lab3

Question 1

The presence of fructose can be detected by using

Answer 1

Seliwanoff’s reagent

Question 2

Seliwanoff’s reagent

Answer 2

(resorcinol solution in hydrochloric acid).

Question 3

Seliwanoff’s test positive result

Answer 3

A salmon or red colour occurs.

Question 4

it is a plant polysaccharide. It is one of the main ingredients of human food.

Answer 4

Starch

Question 5

starch consists of two fractions:

Answer 5

amylose and amylopectin.

Question 6

is a linear unbranched polymer of glucose residues combined with α-1,4-glycosidic bonds.

Answer 6

Amylose

Question 7

contains additional branches,

where there are α-1,6 bonds.

Answer 7

Amylopectin

Question 8

animal polysaccharide - is built similarly to amylopectin, but has a higher degree of branching.

Answer 8

Glycogen

Question 9

Both polysaccharides form coloured products in reaction with iodine. In this reaction, amylose, gives a

Answer 9

blue-coloured product,

Question 10

purple-coloured,

Answer 10

amylopectin

Question 11

a brownish-red colour.

Answer 11

glycogen

Question 12

The degradation products of

starch (dextrins) with long chains (amylodextrins) turn a color _

Answer 12

bluish-violet

Question 13

Products of medium chain length (erytrodextrins) dye

Answer 13

red

Question 14

short chains (achromo-dextrins) take on the

Answer 14

colour of iodine.

Question 15

Starch molecules contained in the starch gruel are surrounded by

Answer 15

a water jacket.

Question 16

The addition of water-binding substances (e.g. ammonium

sulphate) causes the ________ of starch from the solution.

Answer 16

precipitation

Question 17

Baker’s yeast readily ferments glucose, fructose, maltose and sucrose, however it does not ferment

Answer 17

lactose.

Question 18

The end products of this process Baker’s yeast are

Answer 18

ethanol and carbon dioxide.

Question 19

Molisch’s test for Carbohydrates (-) and (+) result

Answer 19

• no color

+ Purple ring

Question 20

Fehling’s test color result

Answer 20

blue to red

(+) red

Question 21

Benedict’s test result

Answer 21

Blue- non
green/yellow- traces of reducing sugar
orange- moderate
brick red- large amount of reducing sugar

Question 22

Fermentation of glucose positive result

Answer 22

gas bubbles

Question 23

Test for fructose

Answer 23

Seliwanoff’s reagent

Question 24

seliwanoff’s color

Answer 24

+ Ketose (monosach)- deep cherry red
+ ketose containg (disach)- cherry red
- Aldose- faint pink/ red
- no color

Question 25

Test for pentoses/bials test

Answer 25

+ green

Question 26

Test with iodine

Answer 26

+ black

- reddish orange

Question 27

sodium potassium tartrate

Answer 27

Fehling’s reagent

Question 28

sodium citrate

Answer 28

(in Benedict’s reagent).