STARCH

Introduction:
Starch is a polysaccharide, that is present in plants. Starch is synthesize with photosintesis.
The objectives of this lab experiment is to test the presence of starch in some leaves.
 
Materials:

-Bunsen burner
-Tripod stand
-Wire gauze
-250 cm3 beaker
-Boiling tube
-Forceps
-Test tube holder
-Leaf to be tested
-90% ethanol 
-Iodine or potassium iodine solution.

Objectives:

- Identify the presence of starch in leaves.

- Relate the presence of starch with photosynthesis.

- Identify the presence of starch in some food.

Procedure:

- Remove a green leaf from a plant that has been exposed to sunlight for few hours.

- Half-fill a 250cm3 beaker with water. Heat the water until it boils. Keep the water at boiling point.

- Use the forceps to place the leaf in the boiling water. Boil for 2 minutes.

- Turn off the Bunsen Burner.

- Place boiled leaf in a boiling tube containing 90% ethanol.

- Place the boiling tube in hot water and boil for 10 minutes or until the leaf decolourizes. (It may be necessary to replace the ethanol).

- Gently remove the leaf and wash with a fine trickle of cold tap water.

- Spread the leaf evenly on a white tile.

-Add a few drops of iodine/potassium iodine solution to the leaf and note any observations.

You could observer some starch spots more dark. Lugol stains specifically starch with a dark-blue.

 Questions:

1.Which is the origin of the starch that you can see in the leaf?

The origin is the photosynthesis.

2.Complete the reaction and write the name of this process?

CO₂ + H₂O-->C₆ H₁₂ O₆ + O₂     

3- Explain the significance of boiling the leaf in water. 
It losesthe turgent condition. 
4- Explain the significance of boiling the leaf in ethanol. 
It loses the color, so the chlorophyll dissapears.
5- Explain the significance of rinsing the leaf in water.
Beacuse the lugol isn't soluble with ethanol. 

SECOND PART:

Introduction:
The objectives of this experiment was to identify starch in differents food.

Material:

- Jam

- Hotdog

- Potato

- Iodine

- Knife

-Three watch glass

Procedure:

- Put each food in different watch glass.

- Open the hotdog in the middle and cut an small piece of potato.

- Then put one piece of hotdog, potato and jam in the watch glasses. 

- Use the dropper to put iodine.

- Finaly compare the potato with the rest.

Observations:

In the photo you can see the potatos colour is different of the rest, because the potato have a lot of starch.