P13 OBSERVING CELLS/ MICROSCOPY

OBJECTIVES 

The purpose of this practice is to provide an overview of the microscope and how to use it. Also to observe the differences between animal and plant cells, preparing a sample of onion epidermis and observing others samples.

MATERIAL

• Distilled water

• An Onion

• A knife

• Safranin colouring fluid

• Microscopes and loupes

• Different samples of cells

• Forceps

• A loupe

• A slide and a coverslip

• A mortar. 

OBSERVING ANIMAL AND PLANT CELLS

Mouse ear 

Mouse intestine

Plant cells

ONION'S PROCEDURE

Make a cut in the onion, in order to have a piece of its epidermis.

Wash the piece well with distilled water.

Dye the piece of epidermis with safranin for 30 seconds.

Wash the piece again carefully; therefore we do not damage the piece.Cover up the piece with a slide and a coverslip. 

QUESTIONS

 1. Parts of a microscope:2.  DIFFERENCES BETWEEN A LOUP AND A MICROSCOPE

  

In the binocular loupe the three-dimensional images are observed, in the two-dimensional microscope, since the samples are cut with a micrometer and placed in a sample.A big difference is the magnification, the loupe increases by 40x (you can see things you see at first glance) and the microscope allows you to see structures such as cells and microorganisms (1000x).

The microscope has artificial light, coming from below, instead the loupe  may not bring it and use it with natural light, the light will come from above.

Under the microscope the platinum can be moved and in the magnifying glass no.To see a sample in the microscope it is necessary to dye it and to prepare it and in the magnifying glass no.

3. HOW DO THE MICROSCOPE AUGMENT?

There are two lenses, ocular and objectives. To calculate the total augment we have to multiply the augments of the ocular by the augments of the objective.

4. DIFFERENCES BETWEEN ANIMAL AND PLANT CELLS. 

	Plant cells	Animal Cells
Cell wall	X
Chloroplasts	X
Centriols		X
Vacuols	Biggers.	Smaller.
Nucleus	Place on one side of the cell.	Central position.
Ciotesqueletum		X
Flagellum		Some.

P12 DNA

OBJECTIVE

We want to reveal the presence of DNA in aliments like kiwis and bananas and we also want to know the procedure to extract it.

MATERIAL 

• Test tubes
• Paper filter
• A funnel
• Graduated cylinder
• Erlenmeyer
• Beaker 600 mL
• Spatula
• Pipette
• Mortar and peatle. 
• Microscope
• Weighing machine
• Freezer
• Commercial soap for washing the dishes (FAIRY)
• Distilled water
• Ethanol of 96º
• Sodium chloride 2M
• A Banana
• Pineapple juice
• Strainer
• Acetic orcein

PROCEDURE

We can use either a kiwi or a banana, the procedure is exactly the same.

• Take the ethanol and put it on the freezer so that it can be cold.

• Weigh 100 g of banana in a weighing machine and crush it until it has taken the form of porridge.  

• Prepare a solution of 3g of Sodium chloride, 100 mL distilled water and 10 mL of the commercial soap in 600Ml Beaker and add the porridge inside the beaker.
• Mixed everything and then get another 600mL and strain the porridge, to make it juice, then you can throw away the rest.
• Prepare a graduated cylinder, with a funnel and filter paper inside and strain the juice again, we only need 5mL, we add 1 Ml of pineapple juice in.

• Then we put 6 mL of ethanol inside and mix it with a spatula slowly.
• Deposit the DNA strands in a slide and add some drops of acetic orcein and left it for 5 minutes.
• Wash the preparation with distilled water, dry and then cover it with a coverslide.  

RESULTS

CUESTIONS

How can you release DNA from the surrounding membranes?
The soap break down cell membranes and release DNA.

Why do we use Pineapple juice? Because it contains an enzim that destroys the proteins of the DNA molecular. 

How do we get the precipitation of DNA dispersed? With ethanol, it precipitates DNA strands and join the in a clum. 

P11 MILK COMPONENTS

OBJECTIVES 

In this practice, we want to observe and reveal the components of milk. Also we want to  know its pH and  the amount of casein. And demonstrate if there are proteins, starch, fats and reducing glucids  in milk.

MATERIAL 

200 mL Beaker

Glacial Acetic Acid

Full-Fat Milk

Wiro Gauze

Lab burner

Watch Glass

A Pipette

Thermometer

Test tube rack

5 test tubes

Iodine solution

Sudan III

Fehling A and Fehling B

Spatula

CuCO4

NaOH (dissolution of 20% in distilled water)

Distilled water

Paper indicators pH

Dropper

PROCEDURE

1.       TO SEPARATE THE CASEIN FROM MILK.

•     Take a beaker of 200 mL and add in fool-fat milk.
•    Then heat the milk in the lab burner and boil it until the milk reaches 40 degrees.
•    Afterwards, prepare dissolution of 1 ml of glacial acetic acid and 10 mL of distilled water.
•     Put a few drops of the solution in the milk.
•   Then, with the help of the strainer, strain the amount of casein and left the serum.

Calculations

We have 200 mL of milk, and the density of its is 1,03 g/ml.  The weight of the casein is 25g.

200 x 1,03 = 206

If we have 25 g of casein in 206 g of milk, which weight of casein will we have in 100 g of milk? 12’1%. (12,1 g of casein in 100 g of milk).

From here all practices are done with the serum.

2.  To know the pH of the milk:

You have to put a paper indicator o pH inside a test tube with the serum of the milk, and it will show you the number of the pH rang ( 1-7 is acid, 8-14 basic). 

3. TO REVEAL THE PROTEINS

• Take a beaker and put 100 mL of distilled water.
• Add in 10mL of the fool-fat milk.
• Then get two drops of the mixture and put it in a test tube.
• Add in 2 mL of the NaOH dissolution and 5 drops of CuCO4.

If the mixture changes to black colour, or similar to purple, we have revealed proteins. 

4. TO REVEAL THE STARCH

Put 2mL of the serum of milk in a test tube, then add 3 drops of Iodine solution in it. There wasn’t a change of colour from yellow to purple that means that there isn’t starch in milk. 

5. TO REVEAL THE FATS

Put 2 mL of the milk serum in a test tube, then add two drops of Sudan III in. If lipids are present the Sudan III  is dissolved, and it turns pink in the whole milk. 

6.  TO REVEAL REDUCING GLUCIDS 

• Put 3 mL of milk serum in a test tube.
• Add 3 drops of Fehling A and another 3 of Fehling B and mix it.
• Take a beaker with distilled water and add the test tube in.
• Warn it until the colour changes.

Results: the colour changed  from blue to brown.

Conclusion:  milk contains lactose that is a reducing glucid because is a discard made of glucose and galactose joined by a monocarbonyl bond.  

RESULTS 

MILK	TEST	RESULT
pH	Paper pH	6 – 7
% casein	Calculate it	12'14 %
Proteins	Test Biuret	+
Starch	Lugol	-
Fats	Sudan III	+
Reducing glucids	Fehling Test	+