Cell Transport Notes
Review of Solutions
• Solutions- mixture of a solute and a solvent
• Solvent - the liquid into which the solute is dissolved. Ex) water
• Solute - substance that is dissolved. Ex) Salt
Methods of Transport across membranes
1. Passive Transport- does not require energy
a. Diffusion
b. Osmosis
c. Facilitated Diffusion
2. Active Transport- requires energy to transport molecules against a concentration gradient
Diffusion
• Movement of molecules from an area of high concentration to an area of low
concentration.
• Movement of smaller molecules from one side of a membrane to another
• Osmosis- diffusion/ movement of water molecules
Tonicity (descriptive words used to compare solutions)- Water will diffuse to where there is
more solute.
• Hypotonic Solution - One solution has a lower concentration of solute than another.
• Hypertonic Solution - one solution has a higher concentration of solute than another.
• Isotonic Solution - both solutions have same concentrations of solute.
________________
________________
________________
Facilitated Transport
• The molecules move from an area of high concentration to an area of low concentration
• Movement does not require energy (passive transport)
• The movement of larger molecules (like sugar molecules)
• Uses a membrane protein to go through the membrane
Active Transport
1. The molecules move from an area of low concentration to an area of high concentration
2. AGAINST the concentration gradient- like walking uphill)
3. Movement requires energy (in the form of ATP)
4. Ex) Sodium- Potassium Pump
Bulk Transport- Active
1. Endocytosis- the cell membrane folds into a pouch (vesicle) that encloses the large
particles
• Pinocytosis- small particles (like drinking)
• Phagocytosis- very large particles (like eating)
2. Exocytosis- the release of cell products and wastes from the cell