BioChem Of Carbohydrates Flashcards
Biological importance of carbohydrates
- source and storage of energy
- molecular tag
- backbone of other macromolecules ( DNA )
- structural components ( cellulose )
- some derivates make drugs ( cardiac glycosides )
Criteria for Classification of monosaccharides
Based on
1 number of c-atoms in chain
2 function group ( aldehyde or ketone )
Chemical name of glucose and why
-polyhydroxy aldehyde as it has an aldehyde and several hydroxy groups
Number of c-atoms and name ( from 3 )
3 triose
4 tetrase
5 pentase
6 hexase
Stereoisomers of carbohydrates
-can form optical isomers
How are optical isomers formed and prerequisite for a compound to form it
-diff In directon of rotation of polarized light
-must have a chiral center
c-atom bonded to 4 diff atoms or group of atoms
Characteristics of stereoisomers
-the two isomers are mirror images of each other and cannot be superimposed
Name of isomers based on direction of rotation of light
- detrorotators ( D ) to the right
- leverotatory ( L ) to the left
How do we designate stereoisomers to carbohydrates
-use penultimate chiral carbon
furthest chiral center from carbonyl group
Types of monosaccharides rings and how are they formed
1 pyranose ring ( C1 binds to OH of C5 ) eg glucose
2 furanose ( C1 binds to OH of C4 ) eg ribose
Types of carbohydrates based on number of units
1 mono
2 Di
3 oglio ( 2-10 )
4 poly ( >10 )
What is a hemiacetal and hemiketal and position of anomers
-product formed when adding alcohol to carbonyl
- aldehyde ( aldoses ) C1
- ketone ( ketoses ) C2
Alpha and beta designations on rings and what is anomeric
- position of OH on anomeric carbon
- alpha below ring
- beta above
-c-atom on carbonyl group
What are anomers
-stereoisomers of sugars which differ only on arrangement of atoms or atom on carbonyl c-atom
Mutarotation
-reaction which interchanges anomers to each other’s forms
Important monosaccharides
1 ribose - backbone of RNA
2 deoxyribose - backbone of DNA
3 galactose - incorporated with glucose to lactose( milk sugar )
4 glucose - ( blood sugar / dextrose ) metabolism in body to produce energy
5 fructose - ( fruit sugar / levulose ) present in plants for energy release the one metabolized
Stereoisomers found naturally in nature of carbohydrates
D
Derivatives of monosaccharides and product formed
1 amino sugars - OH replaced by NH2 eg in glucose it gives glucosamine
2 sugar acids - oxidation of alcohol or aldehyde to give carboxylic acid
- oxidation of C1 : aldonic acid
- oxidation of C6 : alduronic acid
- oxidation of C1 + C6 : aldaric acid
Modifications of amino sugars
Can be sulfated or acetylated to form
N- acetyl or N-sulfate groups
Glycosidic bond formation
-elimination of water between anomeric group of one sugar and OH of another sugar
Two types of glycosidic bonds
1 O-glycoside : bond between 2 monosaccharides
2 N-glycoside : between anomeric group and amine of another ( nucleoside )
What is a disaccharide
-compound formed between 2 monosaccharides via a glycosidic bond
Important disaccharides and monosaccharide a-b designation and function
1 sucrose : glucose(a) + fructose(b) / a(1-4) bond { plant sugar
2 lactose : galactose(b) + glucose(a) / b(1-4) bold { milk sugar
3 maltose : glucose + glucose / a(1-4) bond { intermediate product during starch breakdown
4 cellebiose : glucose(b) + glucose(b) / b(1-4) bond { intermediate during cellulose breakdown
What is a polysaccharides
-carbohydrate compound with >10 units in the polymer
