Onion and Epithelial Cell Lab Exercise

Purpose

• Increase student familiarity with cell structures.
• Improve microscope skills.
• Introduce use of stains.
• Improve student drawing skills.

Equipment:

• slide and cover slip.
• light microscope.
• onion cell, epithelial cells and algae specimens prepared as described below.
• tincture of iodine.

Procedure:

Note: After each section rinse and dry the slide and cover slip.

Onion

1. Prepare an onion cell wet mount by slicing a very thin section of onion root.
2. Sketch drawing as described in data section.
3. Apply a single drop of iodine tincture to onion wet mount.
4. Sketch drawing as described in data section.

Epithelial cell

1. Prepare an epithelial cell wet mount by scraping the inside of your cheek with a clean toothpick.
2. Sketch drawing as described in data section.
3. Apply a single drop of iodine tincture to epithelial wet mount.
4. Sketch drawing as described in data section.

Algae

1. Prepare an algae cell wet mount using a miniscule piece of algae from class supply.
2. Sketch drawing as described in data section.
3. Apply a single drop of iodine tincture to algae wet mount.
4. Sketch drawing as described in data section.

Data Section:

1. All drawings should use a petri dish as template for field of view.
2. Each individual drawing should provide a level of detail and accuracy reflecting the approximately 5 minutes it takes for each drawing.
3. Create three no-stain drawings of onion, epithelial and algae cells.
4. Create three stain drawings of onion, epithelial and algae cells.

Analysis:

1. What cell structures are found in both plant and animal cells?
2. What structures can you see in the plant cell but not in the animal cell?
3. What do you see with stain that you couldn't see without it?
4. How do the cells compare in shape and size.
5. What do you think you need to do to see more structures?