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AP Biology 2014 > Osmosis > Flashcards

Flashcards in Osmosis Deck (15):
1

Osmosis

the diffusion of water molecules across a selectively permeable membrane.

2

Turgor pressure

The hydrostatic pressure that develops when water enters the cells of the plants and microorganisms.

3

Hydrostatic pressure (Osmotic pressure)

When water moves into a body by osmosis, pressure builds up inside the body.

4

Water potential

The tendency of water to move across a selectivelly permeablme membrane. This is used to account for differences in both concentration and pressure. It is the sum of the pressure potential and the solute potential.

  • Measured in bars (1 bar is approximately equal to 1 atmosphere pressure) or megapascals (1MPa = 10 bars).
  • In a living cell, water potential is always zero or negative.
  • Water potential can be positive or negative.
    • Negative water potentiatl = TENSION

5

Pressure potential

The pressure from any externally apllied force.

  • Is zero unless some force is applied, such as that applied by a cell wall.

6

Solute potential

The osmotic potential.

  • Results from the presence of solutes.
  • Always negative
  • A higher concentration of solutes generates a smaller (or negative) solute potential

7

Solute type/ Solute concentration

Solute type:

smaller molecules (water, NaCl, glucose) can diffuse across the membrane/ tubing while larger molecules cannot.

Solute concentration:

The relative concentration of solutes inside and outside the bag determines the net flow of solutes across the membrane.

  • The GREATER the solute concentration, the FASTER the initial flow of solutes.

8

Diffusion vs. Osmosis

The net movement of substances from an area of higher concentratipn to an area of lower concentration.

  • Results from random movement of molecules.
  • Osmosis is the diffusion of water molecules across a selectively permeable memrane.

9

The Rate of Diffusion

10

Turgor pressure

 

As water enters the cell, the vacuole expands until it exerts a force on the cell wall.

  • In a healthy cells- the wall presses back with a pressure equal  to and opposite of turgor pressure.

11

Hypertonic

The solution surrounding the cell is ______ (higher solute concentration) relative to the contents of the cell.

12

Plasmolysis

The process in which the plasma membrane collapses in a hypertonic solution because the net movement of water is out of the cell, and the TURGOR decreases.

13

Hypotonic

The solution surrounding the cell is ________ (lower solute concentration) relative to the contents of the cell.

  • The NET movement of water is INTO the cell.

14

Isotonic

The solution surrounding the cell is ______ (equal solute concentration) relative to the contents of the cell.

  • There is NO NET MOVEMENT of water in or out of the cell.

15

Lysis

When a cell "exploads"

  • Animal cells do NOT have CELL WALLS and immersing an animal cell into a hypOtonic solution wil cause the cell to expand.
  • Unless the cell has a mechanism for removing EXCESS WATER, the cell will continue to expand until it breaks apart.