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piggy > Biochemistry - Metabolism Part 2 > Flashcards

Biochemistry - Metabolism Part 2 Flashcards

1
Q

Where in the cell is the enzyme glucose-6-phosphatase found?

A

Endoplasmic reticulum

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2
Q

In which tissues are the enzymes of gluconeogenesis found?

A

Liver, kidney, and intestinal epithelium

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3
Q

What product of the pentose phosphate pathway (hexose monophosphate shunt) facilitates steroid and fatty acid synthesis?

A

NADPH

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4
Q

What is the function of NADPH in the erythrocyte?

A

It reduces glutathione

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5
Q

What are the two phases of the hexose monophosphate shunt (pentose phosphate pathway)?

A

Irreversible oxidative phase and reversible nonoxidative phase

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6
Q

What key enzyme regulates the oxidative phase of the hexose monophosphate shunt?

A

Glucose-6-phosphate dehydrogenase

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7
Q

How many adenosine triphosphate molecules are used and produced by the hexose monophosphate shunt (pentose phosphate pathway)?

A

0

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8
Q

What vitamin is required for the nonoxidative phase of the hexose monophosphate shunt?

A

The transketolases that catalyze the nonoxidative reactions require thiamine (vitamin B1) as a cofactor

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9
Q

What four products are formed after both phases of the hexose monophosphate shunt?

A

Ribose-5-phosphate, G3P, F6P, and NADPH are the products

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10
Q

Which product of the hexose monophosphate shunt is used in nucleotide synthesis?

A

Ribose-5-phosphate

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11
Q

How are G3P and F6P utilized in the cell following the hexose monophosphate shunt?

A

These are glycolytic intermediates and can enter glycolysis

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12
Q

Name three sites of fatty acid or steroid synthesis that show high pentose phosphate pathway (hexose monophosphate shunt) activity.

A

Lactating mammary glands, liver, adrenal cortex

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13
Q

Do the reactions of the hexose monophosphate shunt (pentose phosphate pathway) take place in the mitochondria or the cytosol of a cell?

A

The cytosol

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14
Q

Where would you find elevated activity of the pentose phosphate pathway, but no fatty acid or steroid synthesis?

A

In the red blood cells; the reducing equivalents formed are necessary to neutralize oxidative radicals

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15
Q

Name two cells that utilize NADPH for an oxidative burst.

A

Neutrophils, macrophages

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16
Q

During the oxygen-dependent respiratory burst used by neutrophils to destroy bacteria, what enzyme converts hydrogen peroxide to bleach (hypochlorite) in the presence of chloride ion?

A

Myeloperoxidase, which is found in neutrophil azurophilic granules

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17
Q

Why would you expect cells like neutrophils and macrophages to have high concentrations of NADPH oxidase?

A

It is important for the immune response, rapidly releasing reactive oxygen species to kill bacteria

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18
Q

What disease is caused by a deficiency of NADPH oxidase?

A

Chronic granulomatous disease; a genetic immunodeficiency

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19
Q

During the oxygen-dependent respiratory burst that is used by neutrophils to destroy bacteria, what enzyme converts oxygen to superoxide?

A

NADPH oxidase

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20
Q

Which form of glutathione must be readily available in the cell to remove reactive oxygen species to prevent cell lysis?

A

The reduced form (GSH); reducing equivalents are created in the hexose monophosphate shunt

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21
Q

Is glutathione reduced or oxidized when converting hydrogen peroxide to water in neutrophils?

A

Oxidised

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22
Q

Regarding the neutrophil oxygen-dependent respiratory burst, which electron carrier is used to reduce glutathione after the conversion of hydrogen peroxide to water?

A

NADPH

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23
Q

During the oxygen-dependent respiratory burst that is used by neutrophils to destroy bacteria, what enzyme converts superoxide to hydrogen peroxide?

A

Superoxidase dismutase

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24
Q

During the oxygen-dependent respiratory burst that is used by neutrophils to destroy bacteria, what enzyme converts hydrogen peroxide to water in the presence of glutathione?

A

Catalase

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25
Q

What enzyme uses NADPH to replenish reduced glutathione?

A

Glutathione reductase

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26
Q

What enzyme replenishes the NADPH used to reduce glutathione?

A

Glucose-6-phosphate dehydrogenase

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27
Q

What is the end product of the oxygen-dependent respiratory burst that is used to kill bacteria in the phagolysosome?

A

Bleach (HOCl, hypochlorite)

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28
Q

True or False? The white blood cells of patients with chronic granulomatous disease can utilize hydrogen peroxide generated by invading organisms and convert it to reactive oxygen intermediates.

A

True

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29
Q

Patients with chronic granulomatous disease are at an increased risk for infection by which microorganisms?

A

Catalase-positive species like Staphylococcus aureus and Aspergillus

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30
Q

What substance detoxifies free radicals and peroxides in the cell?

A

Glutathione

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31
Q

What molecule is required to maintain a store of reduced glutathione?

A

NADPH

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32
Q

What enzyme is required to produce and maintain NADPH within the cell?

A

Glucose-6-phosphate dehydrogenase

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33
Q

What might you find on the peripheral smear of someone with glucose-6-phosphate dehydrogenase deficiency after they consume fava beans?

A

Haemolytic anaemia (hence the reference to this condition as favism)

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34
Q

What property of fava beans, sulfonamides, primaquine, and antituberculosis drugs allows them to cause hemolytic anemia in persons with glucose-6-phosphate dehydrogenase deficiency?

A

They are all oxidizing agents, and cause oxidative stress to the erythrocyte

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35
Q

What are the precipitates of hemoglobin that are found on microscopy in the red blood cells of patients with glucose-6-phosphate dehydrogenase deficiency called?

A

Heinz bodies (remember: Heinz bodies = precipitated Hemoglobin)

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36
Q

Members of which populations are more likely to have glucose-6-phosphate dehydrogenase deficiency?

A

Mediterranean and African individuals

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37
Q

What is the most common human enzyme deficiency?

A

Glucose-6-phosphate dehydrogenase deficiency

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38
Q

Glucose-6-phosphate dehydrogenase deficiency shows what form of inheritance?

A

X-linked recessive; therefore, symptoms are largely seen in males

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39
Q

People with glucose-6-phosphate dehydrogenase deficiency have _____ (increased/decreased) malarial resistance.

A

increased; this likely accounts for the prevalence of the deficiency in African populations

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40
Q

Phagocytic removal of Heinz bodies from macrophages in patients with glucose-6-phosphate dehydrogenase deficiency results a specific appearance of red blood cells when viewed under a microscope termed ____ _____.

A

Bite cells

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41
Q

What disease is caused by a deficiency of aldolase B?

A

Fructose intolerance

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42
Q

What disease is caused by a defect in fructokinase?

A

Essential fructosuria

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43
Q

What type of disease inheritance is demonstrated in families with fructose intolerance?

A

Autosomal recessive

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44
Q

Patients with fructose intolerance accumulate what metabolic intermediate?

A

Fructose-1-phosphate

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45
Q

Which disorder of fructose metabolism involves the symptoms of hypoglycemia, jaundice, cirrhosis, and vomiting?

A

Fructose intolerance

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46
Q

Which causes milder symptoms: disorders of fructose metabolism or analogous disorders of galactose metabolism.

A

Disorders of fructose metabolism

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47
Q

Why does consumption of sucrose worsen the symptoms of fructose intolerance?

A

Sucrose is made of fructose and glucose

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48
Q

What is the mode of inheritance of fructose intolerance?

A

Autosomal recessive, as is the case with most enzyme deficiencies

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49
Q

What is the treatment for fructose intolerance?

A

Decreased fructose and sucrose intake

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50
Q

In fructose metabolism, the conversion of fructose into fructose-1-phosphate is catalyzed by what enzyme?

A

Fructokinase

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51
Q

Are patients with a deficiency of aldolase B (fructose intolerance) more likely to be hyperglycemic or hypoglycemic?

A

Hypoglycaemic

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52
Q

In fructose metabolism, the conversion of fructose-1-phosphate into dihydroxyacetone phosphate plus glyceraldehyde is catalyzed by what enzyme?

A

Aldolase B; the resulting molecules can enter glycolysis

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53
Q

Which disorder of fructose metabolism causes more serious clinical sequelae?

A

Fructose intolerance

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54
Q

What molecule becomes scarce in fructose intolerance, resulting in inhibition of glycogenolysis and gluconeogenesis?

A

Phosphate

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55
Q

Galactosemia is caused by an absence of what enzyme?

A

Galactose-1-phosphate uridyltransferase

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56
Q

Which has milder symptoms: classic galactosemia, or galactokinase deficiency?

A

Galactokinase deficiency

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57
Q

What is the inheritance pattern of galactokinase deficiency?

A

Autosomal recessive

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58
Q

What enzyme interconverts UDP-glucose and UDP-galactose?

A

4-Epimerase

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59
Q

Galactitol is formed from galactose using which enzyme?

A

Aldose reductase

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60
Q

In galactose metabolism, the conversion of galactose-1-phosphate to glucose-1-phosphate is catalyzed by which enzyme?

A

Galactose-1-phosphate uridyltransferase; deficiency causes classic galactosemia

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61
Q

In galactose metabolism, a block in the conversion of galactose to galactose-1-phosphate is caused by what disease?

A

Galactokinase deficiency

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62
Q

In galactosemia, the build-up of which substance causes damage to organs?

A

Galatitol

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63
Q

What is the treatment for galactosemia?

A

Removing galactose and lactose from the diet

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64
Q

Cataracts, hepatosplenomegaly, and mental retardation are symptoms of what disorder of galactose metabolism?

A

Galactosemia; it is more severe than galactokinase deficiency

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65
Q

In galactose metabolism, a block in the conversion of galactose-1-phosphate to glucose-1-phosphate is caused by what disease?

A

Galactosemia

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66
Q

Galactosemia demonstrates what type of inheritance pattern?

A

Autosomal recessive

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67
Q

Glucose is converted to its alcohol counterpart, sorbitol, and thus trapped in the cell via what enzyme?

A

Aldose reductase

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68
Q

Some tissues convert sorbitol to fructose via what enzyme?

A

Sorbitol dehydrogenase

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69
Q

List the organs that have both aldose reductase and sorbitol dehydrogenase

A

Liver, ovaries, and seminal vesicles

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70
Q

The enzymes aldose reductase and sorbitol dehydrogenase both require what cofactor?

A

NADPH

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71
Q

What organ has only aldose reductase and no sorbitol dehydrogenase?

A

Kidney

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72
Q

What type of cell in the nervous system has only aldose reductase and no sorbitol dehydrogenase?

A

Schwann cells

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73
Q

What parts of the eye have only aldose reductase and no sorbitol dehydrogenase?

A

Lens and retina

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74
Q

Why is sorbitol considered osmotically active?

A

Because of its inability to freely cross the membrane like glucose

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75
Q

In what disease is sorbitol accumulation common?

A

Diabetes

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76
Q

What three conditions are seen in chronic diabetes due to the osmotic damage caused by sorbitol?

A

Cataracts, retinopathy, peripheral neuropathy

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77
Q

What two sugars that are also converted to their respective alcohol forms via aldose reductase are considered osmotically active?

A

Fructose and galactose

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78
Q

Which populations tend to be lactase deficient in adulthood?

A

Asian and African-American populations

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79
Q

A woman gets bloating, cramps, and diarrhea after eating milk and ice cream. What enzyme is likely deficient in this patient?

A

Lactase

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80
Q

What is the treatment for lactase deficiency?

A

Lactase pills or dietary avoidance of lactose

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81
Q

Lactase deficiency causes what type of diarrhea when lactose is consumed?

A

Osmotic diarrhea due to undigested sugars that are not absorbed in the small intestine

82
Q

The amino acids found in proteins in the human body are ______ (R-form/L-form).

A

L-form

83
Q

Name the four amino acids that are both glucogenic and ketogenic.

A

Isoleucine, phenylalanine, threonine, and tryptophan

84
Q

Name the two purely ketogenic amino acids.

A

Leucine and lysine

85
Q

Name the four amino acids that are purely glucogenic.

A

Methionine, valine, arginine, and histidine

86
Q

Which two amino acids become essential during periods of rapid growth?

A

Arginine and histidine

87
Q

What type of amino acids make up histones? Why?

A

Basic amino acids; the positive charge interacts with the negatively charged DNA to bind it in coils

88
Q

What is the significance of an amino acid being considered essential?

A

It must come from the diet

89
Q

Name the two acidic amino acids.

A

Aspartate and glutamate

90
Q

Through what process can glucogenic amino acids be converted to glucose?

A

Gluconeogenesis

91
Q

Name the amino acids that are basic

A

Arginine, lysine and histidine

92
Q

Which two amino acids are positively charged at body pH? Which are negatively charged?

A

Positive: arginine and lysine; Negative: aspartate and glutamate

93
Q

The urea cycle ultimately yields ______, which is excreted in the urine, and _____, which can enter the citric acid cycle.

A

Urea; fumarate

94
Q

In what organ does the urea cycle occur?

A

The liver

95
Q

Does the urea cycle occur in the mitochondria, in the cytosol, or both?

A

Both

96
Q

In the urea cycle, the formation of what substance occurs in the mitochondria (whereas the remaining steps occur in the cytosol)?

A

Carbamoyl phosphate

97
Q

What amino acid is the immediate precursor to urea in the urea cycle?

A

Arginine

98
Q

The urea cycle excretes an excess of which element generated by amino acid catabolism?

A

Nitrogen

99
Q

What amino acid combines with citrulline to form arginosuccinate in the urea cycle?

A

Aspartate

100
Q

What is the rate-limiting enzyme of the urea cycle?

A

Carbamoyl phosphate synthetase I

101
Q

What reaction is catalyzed by carbamoyl phosphate synthetase I?

A

The conversion of CO2 and NH4 into carbamoyl phosphate, a process requiring 2 adenosine triphosphate

102
Q

Where in the cell does the rate-limiting step of the urea cycle occur?

A

In the mitochondria

103
Q

From which molecules are the nitrogen atoms in urea derived?

A

Ammonium and aspartate

104
Q

What enzyme catalyzes the conversion of carbamoyl phosphate and ornithine into citrulline?

A

Ornithine transcarbamoylase

105
Q

What are two metabolic fuels produced by amino acid catabolism?

A

Pyruvate and acetyl-CoA

106
Q

What precursors are converted by arginosuccinate synthetase into arginosuccinate?

A

Citrulline and aspartate

107
Q

What by-product of the urea cycle is released by arginosuccinase?

A

Fumarate, which may enter the tricarboxylic acid cycle, whereas arginine is converted into urea and ornithine in the urea cycle

108
Q

What is the enzyme that creates urea from arginine in the urea cycle?

A

Arginase

109
Q

Ammonia is transported by which amino acid from the muscle to the liver to participate in urea formation?

A

Alanine

110
Q

Trace the pathway of an ammonium group from its creation by amino acid catabolism in muscle to excretion.

A

It is donated to pyruvate to form alanine, which travels to the liver via blood, where it is donated to -ketoglutarate to form glutamate, which can be excreted via the urea cycle

111
Q

Ammonia groups are transported from muscle to liver via which molecule?

A

Alanine

112
Q

What is the fate of alanine in the liver after it donates its ammonia group to the urea cycle?

A

It becomes pyruvate and goes through gluconeogenesis

113
Q

The addition of an ammonia group to -ketoglutarate produces what substance?

A

Glutamate

114
Q

The addition of an ammonia group to pyruvate produces what substance?

A

Alanine

115
Q

Name two categories of hyperammonemia and examples of each.

A

Acquired, as in liver failure; hereditary, as in urea cycle enzyme deficiencies

116
Q

Excess ammonium depletes _____, leading to inhibition of the citric acid cycle.

A

-Ketoglutarate

117
Q

Describe the clinical presentation of hyperammonemia

A

Tremor, slurring of speech, somnolence, vomiting, cerebral edema, and blurring of vision

118
Q

A patient presents with tremor, slurring of speech, somnolence, vomiting, cerebral edema, and blurring of vision, and is diagnosed with hyperammonemia. What two treatments could lower her serum ammonia levels?

A

Benzoate or phenylbutyrate

119
Q

What is the most common urea cycle enzyme deficiency?

A

Ornithine transcarbamoylase deficiency

120
Q

What is the inheritance pattern of ornithine transcarbamoylase deficiency?

A

X-linked recessive

121
Q

You see a patient with a urea cycle enzyme deficiency, but have ruled out ornithine transcarbamoylase deficiency. What is the inheritance pattern?

A

Autosomal recessive (all urea cycle enzyme deficiencies except ornithine transcarbamoylase deficiency have this inheritance pattern)

122
Q

How does ornithine transcarbamoylase deficiency present clinically?

A

Tremor, lethargy, vomiting in a neonate who may be found to have cerebral edema and elevated ammonia on lab studies

123
Q

When would you most likely detect an ornithine transcarbamoylase deficiency in a patient?

A

Typically this is evident in the first days of life, but it may have later onset

124
Q

What molecule is excess carbamoyl phosphate converted into?

A

Orotic acid

125
Q

What serum finding is diagnostic of ornithine transcarbamoylase deficiency?

A

Elevated orotic acid

126
Q

A newborn patient has a blood test which shows increased orotic acid, low BUN, and increased ammonia; what disease do you suspect?

A

Ornithine transcarbamoylase deficiency

127
Q

Which amino acid is the parent compound of tyrosine, thyroxine, dopa, melanin, dopamine, norepinephrine, and epinephrine?

A

Phenylalanine

128
Q

What amino acid is the parent compound of niacin, serotonin, and melatonin?

A

Tryptophan

129
Q

From which amino acid is histamine derived?

A

Histidine

130
Q

From which amino acid is haem derived?

A

Glycine

131
Q

Which amino acid is the parent compound of creatine, urea, and nitric oxide?

A

Arginine

132
Q

From which amino acid is γ-aminobutyric acid derived?

A

Glutamate

133
Q

From which amino acid is porphyrin derived?

A

Glycine

134
Q

From which amino acid are NAD+ and NADP+derived?

A

Tryptophan

135
Q

The reaction in which GABA is derived from glutamate is catalyzed by which enzyme?

A

Glutamate decarboxylase; the reaction also requires vitamin B6

136
Q

Dopa decarboxylase requires what cofactor? What inhibits this cofactor?

A

Vitamin B6; carbidopa

137
Q

What cofactor does dopamine -hydroxylase require?

A

Vitamin C

138
Q

What cofactor does phenylethanolamine N-methyltransferase require?

A

S-adenosylmethionine

139
Q

Dopamine is broken down to homovanillic acid via what two enzymes?

A

Monoamine oxidase and catechol-O-methyltransferase

140
Q

Monoamine oxidase and catechol-O-methyltransferase break down norepinephrine to what product?

A

Vanillymandelic acid

141
Q

Epinephrine is broken down to what product via monoamine oxidase and catechol-O-methyltransferase?

A

Metanephrine

142
Q

In a normal individual, is tyrosine an essential or a nonessential amino acid?

A

Nonessential

143
Q

True or False? Phenylketonuria is a disorder of branched-chain amino acid metabolism.

A

False ; phenylketonuria is a disorder of aromatic amino acid metabolism (remember: aromatic amino acid metabolism = musty body odor)

144
Q

What is an example of dietary phenylalanine?

A

Aspartame (eg, NutraSweet)

145
Q

A woman with phenylketonuria learns she is pregnant; what would you advise her about her diet?

A

It is important to be strict about phenylalanine consumption, since it is a teratogen in women with phenylketonuria

146
Q

Phenylketonuria can result from two defects: (1) decreased levels of the enzyme _____ _____ or (2) decreased levels of _____ _____.

A

Phenylalanine hydroxylase; tetrahydrobiopterin cofactor

147
Q

In individuals with phenylketonuria, is tyrosine an essential or a nonessential amino acid?

A

Essential

148
Q

An infant is found to have mental retardation and growth retardation. He has fair skin, eczema, and a musty body odor. What is this infant;s underlying metabolic disorder?

A

Phenylketonuria

149
Q

What dietary modifications are used to treat phenylketonuria?

A

Decreasing phenylalanine and increasing tyrosine in the diet

150
Q

A child has increased phenylacetate, phenyllactate, and phenylpyruvate in her urine. What is the underlying metabolic disorder?

A

Phenylketonuria

151
Q

What type of inheritance pattern does phenylketonuria demonstrate?

A

Autosomal recessive

152
Q

Normally, tyrosine can be made from what amino acid precursor?

A

Phenylalanine; however, patients with phenylketonuria lack the enzymes to carry out the reaction

153
Q

What would a urinalysis show in a patient who has a deficiency of phenylalanine hydroxylase?

A

Elevated phenylketones

154
Q

What might you see in an infant born to a mother with phenylketonuria and exposed to high in utero levels of phenylalanine?

A

Microcephaly, mental retardation, growth retardation, congenital heart defects

155
Q

True or False? Phenylketonuria is screened for at birth.

A

True; it has a prevalence of 1:10,000 and is part of newborn screening in most states

156
Q

A deficiency of which enzyme results in the disease alkaptonuria?

A

Homogentisic acid oxidase

157
Q

Alkaptonuria results from a defect in the degradation of which amino acid?

A

Tyrosine

158
Q

A patient submits a urine sample for routine urinalysis. A technician notes that it turns black upon standing. What is the underlying metabolic disorder?

A

Alkaptonuria

159
Q

What are the signs and symptoms of alkaptonuria?

A

Dark connective tissue, debilitating arthralgias, pigmented sclerae

160
Q

What is the prognosis for patients with alkaptonuria?

A

Alkaptonuria is a benign disease, although patients may suffer from arthralgias

161
Q

What is the inheritance pattern of alkaptonuria?

A

Autosomal recessive

162
Q

Albinism may be caused by a defect in the ability to synthesize melanin as a result of a deficiency in the enzyme _____, or it may result from a defect in the transporters of the amino acid _____.

A

Tyrosinase; tyrosine

163
Q

Albinism involves decreased amounts of what substance and thus a lack of pigmentation?

A

Melanin

164
Q

Which cells are the embryologic precursors of melanocytes?

A

Neural crest cells; failure of these cells to migrate results in albinism

165
Q

Patients with albinism are at an increased risk for what type of cancer?

A

Skin cancer

166
Q

How many parents must be carriers of a mutation for a child to have albinism secondary to mutated tyrosinase?

A

Two; this is an autosomal-recessive condition

167
Q

Why does albinism show variable inheritance if it is an autosomal recessive disorder?

A

It exhibits locus heterogeneity

168
Q

A patient with homocystinuria due to cystathionine synthase deficiency should be treated with which dietary modifications?

A

A diet that is low in methionine and high in cystine, vitamin B12, and folate

169
Q

A patient has homocystinuria that is caused by a decreased affinity of cystathionine synthase for pyridoxal phosphate. What is the treatment?

A

Large doses of vitamin B6

170
Q

Which amino acid, usually nonessential, becomes essential in patients with homocystinuria?

A

Cysteine

171
Q

A defect in cystathionine synthase leads to what disorder?

A

Homocystinuria

172
Q

A decrease in the affinity of cystathionine synthase for pyridoxal phosphate leads to what disorder?

A

Homocystinuria

173
Q

A defect in homocysteine methyltransferase leads to what disorder?

A

Homocystinuria

174
Q

Homocystinuria may be caused by which three defects?

A

A defect in cystathionine synthase, a decrease in the affinity of cystathionine synthase for its cofactor (pyridoxal phosphate), or a defect in homocystene methyltransferase

175
Q

What test would you order in a patient who has advanced early atherosclerotic disease, tall stature, kyphosis, and lens subluxation?

A

Urine studies, looking for elevated homocysteine

176
Q

A patient has mental retardation, osteoporosis, tall stature, lens subluxation, and a history of stroke and myocardial infarction. What is the underlying metabolic disorder?

A

Homocystinuria

177
Q

What two amino acids can be produced from homocysteine?

A

Methionine and cysteine

178
Q

The production of cysteine from homocysteine requires which vitamin as a cofactor?

A

Vitamin B6

179
Q

What enzyme is required for the conversion of homocysteine to methionine?

A

Homocysteine methyltransferase

180
Q

What enzyme is required for the conversion of homocysteine to cystathionine?

A

Cystathionine synthase

181
Q

What cofactor is required for the conversion of homocysteine to methionine?

A

Vitamin B12

182
Q

Cystinuria is a defect in an amino acid transporter that is located in which part of the body?

A

The proximal convoluted tubule of the kidney

183
Q

What is the prevalence of cystinuria?

A

4.9027777778

184
Q

Cystinuria is a defect in the transport of which four amino acids?

A

Cysteine, ornithine, lysine, and arginine

185
Q

What is the major clinical sequela of cystinuria?

A

Increased risk of staghorn calculi

186
Q

What medication is used to treat cystinuria?

A

Acetazolamide (carbonic anhydrase inhibitor)

187
Q

What symptom is characteristic of cystinuria?

A

Cystine kidney stones (cystine staghorn calculi)

188
Q

How does acetazolamide prevent cystine stone formation?

A

It alkalinizes the urine, increasing the solubility of cystine

189
Q

What is the molecular structure of cystine?

A

Two cysteine molecules connected by a disulfide bond

190
Q

What is the inheritance pattern of cystinuria?

A

Autosomal recessive

191
Q

Maple syrup urine disease is caused by a defect in what enzyme?

A

-Ketoacid dehydrogenase

192
Q

Maple syrup urine disease is the result of the blocked degradation of what type of amino acids?

A

Branched amino acids

193
Q

Which three branched amino acids are elevated in the blood of a patient with maple syrup urine disease?

A

Isoleucine, leucine, and valine (remember: I Love Vermont maple syrup from maple trees, with branches)

194
Q

What is the prognosis for a neonate diagnosed with maple syrup urine disease?

A

Most children with the disease die in infancy

195
Q

What is Hartnup disease?

A

A disorder in which a defective neutral amino acid transporter leads to tryptophan wasting in the urine and gastrointestinal tract

196
Q

What are the clinical signs and symptoms of Hartnup disease?

A

Hartnup disease causes pellagra due to inability to synthesize niacin; the result is diarrhea, dermatitis, and dementia

197
Q

How is Hartnup disease inherited?

A

Autosomal recessive

198
Q

Glucagon and epinephrine activate the second messenger cAMP via what enzyme?

A

Adenylyl cyclase

199
Q

What two factors in muscle, by activating phosphorylase kinase, ensure that glycogenolysis is coordinated with muscle activity?

A

Calcium and calmodulin

200
Q

What enzyme activates glycogen phosphorylase kinase?

A

Protein kinase A

piggy (83 decks)

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