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BMS 102 > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

Carbohydrates are stored in plants as _____ and in animals as _____

A

Starch; Glycogen

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2
Q

Ratio of Carbon to Hydrogen to Oxygen in a carbohydrates

A

1 Carbon to 2 Hydrogens to 1 Oxygen

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3
Q

What are the classifications of carbohydrates?

A

Monosaccharides, Disaccharides, and Polysaccharides

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4
Q

3 Monosaccharides

A

Glucose, fructose, galactose

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5
Q

3 Disaccharides

A

Maltose, lactose, and sucrose

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6
Q

Maltose

A

Glucose and glucose

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7
Q

Sucrose

A

Glucose and fructose

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8
Q

Lactose

A

Glucose and galactose

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9
Q

3 polysaccharides

A

Starch, glycogen, and cellulose

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10
Q

A monosaccharide with an aldehyde group is referred to as…?

A

Aldose

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11
Q

A monosaccharide with a ketone is referred to as…?

A

A ketose

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12
Q

The smallest known monosaccharides are….

A

Glyceraldehyde and dihydroxyacetone

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13
Q

Aldehyde functional group

A

Hydrogen, carbonyl, carbon

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14
Q

Ketone functional group

A

Carbon, carbonyl, carbon

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15
Q

How to name monosaccharides

A 
-either by the functional group: aldehyde or ketone (aldose, ketone) or by the number of Carbon atoms present 
if 3 carbon atoms...triose
if 4 tetrose
5 pentose
6 hexrose
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16
Q

Glyceraldehyde

A

Three carbon monosaccharide with an aldehyde functional group

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17
Q

Enantiomers

A

Non super imposable mirror images

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18
Q

Can monosaccharides exist as enaontimores and diasteromers

A

Yes - both

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19
Q

How are D and L forms assigned?

A

By the chiral carbon atom furthest from C1

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20
Q

D - designation

A

Dextrarotary
Rotates plane of light clockwise
+
-OH is on the right

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21
Q

L - designation

A

Levorotary
Rotates plane of light in an anti clockwise direction
-
OH is on the left

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22
Q

If the rotation value is 0 what does this mean?

A

The mixture is racemic and is designated as +/-

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23
Q

In very simple carbohydrates what is the most oxidized group

A

The aldehyde or ketone group, which is always designated/drawn at the top and the carbon is numbered as 1

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24
Q

Fischer projections

A
  • horizontal lines represent bonds projecting out of the page and vertical lines represent bonds projecting into the page
  • aldehyde/ketone always at the top
  • chiral carbon atom represented at point where both horizontal and vertical lines cross
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25
Q

Epimers

A

Sugars that are diastereoisomers and differ only in configuration at a single asymmetric center

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26
Q

D-glucose and D-galactose are abundant six carbon _____ while D - fructose is a six carbon ____

A

Aldoses; ketose

*ketoses have one less asymmetric center than aldoses with the same number of carbon atoms

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27
Q

When a monosaccharide is more than 5 arbors in length what usually happens?

A

They form a cyclic structure

-this occurs naturally and is due to the aldehyde or ketone group reacting with an -OH at the other end

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28
Q

Hemiacetal

A

When an aldehyde functional group reacts with the alcohol group

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29
Q

Hemiketal

A

When a ketone and an alcohol react

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30
Q

How are hemiacetal and hemiketal different?

A

They are both cyclic ring structures of carbohydrates; one has a hydrogen attached and one does not (b/c it originated from a ketone)

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31
Q

alpha and beta designations of glucose

A

BUDA

Beta is up, down is alpha

32
Q

What is a six membered ring called

A

A pyranose because of its similarity to pyre

33
Q

Anomeric carbon

A

Carbon one; to the right of the oxygen

34
Q

For an aldehexose such as glucose

A

The same molecule can provide both the aldehyde and the alcohol group needed for the reaction
The C-1 aldehyde in the open chain form of glucose reacts with the C-5 hydroxy group to form an intramolecular hemiacetal
(results in a pyranose)

35
Q

When glucose is in the cyclic form what is its true name?

A

d-glucopyranose

36
Q

How is a 5-membered cyclic hemiketal formed

A

C-2 keto group in the open chain form can form an intramolecular hemiketal by reacting with the C-5 hydroxyl group to form a 5 membered cyclic hemiketal…which is called fructofuranose because of its similarity to furan

37
Q

Haworth Projections

A

Give a simple 2D image of a monosaccharide where the carbon atoms in the ring are not written out

38
Q

What are the two conformations in solution that glucose can take

A

Chair and boat
-chair form predominates because al axial positions are occupied by hydrogen atoms - boat form is to favored due to stearic endurance

39
Q

Fehling’s solution

A

monosaccharides in solution change from blue to red ppt (both aldehyde & ketone essentially)

40
Q

Benedict’s reagent

A

blue-copper containing solution gives a very distinct brick red ppt (copper II oxide)

41
Q

Tollen’s reagent

A

diamminesilver I complex forms a silver ppt forming a ‘silver mirror’ on inside of test tube

42
Q

Which reagents rely on oxidation-reduction reactions

A

Fehling’s, Beneficts and Tollen’s

43
Q

All monosaccharides and all common disaccharides (minus sucrose) are _____ sugars

A

Reducing

44
Q

What ca an aldehyde group be reduced to?

A

An alditol

45
Q

Sodium borohydride

A

Converts D-glucose to D-glucitol or D-sorbitol

46
Q

Aldose reductase

A

In the body this enzyme acts on glucose to form sorbitol

47
Q

Define the term anomer

A

Anomers are isomers that differ in the arrangement of bonds around the hemiacetal carbon

48
Q

Why does cyclisation of D-glucose give 2 isomers, alpha-D-glucose and B-D-glucose?

A

When carbonyl group of C1 of D-glucose reacts with C-5 hydroxyl group, a new chiral carbon is created (C1). In the alpha-isomer of the cyclic sugar, the C1 hydroxyl group is below the ring; in the beta -isomer, the C1 hydroxyl group is above the ring

49
Q

When discussing sugars what is meant by an intramolecular hemiacetal

A

An aldehyde sugar forms an intramolecular hemiacetal when the carbonyl group of the monosaccharide reacts with a hydroxyl group on one of the other carbon atoms

50
Q

How is glucose used industrially?

A

To make vitamin C, citric acid, bioethanol, gluconic acid and sorbitol

51
Q

Sorbitol

A

Used as a sweetener in chewing um because it still tastes sweet but it prevents bacteria building up and dental plaque

52
Q

Fructose

A
  • levulose or fruit sugar (sweetest of all simple sugars found in honey and corn syrup)
  • Derived from the digestion of table sugar
  • can be produced anaerobically be fermentation of yeast/bacteria
  • can undergo Maillard reaction with amino acids
  • Fructose malabsorption leading to increased fructose in intestine resulting in irritable bowel syndrome
  • some plants store fructose as a polymeric form known as inulin
53
Q

Galactose

A
  • Less sweet than glucose, found in hemicellulose as a polymer called galactan – can be hydrolysed to galactose
  • Together with a modified form (N-acetylgalactosamine) is an important component of blood group antigens
  • Galactose can be metabolised to glucose by the Leloir Pathway
  • Glucose can be converted to galactose in humans by hexogenesis
  • Galactosaemia – defects in galactose metabolism (very serious for newborns
54
Q

What pathway can galactose be metabolized to glucose by?

A

The leloir pathway

55
Q

Glucose can be converted to galactose in humans by

A

Hexogenesis

56
Q

Galactosaemia

A

Defects in galactose metabolism

*very serious for newborns

57
Q

What is the linkage in maltose?

A

alpha 1,4 glycosidic linkage

*maltose is a reducing sugar that is about half as sweet as glucose and often used in confectionary

58
Q

What is the linkage in lactose?

A

Beta-1-4 glycosidic linkage

-reducing sugar and principal sugar found in milk

59
Q

What is the linkage in sucrose

A

Alpha 1,2 glycosidic linkage

-NON reducing sugar

60
Q

Homopolysaccharides

A

Homoglycans

Composed of a single type of sugar

61
Q

Heterpolysaccharides

A

Heteroglycans

Composed of more than 2 types of sugar units

62
Q

Structural features that define polysaccharides

A
  1. Monomeric units
  2. Sequence of sugar units
  3. Types of glycosidic bonds linking the monomeric units
  4. Approximate number of sugar units
  5. Degree of structural “branching”
63
Q

Starch

A

Homopolymer; is the nutritional reservoir in plants that comes in two forms

64
Q

2 forms of starch

A

amylose and amylopectin

65
Q

Amylose

A

Unbranched chain of alpha-D-glucose units with alpha-1,4 glycosidic bonds

66
Q

Amylopectin

A

Has a glucose backbone - branches leading to one reducing and many non reducing ends
-branches are attached to the main chain from the C1 of one alpha-d-glucose to the C6 hydroxy group of alpha d-glucose in the main chain through alpha- 1,6 glycosidic bonds

67
Q

What bonds are in the main chain of starch

A

alpha 1,4 glycosidic bonds

68
Q

Amylose and amylopectin are rapidly hydrolyzed by what enzyme?

A

Alpha-amylase; secreted by the salivary glands and pancreas

69
Q

Glycogen

A
  • Storage polysaccharide: represents a major energy store in humans and animals
  • Glycogen is a highly branched molecule structurally similar to amylopectin but has more numerous -1,6 glycosidic linkages (thus higher molecular weight)
  • As glycogen is similar to starch – sometimes referred to as ‘animal starch’
  • Like amylopectin, glycogen consists of a single reducing end and numerous non-reducing ends
70
Q

What is the most common homopolymer in animal cells?

A

Glycogen

71
Q

Where is glycogen found

A

Liver and muscle

72
Q

Cellulose

A

Structural polysaccharide: represents a major structural component of wood and plant fibres

  • Cellulose consists of a linear chain of several hundred to thousands of -D-glucose units (typically 3000 units
  • D-glucose units are linked by -1,4 glycosidic bonds
  • Cellulose is the most abundant polysaccharide
73
Q

What bond do humans not posses the enzyme to break

A

Beta 1,4 glycosidic bonds

74
Q

Chitin

A
  • Structural polysaccharide: homopolysaccharide makes up protective exoskeletons of arthropods (not in humans)
  • Structurally chitin is similar to cellulose and functionally it is similar to the protein keratin
  • Chitin is composed of the glucose derivative N- acetylglucosamine linked by -1,4
75
Q

Glycoprotein

A

Sugars are attached either to amide nitrogen in side chain of asparagine (N-linkage) or to –OH group in side chain of serine or threonine (O-linkage) - known as glycosylation
-N-linked glycoproteins have a common pentasaccharide core (3 mannoses and 2 N-acetylglucosamines

76
Q

Proteoglycans

A

Important structural roles: serve as lubricants, structural components in connective tissue, help cells adhere to the extracellular matrix and can bind important factors that help stimulate cell proliferation
-The Proteoglycan aggrecan and the protein collagen are key components of cartilage

77
Q

Mucins (mucoproteins)

A
  • Protein component extensively glycosylated to serine or threonine residues by N-acetylgalactosamine
  • Defining feature is the protein backbone known as the variable number of tandem repeats (VNTR
  • synthesized in specialised cells within the bronchus, gastrointestinal tract and urogenital tract

BMS 102 (5 decks)

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