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(JJ) BIOCHEMISTRY > carbs powerpoint (lab) > Flashcards

carbs powerpoint (lab) Flashcards

1
Q

Molisch’s Test named after…?

A

Austrian botanist Hans Molisch

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2
Q

molischs test for the presence of _________________

A

carbohydrates

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3
Q

Reagents: A solution of naphthol in ethanol (95%)
* Sample: 2ml of 5% solution s of glucose, sucrose and starch

A

Molisch’s test

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4
Q

A positive
reaction is indicated by appearance of a PURPLE RING at the interface between the acid
and test layers.

A

Molisch’s test

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5
Q

Glycosidic bonds are hydrolyzed by conc. H2SO4, producing monosaccharides, dehydrated to furfural-forming substances — a
negative result is a good evidence of the absence of carbohydrates.

A

Molisch’s test

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6
Q

All carbohydrates – monosaccharides,
disaccharides, and polysaccharides – should
give a positive reaction

A

Molisch’s test

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7
Q

Reagent: NaOH (used to neutralize citric acid added for
hydrolysis)
* Sample: 1 ml of 5% glucose solution
1 ml of 5% sucrose solution
1 ml of 5% starch solution
Boiled and note the odor and color

A

Moore’s Test

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8
Q

Test is based on the liberation of aldehyde
A positive result will give a brown color with caramel like odor

A

Moore’s Test

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9
Q
  • Sucrose negative result (no free aldehyde group), Colorless
  • Glucose and Starch positive result
A

Moore’s Test

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10
Q

The Anthrone test is another general test for…?

A

carbohydrates

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11
Q

The H2SO4 hydrolyses
bound sugars to yield furfural or furfural derivatives. This reacts with __________ to form
colored compounds.

A

anthrone

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12
Q

Sample: 1 ml of 5% glucose solution, 1 ml of 5% sucrose solution, 1 ml of 5% starch
solution
Positive Result: Bluish green complex
All

A

anthrone test

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13
Q

The furfural or hydroxyfurfural formed condenses with two molecules of
napthol from anthrone reagent to form a ____-______ complex.

A

blue-green

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14
Q

Anthrone test and Molisch test are two types of _________ tests.

A

analytical

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15
Q

key difference between Anthrone and Molisch test

A

anthrone: detect carbs in blue-green
molisch: detect carbs in violet

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16
Q

formation of a crystalline dicarboxylic acid that is insoluble in dilute HNO3 (Nitric
Acid);
reaction unique for galactose and galactose compounds.

A

Mucic acid test

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17
Q

______ Acid – (colorless) catalyzes the hydrolysis of lactose to glucose and galactose, then oxidizes
both sugars to the _________________ acids (mucic acid crystals)

A

Nitric; tetrahydroxy

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18
Q

Specific test for galactose

A

Mucic acid test

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19
Q

Results: Galactose - white sandy precipitate
□ Lactose -white flakes precipitate
□ Glucose - Negative

A

Mucic acid test

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20
Q

(Theodor Seliwanoff)

A

Seliwanoff ’s Test

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21
Q

_______ is a chemical product resulting from the hydrolysis of pentoses

A

Furfural

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22
Q

Ketoses undergo dehydration to yield furfural derivatives more rapidly than aldoses, and form
complexes with resorcinol which are colored.

A

Seliwanoff ’s Test

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23
Q

Test to distinguish aldose (-) from ketose (+)
- Specific test for fructose
- Useful for detecting the presence of ketose

A

Seliwanoff ’s Test

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24
Q

Results:
- Sucrose and Fructose ⇛ Red/Cherry Red
- Lactose, Maltose, Glucose and Galactose ⇛ yellow

A

Seliwanoff ’s Test

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25
Q

Why should glucose and maltose give positive results upon
prolonged boiling with seliwanoff’s Reagents?

A
  • The high concentration of glucose or other sugar may interfere by
    producing similar colored compounds with seliwanoff’s reagent.
26
Q

(Seliwanoff’s Test) Prolonged boiling can transform __________ to __________ by catalytic
action of acid and form cherry red complex giving a false- positive
result.

A

glucose to fructose

27
Q
  • A color reaction that is specific for pentoses.
A

BIAL’S TEST

28
Q

(Bial’s test) It involves the decomposition
of these sugars when heated with conc. HCl (dehydrating agent) to
furfural, which condenses with orcinol (3,5- dihydroxytoluene) to form _________ to _________ colored compounds.

A

blue
to green

29
Q

Sample: 5% ribose, glucose, fructose, galactose, maltose, lactose, sucrose
* Reagents: Orcinol, conc. HCl, Ferric chloride
* Result:
- Positive: Ribose (Pentose, 5 carbons)

A

Bial’s test

30
Q

Detecting Dextrin from Starch

A

IODINE TEST

31
Q

Iodine Test for Starch

A

deep blue

32
Q

(Iodine test) Preparation of Dextrin from starch

A

violet

33
Q

(Iodine test) Gum Arabic ( a non-digestible carbohydrate) with Iodine

A

No blue or red-brown color

34
Q

(Iodine test) Agar-agar (starch) with Iodine –

A

dark brown color

35
Q
  • a galactose based heterogenous polysaccharide derived
    from algae
A

Agar-agar (starch)

36
Q

is a REDUCITON chemical test used to differentiate
between water-soluble aldehyde and ketone functional
groups,

A

Fehling’s Test

37
Q

The REDUCTION test was developed by German chemist Hermann von
Fehling in 1849.

A

Fehling’s Test

38
Q

Fehling’s A is a _____ _________
solution of copper(II) sulfate

A

blue aqueous

39
Q

Fehling’s B is a _____ solution of aqueous potassium sodium
tartrate (also known as Rochelle salt) and a strong alkali
(commonly sodium hydroxide).

A

clear

40
Q

Equal volumes of the two mixtures are mixed together to get
the final Fehling’s solution, which is a deep _______ color

A

blue

41
Q

A positive result is indicated by the formation of a brick red
precipitate

A

fehling’s test

42
Q

All sugar solutions produced a Brick red ppt except:
- Sucrose- Blue solution

A

fehling’s test

43
Q

sugars that doesn’t have any free ketone or aldehyde groups

A

NON- REDUCING SUGARS

44
Q

is sucrose a non-reducing sugar?

A

yes

45
Q

like glucose and lactose, have
free ketone or aldehyde functional groups,
which enable the formation of a hemiacetal

A

reducing sugars

46
Q

Benedict’s Test

A

test for the presence of
reducing sugars.

47
Q

determines the presence of
non-reducing sugars in a test solution.

A

Benedict’s Test for non-reducing sugars

48
Q

(benedict’s test)
- copper(II) sulphate/cupric sulfate
- sodium carbonate
- sodium citrate

A

The principal reagent in Benedict’s Test for Reducing Sugars

49
Q

(benedict’s test) sugars which do not have an aldehyde or a
keto functional group - the reducing species

A

Non-reducing sugars

50
Q

(benedict’s test) The absence of the aldehyde or keto group, cannot reduce ______ (__)
(blue) to the _______ (__) (red).

A

copper (II); copper(I)

51
Q

(benedict’s test) Sucrose is the most common disaccharide ___-___________ sugar.

A

non-reducing

52
Q

A Positive test produced a BRICK RED PRECIPITATE.
- (from blue to green to yellow to orange to brick red)

A

benedict’s test

53
Q

used to test forthe presence of
glucose in urine.

A

benedict’s test

54
Q

TRUE/FALSE? Only glucose is indicative of diabetes.

A

TRUE

55
Q

presence of reducing sugars.

A

NYLANDER’S TEST

56
Q
  • Indicated by the formation of a dark brown to black precipitate
  • all sugars are positive except for Sucrose
A

NYLANDER’S TEST

57
Q

Yellow color; Reducing sugars will give a mahogany red color due to
the formation of sodium picramate

A

Picric acid test

58
Q

detecting the
presence of monosaccharides from disaccharides.

A

Barfoed’s test

59
Q

invented by Danish chemist ________ _________ Barfoed
and is primarily used in botany

A

CHRISTEN THOMSEN

60
Q

Disaccharides may also react, but the reaction is much
slower.) thus they produced a negative results (blue solution)

Monosaccharides produced a brick red precipitate.

A

BARFOED

61
Q

What product is formed when picric acid is reduced?

A

Sodium picramate

(JJ) BIOCHEMISTRY (11 decks)

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