Cell Transport

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Slide 18

Effects of Osmosis on Life

Osmosis- diffusion of water through a selectively permeable membrane

Water is so small and there is so much of it the cell can’t control it’s movement through the cell membrane.

Slide 19

Hypotonic Solution

Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water)

Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!

Osmosis Animations for isotonic, hypertonic, and hypotonic solutions

Slide 20

Hypertonic Solution

Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water)

Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!

Osmosis Animations for isotonic, hypertonic, and hypotonic solutions

shrinks

Slide 21

Isotonic Solution

Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell.

Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)

Osmosis Animations for isotonic, hypertonic, and hypotonic solutions

Slide 22

What type of solution are these cells in?

A

C

B

Hypertonic

Isotonic

Hypotonic

Slide 23

How Organisms Deal with Osmotic Pressure

Paramecium (protist) removing excess water video

Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called tugor pressure.

A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.

Salt water fish pump salt out of their specialized gills so they do not dehydrate.

Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.