L.21 MITOSIS IN AN ONION ROOT

INTRODUCTION:

Mitosis is the process in which a eukaryotic cell nucleus splits in two, followed by division of the parent cell into two daughter cells. So the goal of this experiment is to view the different stages of a mitosis in the microscope.

MATERIALS:

-Onion
-Orceine A and B
-Dropper
-Watch glass
-Beaker
-Forceps
-Bunsen burner
-Lighter


PROCEDURE:

1- A week ago we left an onion in a beaker with some water, (only the tip of the onion touched it) so its roots will grow so we can see the process of mitosis.
2- To start our experiment we took the onion and cut the tip of a root and put it in the watch glass.
3- Then with the dropper we took the orceine A and put some drops on the root and we took the watch glass with the wooden forceps and put it on the bunsen burner so the orceine and the root would heat. Some fumes began to evaporate. We had to be careful to not to burn the root so the watch glass could not be too hot, we should be able to touch it with our hand!!
4- After that we took the root with the forceps and put it on a slide and added a couple of drops of orceine B, we waited a couple of minutes.
5- Then with the scalpel we cut 3mm leaving the tip, and always knowing where the tip is.
6- Finally we added a coverslip and used the squash method so we could observe the cells on the microscope.

RESULTS:

We didn't observed nothing.

L. 20 THE CHLOROPLAST AND THE PHOTOSYNTHESIS

INTRODUCTION:

We investigate the photosynthesis in an algae. During the photosynthesis, plants and algae produce oxygen. We observed how light intensity affects the rate at which photosynthesis occurs and the rate of oxygen production.

MATERIALS: 

- Algae (Elodea)

- 600 ml beaker

- Test tube

- Funnel

- Tap water

- Light source

- Metric ruler

PROCEDURE:

1- First we assigned the different distances to do the experiment and compare the results to each group.

2- We took the 600 ml beaker and placed 7 g of an algae under a clear funnel inside the beaker (the wide end goes over the algae like in the image). The funnel was raised off the bottom on pieces of blue-tack to allow unhampered diffusion of CO2 to Elodea.

3-We didn't have sodium bicarbonate so we filled the beaker with tap water, the algae and the funnel should be completely under the water.

4- Then we filled a test tube with tap water and placed the thumb over the end of the test tube. We turned the test tube upside down taking care that no air enters and no water comes out and we put this test tube over the end of the funnel (the skinny part)

5- We marked the level of the water on the surface of the test tube with a marker pen.

6- Each group placed the preapartion close to a light source, each group placed the preparation in a different distance 5, 10, 20 and 25 cm, and one with no light source.

7- We also measured the temperature.

8- Finally we left this preparation for and hour and a half. After this time we measured the difference of gas accumulation on the top of the test tube.

QUESTIONS:

1- Identify the dependent and the independent variable of this experiment.

Dependent: gas production.
Independent: distance (intensity of the light)

 

2-Using the data from your results prepare a graph and describe what happened to the amount of gas in the test tube.

	Distance (cm)	Gas production (cm)	Temperature
Laura & Andrea	25	0,5	22,7
Edu & Ignacio	0	0	21,5
Inés & Maria	20	0,3	22,5
Paula & Myriam	5	0,5	26,5
Lizza & Anna	10	0,4	24

3-How much gas was producted in the test tube after one hour? And an hour and a half?

It's in the graph.

 

4-Write the photosynthesis equation. Explain each part of the equation. Which subtances are produced by photosynthesis. Which gas is produced that we need in order to live? 
Plants take in carbon dioxide by diffusion through their stomata. Light energy enters the plant via leaves and water and nutrients enter through roots. The plant is then able to make glucose and oxygen. The glucose moves from the leaves to the plant and the oxygen diffuses out of the leaves. The gas that we need in order to live is oxygen.

Investigation: 

-Which is the origin of the oxygen that we breathe?

 The trees and plants that are around us and other organisms that do the photosynthesis.

-Where are the lungs of our planet?

Phytoplankton need two things for photosynthesis and thus their survival: energy from the sun and nutrients from the water. Phytoplankton absorb both across their cell walls.

In the process of photosynthesis, phytoplankton release oxygen into the water. Half of the world's oxygen is produced via phytoplankton photosynthesis. The other half is produced via photosynthesis on land by trees, shrubs, grasses, and other plants.

L. 19 CELLS ORGANELLES

Tomato chromoplasts (400X)

Potato amyloplasts, stained with lugol (1000X)

Chloroplasts of vallisneria

Carrot (1000X)

red cabadge cloroplasts (400X)

Red cabadge (100X)

Red cabadge stoma (1000X)

L.18 LIFE IN A DROP OF WATER

L.17 GRAM STAINING

OBJECTIVES:

- Differenciate yogurt bacteria.
- Relate the staining procedure with the structure of the cells.

MATERIALS:

- 1 Slide
- 1 Cover slip
- Tongs
- Needle
- Gram stain: crystal violet, iodine and safranin.
- Descolorize reagent: ethanol 96%
- Microscope
- Yogurt

PROCEDURE:

- Prokariotic cell observations: GRAM STAINING

1. Prepare a heat-fixed sample of the bacteria to be stained.
2. Cover the smear with crystal violet for an exposure of 1 min.
3. Rinse with distilled water.
4. Apply Iodine solution for 1 min.
5. Rinse the sample with distilled water.
6. Decolorize using ethanol. Drop by drop until the purple stops flowing. Wash immediately with distilled water.
7. Cover the sample with the safrain stain for an exposure time of 45 seconds.
8. Rinse the sample with distilled water.
9. Gently dry the slide with paper.

=> Gram staining is a method of differentiating bacterial species into two large groups: Gram positive 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. 

Gram stain:
- Complete the table that you have below:

	GRAM POSITIVE	GRAM NEGATIVE
Crystal violet: Color?	Violet	Violet
Iodine	Contrast	Contrast
Ethanol: Decolorize?	No,  too thick retaining the dye	Yes, open the pores and the Coloring goes.
Safranin: Color?	No	Reddish

L.16 EPIDERMIS CELLS

OBJECTIVES:

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

MATERIALS:

- 1 Slide

- 1 Cover slip
- Distilled water
- 10% Salt water
- Scissors
- Needle

PROCEDURE:

Plant cells observation:
1. Cut the stalk of the leek.
2. In the place of the cut, pull out the transparent part of the epidermis using forceps.
3. Using the brush, place the peel onto the slide containing a drop of tap water.
4. Take a cover slip and place it gently on the peel with the aid of a needle.
5. View it in the microscope.
6. Describe the change in the shape of the cells.
7. Draw a diagram with the parts of a stome: stoma,cell guards,epidermis cells.

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

RESULTS AND CONCLUSIONS:

1. What is the major function of a cell membrane?
The basic function is to maintain the plasma membrane via the differential intracellular environment. The combination of active and passive transport makes the plasma membrane selective barrier that allows the cell to differentiate medium.
2. What is the major function of the cell wall?
Cell wall protects the cell contents and gives rigidity to the cellular structure.
3. How does salt affect the cells shape? And the stomes?
altering the sodium concentration gradient both outside and inside the cell ions.

L.15 ANIMAL CELLS vs PLANT CELLS

INTRODUCTION:

We compared the animal cells and the plant cells. Animal cells are similar to plant cells in that they are both eukaryotic cells and have similar organelles. Animal cells are generally smaller than plant cells. While animal cells come in various sizes and tend to have irregular shapes, plant cells are more similar in size and are typically rectangular or cube shaped. A plant cell also contains structures not found in an animal cell. Some of these include a cell wall, a large vacuole, and plastids. Plastids, such as chloroplsts, assist in storing and harvesting needed substances for the plant. Animal cells also contain structures such as centrioles, lysosomes, cilia, and flagella that are not typically found in plant cells.

Our Objectives:

- Identify the major components of cells. 

- Differentiate between animal and plant cells.

- Measure dimensions of the entire cell and the nucleus.

MATERIALS:

- Toothpick
- 2 Slides
- 2 Cover slips
- Distilled water
- Methylene blue
- Iodine ( safranin)
- Onion
- Glycerine
- Watch glass
- Droper
- Needle
- Brush
- Cellulose paper
- Microscope

PROCEDURE:

- Plant cells observation: 
1. Pour some destilled water into a watch glass.
2. Peel of the leaf from half a piece of onion and using forceps, pull out a piece of transparent onion peel (epidermis) from the leaf.
3. Put the epidermisin the watch glass containing distilled water.
4. Take a few drops of safranin in a droppper and transfer into another watch glass.
5. Using a brush (or a needle), transfer the peel  into the watch glass containing the dye. Let this remain in the safranin solution for 30 seconds, so that the peel is stained.
6. Take the peel from the odine solution and place it in the watch glass containing distilled water.
7. Take a few drops of glycerine in a dropper and pour 2-3 drops at the center of a dry glass slide.
8. Using the brush, place the peel onto the slide containing glycerine.
9. Take a coverslip and place it gently on the peel with tha aid of a needle.
10. Remove the extra glycerine using cellulose paper.
11. View it in the microscope.

- Cheek cells observation:
1. Gently scrape the inner side of the cheek using a toothpick, which will collect some cheek cells.
2. Place the cells on a glass slide that has water on it.
3. Mix the water and the cheek cells using a needle and spread them.
4. Dry the sample under the light to fix the sample on the slide.
5. Take a few drops of methylene blue solution using a dropper and add this to the mixture on the slide.
6. After 2-3 minutes remove any excess water and stain from the slide using cellulose paper.
7. Take clean cover slip and lower it carefully on the mixture with the aid of a needle.
8. Using the top of the needle, press the cover slip gently to the spread the epithelial cells.
9. Remove any extra liquid around the cover slip using cellulose paper.

RESULTS AND CONCLUSIONS:

Plant cells: 


MR= MA/ NA
cell:
MR= 6,9/400= 0'017cm
0'17cmx10000= 172'5 microns

nucleous: 
400= 0'7x10000/X
X= 7000/400= 17'5 microns



 Eduard cheek cells:

400= 1'5x10000 microns/ X 
X= 1'5x10000 microns/ 400= 37'5

400= 0'3x10000 microns/ X
X=  0'3x10000microns/400= 7'5 microns