Week 3 - Plasma Membrane Transport & Mitosis Flashcards
What is plasma membrane in terms of transport?
- Both a barrier and gateway between cytoplasm and extracellular fluid
- Some molecules pass easily through, others do not (selectively permeable)
- Atoms and molecules use Passive or Active processes
What is passive transport?
- No ATP required
- Molecules moves DOWN their concentration gradient (from high to low)
What is simple diffusion?
Non-polar, fat-soluble (hydrophobic) molecules diffuse through phospholipid bilayer
(e.g., oxygen (O2) into a cell)
What is facilitated diffusion?
- Polar (electrolytes), fat-insoluble / water-soluble (hydrophilic) molecules
- Carrier or channel protein (e.g., glucose)
What is osmosis?
- Simple diffusion of H2O across a selectively permeable membrane
- Between the phospholipids or Aquaporins (channels)
What is osmolarity?
- Concentration of solute particles (stuff) in solution
- When solutions of different osmolarity are separated by a plasma membrane, osmosis occurs
- Water moves DOWN its concentration gradient
- Until water concentration same on both sides (equilibrium)
What happens when osmosis occurs?
- Water enters or leaves a cell
- Changing cell volume disrupts cell function
What is tonicity?
The ability of a solution to cause a cell to shrink or swell
What is hypotonic?
Hypotonic solution has a lesser solute concentration (thus more water) than cell.
What is isotonic?
Isotonic solution has same solute concentration (thus water concentration) as that of cell.
What is hypertonic?
Hypertonic solution has a greater solute concentration (thus less water) than cell.
What is active transport processes?
- Molecules moves UP their concentration gradient (from low to high)
- ATP (energy) required
What is vesicular transport?
- Requires ATP
- Large molecules in vesicles (Sacs)
- Vesicle phospholipids merge with phospholipids of plasma membrane or other
membranous structures
What is exocytosis?
Secrete molecules out of cell
What is endocytosis?
Bring molecules into cell
