Carbohydrates

Question 1

functions of carbs>

forms what when binded to proteins and lipids?

Answer 1

energy source and energy storage

structural component of cell walls and exoskeletons

informational molecules in cell-cell signaling –The “Sugar Code”

can bind to:

proteins: forms glycoproteins and proteoglycans
lipids: glycolipids

Question 2

empirical formula of monosaccharrides?

Answer 2

(CH2O)n

3=

Question 3

How to know D or L?

Answer 3

review slide

look at OH group when aldehyde is on top (and pointing away)
right = detro
left = levo

*not same as R/S

Question 4

general number of stereoisomers?

Answer 4

# stereoisomers = 2^n
(where n = # of chiral carbons)

Question 5

what is an epimer?

Answer 5

2 sugars that differ only in configuration of one chiral atom

Question 6

general number of epimers for monosaccharides?

Answer 6

of epimers = (# of chiral C) - 1

Question 7

diff between hemi acetal and hemiketal?

Answer 7

refer to diagram

hemiacetal: aldehyde = alcohol

Question 8

what is a mutarotation?

Answer 8

conversions between alpha and beta anomers

Question 9

what is the anomeric C?

Answer 9

“reducing end” = important property of sugars

C linked to the oxygen on right of ing

Question 10

names of cyclic forms of monosaccharides?

Answer 10

5 C ring = furan ring

6 C ring = pyran ring

Question 11

what is fehling’s reaction?

Answer 11

used to determine glucose levels in blood or urine. oxidizing monosaccharides to give carboxylic acid

not accurate. should measure hydrogen peroxide instead

Question 12

linkage in disaccharide

Answer 12

glycosidic linkage

Question 13

types of polysaccharides?

Answer 13

1. homopolysacc: energy storage and structural
   - can be unbranched and branched
2. heteropolysacc: cellular and structural
   - can be two or more monomers
   - can be branched or unbranched

Question 14

describe starch as storage polysaccharide

Answer 14

main storage homopolysaccharides in plants

starch is a mixture of 2 homopolysaccharides

• amylose (unbranched)
• amylopectin (branched)

Question 15

links in amylose and amylopectin and glycogen??

Answer 15

amylose: alpha 1-4
amylopectin: alpha 1-4, but branches are alpha 1-6 (branch is every 24-30 glucose residues)
glycogen: alpha 1-4, but branches are alpha 1-6 (branch is every 8-12 residues)

Question 16

structure of cellulose?

Answer 16

• fibrous, water insoluble polymer
• in plant cell walls
• most abundant polysacc in nature

glucose monomers form beta 1-4 links
-H bonds form adjacent monomers. chairs are 180 to one another = max H bonds

Question 17

roles of mono and oligosacc once added onto proteins?

Answer 17

1. Cell-cell interactions, through special receptor proteins (e.g. Lectins)
2. Stabilize proteins against degradation, hence most surface proteins
3. Mechanisms in proper folding of protein, eg. Glycophorin
4. Protein targeting signals for intracellular proteins

Question 18

2 types of heteropolysaccharide linked additions?

Answer 18

N-Linked oligosaccharides

O-Linked oligosaccharides

Question 19

what lipids are modified with oligosaccharides?

Answer 19

sphingolipids and phospholipids