Carbohydrates

Question 1

General test for Carbohydrates

Answer 1

Molisch’s Test

Question 2

Reagent and positive result for Molisch’s Test

Answer 2

Reagent: [5% α-naphthol + 95% ethanol] + conc. H2SO4 Sulfuric Acid
+ result: violet ring

Question 3

Test for reducing sugars

Answer 3

Benedict’s Test

Question 4

Reagent and positive result Benedict’s Test

Answer 4

Reagent: CuSO4 + Na2CO3 + Na citrate
+ result: brick red ppt. ( - suc, fruc)

Question 5

Test to detect monosaccharides

Answer 5

Barfoed’s Test

Question 6

Reagent and positive result for Barfoed’s Test

Answer 6

Reagent: CuSO4 + acetic acid
+ result: red/brown ppt (5mins for mono) (Fru, Gal, Arab, Glu)

Question 7

Test to distinguish ketose from aldose

Answer 7

Seliwanoff’s Test

Question 8

Reagent and positive result for Seliwanoff’s Test

Answer 8

Reagent: conc. HCl + 1, 3 - dihydroxybenzene (resorcinol)
+ result: cherry-red sol ketose (suc, fruc)

Question 9

Test to distinguish pentose from hexose

Answer 9

Bial’s (Orcinol) Test

Question 10

Reagent and positive result for Bial’s (Orcinol) Test

Answer 10

Reagent: Orcinol (5-methyl-1, 3-dihyroxybenzene)
+ result: blue to green sol. (Pentose; Arab); brown (hexose)

Question 11

Test to detect galactose

Answer 11

Galactaric (Mucic) Acid Test

Question 12

Reagent and positive result for Mucic Acid Test

Answer 12

Reagent: conc. Nitric Acid
+ result: white ppt.

Question 13

Test for starch

Answer 13

Iodine Test

Question 14

Reagent and positive result for Iodine Test

Answer 14

Reagent: I2/Kl
+ result: blue color

Question 15

Test for presence of α-linked disaccharide

Answer 15

Fermentation Test

Question 16

Reagent and positive result for Fermentation Test

Answer 16

Reagent: yeast sol.
+ result: bubbles/release of CO2 (Suc, Mal) (- Lac)

Question 17

Structurally are polyhydroxy aldehyde or ketone

Answer 17

Carbohydrates

Question 18

simple sugar; cannot be broken in smaller groups

Answer 18

Monosaccharides

Question 19

Consists from two to ten simple sugar residue

Answer 19

Oligosaccharides

Question 20

this means that the aldehydes and ketones has several OH groups

Answer 20

Polyhydroxy

Question 21

saccharides that often occur in nature

Answer 21

Disaccharide and Trisaccharide

Question 22

The polymers of simple sugars

Answer 22

Polysaccharide

Question 23

the sweetest sugar; fruit sugar (ketohexose)

Answer 23

Fructose

Question 24

Structure of Fructose

Answer 24

R, = O, C3 ⬇️OH, R

R = CH2OH

Question 25

least fermentable; milk sugar (Aldohexose)

Answer 25

Galactose

Question 26

Structure of Galactose

Answer 26

O=C–H, C4 ⬅️, R

Question 27

Structure of Galactose

Answer 27

O=C–H, C4 ⬅️, R

Question 28

originally commercialized as sweetner; inhibitor of sucrose (Aldopentose)

Answer 28

Arabinose

Question 29

Structure of Arabinose

Answer 29

O=C–H, C3⬇️>, R