Carbohydrate Flashcards
What are carbohydrates?
Polyhydroxyl aldehyde and ketones or compounds which yield any of these compounds upon hydrolysis.
What is the reserved carbohydrate in bulb of onion and garlic?
Inulin
What is the fate of excess carbohydrate?
Converted to fat (triglycerides) and stored for later use.
Immunological specificity is also a function of carbohydrate, true/false?
True (blood group polysaccharides)
What are monosaccharides?
They are the simplest form of carbohydrate, they contain a single unit of sugar and can not be hydrolysed into smaller units.
Examples of monosaccharides
Glyceraldehyde
Glucose
Galactose
Fructose
What are disaccharides?
Disaccharides are carbohydrates with two monosaccharides, they are formed by the combination of two monosaccharides with the elimination of water.
Homopolysaccharides?
These are polysaccharides made up of the same monosaccharide units.
Oligosaccharides
Carbonhydrates with 5-10 sugar molecules.
Polysaccharides
Carbohydrates with 11 or more monosaccharides.
Heteropolysaccharide
Polysaccharides made up of different monosaccharides.
Examples of disaccharides
Maltose
Sucrose
Lactose
Glucose + Galactose = ?
Lactose
Glucose + Glucose =?
Maltose
Types of isomers sugars can undergo?
Structural isomer
Stereoisomer
Structural isomer?
Compounds that have the same molecular formula but different structural formula
Examples of structural isomers of sugars
Aldose-ketose isomerism:
Glucose and fructose
Stereoisomers?
Compounds with same molecular and structural formula but differ in spatial configuration of their atoms.
Asymmetric carbon?
Carbon atoms attached to two carbon atoms and two other non-carbon atoms. Also called chiral centers.
What monosaccharide is not optically active and why?
Dihydroxyacetone because it has no chiral center.
D-Galactose is a structural isomer of D-Glucose
True/False
False.
D-Galactose is an epimer of D-Glucose.
How is D-manose different from D-Glucose?
D-manose differs to D-Glucose only with respect to carbon 2.
What are epimers?
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).
Diastereoisomers
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.
What is anomerism?
This is the phenomenon where the configuration of stereoisomers differ only at the anomeric carbon.
E.g alpha-D-glucose & beta-D-glucose
Anomeric carbon?
This is the carbon with the functional group attached to it.
Explain D & L isomerism
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
L-Glucose can be digested by man
True/False
False. Only D-Glucose can be digested by man
What is Mutarotation
Mutarotation is the change in specific optical rotation by interconversions of alpha & beta D-Glucose to an equilibrium mixture of the two forms.
In a mixture of glucose after 18 hours what is the percentage of alpha and beta D-Glucose present?
63% beta D-glucopyranose
36 alpha D-glucopyranose
1% glucofuranose
What happens when monosaccharides are treated with conc sulphuric acid?
Dehydration and removal of 3 molecules of water. Hexoses give hydroxymethyl furfural and pentoses give furfural.
What chemical reactions of carbonhydrates forms the basis of Molisch test?
Dehydration of mono saccharides with sulphuric acid.
What’s an enediol?
Enediol is the enol form of sugar because two hydroxyl groups are attached to the double-bonded carbon.
How are enediol formed?
Monosaccharides are treated with dilute alkali solution which converts both aldose and ketose into enediol.
Importance of D-Glucose
Blood sugar
Main source of energy in the body
Importance of D-fructose
Constituent of sucrose
Common sugar
Constituent of honey
Importance of D-Galactose
Constituent of glycoproteins
Constituent of glycolipids
Constituent of lactose
Importance of D-manose
Constituent of glycoproteins
Constituent of globulins
Constituent of mucoprotein
What is dextrorotatory
This is a condition where a beam of plane polarised light that passes through a solution of glucose gets rotated to the right.
What is used to detect the presence of glucose in urine?
Benedict’s reagent
What is glucosuria
This is the condition where glucose is found in the urine (as a result of diabetes mellitus).
Non-reducing sugars can form ozazones?
T/F
F.
Only non-reducing sugars can form ozazones by heating with excess phenylhydrazine
What ozazone crystals does mannose form?
Needle-shaped crystals. Same with glucose & fructose
What shape of ozazone crystals does lactose form?
Hedgehog or pincushion with pin shape
What shape of ozazone crystals does maltose form?
Sunflower or petal-shaped crystals.
The closed chain structure of glucose is called?
Fischer projection
Clinical correlates of ozazone?
May be used to differentiate sugars in biological fluid like urine or blood
What serves as the general carbonhydrates test?
Molisch test
Clinical importance of mucic acid?
Forms in soluble crystals, forms a basis for test for galactose
How is mucic acid formed?
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.
Examples of saccharic acids?
Glucosaccharic acid
Mannaric acid
Mucic acid
Clinical importance of calcium gluconate?
Solution is given intravenously to raise calcium levels in blood
How are aldonic acids formed
Oxidation of aldose sugars in the presence of hypobromous acid leads to oxidation of the aldehyde group into carboxy group to produce aldonic acids
Another name for saccharic acids?
Alderic acid
Hownis uronic acid made?
When the aldehyde group is protected, the terminal primary alcohol is oxidized to carboxylic acid forming uronic acid
Clinical importance of uronic acids
Glucuronic acid is used by the body during detoxification of drugs and other xenobiotics.
It is also used for the synthesis of other heteropolysaccharides.
Hexoses give what molecule after dehydration using sulphuric acid
Hydroxymethyl furfural + 3 molecules of water
What are the reactions monosaccharides undergo?
Dehydration using conc sulphuric acid
Oxidation
Reduction using H in the presence of sodium amalgam
How is D-sorbitol formed?
D-Glucose is reduced with H in the presence of sodium amalgam to form a corresponding alcohol called D-sorbitol
Why can fructose be reduced to two sugar alcohols
Because it is a ketose and ketose forms to alcohols due to the appearance of a new asymmetric carbon atom.
Galactose is reduced to what?
Dulcitol
What sugar alcohol is used to identify bacterial colonies?
Sorbitol, mannitol & dulcitol
What leads to diabetic cataract in the eyes of a human?
Increased concentration of dulcitol and sorbitol in the lens of eyes
