L3. OSMOSIS

INTRODUCTION:

We do an osmosis experiment to know about the osmosis phenomena, that is the spontaneous movement of solvent molecules through a semipermeable membrane into a region of higher solute concentration in the direction that tends to equalize the solute concentrations on the two sides. Now, we understand the process of osmosis in plasmatic membranes. The membranes are semipermeable. The water travel through the plasma membrane in order to the intra and extra cellular concentrations. The important of this practice, is to know when it produce hypertonic concentration that becomes  the plasmolysis, the water moves out to the cell, and hypotonic concentration, that becomes turgid, because the water moves inside the cell. 

MATERIALS:

- Egg

- Potato

- Salt

- Distilled water

- Acetic acid

- Spatula

- 600 mL Beaker

- 3 Clock glass

- Pen

- Spoon

- Knife

PROCEDURE:

EGG: 

The experiment is divided in two parts:  

1). 
We watch that under the hard outer shell of a chicken egg, there is a semipermeable membrane that allows air and moisture to pass throgh. Because water molecules can move into and out of the egg but larger molecules cannot, the semipermeable egg membrane allows for an exploration of concepts of diffusion and osmosis. 

- Before the egg osmosis experiment could begin, the egg's hard outer shell must be removed. Let's start with this:

• Take a 600mL beaker and put inside the egg. And we wait a few minutes to dissolve the shell.  
• Cover the egg with vinegar and make note of what's happening, remembering our experiment of last week.

Once the egg's shell is removed and the egg is rinsed dry and clean, measure and weigh the egg. Record the dimensions off each egg on the paper sheet on the table.

• Clean the beaker and put the egg inside again
• Cover with distilled water. Make note of the volume of solution inside the beaker.

2).

• Left the egg one day in the distilled water. After about a day, carefully remove the egg using a spoon. Rise the egg with water and let it dry.
• Measure again the dimensions and record its weight.
• Make note of the solution volume in the beaker and notice if there has been any difference.
• Observe the results and write your conclusions. 

POTATO:

•  Lay out three watch glass
•  Slice the potato in three parts lengthwise. Each slice must be 1,5cm thick
•  Place each slice onto a watch glass and make a hole in the middle of each slice. (the hole doesn't have to cross the slice).
• In the first hole, don't put anything. In the second one fill it with salt and in the third, put distilled water
• left this preparation 30 minutes approximately, and make note of what is happening.

RESULTS AND CONCLUSIONS:

In our first experiment, with the egg we have observed that when we put the egg with acetic acid the shell that was covering the egg, would undoing. the egg with distilled water bloat, the water is directed toward the semipermeable membrane of the egg. The egg with the pass of the days it becomes viscous. At the end, the dimension of the egg increased for the hypotonic concentration. 

FInally our hypothesis of the last experiment that we made with potatoes, we thought that in the firs slice, with nothing in the hole, there would be no reaction. In the second one, with salt the potato will be flaccid, because the water inside will go out because the potato is a hypotonic and the salt is a hypertonic. And the potato with distilled water, it becomes turgid. In this case the potato it's a hypertonic and the water hypotonic. The objective is to compare the appearance and the turgid of the slices.

QUESTIONS:

EGG EXPERIMENT:

1.- What is happeningwhen the shells are soaking of acetic acid? 
(Ca(CH3COOH)2) and CO2 are produced. This makes bubbles loss.

2.- Write the results of the dimensions and weigh of the egg before and after immersing it in distilled water. Write and draw a simple diagram of the water direction.
Before: 156'0g
after: 186'0g

POTATO EXPERIMENT:

3.- Explain the results of the experiment.

In the first potato was nothing so there have been no changes. 
In the second one we put salt, we can observe that the water  that is inside of the potato has gone out. The cell of the potato has become flaccid. 
In the third one we put distilled water, this water have been disappear and the cell become turgid. 

4.- Why have we left the first slice without any treatment ( salt or distilled water)?
To compare all the results. 

5.- Which are the dependent and independent variables?
The independent variable, we can modify, i mean are the potato with salt and the potato with distilled water.
The dependent isn't modify. 

GENERAL QUESTIONS:

6.- How can you explain (through osmosis) the ability of plant roots to draw water from the soil?
Plants are made up of water and the salt concentration is higher, the water is directed where it is found in the highest concentration of salt.

7.- What will it happen if a saltwater fish is placed in a fresh water (low concentration of salts) aquarium?
It will die. 

8.- Look at the image you have below and explain what is happening to the erythrocytes in each situation:

1. PLASMOLYZED (hypertonic)
2. ISOTONIC (flaccid)
3. TURGID (hypotonic)