Name: ______Date: ______Period: ______

Osmosis & Tonicity

Composition of the Cell Membrane & Functions

Use the word bank to fill in the blanks below.

The cell membrane is also called the ______membrane and is made of a phospholipid ______. The phospholipids have a ______head and two ______tails. The head of a phospholipid is made of an alcohol and ______group, while the tails are chains of ______. Phospholipids can move freely and allow water and other ______molecules to pass through, into or out of the cell.

Match the cell membrane structure or its function with the correct letter from the cell membrane diagram.

_____ attracts water_____ repels water_____ makes up the bilayer

_____ helps maintain flexibility of the membrane_____ helps transport certain materials across the membrane

Define osmosis- ______

In which direction does water move across membranes (against or down the concentration gradient)? ______

Define each type of solution:

a. isotonic- ______

b. hypertonic- ______

c. hypotonic- ______

Dialysis Bag Tonicity

Determine the percentage of water inside and outside the dialysis bags below. Use arrows to show the direction of water movement into or out of each dialysis bag. On the line below, identify the solution the dialysis bag is in (hypertonic, hypotonic or isotonic).

1.______2.______3.______

Read the statements below and determine the tonicity described (hyper, hypo or iso).

______Solution with a low solute concentration

______Solution with a low water concentration

______Solution in which the solute concentration is the same

______Condition that plant and animal cells require (homeostasis)

______Red blood cell bursts (cytolysis)

______Plant cell loses water and plasmolysis occurs

______Solution with a higher solute concentration

______Solution with a high water concentration

Determine the tonicity of each solution (hyper, hypo or iso).

A: ______

B: ______

C: ______

D: ______

E: ______

F: ______

  1. Cell F is a plant cell. The cytoplasm is retreating (pulling away) from the cell wall. What process is occurring?

______

Multiple Choice Questions:

  1. In osmosis, water always moves toward the ____ solution: that is, toward the solution with the ____ solute concentration.
  2. hypotonic, lesser
  3. hypertonic, greater
  4. hypertonic, lesser
  5. hypotonic, greater
  1. The concentration of solutes in a red blood cell is about 2%. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions?
  2. a hypertonic sucrose solution
  3. a hypotonic sucrose solution
  4. a hypertonic urea solution
  5. a hypotonic urea solution
  1. Sea water is dangerous to drink because
  2. one cup of sea water contains enough sodium to poison you.
  3. sea water is hypertonic to your body tissues and drinking it will cause you to lose water.
  4. sea water is isotonic to your body fluids and you will absorb too much water.
  5. the salt causes hypertension and you will promptly die of a stroke.
  1. If the volume of a cell increases when it is placed in a solution, that solution is said to be ______to the cell.
  2. hypertonic
  3. subatomic
  4. isotonic
  5. hypotonic
  1. Inside dialysis bag* A is a 50% glucose solution and inside bag B is a 20% glucose solution. Both bags are put into beakers containing 100% water. What will happen?

*Dialysis bags are membranes that let water through but not glucose.

  1. Bag A will gain weight.
  2. Bag B will gain weight.
  3. Both bags will gain weight.
  4. Both bags will lose weight.

Short Response Questions: Read the paragraphs and compose short responses to each writing prompt. Use complete sentences.

  1. Wallway is a new general herbicide for aquatic plants. Its main ingredient is a marine salt solution. It is effective against freshwater but not saltwater plants. It works by breaking down the cell walls of the plants.

Writing Prompt: What effect would Wallway herbicide have on the freshwater plants?

______

  1. Strawberry jelly is a very strong solution of sugar. By contrast the cytoplasm in a bacteria is a much weaker solution.

Writing Prompt: The cell wall of a microbe is made up of a semi-permeable membrane. Would water flow from the microbe to the jam, or from the jam to the microbe by osmosis?

______

Explain why bacteria find it difficult to survive in jam.

______

READ THE INFORMATION BELOW!

In each diagram below, a “cell” with a semipermeable membrane has been placed in a beaker containing substances that are dissolved in water. The membrane is permeable to water and iodine. It is NOT permeable to glucose, sodium (Na+), or starch.

Beaker 1

What is the % of water inside the cell? ______

What is the % of water outside the cell? ______

Will osmosis occur? ______

If so, in what direction will osmosis occur (into or out of the cell)? ______

Will glucose cross the cell membrane? ______

The cell will (circle one)-swellshrink

How do you know? ______

This diagram shows the cell in a(n) ______solution. (hypertonic, hypotonic, isotonic)

Beaker 2

What is the % of water inside the cell? ______

What is the % of water outside the cell? ______

Will osmosis occur? ______

If so, in what direction will osmosis occur (into or out of the cell)? ______

Will glucose cross the cell membrane? ______

The cell will (circle one)-swellshrink

How do you know? ______

This diagram shows the cell in a(n) ______solution. (hypertonic, hypotonic, isotonic)

Beaker 3

What is the % of water inside the cell? ______

What is the % of water outside the cell? ______

Will there be a net (overall) change in these concentrations? ______

Will osmosis occur? ______

Why or why not? ______

______

Will starch diffuse? ______Will glucose diffuse? ______

If iodine were placed in the beaker, what would you see immediately? ______

What would you see after several hours? ______

This diagram shows the cell in a(n) ______solution. (hypertonic, hypotonic, isotonic)