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EoM 4 > Carbs & Pathways > Flashcards

Carbs & Pathways Flashcards

1
Q

Empirical formula for most carbohydrates

A

(CH2O)n

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2
Q

Functions of carbohydrates (5)

A

1) energy source and storage
2) structural component of cell walls and exoskeleton
3) lubricant
4) protection
5) communication in cell-cell signaling

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3
Q

Number of sugars in a oligosaccharide

A

3-10

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4
Q

Number of sugars in a polysaccharide

A

> 10

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5
Q

What is it called if the carbonyl group is at the end of the carbon chain

A

aldehyde/aldose

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6
Q

What is it called if the carbonyl group is not at the end of the carbon chain

A

ketone/ketose

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7
Q

same composition and same order of atomic connections but different molecular arrangements in space

A

stereoisomers

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8
Q

Pairs of stereoisomers that are mirror images of one another but cannot be superimposed on each other

A

enantiomers

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9
Q

When the -OH group on the carbon next to the terminal alcohol carbon is on the right

A

D isomer

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10
Q

When the -OH group on the carbon next to the terminal alcohol carbon is on the left

A

L isomer

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11
Q

Pairs of stereoisomers that are not mirror images of each other

A

diastereomers

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12
Q

Two sugars that differ only in configuration around one carbon atom

A

epimers

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13
Q

Six-sided carbohydrate ring structure

A

pyranose

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14
Q

Five-sided carbohydrate ring structure

A

furanose

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15
Q

The addition of an -OH group to the carbonyl carbon of an aldehyde

A

hemiacetal

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16
Q

The addition of an -OH group to the carbonyl carbon of an ketone

A

hemiketal

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17
Q

Which carbon from the linear carbohydrate becomes the chiral center

A

C1 (now called the anomeric carbon)

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18
Q

What does the former carbonyl carbon become in a ring structure carbohydrate?

A

hydroxyl group

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19
Q

In a carbohydrate ring, if the -OH group is on the opposite of the ring as CH2OH, the configuration is…

A

alpha

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20
Q

In a carbohydrate ring, if the -OH group is on the same of the ring as CH2OH, the configuration is…

A

beta

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21
Q

Bond formed when the -OH from another carbohydrate comes together with the hemiacetal/hemiketal of the carbohydrate

A

glycosidic bond

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22
Q

Glycosidic bond with a methanol, glycerol, sterol, phenol or base

A

aglycone

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23
Q

What is formed from a glycosidic bond between a sugar and steroid

A

cardiac glycosides

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24
Q

Monosaccharides can be oxidized by mild oxidizing agents such as…

A

Cu2+ ions

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25
Q

What is the carbonyl carbon oxidized to in reducing sugars

A

carboxyl group

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26
Q

Two reducing sugars we learned

A

lactose and maltose

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27
Q

Two non-reducing sugars we learned

A

sucrose and trehalose

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28
Q

Polysaccharide storage in plants

A

starch

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29
Q

Two types of starches in plants

A

Amylose and Amylopectin

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30
Q

Unbranched polymer of alpha-1 -> alpha-4 linked D-glucose molecules

A

amylose

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31
Q

Polymer of alpha-1 -> alpha-4 linked D-glucose with alpha-1 -> alpha-6 branches every 24-30 residues

A

amylopectin

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32
Q

Polymer of alpha-1 -> alpha-4 linked D-glucose with alpha-1 -> alpha-6 branches every 8-12 residues

A

glycogen

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33
Q

Benefit of storing glycogen over glucose

A

Can store higher concentrations as glycogen

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34
Q

What is inulin a polysaccharide of?

A

Fructose

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35
Q

Inulin is soluble in water and not digested. What is its ultimate fate in the body?

A

Filtered through the kidneys and excreted in urine

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36
Q

What is inulin excretion used to determine?

A

glomerular filtration rate (GFR)

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37
Q

Polysaccharide made by yeast and bacteria which is made up of a1-a6 linked poly-D-glucose also with a1-a3, a1-a2, and a1-a4 branches.

A

Dextrans

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38
Q

Where can dextrans be found in the human body?

A

dental plaque

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39
Q

Linear, unbranched glucose polymer whose residues have the beta configuration

A

cellulose

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40
Q

Contain amino sugars and uronic acids.

A

Glycosaminoglycans

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41
Q

Proteins containing branched or unbranched oligosaccharide chains. Carbohydrates attached via their anomeric carbon.

A

Glycoproteins

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42
Q

Too little glucose

A

hypoglycemia

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43
Q

Symptoms of hypoglycemia

A

lethargy, coma, permanent brain damage, death

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44
Q

Too much glucose

A

hyperglycemia

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45
Q

Symptoms of hyperglycemia

A

impaired blood flow, changes in osmolality of bodily fluids, intracellular acidosis, and increased superoxide radical production

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46
Q

What is this process doing? Drop of blood added to test strip containing glucose oxidase. The glucose is then oxidized to gluconolactone which has water added to it to form gluconic acid. Gluconic acid reacts with ferricyanide to form ferrocyanide. An electrode test strip oxidizes ferrocyanide which generates current.

A

measuring blood glucose

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47
Q

Normal A1C

A

5%

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48
Q

Diabetics A1C goal

A

7%

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49
Q

Level that untreated diabetic A1C can reach

A

13%

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50
Q

Sugar in which the anomeric carbon is not involved in a glycosidic bond and therefore can undergo oxidation

A

reducing sugar

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51
Q

sugar in which the anomeric carbon is involved in a glycosidic bond and cannot undergo oxidation

A

non-reducing sugar

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52
Q

Isomers of monosaccharides that differ in configuration about the C1 carbon

A

anomers

53
Q

Four roles of glucose as a precursor

A

1) synthesis of structural polymers
2) oxidation via pentose phosphate pathway
3) oxidation via glycolysis
4) storage

54
Q

What is the most highly conserved metabolic pathway?

A

Glycolysis

55
Q

Net yield from glycolysis (one glucose molecule)

A

2 ATP, 2 NADH, 2 pyruvate, 2 H20

56
Q

What three things use only glucose for energy

A

brain, red blood cells, and sperm

57
Q

What cells do not need insulin for their glucose transporters

A

liver cells

58
Q

Compare general hexokinase and glucokinase, the enzyme catalyzing the first step in glycolysis

A
  • Hexokinase is in most tissues, glucokinase in liver
  • affinity for glucose much higher in hexokinase
  • hexokinase inhibited by glucose-6-phosphate, glucokinase is not
59
Q

Positive regulators of phosphofructokinase-1 (2)

A

1) AMP (indication of low energy in cell)

2) fructose-2,6-bisphosphate

60
Q

Negative regulators of phosphofructokinase-1 (3)

A

1) ATP (indication of high energy in cell)
2) citrate
3) H+

61
Q

Key regulatory enzyme in glycolysis which is activated by fructose-1,6-bisphosphate and dephosphorylation and inhibited by ATP and phosphorylation

A

pyruvate kinase (converts phosphoenolpyruvate to pyruvate)

62
Q

Cancer cells carry out glycolysis at much higher rate than normal cells, even when oxygen is available

A

Warburg effect

63
Q

Fate of pyruvate under anaerobic conditions in humans

A

lactic acid

64
Q

Fate of pyruvate under anaerobic conditions / fermentation

A

ethanol

65
Q

Fate of pyruvate under aerobic conditions

A

converted to Acetyl-CoA in mitochondria

66
Q

Where do we get galactose usually

A

lactose digestion

67
Q

What is galactose metabolized into

A

glucose-1-phosphate

68
Q

An excess build up of what causes cataracts and CNS damage

A

galactitol

69
Q

Defect in galactose-1-phosphate uridyltransferase (GALT) which results in a galactose-1-phosphate and galactitol build up

A

Galactosemia

70
Q

What is galactose-1-phosphate toxic to (in excess)

A

the liver

71
Q

Treatment for galactosemia

A

removal of lactose and galactose from the diet

72
Q

What is fructose converted to in the liver

A

fructose-1-phosphate

73
Q

What does aldolase B cleave fructose-1-phosphate into in glycolysis/fructose metabolism

A

dihydroxyacetone phosphate (DHAP) and Glyceraldehyde

74
Q

Why can fructose-1-phosphate accumulate easily

A

the activity of fructokinase exceeds that of aldolase B

75
Q

What type of regulator is fructose-1-phosphate for several enzymes of carbohydrate metabolism

A

allosteric regulator

76
Q

What can accumulation of fructose-1-phosphate do in the liver?

A

inhibit oxidative phosphorylation and cause damage

77
Q

How does fructose build-up lead to high concentration of uric acid?

A

ADP and AMP accumulate

78
Q

Results of fructose bypassing phosphofructokinase-1 in glycolysis (2)

A

1) high levels of lactic acid

2) high levels of lipogenesis

79
Q

Two genetic deficiencies of fructose metabolism

A

1) aldolase B deficiency - fructose intolerance

2) fructokinase deficiency - essential fructosuria

80
Q

Gluconeogenesis occurs primarily in the ____ (90%) and some in the _____ (10%)

A

Liver; Kidney

81
Q

Glucose can be made via gluconeogenesis from what three precursors

A

1) amino acids
2) lactate
3) glycerol

82
Q

Three irreversible reactions in glycolysis

A

1) glucose to glucose-6-phosphate (E: hexokinase)
2) phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate (E: phosphofructokinase-1)
3) conversion of phosphoenolpyruvate to pyruvate (E: pyruvate kinase)

83
Q

The reaction of pyruvate to oxaloacetate by pyruvate carboxylase requires what other three things

A

1) bicarbonate
2) ATP
3) biotin (co-factor)

84
Q

Strong allosteric activator of pyruvate carboxylase

A

acetyl CoA

85
Q

What stimulates and inhibits PEP carboxykinase (PEPCK)

A

1) glucagon stimulates

2) insulin stmulates

86
Q

high levels of citrate is an indicator of what

A

that the cell is meeting its energy needs

87
Q

The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate by fructose 1,6-bisphosphatase-1 (FBPase-1) is a key regulatory step in gluconeogenesis. What inhibits it?

A

AMP

88
Q

Fructose 2,6-bisphosphate is an important regulator of both PFK-1 (glycolysis) and FBPase-1 (gluconeogenesis). Which enzyme, part of a single protein, forms it and which breaks it down?

A

Formed from fructose-6-phosphate by phosphofructokinase-2 (PFK-2). Broken down by fructose 1,6-bisphosphatase-2 (FBPase-2)

89
Q

How does Fructose 2,6-bisphosphate regulate PFK-1?

A

Activates it by increasin its affinity for fructose 6-phosphate

90
Q

How does fructose 2,6-bisphosphate regulate FBPase-1

A

it inhibits it

91
Q

What happens to fructose 2,6-bisphosphate levels when glucose is high?

A

1) PFK-2 activated
2) more F26BP produced
3) PFK-1 more active
4) increased glycolysis

92
Q

What happens to fructose 2,6-bisphosphate levels when glucose is low?

A

1) FBPase-2 activated
2) less F26BP present
3) inhibition of FBPase-1 relieved
4) increased gluconeogenesis

93
Q

Name of the enzyme catalyzing the conversion from glucose 6-phosphate to glucose

A

glucose 6-phosphatase

94
Q

Where is glucose 6-phosphatase located

A

Endoplasmic reticulum of only liver and kidney

95
Q

Glycerol is phosphorylated by glycerol kinase and enters gluconeogenesis at level of….

A

dihydroxyacetone phosphate (DHAP)

96
Q

Lactate generated by glyolysis in muscle is transported to live. In the liver lactate is converted to glucose, which can then be transported back as fuel. What is this process called?

A

Cori cycle

97
Q

How is glycogen stored in cells?

A

In large cytosolic granules

98
Q

Structure of glycogen

A

1-4 linked glucose with 1-6 branches

99
Q

The addition and removal of glucose to glycogen occurs at which end

A

non-reducing ends

100
Q

Three enzymes which catalyze glycogen breakdown

A

1) glycogen phosphorylase
2) glycogen debranching enzyme
3) phosphoglucomutase

101
Q

Removes glucose from non-reducing ends of glycogen

A

glycogen phosphorylase

102
Q

What does glycogen phosphorylase needs a a cofactor

A

Pyridoxal Phosphate

103
Q

When does glycogen phosphorylase stop and what is required to alleviate this?

A

The enzyme stops when it reaches four glucose molecules from an a1-a6 branch point. Further degradation requires glycogen debranching enzyme

104
Q

Two activities of glycogen debranching enzyme

A

1) transferase activity moves 3 glucose molecules from branch to non-reducing end
2) glucosidase activity removes remaining glucose molecule

105
Q

Enzyme catalyzing conversion of glucose 1-phosphate to glucose 6-phosphate

A

phosphoglucomutase

106
Q

Glucose 6-phosphate is converted to glucose by glucose 6-phosphatase. Where is this enzyme found?

A

It is expressed by liver and kidney cells

107
Q

Starting point of glycogen synthesis

A

glucose 6-phosphate

108
Q

Glucose 6-phosphate is converted to glucose 1-phosphate at the beginning of glycogen synthesis. What happens next?

A

It’s converted to UDP-glucose by UDP-glucose pyrophosphorylase

109
Q

When the glucose residue is added to the non-reducing end of the growing glycogen chain by glycogen synthase, what is removed?

A

UDP is removed from UDP-glucose.

110
Q

Describe the initiation of a glycogen branch chain

A

Requires a primer, which is usually a preformed a1-a4 plyglucose chain or branch having at least 8 glucose residues

111
Q

What acts as both an enzyme and primer for a newly formed glycogen chain?

A

Glycogenin

112
Q

Structure of glycogen phosphorylase

A

Homo dimer. Each subunit exists in two forms, a (catalytically active) and b (less active)

113
Q

What is the activity of glycogen phosphorylase when its Ser residues are phosphorylated?

A

Active (a form).

114
Q

Enzyme phosphorylating glycogen phosphorylase

A

phosphorylase b kinase

115
Q

Enzyme dephosphorylating glycogen phosphorylase

A

phosphoprotein phosphatase 1 (PP1)

116
Q

Glycogen phosphorylase regulation in the muscle. What does epinephrine do?

A

Increase Ca2+, increased AMP stimulates kinases

117
Q

Glycogen phosphorylase regulation in the liver. What stimulates intracellular kinases?

A

glucagon

118
Q

Four things inhibiting glycogen phosphorylase

A

1) ATP
2) glucose 6-phosphate (muscle)
3) glucose (liver)
4) insulin

119
Q

What form is glycogen phosphorylase in when glucose levels are low?

A

glycogen phosphorylase a

120
Q

What form is glycogen phosphorylase in when glucose levels are high?

A

glycogen phosphorylase b

121
Q

Is glycogen synthase phosphorylated in its active “a” form?

A

No. It’s unphosphorylated

122
Q

Is glycogen synthase phosphorylated in its inactive “b” form?

A

Yes.

123
Q

Activators of glycogen synthase (3)

A

1) insulin
2) glucose 6-phosphate
3) glucose

124
Q

Inhibitors of glycogen synthase (2)

A

1) glucagon

2) epinephrine

125
Q

What type of receptor do muscle cells lack (in relation to energy metabolism)

A

Glucagon receptors

126
Q

What is special about pyruvate kinase in muscle cells?

A

It isn’t phosphorylated by protein kinase A. Glycolysis stays active when levels of cAMP are high

127
Q

Three things that muscle cells due in response to insulin

A

1) increase glucose uptake
2) increase glycogen synthesis
3) increase glycolysis

128
Q

Is hypoglycemia too little glycogen or glucose?

A

Glycogen

EoM 4 (6 decks)

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