Question

osmosis, tonicity and water potential notes
key idea: what are some factors that contribute to the way in which water moves within and between cells?
topic i: osmosis
the passive process of water entering and leaving the cell is known as osmosis. in this process water will flow from areas of high concentration to areas of low water concentration. since water is polar, this process happens extremely slowly without the aid of proteins. in short, movement of water in a capacity high enough to support the cell must be facilitated by a protein. the protein that transports water in cells is known as an aquaporin.

1. what is osmosis?
2. since water moves from high concentration to low concentration, is it active or passive?
3. why is osmosis an example of facilitated diffusion?
4. what protein transports water into and out of the cell?

topic ii: tonicity
water in cells is rarely alone. since water is an excellent solvent, there are often various solutes that influence the way in which water will move within and between cells. we measure the relative amounts of solute and solvent with tonicity. tonicity describes the amount of solute outside the cell in question. hypertonic is used to describe situations where there is more solute outside the cell than inside. hypotonic is used to describe situations where there is less solute outside the cell than inside. isotonic is used to describe situations where there is an equal amount of solute and solvent on either side of the cell.

1. define the following terms:

a. hypertonic-
b. hypotonic-
c. isotonic-

1. when water reaches equilibrium, will it stop moving?

water will always move from areas of high concentration to areas of low concentration to reach dynamic equilibrium. in areas where there is a lot of solutes, there is little water. in areas where there are little solutes, there is a lot of water.

1. identify how water would move, and the ultimate consequence to cells placed in the following solutions:

a. hypertonic-
b. hypotonic-
c. isotonic-

Explanation:

1. Osmosis is the passive process of water entering and leaving the cell, flowing from high - water concentration areas to low - water concentration areas.
2. Since it moves down the concentration gradient without energy input, it is passive.
3. Osmosis is an example of facilitated diffusion because for significant water movement to support the cell, it needs aquaporin proteins to facilitate it.
4. Aquaporin is the protein that transports water into and out of the cell.

For tonicity terms:
A. Hypertonic describes a situation where there is more solute outside the cell than inside.
B. Hypotonic describes a situation where there is less solute outside the cell than inside.
C. Isotonic describes a situation where there is an equal amount of solute and solvent on either side of the cell.

1. When water reaches equilibrium, it does not stop moving; it reaches a dynamic equilibrium.

3.
A. In a hypertonic solution, water moves out of the cell, and the cell may shrink.
B. In a hypotonic solution, water moves into the cell, and the cell may swell or burst.
C. In an isotonic solution, there is no net movement of water, and the cell maintains its shape.

Answer:

1. Osmosis is the passive process of water entering and leaving the cell, flowing from high to low water - concentration areas.
2. Passive.
3. Because significant water movement to support the cell needs aquaporin proteins for facilitation.
4. Aquaporin.

A. A situation where there is more solute outside the cell than inside.
B. A situation where there is less solute outside the cell than inside.
C. A situation where there is an equal amount of solute and solvent on either side of the cell.

1. No.

3.
A. Water moves out of the cell, cell may shrink.
B. Water moves into the cell, cell may swell or burst.
C. No net movement of water, cell maintains its shape.