Carbohydrate Structure & Function_Molecules Flashcards Preview

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Flashcards in Carbohydrate Structure & Function_Molecules Deck (97):
1

What is the general formula of carbohydrates

(CH2O)n

2

What is monosaccharides?

Basic building block and major energy source

3

What is disaccharides?

2 monosaccharides units

4

What is oligosaccharides?

3 - 20 monosaccharides units

5

What is complex carbohydrates?

Glycoproteins and glycolipids

6

What is polysaccharides?

Tens to thousands of monosaccharide units

7

What are the two types of polysaccharides?

1) Storage polysaccharides - energy store
2) Structural polysaccharides

8

What does monosaccharides used to create?

1) Disaccharides
2) Oligosaccharides
3) Polysaccharides
4) Complex carbohydrates

9

What are carbohydrates used for?

1) Most abundant biomolecules in nature
2) Major food source for energy generation
3) Major component of nucleic acids
4) Provide structural components
5) Cells Glyocalyx composed of: glycoproteins and glycolipids

10

What do carbohydrates provide structural components for?

1) Extracellular matrix
2) Physiological lubricants e..g Synovial Fluid

11

What is monosaccharide consisted of?

They consist of a chain of carbons with a hydroxyl group at each carbon except one.

12

What does the "D" in D-glucose refer to?

To the orientation of substituents at the asymmetrical carbon farthest removed from the carbonyl carbon.

13

What is mutarotation?

A process which allows for greater than or equal to 5C monosaccharides to form cyclic structure around the anomeric carbon

14

When most monosaccharides spontaneously form ring structures, what bond does the aldehyde or keto group form?

Hemiacetal bond with one of the hydroxyl group

15

What is a furanose ring?

Ring that contains five atoms

16

What is a pyranose ring?

Ring that contains six atoms

17

What do alpha and beta glucopyranose?

Anomers and can interconvert spontaneously via linear form

18

What is maturation caused by

Occasional opening and reclosure of the ring
Greatly acceerated in the presence of acid or bases

19

What are common monosaccharides?

1) D-Fructose
2) D-Glucose
3) D-Mannose
4) D-Galactose

20

Why is fructose different from other common monosaccharide?

Differ from others in bonding structure - ketose

21

What are the bonding structure for common monosaccharides other than fructose?

Aldohexoses

22

How do the monosaccharides differ from one another?

Differ in how constituent groups are arranged in space - stereoisomers
Differ in biological properties and activities

23

How are monosaccharides same to each other?

Same physical and chemical properties

24

What are enantiomers?

1) When stereoisomers are mirror images
2) Differ from one another around ALL chiral carbons = D&L forms

25

Glyceraldehyde has 1 chiral (asymmetrical) carbon how many stereoisomers are formed?

2^1 = 2 stereoisomers

26

By convention what is a D form?

Form with -OH on right of the chiral carbon furthest away from the anomeric carbon

27

Glucose has 4 chiral carbons how many stereoisomers are formed?

2^4 = 16 stereoisomers
8 mirror image pairs = D&L forms

28

What is the most common in biological systems?

D forms

29

What are epimers?

stereoisomers that differ around 1 chiral C

30

How do monosaccharides combine?

By forming glycosidic bonds

31

Where are glycosidic bonds formed between?

Between the anomeric carbon of one saccharide and a hydroxyl group on another molecule

32

The formation of glycosidic bond is called what?

Condensation reaction

33

What configuration is the glycosidic bond formed in?

In alpha or beta configuration

34

What are common disaccharides?

1) Maltose
2) Sucrose
3) Lactose

35

Once the glycosidic bond is formed, is mutarotation possible?

No, the bond is locked in its confirmation

36

When does alpha linkages form?

When both reacting groups are on the same side of the ring structure

37

When does beta linkages form?

When reacting groups are different sides of the ring structures

38

What can act as a reducing agent?

Where the anomeric C is free to maturate it can act as a reducing agent

39

How do you detect reducing sugars in urine?

Used in dip-stick tests

40

What are all monosaccharides?

Reducing sugars

41

What are polysaccharides also known as?

Glycans

42

Most sugars are present in what?

polysaccharides

43

What are the two types of polysaccharides?

1) Storage Polysaccharides
2) Structural Polysaccharides

44

What are examples of Storage polysaccharides?

1) Homopolymers of glucose
2) Starch in plants (rice, wheat, potatoes,...)
3) Glycogen in animals

45

What are examples of Structural polysaccharides?

1) Cellulose in plants - also homopolymers of glucose
2) Glycoasminoglycans in animals (aka mucopolysaccharide)

46

What are glycosaminoglycans in animals?

Polymers of repeating disaccharide units

47

What are glycosaminoglycans in animals used for?

Major constituents of the extracellular matrix and physiological lubricants

48

What is glycogen?

Homopolymers of glucose and the storage form of glucose in animals

49

What is the structure of glycogen?

Branched chains of alpha 1-4 linked glucose with alpha 1 - 6 linkages at branch points.

50

Which is more highly branched: glycogen or amylopectin?

Glycogen

51

What does glycogen form?

Granules

52

How is glycogen synthesised and broken down?

One unit at a time at the non reducing ends

53

What does the highly branched nature of glycogen enable?

Rapid release or storage of glucose

54

What does glycogen constitute up to?

Up to 10% of liver mass and 1 - 2% of muscle mass

55

What does liver glycogen do?

Glucose reserve for maintenance of blood glucose levels

56

What does muscle glycogen do?

Glucose reserve for muscle activity

57

What are the homopolymers of glucose?

1) Glycogen
2) Starch

58

What is starch?

Homopolymer of glucose

59

How many forms of starch are there?

Two forms

60

What are the two forms of starch?

1) Amylose
2) Amylopectin
3) Cellulose

61

What is the structure of amylose?

Linear polymer of glucose units linked in alpha 1 - 4 linkages

62

What is the structure of amylopectin?

Branched and made of amylose polymers linked together via alpha 1 - 6 linkages.

63

What can starch do?

Act as storage polysaccharides in plants - stored packed in granules

64

What is the structure of cellulose?

Glucose units are linked in beta 1 - 4 glycosidic bonds

65

What do cellulose form?

Linear fibres - major component of wood

66

Is cellulose digestible?

No, its indigestible - humans don't have enzymes that can break it down

67

What are structural polysaccharides used for?

Are the molecules that provide:
1) compressibility to cartilage
2) Viscosity to synovial fluid (shock absorption) and vitreous humour (lubrication) of the eye
3) 'slimy' texture to mucus - protection against dehydration and infection

68

What do glycosaminoglycans contain?

Contain modified monosaccharides

69

What are glycosaminoglycans?

Long linear heteropolymers
over 100 monosaccharides long in repeating disaccharide units

70

What do disaccharide units usually comprise of?

disaccharide unit usually comprises of a sulphated amino sugar and an acidic sugar linked in beta linkages.

71

Glycosaminoglycans have what charge and are under what linkage?

Negative charge and beta linkage
= an extended, linear structure

72

Most GAGs are covalently linked to what?

A core protein, forming proteoglycans.

73

How are the GAGs linked to a core proteins?

Linked via -OH group of serine or threonine

74

What structure does the proteoglycan have?

GAGs extend from the core protein in a "Bottle - brush" structure

75

What does the Bottle - brush structure of proteoglycan allow for?

- absorbs large quantities of water

76

What does the bottle brush structure ensure that GAGs do?

1) Are viscous in solution
2) Form gels at high concentration

77

What are examples of glycosaminoglycans?

1) Chondroitin sulphate - most abundant GAG
2) Keratin sulphate

78

What does hyaluronic acid form?

Forms very large polymers up to 10 micrometer (MW 10^5-10^7). More than 10,000 repeating units. Not covalently linked to protein. Not sulphated

79

How does hyaluronic acid form large aggregates?

Associates with other glycosaminoglycans

80

What are the properties of hyaluronic acid?

1) Highly hydrated
2) lubricant

81

What are the benefits of hyaluronic acid being highly hydrated?

1) Forms viscous solutions at low concentrations
2) Forms gels at high concentrations

82

What are the benefits of hyaluronic acid being a lubricant?

Major component of synovial fluid, vitreous humour of the eye

83

Is Heparin a structural GAG?

No

84

What is heparin structure?

Disaccharide sugars are in alpha linkage, so happen does not have an extended structure

85

Where is heparin found in body?

Packed into granules in mast cells and released at site of injury

86

What does heparin do?

Act as anti-coagulant, preventing fibrin formation

87

What are glycoproteins?

Protein covalently linked to an oligosaccharide

88

What is an oligosaccharide?

1) Usually short, 2 - 10 residues
2) Branched
3) Terminal sugar often = sialic acid

89

How do glycoproteins differ from proteoglycans?

Ratio of protein to carbohydrate much greater for glycoproteins

90

What are glycoprotein chains?

Carbohydrate chains

91

What is the structure of glycoprotein chain?

1) Short
2) Branched
3) Do not contain repeating disaccharide units

92

What are glycoproteins linked to protein via?

O - linkage to Serine, Threonine or Hydroxylysine (in collagen)
N - linkage to Asparagine

93

Most glycoproteins have what attached?

Have both O- and N-linked oligosaccharides attached

94

Over 50% of all proteins are what?

Glycoproteins

95

Cell membrane associated glycoproteins are important for?

1) Membrane structure
2) Cell-cell communication
3) immune recognition

96

All secreted proteins are what?

glycoproteins (e..g plasma proteins)

97

How are secreted proteins delivered?

Glycosylated in ER and Golgi and then delivered to cell surfac e/secreted via endocytosis