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.

 

FEHLING'S TEST: REDUCING SUGARS

Introduction:

Fehling's solution is a chemical test used to differentitate between reducing and non-reducing sugars. This test is based on the reaction of a functional group of sugar molecules with Fehling's reagent. Fehling's have two separate solutions:

Fehling's reagent has to separate solutions: Fehling's A and Fehling's B.

Fehling's A: is a blue aqueous solution of copper (II) sulphate.

Fehling's B: clear and colourless solution of potassium sodium tartrate and sodium hydroxide.

Materials:

-Test tube rack

-10mL Pipet

-Distilled water

-5 test tubes

-5 spatula

-Lactose

-Maltose

-Glucose

-Sucrose

-Starch

-Fehling's A and B solutions

-HCl

Objectives:

- Identify reducing sugars.

- Comprehend redox reactions.

- Understand the relation between structure and reducing ability of some sugars.

Procedure:

1. Take 5 test tubes and label: G, M, S, L, ST

2. Put 2mL of distilled water inside each tube.

3. With different spatulas put a small amount of each sugar. Dissolve the sugar.

4. Add 2mL of Fehling's A solution and then Fehling's B.

5. Place each test-tube in a boiling water bath (250 mL beaker on a hotplate stirrer).

6. Observe what is happening.

Starch Hydrolysis: 

7. Place 2mL of 1% starch in a test tube and add 0,5 mL of 3M HCL. Mix and place this mixture in a boiling water bath for 10 minutes.

8. After 10 minutes, remove the tube from the water bath and let it cool. Neutralize this solution with 1M NaOH and mix well.

9. Transfer 10 drops of this solution to a small test tube.

10. Add 1mL of Fehling's A solution and 1mL of Feghling's B.

11. Heat for a few minutes in a boiling water bath.

12. Record your observations. Compare the results of this test with your results for unhydrolyzed starch in the step 1 of this experiment.

Observations: 

-Lactose: has reducing power

-Maltose: has reducing power

-Glucose: has reducing power

-Sucrose: doesn't have reducing power

-Starch: doesn't have reducing power

SACCHARIDES PROPERTIES

Introduction:
Saccharides are organic molecules consisting of C, H and O atoms. The empirical formula usually is Cn H2n On. Are divided in two groups:
    -Monosaccharides: formed by linear a carbon chain, are the building blocks of oligo and polysaccharides. They have a one functional group: cetone (C=O) or aldehyde (COH). 
    -Oligosaccharides: small polymer containing between 2 and 10 monosaccharides.
    -Polysaccharides: big polymers with more than 10 monosaccharides.

Materials:

-Test tube rack

-10mL Pipet

- 5 spatula

-5 test tubes

-1 dropper

-Distilled water

-Lactose
-Maltose
-Glucose
-Sucrose
-Starch
-Lugol's  iodine

Objectives: 

1- Identify different sugars from its properties.

2- Differentiate monosaccharides and disaccharides.

3- Understand the relation between structure and some proporties.

Procedure:

We started off by testing some physical properties of the saccharides we have in the lab, such as flavour, the structure and color.

To test the flavour we tasted a small part of each saccharide, and we asked ourselves wether it was sweet or sour?

And by obvserving a small amount of each saccharide under magnification we tested the crystal.

Lastly we tested the color of each element, was it creamy, white or transparent?

	GLUCOSE	MALTOSE	SUCROSE		LACTOSE	STARCH
Flavour	sweet	sweet	sweet		no sweet	no sweet
Clystalline	crystaline	no crystaline	crystaline		powder	crystaline
Colour	white	cream	white		white	white
Solubility	soluble	insoluble	soluble		soluble	insoluble
Lugol’s iodine	negative	negative		negative	negative	positive

TO TEST SOLUBILITY:

- Clean and dry 5 test tubes and label them: G, M, L, SU, S

-Pour 5mL of water in each test tube.

-With the help of a spatula, put a small amount of each saccharide inside the labelled test tube and test if they are soluble or insoluble.

- Observe is each saccharide forms a mixture called dissolution or a colloidal suspension.

- Finally, add 2 drops of Lugol's iodine to each test tube and test if the reaction is positive or negative. Lugol's is a solution of elemental iodine (I) and potassium iodine (KI) in water that is ise to test a saccharide. The reaction is positive if iodine reacts by turning from yellow to a purple, dark-blueish colour.