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X Pre Clinical Science > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

What are the 3 structure tiers of carbohydrates?

A

Monosaccharides, disaccharides and polysaccharides

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2
Q

How many units are there in a monosaccharide?

A

single (one)

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3
Q

what are the 2 classes of monosaccharide?

A

aldoses or ketoses

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4
Q

How many carbons are there in monosaccharides?

A

3-7

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5
Q

Name 5 common monosaccharides

A

ribose, glucose, mannose, galactose and fructose

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6
Q

How many monosaccharides are there in a disaccaride?

A

2

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7
Q

What are the monosaccharides joined by to produce disaccharides?

A

glycosidic bond

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8
Q

Name 3 common disaccharides

A

lactose, maltose and sucrose

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9
Q

What are polysaccharides?

A

polymers of 20 or more monosaccharides

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10
Q

Name 3 common polysaccharides

A

cellulose, starch and glycogen

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11
Q

What makes up an aldehyde group?

A

carbon bonded to hydrogen and double bonded to oxygen

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12
Q

What is the name of the monosaccharides that have an aldehyde group?

A

aldoses

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13
Q

What makes up a ketone group?

A

carbon double bonded to oxygen

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14
Q

What is the name of the monosaccharides that have a ketone group?

A

ketoses

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15
Q

What further way can monosaccharides be classified?

A

by the number of carbon atoms they contain

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16
Q

How many carbon atoms are there in a triose, pentose and hexose sugar?

A

3, 5 and 6

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17
Q

What are stereoisomers?

A

molecules made of the same atoms, connected in the same sequence but the atoms are positioned differently in space

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18
Q

Why do almost all monosaccharides exist as 2 stereoisomers?

A

all contain one or more asymmetric (chiral) carbon atom

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19
Q

What are enantiomers?

A

two stereoisomers that are mirror images of each other

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20
Q

What is an example of a molecule that exists as two enantiomers?

A

glyceraldehyde - two stereoisomers that are mirror images of each other

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21
Q

What are the two forms of sugar stereoisomers?

A

D- or L-

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22
Q

What type of sugar stereoisomers are most common in animals?

A

D- isomers

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23
Q

What are epimers?

A

sugars which differ in the configuration around one carbon atom

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24
Q

What structure do the common monosaccarides have?

A

cyclical

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25
Q

What happens to monosaccharides with 5 or more carbons?

A

they exist as ring structures

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26
Q

In the ring structure of a monosaccharide what groups is the covalent bond formed between?

A

carbonyl and hydroxyl

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27
Q

What does the bonding of carbonyl and hydroxyl groups on monosaccharides produce?

A

one of 2 stereoisomers

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28
Q

What are the 2 stereoisomers of glucose that can be produced by the cyclical structure of monosaccharides?

A

alpha and beta anomers

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29
Q

What creates different anomers of monosaccharides of over 5 carbons?

A

the orientation of the HCOH molecules at the end of the monosaccharide

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30
Q

What molecules in animals are derived from simple hexoses?

A

glucose, galactose and mannose

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31
Q

What happens when molecules are derived from hexose?

A

hydroxyl (OH) group is replaced by another group, for example amino (NH2)

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32
Q

What does OIL RIG stand for?

A

oxidation is loss (of electrons) and reduction is gain (of electrons)

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33
Q

What can monosaccharides be oxidised by?

A

relatively mild oxidising agents (e.g. cupric ions)

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34
Q

What are sugars capapble of reducing cupric ions known as?

A

reducing sugars

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35
Q

What is the semi qualitative test for the presence of reducing sugar known as?

A

Fehling’s reaction

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36
Q

What was Fehling’s reaction used for?

A

detect and measure elevated glucose levels in diabetics

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37
Q

When do disaccharides form?

A

when two monosaccharides are covalently linked with the elimination of water to form a glycosidic bond

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38
Q

What molecule is eliminated during the formation of a glycosidic bond?

A

water

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39
Q

What is a homopolysaccharide?

A

polymer of a single type of sugar

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40
Q

What is a heteropolysaccharide?

A

polymer of different types of sugar

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41
Q

What are the 2 forms of homopolysaccharides and heteropolysaccharides?

A

branched and unbranched

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42
Q

What does gluconeogenesis convert to glucose?

A

pyruvate and related three and four carbon compounds (eg lactate and glycerol)

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43
Q

Where does glycogenesis take place mostly in animals?

A

the liver

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44
Q

Where does glycogenesis occur less often in mammals?

A

the renal cortex and the epithelial cells which line the small intestine

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45
Q

What does the path from pyruvate to phosphoenolpyruvate lead through?

A

oxaloacetate

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46
Q

What is oxaloacetate an intermediate of?

A

the citric acid cycle

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47
Q

What can be a starting material for gluconeogenesis?

A

any compound that can be converted to either pyruvate or oxaloacetate

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48
Q

What proteins can be converted to pyruvate and oxaloacetate?

A

alanine and aspartate respectively

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49
Q

What are glycogenic amino acids?

A

amino acids that can yield three or four carbon fragments

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50
Q

Where does the glucose produced by gluconeogenesis pass to?

A

the blood to supply other tissues

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51
Q

Why must gluconeogenesis be regulated?

A

as it is expensive

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52
Q

Where in the cell do glycolysis and glyconeogenesis occur?

A

cytosol/cytoplasm of the cell

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53
Q

What does the formation of one molecule of glucose from pyruvate require in order for it to happen?

A

4 ATP, 2 GTP and 2 NADH

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54
Q

What would happen if glycolysis and glycogenesis were allowed to proceed simultaneously at high rates?

A

the result would be high consumption of ATP and production of heat

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55
Q

How are the glycolysis and glyconeogenesis pathways regulated?

A

when the loss of glucose through glycolysis goes up the movement of pyruvate towards glucose goes down and vice versa

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56
Q

What are the 4 functions of carbohydrates?

A

energy, stored fuel, structural, information carriers

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57
Q

What is glycolysis the process of?

A

glucose is broken down into pyruvate

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58
Q

In what cells does glycolysis occur?

A

all cells

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59
Q

Under what conditions, aerobic or anaerobic, can glycolysis occur?

A

both

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60
Q

How many enzyme catalysed steps are there involved in glycolysis?

A

10

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61
Q

What 2 phases can the enzyme catalysed steps of glycolysis be split into?

A

preparatory and payoff

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62
Q

What net gain of ATP is there at the end of glycolysis?

A

2 ATP molecules

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63
Q

What is produced from pyruvate when glycolysis occurs under aerobic conditions?

A

Acetyl Co-A (acetyl co enzyme A)

64
Q

What is the production of Acetyl Co-A catalysed by?

A

pyruvate dehydrogenase

65
Q

What cycle does the newly formed Acetyl Co-A enter?

A

citric acid cycle

66
Q

What conditions does the production of Acetyl Co-A and the citric acid cycle occur under?

A

aerobic

67
Q

What is produced by the citric acid cycle?

A

NAD and GTP

68
Q

What is GTP later converted into?

A

ATP

69
Q

What occurs after glycolysis in anaerobic conditions?

A

lactate dehydrogenase cataylyses the formation of lactate from pyruvate

70
Q

What else is formed during the formation of lactate from pyruvate?

A

NAD+

71
Q

How many ATP molecules are produced from the complete oxidation of glucose?

A

32

72
Q

What is the name of the storage polysaccharide in plant cells?

A

starch

73
Q

What type of polysaccharide is starch?

A

homopolysaccharide

74
Q

What is found in the branched and unbranched chains of glucose within starch?

A

unbranched: amylose
branched: amylopectin

75
Q

What is the main storage polysaccharide of animals?

A

glycogen

76
Q

what parts of the glucose monomer are the bonds formed between in glycogen?

A

bonds between carbon 1 of one molecule and carbon 4 of another

77
Q

Where are the branch points on glucose molecules in glycogen?

A

at carbons 1 to 6

78
Q

How does branching in glucose compare to branching in starch?

A

glycogen is more extensively branched

79
Q

What do multiple branch points of glycogen mean?

A

it can be broken down quickly when glucose is needed

80
Q

What areas of the body is glycogen found?

A

abundant in the liver but also present in skeletal muscle

81
Q

How are branch points introduced and removed?

A

introduced by branching enzyme and removed by debranching enzyme

82
Q

What enzyme allows liver to be net exporter of glucose.?

A

glucose 6-phosphatase

83
Q

What type of poly saccharide is cellulose?

A

linear, unbranched, homopolysaccharide

84
Q

What are glucose residues linked by in cellulose?

A

beta 1 to 4 glycosydic bonds

85
Q

Where is cellulose found?

A

plant cell walls

86
Q

What are glycogen and starch ingested in the diet broken down by?

A

alpha amylases and glycosidases

87
Q

What bonds do alpha amylases and glycosidases break?

A

alpha 1 to 4 glycosidic bonds between glucose subunits

88
Q

What is lacking in vertebrates that means that they cannot break beta 1 to 4 glycosidic bonds and therefore not digest cellulose?

A

enzyme that can break these bonds

89
Q

What is the name of the protist (bacteria) that produces the enzyme cellulase which breaks down beta 1 to 4 glycosidic bonds?

A

Trichonympha

90
Q

What do ruminants have in their rumen/ hind gut that can breakdown cellulose?

A

symbiotic organisms

91
Q

What type of polymer is chitin?

A

linear homopolysaccharide

92
Q

What type of sugars is chitin composed of?

A

N-acetylglucosamine residues in beta 1 to 4 linkage

93
Q

Can chitin be digested by vertebrates?

A

no

94
Q

What is chitin an important component of?

A

the exoskeleton in insects

95
Q

What is peptidoglycan?

A

heteropolymer of alternating beta 1-4 linked N-acetylglucosamine and N-acetylmuramic acid residues found on the outer layer of of bacterial cell walls

96
Q

Where is peptidoglycan found?

A

bacterial and agal cell walls

97
Q

How does a lysosome kill bacteria that contain peptidoglycan in cell walls?

A

hydrolyses beta 1-4 glycosidic bonds

98
Q

What are glycosaminoglycans (GAGs)?

A

heteropolysaccharides in the extracellular matrix

99
Q

What do glycosaminoglycans do?

A

provide viscosity, adhesiveness, tensile strength and elasticity

100
Q

Give 4 examples of glycosaminoglycans

A 
hyaluronic acid (found in synovial fluid of joints)
chondroitin sulphate (in cartilage and aorta, adds tensile strength)
keratin sulphate (in the cornea and dead cells (e.g. hair)) 
heparan sulphate (interacts with a large number of proteins e.g. growth factors)
101
Q

What length of carbohydrate can be information carriers?

A

poly and oligosaccharides

102
Q

What are oligosaccharides?

A

have between 3 and 10 units

103
Q

What do information carriers provide between cells and extracellular surroundings?

A

communication

104
Q

What are proteins labelled for?

A

transport to specific organelles or for distruction

105
Q

What may be used to label proteins?

A

information carriers

106
Q

What can recognition sites be used for?

A

extracellular signalling molecules such as growth factors or bacteria

107
Q

What do most eukaryotic cells have attached to components of the plasma membrane?

A

specific oligosaccharide chains

108
Q

What is the name of the carbohydrate layer that is formed on the plasma membrane?

A

glycocalyx

109
Q

What are oligosaccharide chains attached to the plasma membrane used for?

A

cell to cell recognition and adhesion, blood clotting, the immune response and wound healing

110
Q

what is the covalent bond formed between in order to create an information carrying poly/oligosaccharide?

A

a protein or lipid to form a glycoconjugate

111
Q

Where are proteoglycans found?

A

cell surface of ECM

112
Q

what are proteoglycans?

A

highly glycosylated proteins attached by serine residues to cell walls

113
Q

Where are glycoproteins found?

A

cell surface or extra cellular matrix

114
Q

What do glycoproteins contain?

A

oligosaccharides covalently linked to 3 different amino acid residues

115
Q

Where are glycolipids found?

A

extracellular surface

116
Q

What are glycolipids covalently linked to?

A

oilgosaccharides

117
Q

What are glycolipids?

A

lipids found within the plasma membrane

118
Q

What are lectins?

A

proteins that bind carbohydrates

119
Q

What do lectins have a role in?

A

cell to cell recognition, signalling and adhesion

120
Q

Where are lectins commonly found?

A

extracellular surface of cells

121
Q

What are selectins?

A

a family of plasma membrane lectins that mediate cell to cell recognition and adhesion in a wie range of processes

122
Q

What immune processes are selectins involved with?

A

movement of leukocytes through the capillary wall from blood to tissues at the sites of infection or inflammation

123
Q

What is phosphofructokinase (PFK)?

A

the enzyme that is crucial to the formation of fructose 1 6 biphosphate in the preparatory stage of glycolysis

124
Q

What happens without PFK in glycolysis?

A

glycolysis cannot be completed

125
Q

What happens if there is a deficiency in PFK?

A

energy is not able to be obtained from glucose

126
Q

How does PFK deficiency present?

A

muscle fatigue, weakness, pain and stiffness during exercise

127
Q

What causes lack of PFK?

A

a genetic defect

128
Q

What population is the PFK genetic defect present in?

A

spaniel

129
Q

Is the PFK defect dominant or recessive?

A

recessive

130
Q

How is PFK deficiency treated?

A

incurable and can only be managed through dietry changes and reducing or avoiding exercise

131
Q

What dietary changes can be made in order to manage PFK deficiency?

A

high protein and low fat diet with low carbs

132
Q

What is an example of a pathological lectin?

A

haemagglutinin (HA) in the influenza virus

133
Q

What does HA do to host cells?

A

attatches to cell surface carbohydrates and allows of the viral membrane to fuse with the cell surface membrane

134
Q

What does fusion of the HA glycoprotein to cell surface membrane mean?

A

genome of the virus can enter the cell where it can then replicate inside the cell

135
Q

What can HA be used for?

A

treatments

136
Q

How can HA be used safely for treatment?

A

inhibited to prevent it from attaching to cells and therefore stop it from binding to cell surface receptors in the first place. The stem of the HA molecule can also be targeted to block changes in the molecule that occur during fusion to the cell surface membrane

137
Q

What do bacteria use as a storage polysaccharide?

A

dextrans

138
Q

What are dextrans polymers of?

A

alpha 1-6 linked glucose subunits

139
Q

Where are the branches located in dextrans?

A

alpha 1-3 and alpha 1-4

140
Q

whereabouts in the body are bacteria that produce and secrete dextrans extracellularly found?

A

the mouth

141
Q

What makes dextrans adhesive?

A

branching structure

142
Q

What do these adhesive dextrans released by bacteria in the mouth form part of?

A

dental plaque that grows on teeth

143
Q

What do the dextran bacteria cause when they become stuck to to the teeth and each other because of their adhesiveness and then proliferate?

A

teeth and gum damage leading to gingivitis and tooth decay

144
Q

What is polysaccharide storage myopathy?

A

genetic condition in horses where they store glucose incorrectly

145
Q

Why is glucose stored with multiple alpha 1-6 branches?

A

to make it easy to be broken down and release glucose

146
Q

What sort of bonds are formed between glucose molecules within polysaccharide storage?

A

alpha 1-4

147
Q

What enzyme makes alpha 1-4 bonds in glycogen formation?

A

glycogen synthase

148
Q

what enzyme breaks alpha 1-4 bonds?

A

amylase

149
Q

What enzyme makes the alpha 1-6 branching bonds during the formation of glycogen?

A

glycogen branching enzyme

150
Q

What is over produced during polysaccharide storage myopathy?

A

glycogen synthase

151
Q

What does the over production of glycogen synthase during polysaccaride storage myopathy mean?

A

more glycogen synthase than glycogen branching enzyme, creating long chains of glycogen with minimal branching. This means that the glycogen is relatively amylase resistant

152
Q

What are the signs of polysaccaride storage myopathy?

A

lack of energy and muscle stiffness due to lack of available glucose

153
Q

What may be broken down as an alternative source of fuel in a horse with polysaccharide storage myopathy?

A

muscle tissue

154
Q

In polysaccharide storage myopathy, what does an overproduction of glycogen synthase mean for glycogen production?

A

glycogen synthase works resulting in overproduction of glycogen relative to how much is broken down

155
Q

How can polysaccaride storage myopathy be managed?

A

incurable but switching to a low-starch, high fat diet can provide an alternative source of fuel

X Pre Clinical Science (17 decks)

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