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Carbohydrates 1 Flashcards

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1
Q

What are Carbohydrates?

A

Aldehyde or ketone compounds with hydrocylngroups e.g.

Polyhydroxyl aldehydes

Polyhydroxyl ketones

Compounds that can be hydrolyzed to PHA or PHK

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2
Q

List the biological functions of Carbohydrates?

A
  1. Fuel source
  2. Energy storage
  3. Structural materials
  4. Intermediate metabolism
  5. Recognition
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3
Q

How do Carbohydrates contribute as a fuel source?

A

When oxidized, they are an important source of energy

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4
Q

How do Carbohydrates contribute to energy storage?

A

Starch in plants

Glycogen in liver and muscle of animals

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5
Q

Give examples where carbohydrates are used as structural material

A
  • DNA and RNA,
  • Cell walls of bacteria and plants
  • Chitin in exoskeleton
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6
Q

Give an example of a carbohydrate that is an intermediate of metabolism

A

Sedoheptulose-7-P

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7
Q

How do carbohydrates play a role in recognition?

A

Glycoproteins and glyycolipids act as markers for cellular recognition, blood group determination, cell adhesion, cell migration, immune response, blood clotting

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8
Q

List the 4 classifications of Carbohydrates

A

Monosaccharides

Disaccharides

Oligosaccharides

Polysaccharides

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9
Q

Describe the characteristics of monosaccharides

A

Cannot be hydrolyzed into simple sugars

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10
Q

Describe the classification of disaccharides

A

Their hydrolysis yields 2 monosaccharides(sugars)

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11
Q

Describe the characteristics of oligosaccharides

A

Hydrolysis produces more than 2 but less than 10 monosaccharides

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12
Q

Describe the characteristics of polysaccharides

A

On hydrolysis produces many monosaccharide units

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13
Q

Give some examples of monosaccharides

A

Glucose, mannose, galactose, fructose and ribose

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14
Q

Give some examples of disaccharides

A

Sucrose, lactose, maltose, cellubiose and gentiobiose

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15
Q

Give some examples of oligosaccharides

A

Raffinose and stachyose

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16
Q

Give some examples of polysaccharides

A

Glycogen, starch and cellulose

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17
Q

Describe the formula of monosaccharides

A
  • General formula: CnH2nOn where n ranges from 3 to 9

- formula may deviate( deoxyribose, sugar acids etc.) deoxyribose ( C5H9O4)

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18
Q

How are monosaccharides found?

A

Found as free sugars and as part of many biologically important molecules

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19
Q

What are the 3 criteria for the classification of monosaccharides ?

A
  1. Number of carbon atoms present in the molecules
  2. Whether the sugar contain an aldehyde or ketone
  3. The stereochemical configuration of the asymmetric carbon atom farthest from the carbonyl carbon
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20
Q

How are ketones named?

A

By inserting ‘ul’ to the name of the aldose

Erythrose-> erythrulose

Ribose-> ribulose

Xylose-> xylulose

Exception: ketohexoses -> fructose

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21
Q

What is the structural difference between ketones and aldosterone

A

Ketones has one less asymmetrical C than aldose

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22
Q

Why do all monosaccharides except DHA have optically active isomeric forms?

A

All monosaccharides except DHA contain one or more asymmetric C chiral center

A chiral/asymmetrical carbon atom is the source of optical isomerism

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23
Q

Describe the difference in the configurations in glyceraldehyde

A
  • The form of glyceraldehyde that caused the rotation of plane polarized light to the right(dextrorotatory)was designated D
  • the form that caused rotation to the left(levatorotary) was designated L
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24
Q

What configuration are most naturally occurring sugars?

A

D configuration

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25
Q

Convention for designating D and L ISO’s,eras was originally based on what?

A

Optical properties of glyceraldehyde

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26
Q

What are 2 ways to define configuration of a molecule/stereochemistry?

A
  • D and L

- (+ and -)

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27
Q

What is C1 and where is it in glyceraldehyde?

A

C1 is at the top of the Fischer projection(aldehyde group)

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28
Q

What are enantiomers?

A

Isomers that are perfect mirror images

D and L isomers are mirror images but non-superimposable

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29
Q

What are diastereoisomers?

A
  • Stereoisomers with more than one chiral carbon
  • not mirror images
  • non-superimposable
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30
Q

What are epimers?

A

Stereoisomers that differ in configuration at a single asymmetric C

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31
Q

Give examples of epimers

A

D-erythrose and D threose differ at C2

Glucose and galactose at carbon 4

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32
Q

Give the results of reactions of aldehydes and alcohols

A
  • Aldehydes react with alcohol once to form a hemiacetal

- hemiacetals react with alcohols to form acetals

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33
Q

Why are hemiacetals rarely isolated?

A

Because they are not as stable as acetals

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34
Q

When are cyclic hemiacetals particularly stable

A

cyclic hemiacetals are particularly stable if they result in five or six membered rings

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35
Q

When are cyclic hemiacetals successfully isolated?

A

If both aldehyde and hydroxyl group are part of the same molecule

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36
Q

In what form do pentoses and ketones exist in aqueous solution?

A

Mainly as ring structures

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37
Q

How are hemiacetals or hemiketoses formed?

A

Intramolecular reaction between carbonyl group and an OH

I.e. Reaction of an aldehyde or ketone with an alcohol

Product is a hemiacetals or hemiketone

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38
Q

What are hemiacetals with five membered rings?

A

Furanoses

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39
Q

What six membered rings that are hemiacetals called?

A

Pyranoses

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40
Q

What happens chirally when hemiacetals are formed?

A

A new asymmetric C at C-1 or C-2 is created

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41
Q

What are aldohexoses?

A

E.g. glucose form a 6- membered pyranoses ring. C1 to C5

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42
Q

Give an example of aldopentoses

A

E.g. ribose- 5 - membered furanose ring

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43
Q

Give an example ketohexoses

A

Fructose-5-member furanose ring

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44
Q

How can aldohexoses exist?

A

As furanoses which are much less stable than pyranoses which they can also exist as

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45
Q

What is the shape of of pyranoses and furanose rings?

A

They are non-planar

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46
Q

What is the effect of C—C bond in rings?

A

It leads to many possible shapes

There is an infinite amount of shapes known as conformers

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47
Q

What are the 2 classes of conformations

A

Chair and boat conformations

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48
Q

Where are boat conformations seen?

A

Seen in so,e hexose derivatives with bulky groups

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49
Q

What did Emil Fischer discover

A

Discover structure of monosaccharides

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50
Q

Describe the Fischer projection

A
  • 2D representation of a 3D molecule projected onto a piece of paper
  • Written vertically; functional group at the top, horizontal bonds project out of the plane of the paper
  • Vertical bonds project behind the plane
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51
Q

What is the purpose of the Haworth formula?

A

Denotes HOW you go from a linear form to a ring form

Shows the stereochemistry of cyclic forms of monosaccharides

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52
Q

How does the Haworth formula work?

A

Work clockwise so that the hemiacetals/kettle bond is formed at C1(making itvanomeric)

The groups on the left are up

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53
Q

How does Haworth formula affect the carbonyl C?

A

The new isomers at the carbonyl C are another’s

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54
Q

What are anomers?

A

Anomers differ only in the configuration at the anomeric C atom alpha and beta isomers- - OH below and above resp.

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55
Q

What are the reactions of monosaccharides?

A
  • Mutarotation
  • Complete oxidation to carbon dioxide and water( via burning or respiration)
  • reactions due to carbonyl group
  • reaction due to alcohol group
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56
Q

What is mutarotation?

A

Change in optical rotation

Ocurrs via the open chain as intermediate

The alpha and beta forms can inter convert in solution-> the equilibrium mixture I.e. mutarotation

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57
Q

How does mutarotation occur in open chains and furanose forms?

A

Only a small % in the open chain and furanose forms

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58
Q

What are the alpha and beta proportions in glucose in solutions?

A

Glucose in solution- 33% alpha and 66%. Beta

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59
Q

What sugar derivative is produced by reduction of a sugar?

A

Sugar alcohol (sorbitol, inositol, galactitol)

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60
Q

What sugar derivative is produced by addition of a sugar to another bimolecule?

A

Glycoprotein, glycolipids

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61
Q

What sugar derivative is produced by a hydroxyl group being replaced with amino group ?

A

Amino sugar -NH2

62
Q

What sugar derivatives are produced by oxidation of a C atom to a carbonyl group?

A

Sugar acid(glucuronic acid)

63
Q

What is a deoxy sugar( derivative of a sugar)?

A

H atom instead of an OH group e.g. L-fructose(L-6-Deoxygal)

64
Q

What sugar derivative is formed from the phosphorylation of a hydroxyl ?

A

Sugar phosphate

65
Q

What sugar derivatives have glycosidic bonds?

A

Glycosides

  • N-glycosidic bond
  • O-glycosidic bond
66
Q

What reactions do monosaccharides undergo due to their carbonyl group?

A

Reduction to polyols, oxidation to acids, reducing sugars

67
Q

What reactions of monosaccharides are due to the alcohol group?

A

Esterification, formation of acetals called glycosides

68
Q

What are the most common reagents to reduce aldose or ketoses to their corresponding polyalcohols, called sugar alcohols or alditols?

A

Sodium borohydride

Or

Catalytic hydrogenation using a nickel catalyst

69
Q

What are names for polyalcohols?

A

Sugar alcohols or alditols

70
Q

How are alditols named?

A

By adding the suffix -itol to the root name of the sugar

E.g. glycerol, myo-inositol and d-ribitol

71
Q

What are sugar acids?

A

Monosaccharides that have had an -OH group oxidized to a carboxyl group

72
Q

How are amino sugars formed?

A

The OH at C-2 is substituted by an amino group

Amino group is often acetylated

73
Q

Where are amino sugars usually present?

A

Many structural polysaccharides such as chitin, GAG and bacterial cell walls

74
Q

Describe the mechanism behind phosphate sugar synthesis

A

Phosphoric acid can react with hydroxyl group of monosaccharides, forming esters called phosphate sugars

75
Q

Describe phosphate sugars at neutral pH

A

Very stable at neutral pH- negative charge due to the phosphate

76
Q

Phosphorylation activates the sugar for….

A

Reaction

77
Q

Phosphate sugars/sugar esters are components of…

A

Nucleotides

78
Q

These sugar esters/phosphate sugars are important intermediates in…

A

CHO metabolism

79
Q

How are phenylhydrazines formed by aldehyde and ketones?

A

Ketones/aldehyde lose carbonyl oxygen and phenylhydrazine loses both hydrogens to form phenylhydrazone and water

80
Q

How do sugars form the simple phenylhydrazone derivatives?

A

Sugars do not form the simple the simple hydrazine derivatives

81
Q

Explain osazone formation

A

Two molecules of phenylhydrazine condense with each molecule of sugar to give osazone

Both C1 and C2 are converted to phenylhydrazones, losing carbonyl oxygen and hydrogen and oxygen

82
Q

Formation of glycosides is an example of__________ _________. Which is a reaction between a hemiacetals and another ________ ________

A

Acetal formation

Hydroxyl group

83
Q

Glycoside are formed when…

A

Anomeric (hemiketals or hemiacetals) hydroxyl group of a monosaccharide undergoes

condensation with the hydroxyl group with another molecule, with elimination of water

84
Q

Glycosides are named after the sugar that provides the ______________ ___________ . Thus if glucose

A

Hemiacetal group

If glucose provides the hemiacetal group- it is glycosides

If galactose provides the hemiacetal group- it is galactoside

85
Q

Give 3 examples of reducing sugars?

A

Glucose, maltose and lactose

86
Q

Give 2 examples of non-reducing sugars

A

Sucrose and trehalose

87
Q

Give the main characteristic of reducing sugars

A

Can reduce oxidizing agents( chemicals containing Fe3+ or Cu2+) because of their free anomeric carbon

88
Q

Why can anomeric carbons of non-reducing sugars not reduce oxidizing agents?

A

Anomeric carbons of non-reducing sugars have been locked up in the formation of glycosidic bonds

89
Q

What is the reaction of hemiacetal and hemiacetal with alcohol?

A

Hemiacetal + alcohol = acetal + water

90
Q

What kind of reaction is glycoside/ acetal formation?

A

Condensation reaction

91
Q

List non-carbohydrate targets of glycosides to bond to

A

Nuclei acids(purine/pyridine bases)

Proteins(form glycoproteins)

Lipids(form glycolipids)

Steroids(via aromatic rings)

92
Q

What kind of glycosidic bond linkage is formed between a carbohydrate and NH2 group of a non-carbohydrate?

A

N-glycosidic linkage

93
Q

What kind of glycosidic bond linkage is formed by a carbohydrate and OH of a non-carbohydrate?

A

O-glycosidic bond

94
Q

What kind of glycosidic bonds form between two carbohydrates?

A

O-glycosidic

95
Q

Glycosidic bonds are…

A

Covalent and stable, except in the presence of strong acids

96
Q

What are the reducing end and terminal end in glycisidic bond formation?

A

Reducing end- where the anomeric carbon is and where the glycosidic bond is formed to extend the molecule

Terminal end- opposite ends of the reducing end

97
Q

How are glycosidic bonds named?

A
  • Named according to the numbers on the carbons which are connected
  • a-bond if the anomeric carbon has an alpha configuration
  • beta-bond if the anomeric carbons has a beta configuration
98
Q

Lactose has a glycosidic bond on the C1 carbon of beta glucose and C4 of glucose. Name the glycosidic bond

A

Beta (1-4) glycosidic bond

99
Q

What keeps oligosaccharides locked in ring structure?

A

Formation of glycosidic bond

100
Q

How many residues does an oligosaccharides have?

A

2-10 residues

101
Q

Describe how many reducing ends does an oligosaccharides have?

A

One reducing end and thus one free anomeric carbon

102
Q

Name the anomers of maltose

A

Alpha and beta maltose

103
Q

How is maltose formed?

A

Formed by the digestion of alpha-amylase during digestion of starch

104
Q

What are the molecules and glycolic bond of maltose?

A

Glycosidic alpha 1-4 bond

2 glucose molecules

105
Q

Is maltose is a reducing sugar?

A

One glucose is a free anomeric C

106
Q

What is the biochem name if table sugar?

A

Sucrose

107
Q

What are the molecules and glycosidic bond that make up sucrose?

A

Contains alpha-D-glucose and beta-D- fructose

Glycosidic bond is alpha 1-2 beta bond

Both anomeric carbon atoms involved in glycosidic bond

108
Q

What synthesizes sucrose?

A

Synthesized by plants

Not by animals

109
Q

Is a sucrose sugar reducing or non-reducing?

A

Non-reducing sugar

110
Q

What are the molecules involved in lactose?

A

Beta-D-galactose and alpha-D-glucose

111
Q

Describe the glycosidic link of lactose

A

Beta-(1-4) alpha glycosidic bond h( can be either beta or alpha, this the alpha anomer but galactose MUST be beta)

112
Q

Where do lactose naturally occur?

A

Only in milk- Milk sugar

113
Q

Is lactose a reducing sugar?

A

Yes, it has a free anomeric carbon

114
Q

What is a homopolysaccharide?

A

A single type of monomer e.g. cellulose

115
Q

What is a heteropolysaccharide. ?

A

More than one type of monomer- contains two components e.g. hyaluronic acid

116
Q

What is the purpose of starch?

A

Storage of CHO in plants-heavily hydrated

117
Q

Describe the components of starch

A

A homopolysaccharide of glucose with 2 components

  • unbrancged polymer-amylose(10-30%)
  • branched polymer- amylopectin(70-90%)
118
Q

Contrast amylopectin and amylose

A

Unbranched polymer- amylose

Branched polymer- amylopectin

119
Q

What is the molecular weight of amylose chains?

A

10^3 is to 10^6

120
Q

What is the glycosidic bond of amylose?

A

Alpha. 1-4

121
Q

How much residues per turn does amylose have?

A

6 residues per turn

122
Q

What happens to amylose in solution?

A

In solution, amylose adopts a helical conformation

123
Q

Explain a detection test for amylose

A

Add iodine to amylose. Iodine fits into helix interior

Forms a blue color.

124
Q

What color does amylopectin produce with iodine and why?

A

A red violet color due to iodine not fitting into tightly coiled conformation nor micelles

125
Q

Describe the glycosidic bond linkages in amylopectin

A

Consists of linear chains with alpha (1-4) but with branches 25-30 residues

Branched portions are alpha (1-6) glycosidic bonds

126
Q

Describe the glycosidic bonds in glycogen

A

Same as amylopectin alpha- (1-4) and alpha (1-6) bonds

127
Q

How does branching of glycogen contrast to that of amylopectin?

A

Glycogen is more branched with branches at every 8-14 residues and not 25 -30 residues

128
Q

What is the purpose of glycogen?

A

Storage form of CHO in animals in the form of granules containing enzymes of metabolism

129
Q

Glycogen branched chains possesses one reducing and several non-reducing ends. Where does enzymatic degradation and lengthening occur?

A

Occur at the non-reducing ends

130
Q

What is the most abundant polymer in the universe?

A

Homopolysaccharide

131
Q

Cellulose is resistant to….

A

Acid hydrolysis and digestive enzymes

132
Q

Describe the structure and glycosidic bonds of cellulose

A

Linear homopolysaccharide of glucose. Beta (1-4) glycisiduc binds

133
Q

Are the properties of cellulose and amylose similar

A

Very different

134
Q

Describe the reaction of iodine and cellulose

A

Negative reaction

135
Q

Is cellulose soluble in water

A

Insoluble in water

136
Q

Describe the structure of chitin

A

Resembles cellulose I.e. unbranched beta (1-4) polysaccharide of a N-acetylglysamine-an amino sugar at C2

137
Q

Is chitin digestible as a digested chain?

A

Undigestible

138
Q

What is the main component of insects and crustaceans?

A

Chitin

139
Q

Give the examples of heteropolysaccharides

A

Heparin, hyaluronic acid and chondroitins

140
Q

Describe glycisaminoglycans

A

Linear chains of repeating disaccharides

One unit is usually an alduronic acid(sugar with carboxylate group)

One unit is usually an amino sugar which may be acetylated forming GlcNac or GalNac

141
Q

What heteropolysaccharide is a components of Extracellular matrix ( ECM)?

A

Glucosaminoglycans

142
Q

One or more of the components of the glycisamines may contain….

A

A sulfate

143
Q

Give the structure of hyaluronic acid

A

A polymer of disaccharides composed of D-glucuronic acid and N-acetylglucosamine

144
Q

Describe the glycosidic bonds of hyaluronic acid

A

Alternating beta 1-4 and beta 1-3 bonds glycosidic bonds

145
Q

What are the functions hyaluronic acid?

A

Functions as a lubricant in synovial fluid

146
Q

Where is hyaluronic acid found?

A

In cartilage, tendons, virteous humor of the eye, arterial walls

CT Virteous humor I see arterial humor

147
Q

What is the molecular weight of hyaluronic acid?

A

50,000 repeats - molecular unit over 10^6

148
Q

Where is chondroitins found?

A

Tendons, cartilage and connective tissue ( CT connective tissue)

149
Q

Describe the monomers in chondroitins

A

Glucoronate and N-acetylgalactosamine

150
Q

Describe the glycosidic bonds of chondroitins

A

Alternating beta (1-3) and beta (1-4) glycosidic bonds

151
Q

What is the molecular weight of chondroitins?

A

Lower molecular weight- about 60 repeat units

152
Q

Where is sulfate located on chondroitin sulfates?

A

C4 and or C6

O Chem 2 (22 decks)

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