvent and Solute
         • Solvent: Water
         • Solute: sugar, salt, etc
       • Preventing Water Movement
         • Hypertonic
           • Water moves out if the solution is hypertonic
             • Has a higher concentration of solute than the cytoplasm
             • Cell loses water and shrinks
         • Hypotonic
           • Water moves in if the solution is hypotonic
             • Has a lower concentration of solute than the cytoplasm
             • Cell loses water and shrinks
         • 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

4. Active Transport

   • Energy is required
     • Need ATP (Adenosine Triphosphate)
   • Low to high concentration
     • Against Concentration gradient
   • 3 Types
     • Ion Pumps
       • Carrier proteins use energy to move substances
       • Sodium - Potassium pump prevents Na ions from building up in the cell maintaining homeostasis
         • Moves out 3 sodium and brings in 2 potassium
     • Endocytosis
       • Into the cell
       • Cell membrane forms a pouch
         • Pouch closes and pinches off to form vesicle inside the cell
     • Exocytosis
       • Out the cell
       • Vesicles inside the cell fuse to the cell membrane and then release