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Biomolecules > Qualitative Analysis of Carbohydrates > Flashcards

Qualitative Analysis of Carbohydrates Flashcards

1
Q

skeletons of
covalently bonded carbon atoms

A

organic compounds

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2
Q

are the
major components of cells and tissues

A

organic compounds

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3
Q

They provide energy for life processes, participate and
regulate metabolic reactions, and transmit information

A

organic compounds

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4
Q

Organic molecules in living organisms
can be classified either

A

carbohydrates
proteins
lipids
nucleic acids

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5
Q

are compounds that contain carbon, hydrogen and oxygen.

A

carbohydrates

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6
Q

includes a variety of compounds such as sugars, starches and cellulose.

A

carbohydrates

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7
Q

serve as energy sources for cells, while cellulose are structural components of the walls that
surround plant cells

what compounds (2)

A

sugars
starches

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8
Q

carbohydrates that have one sugar molecule

A

monosaccharides

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9
Q

carbohydrates with two sugar molecules

A

dissacharides

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10
Q

carbohydrates with many sugar unts

A

polysaccharides

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11
Q

is a chemical test which is used to check for the presence of carbohydrates in a given analyte

A

Molisch’s test

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12
Q

a solution of α-naphthol in ethanol

A

Molisch’s reagent

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13
Q

involves the addition of a solution of α-naphthol in ethanol to the analyte and the subsequent addition of a few drops of concentrated H2SO4 to the mixture

A

Molisch’s test

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14
Q

Molisch’s test reagents (2)

A

H2SO4 (sulfuric acid)
α-naphthol in ethanol

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15
Q

The formation of a ___or a ____-red ___at the point of contact between the H2SO4 and the analyte + Molisch’s reagent mixture confirms the presence of carbohydrates in the analyte.

A

purple
purplish-red

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16
Q

A positive reaction for Molisch’s test is given by almost all carbohydrates but exceptions

A

tetrose
triose

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17
Q

some compounds aside from carbohydrates that give positive results for Molisch’s test

A

glycoproteins
nucleic acids

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18
Q

tend to undergo hydrolysis when exposed to strong mineral acids and form monosaccharides

A

glycoproteins
nucleic acids

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19
Q

In Molisch’s test, the carbohydrate (if present) undergoes dehydration upon the introduction of concentrated hydrochloric or sulphuric acid, resulting in the formation of an ____

A

aldehyde

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20
Q

undergoes condensation along with two phenol-type molecules (such as α-naphthol, resorcinol, and thymol), resulting in the formation of a purple or reddish-purple coloured complex.

What kind of compound formed in molisch’s test

A

aldehydes

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21
Q

study the molisch’s test principle

A

+1

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22
Q

Molisch’s teast procedure

A
  1. Add 2 drops of Molisch reagent (prepared by dissolving 0.1g of ∞napthol in 2 mL of
    ethanol) to 2 mL of sugar solution (glucose, fructose, galactose, sucrose, maltose,
    lactose, starch) and mix.
  2. Incline the tube, and gently add 2 mL of concentrated sulfuric acid down the side of
    the test tube.
  3. A purple color at the interface between the sugar and acid indicates a positive result.
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23
Q

is a chemical test that can be used to check for the presence of reducing sugars
in a given sample

A

Benedict’s test

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24
Q

compounds that Benedict test can be used to dientify

A

free ketone/aldehyde

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25
Q

complex mixture of sodium citrate,
sodium carbonate, and the pentahydrate of copper(II) sulfate

A

Benedict’s solution

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26
Q

what is Benedict’s solution made up of (3)

A

sodium citrate
sodium carbonate
copper (II) sulfate

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27
Q

All those carbohydrates which contain a free aldehyde or Ketonic group and reduce Fehling’s solution and Tollen’s reagent are referred as a

A

reducing sugar

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28
Q

galactose, glucose, glyceraldehyde, fructose, ribose, and xylose

examples are

A

reducing sugar

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29
Q

When exposed to ____ sugars, the reactions undergone by Benedict’s reagent result in the
formation of a brick-red precipitate, which indicates a positive Benedict’s test

A

reducing

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30
Q

When a reducing sugar is subjected to heat in the presence of an alkali, it gets converted into
an ___

A

enediol

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31
Q

Therefore, when reducing sugars
are present in the analyte, the cupric ions (Cu2+) in Benedict’s reagent are reduced to ___ ions

A

cuprous (Cu+)

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32
Q

reagent that can be prepared by mixing 17.3 grams of copper sulfate
pentahydrate (CuSO4.5H2O), 100 grams of sodium carbonate (Na2CO3), and 173 grams of
sodium citrate in distilled water (required quantity).

A

Benedict’s reagent

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33
Q

acts a source
of Cu
2+ ions in Benedict’s reagent

A

copper sulfate

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34
Q

in Benedcit’s reagent, provides an alkaline medium

A

sodium carbonate

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35
Q

review the results of Benedict’s test based on color

A

+1

36
Q

can also be used to check for the presence of glucose in a
urine sample since this test detects any aldehydes and α-hydroxy ketones and glucose is an
aldose whose open-chain forms an aldehyde group, the test yields a positive result when
glucose is present in the analyte

A

Benedict’s test

37
Q

However, a positive reaction can also be given by the
presence of ___ ____ in urine

A

ascorbic acid
homogentisic acid

38
Q

False positive reactions may also be obtained if certain drugs are present, e.g. salicylates,
penicillin, streptomycin, isoniazid, and p-aminosalicyclic acid.

what kind of test

A

Benedict’s test

39
Q

Chemicals present in a concentrated urine which may reduce Benedict’s reaction include

A

creatinine
urate
ascorbic acid

40
Q

Benedict’s test procedure

A
  1. Add 1 mL of the 2% sugar solution (glucose, fructose, galactose, sucrose, maltose,
    lactose, starch) to 5 mL of Benedict’s solution (prepared by mixing 10 g sodium
    carbonate and 17.3 g monosodium citrate dehydrate in 85 mL water, and while
    stirring add 10 mL of water containing 1.73 g copper sulfate then to a final volume of
    100 mL).
  2. Place test tubes in a boiling water bath.
  3. Formation of red to brick precipitate is a positive result.
41
Q

an be defined as the most important complex carbohydrate compounds. It is a polysaccharide and glucoside reserve of plants. It is a renewable and biodegradable product, so it can act as a perfect raw material and a substitute for fossil-fuel components in making detergents, glues, plastics, etc.

A

starch

42
Q

comprise a large number of glucose units that are bound together by glycosidic bonds and are produced by all vegetables and other plant sources through the process of photosynthesis.

A

starch

43
Q

performed to test the presence of carbohydrates/starch

A

iodine test

44
Q

is a chemical test used to distinguish mono- or disaccharides from certain polysaccharides like amylase, dextrin, and glycogen.

A

iodine test

45
Q

based on the fact that polyiodide ions form colored adsorption complex with helical chains of glucose residue of amylase (blue-black), dextrin (black), or glycogen (reddish-brown).

A

iodine test

46
Q

what compounds remain colorless in iodine test (3)

A

monosaccharides
disaccharides
branched polysaccharides (e.g. cellulose)

47
Q

produces an orange-yellow hue in iodine test

A

amylopectin

48
Q

aqueous solution of elemental iodine and potassium iodide

A

Lugol’s iodine

49
Q

on its own is insoluble in water

A

Iodine

50
Q

Addition of potassium iodine results in a reversible reaction of the iodine ion with iodine to form a

A

triiodide ion

51
Q

The appearance of blue-black or purple color represents a ___ test, indicating the presence of start

A

positive

52
Q

This test cannot be performed under acidic conditions as the starch hydrolyses under such circumstances

A

acidic conditions

53
Q

iodine test procedures

A
  1. Add 2-3 drops of Lugol/s iodine solution or (pepared by dissolving 1g of iodine and 2
    g potassium iodide in 100 mL distilled water) to 5 mL of 2% sugar solution (glucose,
    fructose, galactose, sucrose, maltose, lactose, starch).
  2. Starch gives a blue-black color.
54
Q

is a chemical test used for detecting the presence of monosaccharides.

A

Barfoed’s test

55
Q

reduction of cupric (II) acetate to cuprous (I) oxide (Cu2O),

A

Barfoed’s test

56
Q

forms a brick-red precipitate when positive

A

Barfoed’s test

57
Q

may react, but the reaction is much slower because they have to get hydrolyzed first and then react with the reagent cupric acetate to produce cuprous oxide

A

Disaccharides

58
Q

brick red precipitate in Barfoed’s test

A

curpous (I) oxide (Cu2O)

59
Q

This test is used to distinguish reducing monosaccharides from disaccharides by controlling pH and the time of heating.

A

Barfoed’s test

60
Q

If a red precipitate is formed within two minutes, it means that a ____is present. If the red precipitate is formed after ten minutes of heating, a ___is present.

A

monosaccharides
disaccharides

61
Q

Barfoed’s reagent is similar to Benedict’s reagent except that the pH is lower/higher (around 4.5), and the heating time is reduced to two minutes.

A

lower

62
Q

____test would determine if the sample is a reducing sugar, and ____test would determine if it is a monosaccharide or disaccharide.

A

Benedict’s test
Barfoed’s test

63
Q

Barfoed’s reagent is composed of
(2)

A

copper acetate monohydrate
glacial acetic acid

64
Q

Barfoed’s reagent

A
  1. Add 1 mL of the 2% sugar solution (glucose, fructose, galactose, sucrose, maltose,
    lactose, starch) to 3 mL of Barfoed’s reagent (Mix 7 g of copper acetate monohydrate
    with 1 mL of glacial acetic acid in distilled water and make the final volume 100
    mL).
  2. Place test tubes into boiling water bath and heat for 3-10 minutes. Remove the tubes
    from the bath and allow cooling.
  3. Formation of scanty red precipitate is a positive result.
65
Q

is used to differentiate between sugars that have a ketone group (ketose) and sugars that have an aldehyde group (aldoses).

A

Seliwanoff’s test

66
Q

Seliwanoff’s reagent consists of

A

resorcinol
concentrated HCl

67
Q

are more rapidly dehydrated than aldoses

A

ketoses

68
Q

Ketoses undergo dehydration in the presence of concentrated acid to yield

A

5-hydroxymethy furfural

69
Q

complex produced when dehydrated ketose reacts with two equivalents of resorcinol in series of condensation reactions

A

xanthenoid

70
Q

deep cherry red complex seen in positive seliwanoff’s test

A

xanthenoid

71
Q

Other carbohydrates like sucrose and inulin also give a positive result for this test as these are hydrolyzed by acid to give ___

A

fructose

72
Q

is used in the method for the colorimetric determination of fructose in fermentation media.

A

Selifwanoff’s color reaction

73
Q

Seliwanoff’s test procedures

A
  1. Add 1 mL of 1% sugar solution (glucose, fructose, galactose, sucrose, maltose,
    lactose, starch) to 10 mL of the reagent (Dissolve 0.1 g resorcinol in 33 mL
    concentrated hydrochloric acid (HCl) and make the final volume of 100 mL).
  2. Heat the solution in boiling water bath for 5 minutes.
  3. A deep cherry or red color within 5 minutes is a positive result.
74
Q

Silver mirror test (Tollen’s reagent) procedures

A
  1. Wash the tube with a 10% solution of sodium hydroxide (1g NaOH in 10 mL distilled
    water).
  2. Add 2 mL of a 5% (0.5g in 10 mL distilled water) silver nitrate solution (AgNO3) into
    the washed tube, then add one drop of the 10% sodium hydroxide solution.
  3. Add one drop of 28% ammonia solution (add more drops if necessary). Shake
    constantly until silver oxide dissolves, then add 1 mL of 2% sugar solution.
  4. The formation of a silver mirror in the inner surface of the test tube is a positive
    result.
75
Q

is a qualitative laboratory test used to distinguish between an aldehyde and a ketone by exploiting the fact that aldehydes are readily oxidized

A

Tollens’ test

76
Q

Tollen’s reagent is composed of

A

alkaline silver nitrate
aqueous ammonia

77
Q

alkaline silver nitrate chemical formula

A

AgNo3

78
Q

aqueous ammonia solution

A

NH4OH

79
Q

The reaction is accompanied by the reduction of silver ions into metallic silver

A

Tollen’s test

80
Q

must be worn all the time inside the laboratory and especially
when handling the following chemicals

A

protective gloves

81
Q

may cause liver, kidney damage, blood abnormalities, and severe eye
irritation

A

1-Naphthol

82
Q

is extremely corrosive and can cause serious
burns when not handled properly

A

Sulfuric acid

83
Q

(may cause eye and skin irritation

A

resorcinol

84
Q

may explode if heated. Causes severe skin burns

A

Ammonia

85
Q

If swallowed, causes severe irritation and chemical burns to the
gastrointestinal tract, and can cause permanent eye damage/blindness

A

Sodium hydroxide

86
Q

study the table for positive reactions in sugar solution

A

+1

Biomolecules (5 decks)

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