P5: Saccharides properties

P5 .Saccharides properties



    INTRODUCTION

Saccharides are organic molecules consisting of C,H and O atoms. Usually the empirical formula is Cn H2n On  Are divided into three groups:

Monosaccharides: Formed by a linear carbon chain, are the building blocks of oligo and polyacchareides.They have a one funcional group:cetone (C=O) or aldehyde (COH). Pentoses and hexoses can switch from acyciclic to cyclic forms called furanoses and pyranoses. Ex Glucoses,galactoses or fructoses.
Oligosaccharides: small polymer containing between 2 and 10 monosacharides. Ex .Lactose,sucrose or maltose.
Polyasacchairides: Big polymers with more than 10 monosacchair .Ex Starch glycogen,cellulose and chiti
These molecules perform numerous roles in living organisms like storage if energy (starch,glycogen ),structural components cellulose, ribose,chitin or desoxiribose)

Saccaharides yield 4,2 Kcal /gr and are abundant in fruits,sweets,honey,tubers,rice,pastas and cereals. They are a common source of energy in living organisms


Objectives:

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

Material :

Test tube rack
10ml pipet
Dostilled water
5 test tubes
1dropper
5 Spatula
Lactose
Maltose
Glucose
Sucrose
Starch
Lugol's iodine
Distilled water

Procedure:

Complete the properties ' table that you have below from the 5saccharides you have at the lab:

	Glucose(G)	Maltose(M)	Sucrose(SU)	Lactose (L)	Starch(S)
Flavour sweet/ no sweet	NO SWEET	SWEET	VERY SWETT	NO SWEET	NO SWEET
Crystalline form	YES	NO	YES	NO	NO
Colour (White/Cream)	WHITE	WHITE	WHITE	WHITE	WHITE
Solubility soluble/insoluble)	YES	YES	YES	YES	NO
Lugol’s iodine +/-	-	-	-	-	+

1 -In the first part of the experiment we are going to test some physical properties of the saccharides you have in the lab : flavour , cryatal structure and colour .How?

   a) Flavour:Put a small amount of each saccharide in your hand and taste it!Is it sweet or not sweet?
   b) Crystals: Observe a small amount of each saccharide on a clok glass under magnification.
   c )Colour: white ,transparend or creamy

 To test solubility:

2 Clear and dry 5 test tubes and label them "G,M,L,SU,S"
3 Put 5ml of water in each test tube
4 With the aid of a spatula, put a small amount of each saccharide inside the labelled test tube and test if they are soluble or insoluble .
4 Observer if each saccharide forms a mixture called dissolution or a colloidad suspencio

Lugol's iodine Test:

6 Finally,add 2 drop of Lugol's iodine to each test tube and test if the reaction is positive or negative.Lugol's ia a solution of elementari iodine(|) and potassium iodine (KI) in water that is use to test a saccharide.The reaction is positive when iodine reacts by turning from yellow to a purple, dark-blue/ black colour.


QUESTIONS:

1-Write the empirical formulaof each saccharides  thaty you have use.Show structures of the five saccharides.Classiify eeach one in one group: mono,oligo or polysaccharide.
Disacarid ,Lactose( C12H 22O 11H 2O )( C6H10O5) Polisacare and glicos-n. Gluctosa,Fructosa C12H22O11 Disugre( C6H12O11) Maltosa disacarid (C12H22O11)

2- Which of the monosaccharides are aldoses and which are ketoses?
Polysaccharides were those who were not sweet unless it was a lactose monosaccharide
3- Which bond links monosaccharides?
Aldehyde link
4-Which saccharide/s is / are sweet? Is this property related to the structure of thr molecule?
Maltose binding aldei i ketone link sucrose

5- Which saccharides/ s is/ are insoluble?Is property rerlated to the structure of the molecule?
Are insoluble G, M, L SUB link aldosa

6-Whitch saccharide has reacted with Lugol's iodine solution?
Reacted Starch
7-Which kind of foods contain starch ?
Flour
8-Calculate the energy from the nutrion facts label from a cereal:
        a) Calculate the energy that coments from the saccharides.
                96,6
        b) Which% of the total energy come from the saccharides?
               0,4%