Slides in this set
· Contain only the elements Carbon, Hydrogen and Oxygen.
· As well as sugars, carbohydrates include starch, glycogen and cellulose.
Monosaccharides Disaccharides e. Polysaccharides
(monomers) e.g. g. sucrose, (polymers) e.g.
glucose, fructose, maltose, lactose starch, cellulose,
galactose glycogen…read more
· The word means 'single sugar'.
· They have the general formula (CH O)n - The letter 'n' can be any number from
3 to 7.
· They are classified according to the value of n:
- trioses n= 3
- tetrose n= 4
- pentoses n= 5
- hexoses n= 6
- heptoses n= 7
· The most common and important monosaccharide is glucose, which so a six-
carbon or hexose sugar, so has a formula C H O .
· There are two forms of glucose alpha () and beta ().
· Alpha glucose molecules combine to form starch.
· Beta glucose molecules combine to form cellulose.
· There are many isomers of glucose, these are galactose and fructose.…read more
· Formed when two monosaccharide's join together by a glycosidic bond (to form a
· Called a condensation reaction because two molecules combine into one bigger
one. (the removal of a water molecule)
· Hydrolysis reaction is when a large molecule is broken into smaller ones by
reacting with water.
· Three common disaccharides:
- maltose (2 glucose molecules) - formed on digestion of starch by amylase,
enzyme breaks starch down into 2 glucose units.
- sucrose (glucose and fructose)
- lactose (glucose and galactose)
· Lactose is a disaccharide formed by the combination of 2 monosaccharide's; glucose
· Lactose is digested by the disaccharide enzyme lactase to glucose and galactose.
Lactose Glucose + Galactose
· If you don't have enough of the enzyme Lactase, you wont be able to breakdown the
lactose in milk properly- this is called lactose intolerance.
· Lactose is normally found in the microvilli of cells in the wall of the small intestine.
· After lactase breaks down lactose into glucose and galactose, the liver converts the
galactose into glucose.
· Lactase deficiency can be primary or secondary: Primary develops with age, it is
usually inherited and is due to a faulty gene. Secondary occurs when a person cannot
produce enough lactase because of damage to the small intestine through injury or a
· Lactose Intolerance Test:
The person fasts before the test, they are then given a drink containing lactose.
Several blood tests are taken over a 2 hour period and the persons blood glucose levels
are tested (these indicated how efficiently the lactose had been digested). If lactose
is not broken down completely, the blood glucose levels do not rise and so the person is
lactose intolerant.…read more
Reducing and non-reducing sugars
· All monosaccharide's and some disaccharides (maltose and lactose) but not all
are reducing sugars, because they reduce ions.
· You add BENEDICT'S REAGENT (which is blue) to a sample, shake it and then
· If it turns brown or red then there is sugar present.
Non- reducing sugar:
· Sucrose (disaccharide) is a non-reducing sugar.
· First you need to break (hydrolyse) it down into monosaccharide's. You do this
boiling the test solution with dilute hydrochloric acid and then neutralising it
with sodium hydrogen carbonate. Then carry out the Benedict's test.…read more