1. Cellular Transport
CH 2.1
Mr. Traub

2. Osmosis: Diffusion of Water
Osmosis: diffusion of water across a selectively permeable membrane depending on the concentration of solutes on either side of the membrane
Diffusion: movement of particles from an area of higher concentration to an area of lower concentration
Important factor in maintaining homeostasis

3. Osmosis In Action
Before Osmosis After Osmosis

4. What Just Happened?
Two solutions separated by a selectively permeable membrane, only allows water to diffuse across
Water flows to side of the membrane where water has low concentration. (High to Low)
Water diffuses until it has equal concentration on both sides of the membrane
Therefore, an unequal distribution of particles is called a concentration gradient

5. How Osmosis Affects Cells
Most cells, whether in multicellular or unicellular organisms, are subject to osmosis because they are surrounded by water solutions.
Three types of solutions that cells may be in;
Isotonic solution
Hypotonic solution
Hypertonic solution

6. Isotonic Solution
Solute concentration of solution and water equal to that of cell
Water molecules move in and out at the same rate, so cell maintains shape

7. Hypotonic Solution Solute concentration of solution lower than cell
Less dissolved particles outside of cell than inside of cell
More water outside the cell than inside
Hypo = less, under (think hypodermic, hypothermia); Tonic = dissolved particles
Cell expands (and may burst)

8. Hypertonic Solution Solute concentration of solution higher than cell
More dissolved particles outside of cell than inside of cell
Hyper = more (think hyperactive); Tonic = dissolved particles
Water moves out of cell into solution
Cell shrinks

9. Other Types of Cellular Transport
Passive Transport
Active Transport

10. Passive Transport Cell uses no energy to move particles
Transport proteins, carrier proteins, and channel proteins help substances move through the plasma membrane
This is known as Facilitated diffusion

11. Facilitated Diffusion
Allows diffusion of large, membrane insoluble compounds such as sugars and amino acids
Does not require energy (passive)
Highly Selective
Substance binds to membrane-spanning transport protein
Binding alters protein conformation, exposing the other surface
Fully reversible - molecules may enter the cell and leave the cell through the transport protein.
Particles move from areas of high concentration to areas of low concentration.

12. Active Transport
Move particles from region of lower concentration to region of higher concentration
Requires energy from the cell
Carrier protein binds with particle of substance to be transported, chemical energy allows cell to change shape of carrier protein and particle is released on other side of membrane

14. Passive & Active

15. Transport of Large Particles
Endocytosis: process by which a cell surrounds and takes in material from its environment
Exocytosis: expulsion of materials from the cell
Ex: expel waste, secrete hormones

16. Endocytosis & Exocytosis

17. Review