Biology Cell HW Packet

Name ______Hour ______

HW Packet due September 18

Egg Demo / Due:______
Drawings / 0 1 2
Questions / 0 1 2 3
Due:______
Cell Membrane / Data Tables / 0 1 2
Graph / 0 1 2
Analysis / 0 1 2 3 4
Due:______
Cell parts / Drawings / 0 1 2
Osmosis in Elodea / Questions / 0 1 2 3
HW and review / Due:
Questions 1-6 / 0 1 2 3
Cell processes / 0 1 2 3
______/ 24 possible points

Osmosis and Diffusion Demonstration

Write a definition for each term.

Osmosis

Diffusion

Active Transport

Permeable membrane

Impermeable membrane

Selectively permeable membrane

Egg demonstration:

An egg can be used to further demonstrate the properties of cell membranes. We will start this demonstration with an egg that has been soaked in vinegar. We will place the egg in syrup tonight, and then transfer the egg to water the following night. Be sure to make accurate drawings of the egg each day.

Analysis and Conclusions

Answer the following questions using complete sentences. I will be really impressed if you use what you know about cells and cell parts to answer them.

  1. What cell process was demonstrated by Beaker #1?
  1. Use your knowledge of osmosis to explain what happened to the egg in syrup.
  1. Use your knowledge of osmosis to explain what happened to the egg in water.

D. Why did the mass of the egg change each day?

Cell Membrane Investigation using Dialysis Tubing

Osmosis can be a difficult concept to understand especially because it is hard to see happening in living cells that are far too small for us to see without using microscopes. However, we can use an artificial membrane that has many of the same properties of cell membranes. This artificial membrane called “dialysis tubing” allows us to do some important experiments to study osmosis. Like a cell membrane, dialysis tubing is “selectively permeable” – it has extremely tiny holes that allow small molecules to pass through the membrane while molecules larger than the holes are trapped.

In this experiment we are going to make some predictions about the direction of osmosis using starch and dialysis tubing. Some important factual information first:

-Osmosis is the diffusion of water from areas of high water concentration to areas of low water concentration.

-Starch is a large molecule consisting of many sugar molecules hooked together. It is too large to pass through the tiny holes in the dialysis tubing.

-Starch and iodine combine to create a dark purple-black color.

Cell Membrane Lab

  1. Record the following information about the experimental setups for Day 1:

What is A.

What is 1. ______

What is B.

What is 2. _____

Day 1 / Day 2
Color of Liquid In Beaker
Mass of Tubing
Color of Liquid in Tubing

A. 1.

B. 2.

Day 1 / Day 2
Color of Liquid In Beaker
Mass of Tubing
Color of Liquid in Tubing

A. 1.

B. 2.

Day 1 / Day 2
Color of Liquid In Beaker
Mass of Tubing
Color of Liquid in Tubing

Predictions

  1. The beakers and tubing will be stored overnight. Using your knowledge of osmosis, predict what we will see tomorrow.

Color of liquid in tubing / Color of liquid in beaker / Mass of tubing
Beaker #1
Beaker #2
Beaker #3

Cell Membrane Lab Day #2

  1. Record your observations for Day 2 next to the diagrams.
  1. For each beaker, use arrows to clearly show which direction each molecule (such as starch and iodine) moved.

Results

  1. Develop a graph that shows the how the mass of the tubing (Y-axis) changed over time (x-axis) for each beaker. Be sure to include a title, key, and labeled axis (X and Y) on your graph. Neatness counts.

Cell Parts and Plasmolysis

Background:

Eukaryotic cells are comprised of a cell membrane and many individual cell parts (organelles) that are each surrounded by their own membrane. These membranes keep the functions of the cell parts separated and more efficient. Materials must be passed through these membranes and delivered through each of the cell parts. Today we will observe some organelles and observe water loss (by osmosis) from a plant cell, Elodea.

Procedure: Drawings should be in color, colored the colors that you see!!!!

Part A:

  1. We can observe human cheek cells by gently scraping the inner cheek with a toothpick and rubbing this toothpick in a drop of methylene blue solution (stain) on a microscope slide.
  2. Add a coverslip and observe at Low, Medium and High Power. In the square below please draw one typical cheek cell at the power where you can see it best and label: cell membrane, nucleus, nuclear membrane, cytoplasm, and cell wall.

Part B: Please save this slide for Part C!!!!

  1. Pick one leaf of Elodea, place in a drop of water on a microscope slide. Cover with a cover slip.
  2. Observe cells at Low, Medium, and High Power. Draw two typical cells and please label: cell membrane, nucleus, nuclear membrane, cytoplasm,chloroplasts and cell wall.

Part C: Inducing Plasmolysis in Elodea using high concentration salt water.

  1. One partner should watch through the microscope while the other carefully replaces the water under the slide with 6% salt water.
  2. Using you Elodea slide and a tissue wick the water out from under your coverslip. Use a dropper to replace the water with 6% salt water by holding the dropper and inserting one drop under the cover slip.
  3. Observe cells after this change. You should see the cell membrane shrink away from the square cell walls into a small circle in the middle of the cell as the water rushes from the cells due to osmosis.
  4. To emphasize this difference draw one cell from Part C in the box on the left below and one cell from the Elodea that were placed in 6% salt water.

Questions:

  1. Are cheek cells alive?
  1. Why was stain added to the cheek cells?
  1. List any evidence that you have that living things are built from cells.
  1. Is Elodea a plant or animal? List all evidence you can think of to support your claim.

Additional Information: Tap water is typically 1% salts and 99% water. Our 6% salt water is only 94% water and 6% salts.

  1. Add arrows to both drawings of Elodea in Part D showing the direction water molecules are moving.
  2. Why is water moving in that direction? Give all evidence you can think of to support your claim.
  1. Did the Elodealeaf change shape in the salt water? Why or why not?
  1. Did the inside of the Elodea cells change shape in salt water? What cell parts were involved in this change?

Biology Homework: Cell

Review: Go over all homework packets, notes, and labs

  1. Name and describe the job of these cell parts:
  1. Using figures and creating your own percentages for two molecules draw an example of diffusion to reach equilibrium.
  1. Define: equilibrium –
  1. Using figures and creating your own percentages for two molecules draw an example of osmosis to reach equilibrium.
  1. Draw a typical animal cell and label 15 cell parts.
  1. Name all organelles that are surrounded by their own membrane.
    (you should find 6 parts)