L5: SACCHARIDES PROPERTIES

L5: Saccharides properties

1. Introduction

Saccharides are organic molecules consisting of C, H and O atoms. The empirical formula is CnH2nOn.

The groups are:

• Monosaccharides: formed by a linear carbon chain, are the building blocks of oligo and polysaccharides. They have a one functional group: centone or aldehyde.

• Oligosaccharides: small plymer containing between 2 and 10 monosacharides.

• Polysaccharides: big polymers with more than 10 monosaccharides.

Saccharides yield 4,2Kcal/gr and are abundant in fruits, sweets, honey, beans, tubers, rice, pastas and cereals.


2. Objectives

1. Identify different sugars from its properties.
2. Differentiate mono and disaccharides.
3. Understand the relation between structure and some properties.

3. Hypotesis

The hypotesis is to differentiate the disaccharides and polysaccharides with their properties.

4. Material

• Test tube rack
• 10ml Pipet
• Distilled water
• 5 test tubes
• 1 dropper
• 5 spatula

• Lactose
• Maltose
• Glucose
• Sucrose
• Starch
• Lugol's iodine
• Distilled water

5. Procedure

First of all, we took 5 test tubes and test tube rack and one mark each test tube with the initial if it was lactose, maltose, glucose, sucrose ans starch. 

when we had all the saccharides in the corresponding test tube look if you had the properties of saccharides: flavor (sweet / not sweet), crystalline form, color (white / cream). 

when we saw these properties, we put 5ml of water in each test tube, to see the property of solubility (soluble / insoluble) using 10ml pipet. 

Then we took the Lugol's iodone and put a drop in house test tube with dropper. The test tube that was put Canvio dark color, I wanted to say was polysaccharides. In this case it was the starch.

6. Observations

Thanks to the properties of saccharides we could see that the starch was not a disaccharides is a polysaccharides, as it was the only one that had colored cream, was not soluble and with Lugol's iodine test was positive.

7.Conclusions

Lactose, maltose, glucose, and sucrose are disaccharides that meet these properties, while the starch is polysaccharides.

8. Questions


1. Write the empirical formula of each saccharides that you have use. Show of the five saccharies. Classify each one in one group: mono, oligo or polysaccharides.

(CnH2nOn)^N - String name

C6H12O6 = glucose - monosaccharides
C12H22O12 = maltose - disaccharides
C12H22O11 = sucrose - disaccharides
C12H22O11 = lactose - disaccharides

starch - polysaccharides

2. Which of the monosaccharides are aldoses and which are ketoses?

glucose - aldoses
maltose - aldoses
sucurose - ketoses
lactose - aldoses
starch - aldoses

3. Which bond links monosaccharides?

o-glicosidic

4. Which saccharide/s is /are sweet? Is this property related to structure of the molecule?

All saccharides aren't sweet, except the starch that is sweet.

5. Which saccharide/s is/are insoluble? Is this property related to structure of the molecule?

Starch because is a very big molecule and it have a molecular weight high.

6. Which saccharide has reacted with lugol's iode solution?

Starch

7. Which kind of foods contain starch?

fluor, cereals, rice..

8. Calculate the energy from the nutrition facts label from a cereal:

a) Calculate the energy that comes from the saccharides.

23gr saccharides ------ 4,2gr · 23 gr = 96,6 kcal

b) Which % of the total energy comes from the saccharides?