Lecture 14 - Carbohydrates

Question 0

Polymer with up to thousands of monosaccharides units

Answer 0

Polysaccharide (glycan)

Question 1

What kind of bond are monosaccharides (simple sugars) joined by to make oligosaccharides?

Answer 1

Glycosidic bonds

Question 2

List the monosaccharide properties

Answer 2

Colorless crystalline solid
freely soluble in water, but insoluble in nonpolar solvents
unbranched carbon chains
common mono- and disaccharide names end in “-ose”

Question 3

True or false? Simple sugars do not have chiral centers and are therefore optically inactive.

Answer 3

FALSE. Simple sugars have chiral centers and therefore optically active.

Question 4

What are two sugars differing in configuration at only one carbon are called?

Answer 4

Epimers

Question 5

What are sugars characterized by?

Answer 5

By chiral center most distant from the carbonyl carbon

Question 6

Name the six carbon sugars that are common in nature

Answer 6

D-glucose
D-mannose
D-galactose
D-fructose

Question 7

How is hemiacetal formed?

Answer 7

An OH group reacts with the C=O from an aldehyde

Question 8

How is hemiketal formed?

Answer 8

An OH group reacts with the C=O from an ketone

Question 9

What forms O-glycosidic linkage?

Answer 9

2nd OH addition to C=O

Question 10

When is anomer labeled as the α-anomer?

Answer 10

OH is on opposite side of C6 (down)

Question 11

When is anomer labeled as the β-anomer?

Answer 11

OH on the same side as C6 (up)

Question 12

True or false? Equatorial substituents have more steric hindrance than axial

Answer 12

False, LESS

Question 13

How can conversion between anomers happen?

Answer 13

Spontaneously in water via mutarotation

Question 14

What trap sugars within the cell and activate them for further chemistry?

Answer 14

Phosphorylated derivatives (of sugars)

Question 15

___________ contain a single type of monosaccharides.

Answer 15

Homopolysaccharides

Question 16

Give examples of Homopolysaccharides

Answer 16

Starch

Glycogen

Question 17

___________ containing two or more varieties of monosaccharides

Answer 17

Heteropolysaccharides

Question 18

What are homopolysaccharides used for?

Answer 18

Energy storage and as structural elements (cellulose, chitin)

Question 19

Function of heteropolysaccharides

Answer 19

Provide extracellular support for organisms (peptidoglycans)

Question 20

Sugars are very water soluble due to what?

Answer 20

Large number of OH groups

Question 21

Function of starch

Answer 21

An important energy storage role in plants

Question 22

A polymer of (α1 –> 4)-linked D-glucose

Answer 22

Glycogen

Question 23

Function of glycogen

Answer 23

Provides long-term energy storage role in animals and fungi

Question 24

What’s the branching on glycogen?

Answer 24

α1 –> 6 branching every 8 to 12 residues

Question 25

Bacterial and yeast polysaccharides of (α1 –> 6)-linked poly-D-glucose

Answer 25

Dextrans

Question 26

Possible branches of dextrans

Answer 26

α1 –> 3
α1 –> 2
α1 –> 4

Question 27

What breaks down glycogen, starch, and dextrans?

Answer 27

α-amylases
Enzymes in saliva
Intestinal fluid

Question 28

What’s the structure of cellulose like?

Answer 28

Unbranched polymer of D-glucose units are connected by β-1 –> 4 glycosidic bonds (neighbors flipped 180°)

Question 29

True or false? Fungi produces cellulase

Answer 29

True

Question 30

Homopolymer containing N-acetyl-D-glucosamine with β1–>4 bonds

Answer 30

Chitin

Question 31

Describe the structure of bacterial cell wall

Answer 31

Contains bacterial peptidoglycan, a heteropolymer of alternating (β1–>4)-linked N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) with peptide crosslinks

Question 32

What’s the purpose of bacterial peptidoglycan?

Answer 32

Prevents cellular swelling and lysis in water

Question 33

Proteins glycosylated with covalently attached glycosaminoglycans

Answer 33

Proteoglycans

Question 34

Proteins glycosylated (N-link or O-link) with oligosaccharides of varying complexity

Answer 34

Glycoproteins

Question 35

Glycosylated lipids in outer face of plasma membrane, and in nervous tissue

Answer 35

Glycolipids

Question 36

True or false? Glycosylation patterns are not important recognition and signaling

Answer 36

False, THEY ARE

Question 37

Core proteins with glycosaminoglycans covalently attached at serine residues

Answer 37

Proteoglycans

Question 38

What’s the general sequence for proteoglycans?

Answer 38

Ser-Gly-X-Gly

Question 39

True or false? Cell – ECM interactions anchor cells and provide paths for cell migration during development

Answer 39

True

Question 40

True or false? Cell – ECM interactions convey information across the plasma membrane unidirectionally

Answer 40

False, BI-DIRECTIONALLY

Question 41

How is glycoprotein different than proteoglycan?

Answer 41

Glycoprotein glycans are smaller, more branched, and more structurally diverse than proteoglycans.

Question 42

The linking of glycans through glycosidic bonds to -OH of Ser or Thr

Answer 42

O-linkage

Question 43

The linking of glycans through glycosidic bonds to amide N of Asn

Answer 43

N-linkage

Question 44

True or false? Glycosylation encodes information to signal where protein should go, cell – cell interactions, differentiation and tissue development

Answer 44

True

Question 45

True or false? Glycosylation is much more diverse than protein and DNA/RNA sequences

Answer 45

True

Question 46

Proteins that bind carbohydrate groups with high affinity and selectivity by reading the sugar coat

Answer 46

Lectins

Question 47

What do lectins do?

Answer 47

Lectins regulate cell interactions and migration