lab3 Flashcards
The presence of fructose can be detected by using
Seliwanoff’s reagent
Seliwanoff’s reagent
(resorcinol solution in hydrochloric acid).
Seliwanoff’s test positive result
A salmon or red colour occurs.
it is a plant polysaccharide. It is one of the main ingredients of human food.
Starch
starch consists of two fractions:
amylose and amylopectin.
is a linear unbranched polymer of glucose residues combined with α-1,4-glycosidic bonds.
Amylose
contains additional branches,
where there are α-1,6 bonds.
Amylopectin
animal polysaccharide - is built similarly to amylopectin, but has a higher degree of branching.
Glycogen
Both polysaccharides form coloured products in reaction with iodine. In this reaction, amylose, gives a
blue-coloured product,
purple-coloured,
amylopectin
a brownish-red colour.
glycogen
The degradation products of
starch (dextrins) with long chains (amylodextrins) turn a color _
bluish-violet
Products of medium chain length (erytrodextrins) dye
red
short chains (achromo-dextrins) take on the
colour of iodine.
Starch molecules contained in the starch gruel are surrounded by
a water jacket.
The addition of water-binding substances (e.g. ammonium
sulphate) causes the ________ of starch from the solution.
precipitation
Baker’s yeast readily ferments glucose, fructose, maltose and sucrose, however it does not ferment
lactose.
The end products of this process Baker’s yeast are
ethanol and carbon dioxide.
Molisch’s test for Carbohydrates (-) and (+) result
- no color
+ Purple ring
Fehling’s test color result
blue to red
(+) red
Benedict’s test result
Blue- non
green/yellow- traces of reducing sugar
orange- moderate
brick red- large amount of reducing sugar
Fermentation of glucose positive result
gas bubbles
Test for fructose
Seliwanoff’s reagent
seliwanoff’s color
+ Ketose (monosach)- deep cherry red
+ ketose containg (disach)- cherry red
- Aldose- faint pink/ red
- no color
