1. Cell Boundaries

2. Cell Boundaries
Cell Membrane: a thin, flexible barrier surrounding the cell
Cell Wall: a strong supporting layer around the membrane

3. Cell Membrane regulates what enters and leaves the cell
provides protection and support
lipid bilayer
flexible layer
contains proteins attached to carbohydrates

5. Cell Membrane
Proteins form channels and pumps that move materials across the membrane
Carbohydrates help identify the cells
“Mosaic” of different molecules

6. Cell Membrane

7. Cell Wall Present in plants, algae, fungi, and many prokaryotes
H20, O2, CO2 pass through
Support and protection
Outside cell membrane
Made of carbohydrates and proteins
Plants’ cell wall is made of cellulose

8. Diffusion through Cell Boundaries

9. Concentration mass of solute in a given volume of solution
(mass/volume)
12 g salt in 3 L water? 12g/3L = 4g/L
12 g salt in 6 L water? 12g/6L = 2g/L

10. Diffusion In solution: particles move constantly
collide with each other
spread out randomly
Similar to the way people might do at a party

11. Diffusion This process is called diffusion
Particles move from an area of higher concentration to lower concentration
in a crowed room, move away from each other
This process is called diffusion

12. Equilibrium
Concentration of the solute is the same throughout a solution
In a crowed or a half empty elevator, people will spread themselves out at much as possible
In cells, particles will move across the membrane until the concentration is equal on both sides, or equilibrium is reached
After equilibrium is reached:
particles will continue to move across the membrane in both directions
But no further change occurs in concentration

13. Sugar and Equilibrium