Carbohydrate

Question 1

What are carbohydrates?

Answer 1

Polyhydroxyl aldehyde and ketones or compounds which yield any of these compounds upon hydrolysis.

Question 2

What is the reserved carbohydrate in bulb of onion and garlic?

Answer 2

Inulin

Question 3

What is the fate of excess carbohydrate?

Answer 3

Converted to fat (triglycerides) and stored for later use.

Question 4

Immunological specificity is also a function of carbohydrate, true/false?

Answer 4

True (blood group polysaccharides)

Question 5

What are monosaccharides?

Answer 5

They are the simplest form of carbohydrate, they contain a single unit of sugar and can not be hydrolysed into smaller units.

Question 6

Examples of monosaccharides

Answer 6

Glyceraldehyde

Glucose

Galactose

Fructose

Question 7

What are disaccharides?

Answer 7

Disaccharides are carbohydrates with two monosaccharides, they are formed by the combination of two monosaccharides with the elimination of water.

Question 8

Homopolysaccharides?

Answer 8

These are polysaccharides made up of the same monosaccharide units.

Question 9

Oligosaccharides

Answer 9

Carbonhydrates with 5-10 sugar molecules.

Question 10

Polysaccharides

Answer 10

Carbohydrates with 11 or more monosaccharides.

Question 11

Heteropolysaccharide

Answer 11

Polysaccharides made up of different monosaccharides.

Question 12

Examples of disaccharides

Answer 12

Maltose

Sucrose

Lactose

Question 13

Glucose + Galactose = ?

Answer 13

Lactose

Question 14

Glucose + Glucose =?

Answer 14

Maltose

Question 15

Types of isomers sugars can undergo?

Answer 15

Structural isomer

Stereoisomer

Question 16

Structural isomer?

Answer 16

Compounds that have the same molecular formula but different structural formula

Question 17

Examples of structural isomers of sugars

Answer 17

Aldose-ketose isomerism:

Glucose and fructose

Question 18

Stereoisomers?

Answer 18

Compounds with same molecular and structural formula but differ in spatial configuration of their atoms.

Question 19

Asymmetric carbon?

Answer 19

Carbon atoms attached to two carbon atoms and two other non-carbon atoms. Also called chiral centers.

Question 20

What monosaccharide is not optically active and why?

Answer 20

Dihydroxyacetone because it has no chiral center.

Question 21

D-Galactose is a structural isomer of D-Glucose

True/False

Answer 21

False.

D-Galactose is an epimer of D-Glucose.

Question 22

How is D-manose different from D-Glucose?

Answer 22

D-manose differs to D-Glucose only with respect to carbon 2.

Question 23

What are epimers?

Answer 23

Epimers are sugars that differ from eachother in spatial configuration only with respect to one carbon atom other than the reference carbon atom (carbon 5 in glucose).

Question 24

Diastereoisomers

Answer 24

These are non-identical and non-mirror image stereoisomers. This occurs when stereoisomers of a compound have different configurations at one or more (but not all) stereocenters. É.g epimers, anomerism.

Question 25

What is anomerism?

Answer 25

This is the phenomenon where the configuration of stereoisomers differ only at the anomeric carbon. E.g alpha-D-glucose & beta-D-glucose

Question 26

Anomeric carbon?

Answer 26

This is the carbon with the functional group attached to it.

Question 27

Explain D & L isomerism

Answer 27

In this isomerism, the spatial configuration of all H and OH present in the sugar are reversed thereby forming a mirror image of the sugar

Question 28

L-Glucose can be digested by man True/False

Answer 28

False. Only D-Glucose can be digested by man

Question 29

What is Mutarotation

Answer 29

Mutarotation is the change in specific optical rotation by interconversions of alpha & beta D-Glucose to an equilibrium mixture of the two forms.

Question 30

In a mixture of glucose after 18 hours what is the percentage of alpha and beta D-Glucose present?

Answer 30

63% beta D-glucopyranose 36 alpha D-glucopyranose 1% glucofuranose

Question 31

What happens when monosaccharides are treated with conc sulphuric acid?

Answer 31

Dehydration and removal of 3 molecules of water. Hexoses give hydroxymethyl furfural and pentoses give furfural.

Question 32

What chemical reactions of carbonhydrates forms the basis of Molisch test?

Answer 32

Dehydration of mono saccharides with sulphuric acid.

Question 33

What's an enediol?

Answer 33

Enediol is the enol form of sugar because two hydroxyl groups are attached to the double-bonded carbon.

Question 34

How are enediol formed?

Answer 34

Monosaccharides are treated with dilute alkali solution which converts both aldose and ketose into enediol.

Question 35

Importance of D-Glucose

Answer 35

Blood sugar Main source of energy in the body

Question 36

Importance of D-fructose

Answer 36

Constituent of sucrose Common sugar Constituent of honey

Question 37

Importance of D-Galactose

Answer 37

Constituent of glycoproteins Constituent of glycolipids Constituent of lactose

Question 38

Importance of D-manose

Answer 38

Constituent of glycoproteins Constituent of globulins Constituent of mucoprotein

Question 39

What is dextrorotatory

Answer 39

This is a condition where a beam of plane polarised light that passes through a solution of glucose gets rotated to the right.

Question 40

What is used to detect the presence of glucose in urine?

Answer 40

Benedict's reagent

Question 41

What is glucosuria

Answer 41

This is the condition where glucose is found in the urine (as a result of diabetes mellitus).

Question 42

Non-reducing sugars can form ozazones? T/F

Answer 42

F. Only non-reducing sugars can form ozazones by heating with excess phenylhydrazine

Question 43

What ozazone crystals does mannose form?

Answer 43

Needle-shaped crystals. Same with glucose & fructose

Question 44

What shape of ozazone crystals does lactose form?

Answer 44

Hedgehog or pincushion with pin shape

Question 45

What shape of ozazone crystals does maltose form?

Answer 45

Sunflower or petal-shaped crystals.

Question 46

The closed chain structure of glucose is called?

Answer 46

Fischer projection

Question 47

Clinical correlates of ozazone?

Answer 47

May be used to differentiate sugars in biological fluid like urine or blood

Question 48

What serves as the general carbonhydrates test?

Answer 48

Molisch test

Question 49

Clinical importance of mucic acid?

Answer 49

Forms in soluble crystals, forms a basis for test for galactose

Question 50

How is mucic acid formed?

Answer 50

Mucic acid is formed by the oxidation of the first and terminal primary alcohol group of galactose to form dicarboxylic acid under nitric acid and heat.

Question 51

Examples of saccharic acids?

Answer 51

Glucosaccharic acid Mannaric acid Mucic acid

Question 52

Clinical importance of calcium gluconate?

Answer 52

Solution is given intravenously to raise calcium levels in blood

Question 53

How are aldonic acids formed

Answer 53

Oxidation of aldose sugars in the presence of hypobromous acid leads to oxidation of the aldehyde group into carboxy group to produce aldonic acids

Question 54

Another name for saccharic acids?

Answer 54

Alderic acid

Question 55

Hownis uronic acid made?

Answer 55

When the aldehyde group is protected, the terminal primary alcohol is oxidized to carboxylic acid forming uronic acid

Question 56

Clinical importance of uronic acids

Answer 56

Glucuronic acid is used by the body during detoxification of drugs and other xenobiotics. It is also used for the synthesis of other heteropolysaccharides.

Question 57

Hexoses give what molecule after dehydration using sulphuric acid

Answer 57

Hydroxymethyl furfural + 3 molecules of water

Question 58

What are the reactions monosaccharides undergo?

Answer 58

Dehydration using conc sulphuric acid Oxidation Reduction using H in the presence of sodium amalgam

Question 59

How is D-sorbitol formed?

Answer 59

D-Glucose is reduced with H in the presence of sodium amalgam to form a corresponding alcohol called D-sorbitol

Question 60

Why can fructose be reduced to two sugar alcohols

Answer 60

Because it is a ketose and ketose forms to alcohols due to the appearance of a new asymmetric carbon atom.

Question 61

Galactose is reduced to what?

Answer 61

Dulcitol

Question 62

What sugar alcohol is used to identify bacterial colonies?

Answer 62

Sorbitol, mannitol & dulcitol

Question 63

What leads to diabetic cataract in the eyes of a human?

Answer 63

Increased concentration of dulcitol and sorbitol in the lens of eyes