Monosaccharides and Disaccharides Flashcards
What do glucose and glucose form when they join?
Maltose
What do glucose and fructose join to form?
Sucrose
What do glucose and galactose join to form?
Lactose
What happens when monosaccharides join together?
A molecule of water is removed and the reaction is therefore called a condensation reaction.
What is the bond that is formed when monosaccharides join together and lose a molecule of water?
A glycosidic bond.
What happens when water is added to a disaccharide under suitable conditions?
It breaks the glycosidic bond releasing the constituent monosaccharides. This is called hydrolysis.
How do we test for reducing/ non-reducing sugars?
We use Benedict’s test.
How do we deter,one if something is a non-sugar?
They do not change the colour of Benedict’s Reagent when they are heated with it. In order to detect a non-reducing sugar it must first be hydrolysed into its monosaccharide components by hydrolysis.
What do the colours that the Benedict’s reagent turn into mean?
Green- very low
Yellow- low
Brown- medium
Brick-red/ orange-red- high
What is the method to test for reducing sugars?
- Add 2cm^3 of the sample to be tested to a test tube. If the sample is not already in liquid form, first grind it up in water.
- Add 2cm^3 of Benedict’s reagent.
- Heat the mixture in a gently boiling water bath for 5 minutes.
What are NOT reducing sugars?
Sucrose and polysaccharides
What is the method that tests for non-reducing sugars?
- Add 2cm^3 of the sample to be tested to a test tube. Then add 2cm^3 of dilute hydrochloric acid. Heat for 3 minutes to hydrolyse the glycosidic bond.
- Add solution hydrogen carbonate powder to neutralise the solution (should fizz).
- Add 2cm^3 of Benedict’s reagent and heat the mixture in gently boiling water bath for 5 minutes.
What type of structure does starch have?
Starch has an alpha-helical structure.This makes it good for storage as it is compact
What does starch’s structure mean?
Starch is insoluble due to its structure. Therefore, it doesn’t affect water concentration/ osmosis.
What other properties does starch have?
It is the main way that plants store sugar. It is large so cannot diffuse out of cells. When it is hydrolysed it forms a-glucose. It rarely has branches so many enzymes can act on one molecule
Where is starch found?
Starch is found in plants but never animals.
How do we test for starch?
The iodine test is used. The product will turn blue/ black if starch is present
What is cellulose?
Polymer of b-glucose
Each monomer is inverted
What consequences does cellulose have because of its properties?
Forms chains which run parallel with hydrogen bonds between the chains to form microfibrils.
Microfibrils are strong- they group together to form fibres.
Being fibrous (able to make fibres), cellulose is structurally important in plant cell walls.
What structure does glycogen have?
It has a similar structure to starch.
Where is glycogen found?
Found in animals and bacteria- never plants.
How is glycogen different to starch?
Shorter chains and more branches than starch. It is found in granules in the muscles and liver
What properties does glycogen have?
Insoluble so does not affect osmosis.
Compact
More branched than starch so more attachment places for enzymes
