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BIOCHEM > EXPERIMENT #6 > Flashcards

EXPERIMENT #6 Flashcards

1
Q

general molecular formula of Carbohydrates

A

Cn(H2O)n

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2
Q

Carbohydrates were once considered

A

hydrates of carbon.

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3
Q

Simplest carbohydrates

A

Monosaccharides

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4
Q

• monosaccharides, which can either be

A

Polyhydroxy aldehyde
Polyhydroxy ketones

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5
Q

general structure B

A

Ketoses

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6
Q

Polyhydroxy aldehyde (general structure A)

A

Aldoses

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7
Q

monosaccharide usually consists of how many carbons?

A

3-6 carbons.

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8
Q

Examples of monosaccharides are

A

ribose, glucose and fructose.

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9
Q

monosaccharides exist in what from?

A

Cyclic form - the aldehyde and ketone

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10
Q

the aldehyde or ketone group reacts with one of the -OH groups on the other end of the same molecule to form what?

A

cyclic hemiacetal

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11
Q

2 different anomers

A

A-D-Glucose
B-D-Glucose

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12
Q

What is a disaccharide?

A

Two monosaccharides may be combined with the loss of one molecule of water to form a disaccharide.

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13
Q

The bond that connects 2 monosaccharide units in a disaccharide is known as

A

Glycosidic bond

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14
Q

Ex. Do disaccharides

A

Sucrose (sugar)
Lactose’s (milk sugar)

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15
Q

consists of many monosaccharides linked together.

A

Polysaccharides

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16
Q

examples of polysaccharides:

A

Starch
Pectin
Glycogen
Cellulose

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17
Q

Qualitative detection of carbohydrates in solution is usually done in the laboratory using what test

A

Molisch’s test

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18
Q

Reagent if Molisch’s test

A

Concentrated (H2SO4) Sulfuric acid
Molisch’s reagent

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19
Q

carbohydrate that is oxidized by a weak oxidizing agent in basic aqueous solutions,

A

Reducing sugar

20
Q

Not oxidized

A

Non-reducing sugar

21
Q

• All aldoses are the true reducing sugars

A

They contain the aldehyde functional group

22
Q

Why Ketoses do not contain aldehyde?

A

They contain ketones

23
Q

Ketoses shows reducing properties, how?

A

In basic aqueous solution, undergo keto-whole tautomerizatiojn converting them to mixture of aldoses

24
Q

All monosaccharides are reducing sugar or non- reducing sugar?

A

Reducing sugar

25
Q

What disaccharides that are reducing?

A

Those that contains free anomeric carbon

26
Q

What’s with the free anomeric carbon?

A

Has the capacity to open and expose the aldehyde group

27
Q

several weak oxidizing agents that can be used to determine whether a carbohydrate is reducing or not, such as

A

 Benedict’s reagent
 Fehling’s reagent
 Tollen’s reagent
 Nylander’s reagent
 picric acid with sodium carbonate solution.

28
Q

What is common to all weak oxidizing reagents

A

Ph under 7 (basic)

29
Q

All the test for carbohydrates

A

Molisch’s test
Benedict’s test
Picric acid test
Mooore’s test
Barfoed’s test for monosaccharides
Seliwanoff test for ketoses
Bial’s test for pentoses
Iodine’s test for polysaccharides

30
Q

can also be used to quantitatively estimate the amount of sugar in a solution. This is also used to detect glucose in the urine.

A

Benedict’s test

31
Q

PT of Benedict’s test

A

Brick red precipitate (large amount of sugar
Orange red pot. (Moderate)
Green/yellow pot ( traces of reducing sugar)
Blue solution (no sugar)

32
Q

Benedict’s test reagent.

A

Benedicts reagent

33
Q

A positive test is evidenced by the formation of a (Benedicts test)

A

brick red precipitate of cuprous oxide (Cu₂O),

34
Q

Positive result is indicated by the formation of mahogany red colored solution which is due to the reduction of picric acid to picramic acid.

A

Picric acid test

35
Q

Oxidizing agent of picric acid test

A

Picric acid solution

36
Q

Picric acid test’s reagent

A

saturated picric acid solution followed by 0.5 mL of 10% Na2CO3, solution.

37
Q

is used to distinguish aldoses from ketoses

A

Seliwanoff’s Test for Ketoses

38
Q

dehydrates ketoses more rapidly to give furfural derivatives.

A

Seliwanoff’s reagent

39
Q

The resultant furfural derivatives undergo condensation reaction with___________ present in the reagent to give cherry red complex

A

Resorcinol

40
Q

When a reducing
sugar reacts with picric acid, it is converted into its corresponding

A

Aldonic acid and mahogany red ppt (picramic acid )

41
Q

when reducing sugars are boiled with concentrated sodium hydroxide,

A

Moores TEST

42
Q

Moores test undergo what?

A

aldol condensation
to form a resinous substance, a caramel.

43
Q

PT MOORES TEST

A

Caramel with brown color

44
Q

This test is used for distinguishing monosaccharides from reducing disaccharides.

A

Barfoed test

45
Q

PT of Barfoed test

A

Brick red color

BIOCHEM (5 decks)

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