Science Lab : de març 2015

dilluns, 23 de març del 2015

L15. Cells Organelles

Tomato cromoplast (400x)

Chloroplasts of Vallisneria sp

Carrot cromoplast (100x)

Red cabage (100x)

Red cabage cloroplast (400x)

Red cabage stoma (1000x)

dilluns, 9 de març del 2015

Introduction:

Gram staining is a method of differentiating bacterial species into two large groups: gram postive and gram negative.

This differentiation is based by the chemical and physical properties of their cell walls by detecting a peptidoglycan, which is present in a thick layer in gram-positive bacteria.

The result is:

Gram-negative: stain pink or reddish color
Gram-positive: stain purple color

Objectives:

- Differentiate yogurt bacteria
- Relate the stanning procedure with the structure of the cells.

Materials:

- Toothpick
- Slide
- Cover Slip
- Tongs
- Needle
- Gram stain: crystal violet, iodine and safranin.
- Decolorize reagent: ethanol 96%
- Microscope
- Yogurt

Procedure:

- Prepare a heat-fixed sample of the bacteria to be stained.
- Cover the smear with crystal violet for an exposure of 1 min.
- Rinse with destilled water.
- Apply iodine solution for 1 min.
- Rinse the sample with distilled water.
- Decolarize using ethanol. Drop by drop until the purple stops flowing, "Wash immediately with distilled water"
- Cover the sample with the safranin stain for an exposure time of 45 seconds.
- Rinse the sample with tap water.
- Gently dry the slide with paper (only the under part of the slide)

Results:

	GRAM +	GRAM -
Crystal Violet (color?)	PURPLE	PURPLE
Iodine (changes?)	YES	YES
Ethanol (decolorize?)	NO	YES
Safranin (color?)	NO	REDDISH

400x

L13: Epidermis cells

Objective:

- Identify the shape of epidermis cells
- Identify and explore the parts of a stoma
- Mesure dimensions of the entire cell and the stoma

Material:

- Slide
- Cover Slip
- Distilled water
- 10% salt water
- The kit: scissors, needle, forceps
- Leek

Procedure:

plant cells observation:

1- cute the stalk of the leek.
2- In the place of the cut, pull out transparent part of the epidermis using forceps.
3- Using needle, place the peel onto the slide containinga drop of tap water.
4- Take a cover slip and place it gently on the peel with the aid of needle.
5- View it in the microscope.
6. Describe the change in the shape of the cells.

salt treatement:
1- Prepare a 10% of salt solution.
2- Put the salt with a dropper on the left part of the slide (touch the cover slip)
3- Place a piece of cellulose paper in the opposite part of the cover slip, and let the dissolution to go through your sample.