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Biochemistry Laboratory > carbohydrates > Flashcards

carbohydrates Flashcards

1
Q

Classification by number of Monosaccharide units:

A

● Monosaccharides (1) - glucose, fructose, galactose (GFG)
● Disaccharides (2) - maltose, lactose, sucrose (MLS)
● Oligosaccharides (2-10) - raffinose, stachyose
● Polysaccharides (10 or more) - starch, glycogen, cellulose

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2
Q

Simplest sugar and cannot be hydrolyzed further

A

Monosaccharide

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3
Q

Classification by number of Carbon atoms:

A

● Pentoses: five carbon atoms
○ Aldopentoses: ribose and xylose
● Hexoses: six carbon atoms
○ Aldohexoses: glucose, galactose
○ Ketohexoses: fructose

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4
Q

Converts pentoses into furfural and hexoses into 5-hydroxymethylfurfural which then reacts with phenolic compounds

A

Dehydrating acids

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5
Q

Reducing sugars include aldoses containing either a free aldehyde group or a cyclic hemiacetal

A

Copper (II) ions containing solutions

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6
Q

Objective of Benedicts Test

A

To determine the presence or absence of reducing sugar in the solution.

● All monosaccharides are reducing sugars
● A reducing sugar has a free aldehyde group or a free ketone group

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7
Q

Sodium carbonate: _____ g
Sodium citrate: _____ g
Distilled water: _____ mL
Copper sulfate pentahydrate: _____ g

A

Sodium carbonate: 10g
Sodium citrate: 17.3g
Distilled water: 100 mL
Copper sulfate pentahydrate: 1.73g

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8
Q

Na carbonate: provides ________
Na citrate: forms ________

A

Na carbonate: provides alkaline medium
Na citrate: forms complexes with Cu^2+ ions

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9
Q

(Benedict’s Test) Interpretation of Result

A

● Blue - 0, negative/no sugar
● Green - 0.5-1%, traces of reducing sugar
● Yellow - 1-1.5%, low amount of reducing sugar
● Orange - 1.5-2%, moderate amount of reducing sugar
● Brick red - >2%, large amount of reducing sugar

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10
Q

(Benedict’s Test)

Positive color:
Variable color:

A

Positive color: brick red precipitate
Variable color: green (+/-)

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11
Q

Barfoed’s Test Objectives

A

used to detect the presence of reducing monosaccharides

distinguish reducing monosaccharides from disaccharides

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12
Q

(Barfoed’s Test) Interpretation of Result

A

● Positive Result: Brick red precipitate at the bottom of the tube.
● Monosaccharide + barfoed’s reagent = 5 minutes (brick red/red/brown precipitate)
● Disaccharide + barfoed’s reagent = 10 minutes (any color)

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13
Q

(Barfoed’s Test)

Positive color:
Barfoed’s reagent:

A

Positive color: brick red/brown
Barfoed’s reagent: copper sulfate & acetic acid

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14
Q

In Barfoed’s Test, Acetic acid - provides _______
condition that ________ pH

A

acidic, decreases

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15
Q

Seliwanoff’s Test Objective

A

● To detect the presence of ketohexoses in a given sample.
● To distinguish ketoses from aldoses.

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16
Q

Seliwanoff’s Test | Interpretation of Result

Ketose Color
Aldose Color

A

● Ketose reacts to produce a deep cherry red color
● Aldoses may react slightly to produce a faint pink to cherry red color if the test is prolonged.

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17
Q

In Seliwanoff’s Test, ______ and _______also give a positive result for this test as these are hydrolyzed by acid to give fructose.

A

Sucrose and Insulin

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18
Q

Bial’s Orcinol Test Objective

A

● To detect the presence of carbohydrates.
● To distinguish the pentoses and pentosans from other derivatives of carbohydrates like the hexoses.

19
Q

Bial’s Test Interpretation of Result

Positive color:
Negative color:

A

Positive color: blue-green
Negative color: any color besides blue-green

20
Q

The presence of a blue-green complex indicates the presence of _________ in the sample.

A

pentoses

21
Q

Bial’s Solutions

A

5% fructose, 5% sucrose, 5% ribose, 5% glucose

22
Q

Purpose of Mucic Acid Test

A

● Detects galactose and lactose in a
given sample.
● Distinguish galactose containing
saccharides and other sugars.

23
Q

Each test’s objective

Benedict’s Test:
Barfoed’s Test:
Seliwanoff’s Test:
Bial’s Orcinol Test:

A

Benedict’s Test: amount of sugar
Barfoed’s Test: if monosaccharide or disaccharide
Seliwanoff’s Test: if aldose or ketose
Bial’s Orcinol Test: if pentose or hexose

24
Q

What is Mucic Reagent and Nitric Acid

A

● Mucic Reagent is a concentrated
Nitric Acid.
● Nitric Acid causes the formation of
crystals in a solution.

25
Q

(Mucic’s Test) Interpretation of Result

A

● Positive Mucic Acid Test - Crystals are present and the indication is that galactose is present.
● Negative Mucic Acid Test - No crystals are present and the indication is that galactose is absent.

26
Q

Purpose of PHENYLHYDRAZONE TEST

A

● The objective of this test is to detect reducing sugars from non-reducing sugars.
● This is also used to distinguish reducing sugars from each other.

27
Q

MATERIALS AND REAGENTS OF PHENYLHYDRAZONE TEST

A

● Phenylhydrazine HCl
● CH COONa
● Distilled water
● Test tubes
● Carbohydrate solutions (glucose, fructose, xylose, lactose, sucrose and starch)
● Microscope

28
Q

MATERIALS AND REAGENTS OF MUCIC ACID TEST

A

● Carbohydrate Solution (Galactose and Lactose)
● Concentrated HNO3
● Alcohol Lamp
● Microscope
● Mucic Reagent
● Test sample
● Distilled Water
● Test tube
● Test tube stand
● Pipette

29
Q

What is Mucic acid test

A

a test that is highly specific and is used for the detection of the presence of galactose and lactose.

30
Q

Other term for Mucic Acid

A

galactaric acid

31
Q

What is Phenylhydrazone Test

A

a chemical test used to detect and differentiate reducing sugars

32
Q

Phenylhydrazone Test

Differentiation of reducing sugars is based on the ____________________________ and ________________________.

A

Differentiation of reducing sugars is based on the time of appearance of the complex and relative solubility in hot water.

33
Q

Examples of reducing sugars are

A

glucose, fructose, glyceraldehyde and galactose.

34
Q

Buffer is a combination of ?

A

weak acid and weak base.

35
Q

Phenylhydrazone Test is based on the fact that carbohydrates with free or potentially free carbonyl groups react with _______________ to form _______________

A

phenylhydrazine to form osazone.

36
Q

The condensation-oxidation-condensation reaction between three molecules of phenylhydrazine and carbon one and two of aldoses and ketoses yields

A

1, 2-diphenylhydrazine, which is known as osazone.

37
Q

Osazone appears as _______________ of characteristic shape, solubility, melting point, and time of formation.

A

yellow-colored crystals

38
Q

Reaction for Mucic Acid Test

A

CH2OH - (CHOH)4 - CHO + HNO3 -> CH2OH - (CHOH)4 -CHO - NO3 + H^+

39
Q

Limitation of Mucic Acid

A

● It cannot distinguish between the monosaccharide and disaccharide kind of galactose.
● False-positive results occur due to impurities of carbonyl groups at the terminal end.

40
Q

Lactose also yields a _________, due to the _______ of the
________ between the __________ and ________ subunits of the carbohydrate.

A

Lactose also yields a mucic acid, due to the hydrolysis of the glycosidic bond between the glucose and galactose subunits of the carbohydrate.

41
Q

Other monosaccharides like glucose also have a similar structure; however, the resultant precipitate Formed in glucose is ____________ under _______ temperature.

A

water-soluble, room

42
Q

Aldohexoses (monosaccharide) upon treatment with potent oxidizing agents like nitric acid yield _____________________.

A

saccharic acids (dicarboxylic acids)

43
Q

Nitric acid has the capacity to oxidize both aldehyde and primary alcoholic groups present at C1 and C6 respectively of galactose to yield an _____________________ of mucic acid under ______________.

A

insoluble precipitate (rod-shaped crystals), higher temperature.

Biochemistry Laboratory (8 decks)

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