Self-Study - Carbohydrates

Question 1

stereoisomer

Answer 1

spatial isomers; same molecular formula

all monosaccharides with exception of dihydroxyacetone contain at least one chiral carbon center

Question 2

enantiomer

Answer 2

2 stereoisomers that are mirror images and are not superimposable (like R and L hands)

Question 3

diasteroisomer

Answer 3

stereoisomers that are not enantiomers. different configurations at 1/+ (but not all) of the equivalent stereocenters. not mirror images.

note, when 2 diastereoisomers differ from each other at only one stereocenter they are epimers.

Question 4

racemic mixture

Answer 4

one that has equal amounts of left and right-handed enantimoers of a chiral molecule
racemic mixtures are optically inactive (doesn’t rotate polarized light)

Question 5

epimer

Answer 5

stereoisomer that differs in configuration in one stereogenic center (asymmetric carbon)
example: glucose + galactose, glucose + mannose
galactose + mannose are NOT epimers

Question 6

anomers

Answer 6

cyclization of monosaccharides which results in formation of an additional asymmetrical center known as ANOMERIC CARBON (carbonyl carbon, for example a ketone or aldehyde functional group, in a carbohydrate molecule)

alpha anomers
beta anomers

Question 7

D and L sugars

Answer 7

D and L are optical isomers of each other, or non superimposable mirror images
D = (+) = dextrorotatory (rotates light right)
L = (-) = levorotatory (rotates light left)

Question 8

aldose alcohols

Answer 8

monosaccharide that contains only one aldehyde group (CH=O)

Question 9

ketose alcohols

Answer 9

has one ketone group per molecule
most simple ketose = dihydroxyacetone
can isomerize into an aldose

Question 10

sugar alcohols

Answer 10

carboxyl group of monosaccharides reduced to OH group and forms polyhydric alcohols

Question 11

interconversion of sugars, pyranose and furanose

Answer 11

ring structures
monosaccharides with 5/+ carbons mostly form ring via rxn between carbonyl and alcohol groups

furanose: 5C ring formed b/w C1 and C4
pyranose: 6C ring formed b/w C1 and C5
Both have 2 double bonds

Question 12

mutarotation of sugars

Answer 12

change in optical rotation when sugars are dissolved
interconversion b/w alpha and beta forms to yield an equilibrium mixture with 2/3 beta, 1/3 alpha, and minor noncyclic form

Question 13

carbohydrates definition

Answer 13

aldehyde or ketone derivatives of polyhydric alcohols

Question 14

function of carbohydrates

Answer 14

source of energy in animal cells
skeletal framework for tissues and organs
lubricants and support elements of CT
biological specificity and recognition on membranes
components of nuclei acids

Question 15

monosaccharides

Answer 15

single polyhydroxy-aldehyde or polyhydroxy ketone units

Question 16

oligosaccharides

Answer 16

2-10 monosaccharide units joined by glycosidic linkages

Question 17

polysaccharides

Answer 17

polymers that may contain hundreds of monosaccharide units. divided further into homo/heteropolysaccharides

Question 18

chiral center

Answer 18

tetrahedral carbons with 4 different substituents

Question 19

what is fructose? and what does it yield?

Answer 19

a ketohexose; can form furanose or pyranose ring

& yields a mixture of D-sorbitol and D-mannitol

Question 20

physiologically important monosaccharide derivatives

Answer 20

sugar alcohols
sugar acids
amino sugars
sugar phosphates
deoxy sugars

Question 21

reduced D-GLUC forms?

Answer 21

sorbitol (changed aldehyde to hydroxyl group)

Question 22

sugar acids

How are they formed? Which 2 are important?

Answer 22

carboxyl group is oxidized to a carboxylic acid group
aldonic and uronic acid
adlonic acid - lactone intermediates are key in sugar synthesis rxn
uronic acid - has both carbonyl and carboxylic acid groups; functions in structural complex (proteoglycans)

Question 23

amino sugars

Answer 23

OH group is replaced by an amino group

amino sugars are found in structural polysaccharides and glycosphingolipids

Question 24

sugar phosphates

Answer 24

phosphoric acid esters of monosaccharides; found as intermediates in carbohydrate metabolism

Question 25

deoxy sugars

Answer 25

1/+ OH groups of furanose (5 member ring with O at top; 2 db) or pyranose (6 member ring) ring substituted by H

2-deoxyribose = impt component of deoxy-ribonucleotides

Question 26

glycosides formed by?

Answer 26

OH groups at anomeric carbon of monosaccharides react with OH or NH group of another cmpd

adjoining bonds = glycosidic bonds

Question 27

glycosidic linkages

Answer 27

linkages may be alpha or beta, depending on anomeric carbon position

Question 28

What kind of bonds are found in nucleotides?

Answer 28

N-glycolytic bonds

Question 29

monosaccharides are joined to form?

Answer 29

di, oligo, and polysaccharides

Question 30

examples of disaccharides

Answer 30

maltose
lactose
sucrose

Question 31

maltose formed from?

Answer 31

glucose + glucose

Question 32

lactose formed form?

Answer 32

galactose + glucose

Question 33

sucrose formed from?

Answer 33

glucose + fructose

Question 34

what are polysaccharides also called?

Answer 34

glycans

Question 35

homopolysaccharides contain?

Answer 35

one type of monosaccharides

Question 36

heteropolysaccharides contain?

Answer 36

two/+ different types of monosaccharides

Question 37

What is starch?

Answer 37

storage polysaccharide of plants consisting of amylose and amylopectin

Question 38

What is glycogen?

Answer 38

storage form of carbohydate in man
contains about 10 glucose units
found mainly in liver and muscle tissue

Question 39

What is cellulose?

Answer 39

major structural polysaccharide in plants
most abundant carbohydrate
unbranched polymer of glucose residues held by beta-1, 4 linkages

Question 40

What are glycosaminoglycans?

Answer 40

polysaccharides containing amino sugars and uronic acids

Question 41

What are proteoglycans?

Answer 41

chains attached to protein

major component of CT