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Biochemistry > Experiment 6: Qualitative Analysis of Carbohydrates > Flashcards

Experiment 6: Qualitative Analysis of Carbohydrates Flashcards

1
Q

Carbohydrates

A

Hydrate of carbon
Empirical Formula: CnH2nOn or Cn(H2O)n

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2
Q

Disaccharide

A

Two monosaccharide units connected by glycosidic bond

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3
Q

Polysaccharide

A

Hundreds-thousands of monosaccharide units connected by glycosidic bond

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4
Q

Molisch Test Purpose

A

Test ALL carbohydrates

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5
Q

Molisch Test Reagent

A

alpha-naphthol with sulfuric acid

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6
Q

Molisch Test Positive and Negative Result

A

Positive: Purple ring at the interface
Negative: Colorless

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7
Q

Molisch Test Reaction

A

(1) Dehydration of carbohydrate to alkene
(2) Formation alpha-naphthol complex

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8
Q

Molisch Test Procedure

A
  1. +5 drops of Molisch reagent in each test tube
  2. TIlt test tubes
  3. +15 drops of concentrated sulfuric acid to flow down
  4. Note observations
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9
Q

Iodine Test Purpose

A

Find starch and glycogen (storage)

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10
Q

Iodine Test Reagent

A

Iodine Solution

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11
Q

Iodine Test Positive and Negative Result

A

Positive: Dark blue mixture
Negative: Yellow (iodine solution)

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12
Q

Iodine Test Reaction

A

Formation of Iodine complex
-I2 in KI+I—->I3- (surrounded by starch)

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13
Q

Iodine Test Procedure

A
  1. +5 drops of iodine solution into each test tube
  2. Note observations
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14
Q

Benedict Test Purpose

A

Detect reducing sugars (have free anomeric carbon

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15
Q

Benedict Test Reagent

A

Copper (II) sulfate in citrate and carbonate (basic)

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16
Q

Benedict Test Positive and Negative Result

A

Positive: Red-orange solution
Negative: Green blue solution (copper color)

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17
Q

Benedict Test Reaction

A

Oxidation of free aldehyde or ketone group (results in ring opening) and formation of brick-red precipitate (Cu2O)

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18
Q

Benedict Test Procedure

A
  1. +25 drops of Benedict’s reagent into each test tube
  2. Heat test tubes in boiling water for 2 minutes.
  3. Remove and note observations
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19
Q

Barfoed’s Test Purpose

A

Differentiate monosaccharide to disaccharide

20
Q

Barfoed’s Test Reagent

A

Copper (II) acetate in glacial acetic acid (acidic environment)

21
Q

Barfoed’s Test Positive and Negative Result

A

Monosaccharide: Fast formation of red precipitate
Disaccharide: Slow formation of red precipitation (Needs to break the glycosidic bond and to reveal anomeric carbon)

22
Q

Barfoed’s Test Reaction

A

Oxidation of free aldehyde or ketone group (ring opening) and formation of brick-red precipitate (Cu2O)

23
Q

Barfoed’s Test Procedure

A
  1. +25 drops of Barfoed’s reagent
  2. Heat for 5 minutes
  3. Record time (fast formation of precipitate is monosaccharide, slow is disaccharide)
24
Q

Seliwanoff’s Test Purpose

A

Detect ketose

25
Q

Seliwanoff’s Test Reagent

A

Resorcinol in concentrated HCl

26
Q

Seliwanoff’s Test Positive and Negative Result

A

Positive: Cherry Red solution (or slightly pink)
Negative: No significant color changes (color based on HCl color)

27
Q

Seliwanoff’s Test Reaction

A

(1) Dehydration of ketohexose to 5-hydroxymethylfurfural

(2) Complexation of resorcinol to 5-hydromethylfurfural (creates the red color)

28
Q

Seliwanoff’s Test Procedure

A
  1. +25 drops of Seliwanoff’s reagent into each test tube
  2. Heat test tubes in boiling water bath
  3. Take note of color changes and time it takes for it to form
29
Q

Bial’s Test Purpose

A

Find pentose

30
Q

Bial’s Test Reagent

A

Orcinol, ferric (III) chloride (catalyst), concentrated HCl

31
Q

Bial’s Test Reaction

A

(1) Dehydration of pentose to furfural
(2) Formation of orcinol complex

32
Q

Bial’s Test Positive and Negative Result

A

Positive: Blue green solution (FeCl3)
Negative: Yellow (Concentrated HCl color)

33
Q

Bial’s Test Procedure

A
  1. +25 drops of Bial’s Orcinol reagent
  2. Heat test tubes in boiling water and note observations
34
Q

Samples that got positive results in Molisch Test

A

All of them

35
Q

Samples that got positive results in Iodine test

A

Amylose

36
Q

Samples that got positive results in Benedict Test

A

Xylose, glucose, galactose, fructose, maltose, lactose

37
Q

Samples that got positive results in Barfoed’s Test

A

Xylose, glucose, galactose, fructose, maltose (slow), lactose (slow)

38
Q

Samples that got positive results in Seliwanoff Test

A

Fructose amd sucrose

39
Q

Samples that got positive results in Bial’s Test

A

Xylose

40
Q

Xylose structure

A

-Aldopentose (5 carbons and aldehyde)
-Monosaccharide
*Glucose OH order (bad finger) but only has 5 carbons

41
Q

Glucose structure

A

-Aldohexose (6 carbons and aldehyde)
-Monosaccharide
*Bad finger -OH formation

42
Q

Galactose structure

A

-Aldohexose (6 carbons and aldehyde)
-Monosaccharide
*C3 and C4 OH direction at left

43
Q

Fructose structure

A

-Ketohexose (6 carbons and ketone)
-Monosaccharide
*Glucose (bad finger) but ketone

44
Q

Maltose structure

A

alpha Glc(1–>4)Glc linkage

45
Q

Lactose strcuture

A

Beta Gal(1–>4)Glc linkage

46
Q

Sucrose structure

A

Alpha Glc(1–>2)beta Fru linkage

Biochemistry (6 decks)

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