Lecture 14 - Carbohydrates Flashcards Preview

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Flashcards in Lecture 14 - Carbohydrates Deck (48):
0

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

Glycosidic bonds

1

Polymer with up to thousands of monosaccharides units

Polysaccharide (glycan)

2

List the monosaccharide properties

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

3

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

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

4

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

Epimers

5

What are sugars characterized by?

By chiral center most distant from the carbonyl carbon

6

Name the six carbon sugars that are common in nature

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

7

How is hemiacetal formed?

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

8

How is hemiketal formed?

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

9

What forms O-glycosidic linkage?

2nd OH addition to C=O

10

When is anomer labeled as the α-anomer?

OH is on opposite side of C6 (down)

11

When is anomer labeled as the β-anomer?

OH on the same side as C6 (up)

12

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

False, LESS

13

How can conversion between anomers happen?

Spontaneously in water via mutarotation

14

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

Phosphorylated derivatives (of sugars)

15

___________ contain a single type of monosaccharides.

Homopolysaccharides

16

Give examples of Homopolysaccharides

Starch
Glycogen

17

___________ containing two or more varieties of monosaccharides

Heteropolysaccharides

18

What are homopolysaccharides used for?

Energy storage and as structural elements (cellulose, chitin)

19

Function of heteropolysaccharides

Provide extracellular support for organisms (peptidoglycans)

20

Sugars are very water soluble due to what?

Large number of OH groups

21

Function of starch

An important energy storage role in plants

22

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

Glycogen

23

Function of glycogen

Provides long-term energy storage role in animals and fungi

24

What's the branching on glycogen?

α1 --> 6 branching every 8 to 12 residues

25

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

Dextrans

26

Possible branches of dextrans

α1 --> 3
α1 --> 2
α1 --> 4

27

What breaks down glycogen, starch, and dextrans?

α-amylases
Enzymes in saliva
Intestinal fluid

28

What's the structure of cellulose like?

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

29

True or false? Fungi produces cellulase

True

30

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

Chitin

31

Describe the structure of bacterial cell wall

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

32

What's the purpose of bacterial peptidoglycan?

Prevents cellular swelling and lysis in water

33

Proteins glycosylated with covalently attached glycosaminoglycans

Proteoglycans

34

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

Glycoproteins

35

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

Glycolipids

36

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

False, THEY ARE

37

Core proteins with glycosaminoglycans covalently attached at serine residues

Proteoglycans

38

What's the general sequence for proteoglycans?

Ser-Gly-X-Gly

39

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

True

40

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

False, BI-DIRECTIONALLY

41

How is glycoprotein different than proteoglycan?

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

42

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

O-linkage

43

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

N-linkage

44

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

True

45

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

True

46

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

Lectins

47

What do lectins do?

Lectins regulate cell interactions and migration