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USMLE > Biochemistry Metabolism > Flashcards

Biochemistry Metabolism Flashcards

1
Q

What is the rate determining step of Glycolysis?

A

Fructose-6-P –> Fructose 1,6-BP via PFK-1

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2
Q

Which cofactors positively regulate glycolysis?

A

AMP, fructose 2,6 BP

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3
Q

Which cofactors negatively regulate glycolysis?

A

ATP, citrate

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4
Q

Where does glycolysis occur and what is the end product?

A

Cytosol, pyruvate

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5
Q

What happens with pyruvate after glycolysis? (2 options)

A

Aerobic metabolism via TCA cycle and Ox-pphos in mitochondria
Anaerobic metabolism via Lactate dehydrogenase to lactate

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6
Q

What is the rate limiting step in gluconeogenesis with which enzyme?

A

Fructose 1,6-BP –> Fructose 6 P via Fructose 1,6- bisphosphatase

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7
Q

Negative regulators of gluconeogenesis

A

AMP, fructose-2,6,BP

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8
Q

What is the rate determining step and enzyme for TCA cycle?

A

Isocitrate –> alpha-ketoglutarate via Isocitrate dehydrogenase

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9
Q

What is the positive regulator of TCA cycle?

A

ADP

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10
Q

What negatively regulates the TCA cycle?

A

ATP, NADH

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11
Q

What is the rate-determining enzyme for glycogenesis

A

Glycogen synthase

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12
Q

What positively regulates glycogenesis?

A

Insulin, G6P and cortisol

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13
Q

What negatively regulates glycogenesis

A

Epinephrine, glucagon

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14
Q

What is the rate determining enzyme for Glycogenolysis

A

Glycogen phosphorylase

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15
Q

What positively regulates glycogenolysis

A

epinephrine, glucagon, AMP

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16
Q

What negatively regulates glycogenolysis

A

G6P, insulin, ATP

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17
Q

What is the function of the HMP shunt?

A

Produce NADPH

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18
Q

What is the rate determining enzyme of HMP shunt?

A

G6PD

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19
Q

What negatively regulates HMP shunt?

A

NADPH

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20
Q

What is the rate determining enzyme for de novo pyrmidine synthesis

A

Carbamoyl phosphate synthetase II

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21
Q

What is the rate determining enzyme of de novo purine syntesis

A

PRPP amidotransferase

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22
Q

What is the rate determining enzyme for urea cycle?

A

Carbamoyl phosphate synthetase I

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23
Q

What positively regulates urea cycle?

A

N-acetylglutamate and proteins

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24
Q

What negatively regulates fatty acid oxidation?

A

Malonyl-CoA

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25
Q

What is the rate limiting enzyme of fatty acid oxidation?

A

Carnitine acyltransferase I

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26
Q

Which two products does HMG-CoA ultimately make?

A

Cholesterol or ketones (beta-hydroxybutyrate)

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27
Q

Which step is pyruvate dehydrogenase involved in and which cofactor does it use?

A

Pyruvate –> Acetyl CoA; Thiamine

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28
Q

Which step is pyruvate kinase involved in?

A

PEP–> pyruvate

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29
Q

Which step is isocitrate dehydrogenase involved in?

A

Isocitrate –> alpha-KG

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30
Q

Which step is alpha-KG dehydrogenase involved in and what cofactor does it use?

A

alpha-KG–> Succinyl CoA; Thiamine

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31
Q

How much ATP does aerobic metabolism produce for heart and lungs using which shuttle?

A

32 net via malate-aspartate

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32
Q

How much ATP does aerobic metabolism produce for muscle using which shuttle?

A

30 net via G3P shuttle

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33
Q

What does arsenic poison due?

A

Causes glycolysis to produce 0 ATP

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34
Q

What 4 processes is NADPH used in?

A

Anabolic processes
Respiratory burst
Cytochrome P450 system
Glutathione reductase

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35
Q

Which processes is NAD+ usually used in?

A

Catabolic processes

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36
Q

What is the first committed step in glycolysis?

A

Glucose –> G6P (irreversible)

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37
Q

Which two enzymes are involved in the conversion of glucose to G6P

A

Hexokinase (most tissues except liver and pancreas) and Glucokinase (pancreas and liver)

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38
Q

Which enzyme is expressed at low glucose concentrations?

A

Hexokinase

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39
Q

Does hexokinase have a high or low Km?

A

low (high affinity for glucose)

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40
Q

Does hexokinase have a high or low Vm?

A

low (lower capacity)

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41
Q

Which enzyme mutation causes maturity-onset diabetes of the young?

A

Glucokinase

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42
Q

Which kinase responds to insulin levels?

A

Glucokinase

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43
Q

Which enzyme is inhibited by G6P?

A

Hexokinase

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44
Q

Which enzyme reactions produce ATP in glycolysis?

A

Phosphoglycerate kinase and pyruvate kinase

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45
Q

How does glucagon influence cAMP levels, FBPase-2 and PFK-2 levels?

A

Increase cAMP, increase FBPase-2 and decrease PFK-2

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46
Q

How does phosphorylation affect FBP-2ase and PFK-2

A

Activates FBP-ase2 and inactivates PFK-2

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47
Q

How does insulin influence cAMP, FBP-2ase and PFK-2 levels?

A

Decrease cAMP, decrease FBP-ase2 and increase PFK-2

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48
Q

What is the mnemonic for the 5 cofactors needed for the pyruvate dehydrogenase complex?

A

Tender Loving Care for Nancy

Thiamine (B1), Lipoic Acid, CoA (B5), FAD (B2), NAD (B3)

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49
Q

What activates PDH complex and alpha-KG complex?

A

increase NAD+/NADH, ADP, and Ca++

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50
Q

How does arsenic poisoning affect TCA?

A

Inhibits Lipoic acid so a-KG DH and PDH complexes cannot function (TCA cycle inhibited)

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51
Q

What is the clinical presentation of Arsenic poisoning?

A

Vomiting, rice-water stools, garlic breath

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52
Q

How Pyruvate dehyrdogenase deficiency inherited?

A

X-linked

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53
Q

What are the clinical findings of PDH deficiency?

A

neurologic defects, lactic acidosis (pyruvate gets shunted to lactate buildup bc cannot enter TCA) and increase serine alanine in infancy

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54
Q

What is the treatment for PDH complex deficiency?

A

High fat content diet or increase lysine and leucine diet (ketogenic diet)

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55
Q

What are the 4 products that pyruvate can be metabolized to?

A

Alanine (muscles, uses B6)
OAA (TCA replenisher, gluconeogenesis, uses B7)
Acetyl-CoA (TCA, uses B1, B2, B3, B5)
Lactate (uses B3)

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56
Q

Which cells rely on Corii cycle (pyruvate –> lactate)?

A

RBCs, WBCs, kidney medulla, lens, testes, cornea

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57
Q

Which step in TCA cycle produces GTP?

A

Succinyl CoA –> Succinate

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58
Q

What is the mnemonic for the TCA cycle?

A 
Citrate Is Krebs Starting Substrate For Making Oxaloacetate
Isocitrate
alpha-Ketoglutarate
Succinyl coA
Succinate
Fumarate
Malate
OAA
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59
Q

How much ATP does the TCA cycle produce per glucose?

A

10

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60
Q

Which complex of the electron transport chain does Rotenone inhibit?

A

Complex 1

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61
Q

Which complex of the ETC does Antinomycin inhibit?

A

Complex 3 (succinate dehyrdogenase)

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62
Q

Which complex of the ETC do Carbon monoxide and cyanide inhibit?

A

Complex 4

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63
Q

What effect do complex inhibitors of the ETC have on ATP levels and proton gradient?

A

decrease proton gradient and ATP synthesis

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64
Q

Which molecule directly inhibits ATP synthase?

A

Oligomycin

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65
Q

What is the effect of Oligomycin on ATP and proton gradient?

A

Increase proton gradient, decrease ATP production

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66
Q

What is the effect of uncoupling agents of the etc?

A

Increase oxygen consumption, decrease ATP production, but electron transport continues. produce heat

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67
Q

What are three ETC uncouplers?

A

2,4-Dinitrophenol (weight loss), Aspirin (fevers after OD), thermogenin in brown fat

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68
Q

What is the pentose phosphate pathway? (HMP shunt)

A

Metabolic pathway to produce NADPH

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69
Q

Which cells primarily use HMP shunt?

A

Red blood cells, liver and adrenal cortex cells, lactating mammary glands

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70
Q

How is NADPH generated?

A

Excess G6P is converted to 6-PG via G6DH and NADPH is produced

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71
Q

What are 3 major functions of NADPH?

A

Glutathione reduction (prevents oxidative damage)
Ribose synthesis for nucleotides
Cholesterol and fatty acid biosynthesis

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72
Q

Heinz bodies and bite cells are indicative of which malignancy?

A

G6PDH deficiency

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73
Q

How is G6PDH deficiency inherited ? What is its protective role?

A

Autosomal recessive, provides malarial resistance

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74
Q

What are the precipitating factors for hemolytic anemia in G6PDH?

A

recent infection, fava beans, sulfonamides, primaquine, antituberculosis drugs

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75
Q

How does glutathione provide fight against free radicals?

A

Used by glutathione peroxidase to neutralize H2O2 into 2H2O

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76
Q

Where does fructose metabolism occur?

A

Liver

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77
Q

What is essential fructosuria a disorder of?

A

Defect in fructokinase so cannot convert fructose to fructose-1-P

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78
Q

Which steps of fructose metabolism consume ATP?

A

fructokinase and triose kinase (Glyceraldehyde to G3P)

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79
Q

Which step of fructose metabolism consume NADH?

A

Glycerol to glyceraldehyde

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80
Q

What is the end product of fructose metaoblism?

A

G3P, enters glycolysis

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81
Q

What are the symptoms of essential fructosuria and how is it inherited?

A

Fructose in blood and urine; AR

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82
Q

What are the symptoms of fructose intolerance?

A

Hypoglycemia, jaundice, cirrhosis and vomiting

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83
Q

What is fructose intolerance a defect of

A

Aldolase B so cannot convert Fructose 1 P to DHAP or Glyceraldehyd

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84
Q

How does fructose intolerance lead to hypoglycemia?

A

Lowers availability of phosphate so glycogenolysis and gluconeogenesis cannot take place

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85
Q

What is the treatment for fructose intolerance?

A

Avoid foods with sucrose and fructose

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86
Q

What are the urine dipstick results for fructose intolerance?

A

negative; urine dipstick measures glucose and you don’t have enough glucose in this d/o

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87
Q

Describe the mnemonic FAB GUT

A

Fructose is to Aldolase B as Galactose is to Uridiyltransferase; defects in both lead to phosphate depletion

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88
Q

What is the end-product of galactose metabolism?

A

Glucose-1-P, enters glycogenesis or glycolysis

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89
Q

What are the symptoms of galactokinase deficiency

A

Galactose in blood and urine, infantile cataracts

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90
Q

How can galactokinase deficiency present?

A

Failure to track objects or develop social smile

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91
Q

When do symptoms of galactose metabolism issues develop?

A

When infant begins feeding (breastmilk has lactose)

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92
Q

Which enzyme is absent in classic galactosemia?

A

galactose-1-phosphate uridyltransferase?

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93
Q

What are the symptoms of galactosemia?

A

Hepatomegaly, infantile cataracts, jaundice, failure to thrive

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94
Q

What causes infantile cataracts in galactose metabolism disorder?

A

Accumulation of galactitol, which accumulates in lens

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95
Q

What is the treatment for galactosemia in infants?

A

exclude galactose and lactose from diet

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96
Q

Infection with which agent leads to sepsis in neonates with galactosemia?

A

E. Coli

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97
Q

Which enzyme converts Glucose to Sorbitol?

A

Aldose reductase (with NADPH)

98
Q

What care sorbitol accumulation in cells cause?

A

Osmotic damage (cataracts, peripheral neuropathy, retinopathy)

99
Q

Which enzyme converts sorbitol to fructose?

A

Sorbitol dehydrogenase

100
Q

Which organs contain both aldose reductase and sorbitol dehydrogenase?

A

Liver, ovaries and seminal vesicles

101
Q

Which organs only contain Aldose reductase?

A

Schwann cells, retina, kidneys and lens

102
Q

What are the 10 essential amino acids? (PVT TIM HALL)

A 
Phenylalanine
Valine
Threonine
Tryptophan
Isoleucine
Methionine
Histidine
Arginine
Leucine
Lysine
103
Q

Which amino acids are ketogenic?

A

Leucine and Lysine

104
Q

Which amino acids are glucogenic?

A

Histidine, Valine, Methionine

105
Q

What charge do acidic amino acids carry at body pH?

106
Q

Which two amino acids primarily compose histones?

A

Arginine and LYsine

107
Q

Which two amino acids are essential during periods of growth?

A

Arginine and Histidine

108
Q

What are the components of the urea cycle? (Orange Cars Citrus Asparagus Are Fun Artsy Urinators)

A

Ornithine + Carbamoyl phosphate –> Citrulline + Aspartate –> Arginosuccinate–> Fumarate –> Arginine –>Urea

109
Q

What is the function of urea cycle?

A

Convert excess NH3 from protein metabolism to urea and excrete in urine

110
Q

What does a defect in any step of the urea cycle lead to?

A

Hyperammonemia (elevated NH3 in blood)

111
Q

What are the symptoms of hyperammonemia?

A

Asterixis, slurring of speech, somnolence, vomiting, cerebral edema, blurring of vision

112
Q

Where is carbamoyl phosphate synthetase I found?

A

Mitochondria of liver

113
Q

What is the Cahill cycle?

A

Conversion of Glucose to Ammonia (Alanine) in muscle, and Alanine (NH3) to glucose in liver

114
Q

What is the consequence of hyperammonemia on metabolism?

A

Overactivity of Cahill cycle uses up alpha-ketoglutarate leading to inhibition of TCA cycle

115
Q

What is lactulose used for and how does it function?

A

Decreases ammonia levels by acidifying GI tract and trapping NH4+ for excretion

116
Q

What are 6 primary treatments for hyperammonemia?

A

Lactulose, Rifaximin, Benzoate, Phenylacetate, Phenylbutyrate

117
Q

What is the function of Rifaximin in lowering ammonia levels?

A

Decreases colonic ammoniagenic bacteria

118
Q

How do benzoate, phenylacetate and phenylbutyrate function to decrease ammonia?

A

bind to NH4+ and lead to excretion

119
Q

How do N-acetylglutamate synthase deficiency and carbamoyl phosphate synthease I deficiency present in neonates?

A

Hyperammonemia–> poor control of respiration, body temperature, developmental delay, intellectual disability

120
Q

How is ornithine transcarbamylase deficiency inherited?

121
Q

How does ornithine transcarbamylase deficiency present?

A

elevated orotic acid in blood and urine, decrease BUN, symptoms of hyperammonemia (asterixis, slurring of speech, somnolence, vomiting, cerebral edema)

122
Q

Which amino acid forms Heme?

A

Glycine (+B6)

123
Q

Which amino acid forms NAD+/NADP+

A

Tryptophan (+B2, B6)

124
Q

Which amino acid forms GABA and Glutathione?

A

Glutamate (+B6 for GABA)

125
Q

Which amino acid forms Creatine, Urea and Nitric Oxide?

126
Q

Which amino acid forms Dopamine, NE, E, Tyrosine, Melanin?

A

Phenylalanine

127
Q

Which enzyme is deficient in autosomal recessive Phenylketonuria?

A

Phenylalanine hydroxylase

128
Q

Which amino acid accumulates in PKU?

A

Phenylalanine

129
Q

What is the key clinical presentation of a baby with PKU?

A

MUSTY BODY ODOR, pale skin, eczema, seizures, growth retardation, intellectual disability

130
Q

What is the treatment for PKU?

A

Avoid aspartame and phenylalanine, increase Tyrosine in diet and BH4 supplementation

131
Q

If a mother has PKU how does neonate present?

A

microcephaly, intellectual disability, cardiac defects, growth retardation

132
Q

Which enzyme is deficient in maple syrup urine disease?

A

branched-chain alpha-ketoacid dehydrogenase (or B1)

133
Q

What is the defect in maple syrup urine disease?

A

Blocked degradation of branched amino acids Isoleucine, Leucine, Valine

134
Q

List the branched amino acids (I Love Vermont Maple Syrup)

A

Isoleucine, Leucine, Valine

135
Q

How does maple syrup urine disease present?

A

vomiting, poor feeding, urine smells like burnt sugar/maple syrup

136
Q

What are the long-term consequences of untreated maple syrup urine disease?

A

Intellectual disability, severe CNS defects, death

137
Q

How is maple syrup urine disease treated?

A

Avoid Isoleucine, Leucine, Valine in diet; B1 supplementation

138
Q

What is Alkaptonuria?

A

Autosomal Recessive defect in Tyrosine metabolism to Fumarate

139
Q

Which enzyme is deficient in Alkaptonuria and what accumulates in tissues?

A

Homogentisate oxidase is deficient; pigment-forming homogentisic acid accumulates in connective tissue

140
Q

Clinical presentation of Alkaptonuria

A

Bluish-black pigments on sclerae (ochronosis) and connective tissue; urine turns black on prolonged exposure to air

141
Q

What is a rheumatic consequence of alkaptonuria?

A

Debilitating arthralgias (homogentisic acid is toxic to cartilage); osteoarthropathy

142
Q

How is homocysteinuria inherited?

A

Autosomal Recessive

143
Q

Which enzymes may be deficient/defective in Homocysteinuria?

A

Cystathione synthase or Methionine Synthase

144
Q

What is the treatment for Cystathione synthase Homocysteinuria?

A

Lower methionine intake, increase cysteine intake, increase B12 and folate intake

145
Q

What is the treatment for methionine synthase deficient homocysteinuria

A

increase methionine in diet

146
Q

What are the clinical findings of homocysteinuria?

A

Excess homocysteine in urine, intellectual disability, Marfanoid habitus, kyphosis, thrombosis, atherosclerosis, and lens subluxation

147
Q

Which amino acids are lost in urine of patients suffering from cysteinuria?

A

Cystine, Ornithine, Lyscine, Arginine (COLA)

148
Q

What is the treatment for cysteinuria

A

Alakanization of urine (Acetazolamide, postassium citrate) and chelating agents (penicillamine)

149
Q

Which second messenger system does Insulin use to stimulate glycogenesis?

A

Tyrosine Kinase to activate Protein phosphatase to activate glycogen synthase

150
Q

Which second messenger system do Glucagon and epinephrine (Beta receptor) use to activate glycogenolysis?

A

Adenylate cyclase –> cAMP–> PKA –> glycogen phosphorylase –> glycogenolysis

151
Q

Which second messenger does epinephrine on alpha receptors (liver) use to activate glycogenolysis?

152
Q

Is glycogen synthase activated or inactivated by phosphorylation?

A

inactivated

153
Q

Is glycogen phosphorylase activated or inactivated by phosphorylation?

154
Q

Which method identifies glycogen in cells (Glycogen storage dz dx)?

A

Periodic acid-Schiff stain

155
Q

What is Glycogen Storage Disease Type I?

A

Von Gierke’s disease

156
Q

Which enzyme is deficient in Von Gierke’s (Type I)?

A

Glucose-6-phosphatase

157
Q

What are the findings in Von Gierke’s

A

Severe fasting hypoglycemia, gout (increased uric acid), increased triglycerides, hepatomegaly and increased glycogen in liver

158
Q

What is the treatment for Von Gierke’s

A

glucose and cornstarch supplementation, avoidance of fructose and galactose

159
Q

Which enzyme is deficient in Pompe disease (Type II glycogen storage disorder)?

A

alpha-1,4 glucosidase in lysosomes

160
Q

What are the clinical findings of Pompe disease?

A

Cardiomegaly, hypertrophic cardiomyopathy, exercise intolerance, early death

161
Q

What enzyme storage disease is Cori?

162
Q

Which enzyme is defective in Cori disease?

A

Debranching enzyme (alpha 1,6 glucosidase)

163
Q

What are the findings of Cori disease?

A

Normal blood lactate, gluconeogenesis intact; milder fasting hypoglycemia, dextrin-like structures in cytosol

164
Q

Which type of glycogen storage disease is McArdle?

165
Q

Which enzyme is affected in McArdle disease?

A

Glycogen phosphorylase

166
Q

What are the clinical findings in McArdle disease?

A

Muscle cramps, myoglobinuria with strenuous exercise, arrhythmia from electrolyte abnormalities

167
Q

Name the 4 Glycogen Storage diseases

A

Von Gierkes, Pompe, McArdle and Cori

168
Q

Name the 6 Sphingolipidoses Lysosomal Storage Diseases

A

Gaucher, Fabry, Niemann-Pick, Tay-Sachs, Krabbe and Metacrhomic Leukodystrophy

169
Q

Which enzyme is defective in Gaucher disease?

A

Glucocerebrosidase

170
Q

What are the clinical findings of Gaucher disease

A

Jaundice, hepatosplenomegaly, aseptic necrosis of femur, pancytopenia, osteoporosis

171
Q

What are gaucher cells on histology?

A

Lipid laden macrophages (crumpled tissue appearance)

172
Q

How is Gaucher disease inherited

A

Autosomal recessive

173
Q

What is the enzyme deficiency in Krabbe disease?

A

Galactocerebrosidase

174
Q

Which molecules accumulate in Krabbe disease?

A

Galactocerebroside, psychosine

175
Q

Clinical findings of Krabbe disease

A

Peripheral neuropathy, optic atrophy, globoid cells, developmental delay

176
Q

How is Krabbe disease inherited

A

Autosomal recessive

177
Q

How is Tay Sachs disease inherited?

A

Autosomal Recessive

178
Q

Which enzyme is deficient in Tay Sachs disease?

A

Hexosaminidase A

179
Q

Which substance accumulates in Tay Sachs disease?

A

GM2 Ganglioside

180
Q

What are presenting symptoms of Tay Sachs disease?

A

Developmental delay, progressive neurodegeneration, “cherry red spot” on macula, hepatosplenomegaly

181
Q

What do you see on histology of Tay Sachs

A

Lysosomes with onion skin

182
Q

How is Metachromatic Leukodystrophy inherited

A

Autosomal Recessive

183
Q

What are the clinical findings of Methachromatic leukodystrophy?

A

Ataxia, central and peripheral demyelination, dementia

184
Q

Which enzyme is deficient in Methachromatic Leukodystrophy

A

Arylsulfatase A

185
Q

Which component builds up in Metachromatic Leukodystrophy?

A

Cerebroside Sulfate

186
Q

members of Ashkenazi Jewish population are at risk of which lysosomal disorders?

A

Gaucher, Tay-Sachs, Niemann-Pick

187
Q

Which enzyme is deficient in Niemann-Picks disease?

A

Sphingomyelinase

188
Q

Which substance builds up in Niemann-Pick

A

Sphingomyelin

189
Q

Clinical findings of Niemann-Pick

A

Progressive neurodegeneration, foam cells, hepatosplenomegaly, “cherry red” spot on macula

190
Q

How is Fabry disease inherited

191
Q

Which enzyme is deficient in Fabry disease?

A

alpha-galactosidase A

192
Q

Which substance builds up in Fabry disease?

A

Ceramide Trihexoside

193
Q

Clinical findings of Fabry

A

Peripheral neuropathy, angiokeratomas, hypohidrosis (no sweating)

194
Q

Later findings of Fabry

A

Cardiovascular disease, renal failure

195
Q

Name the two mucopolysaccharidoses Lysosomal storage disease

A

Hunter and Hurler

196
Q

Which enzyme is defective in Hurler

A

alpha-L-iduronidase

197
Q

Which substances build up in Hurler

A

Heparan sulfate, dermatan sulfate

198
Q

Cllinical findings of Hurler

A

Developmental delay, corneal clouding, gargoylism, hepatosplenomegaly, airway obstruction

199
Q

Clinical findings of Hunter

A

Mild Hurler and aggressive behavior (no corneal clouding)

200
Q

Defective enzyme in Hurler

A

Iduronate Sulfatase

201
Q

Which substances build up in Hunter

A

Dermatan sulfate, Heparan Sulfate

202
Q

How is Hunter inherited

203
Q

How is citrate transported from mitochondria to cytosol?

A

Citrate shuttle

204
Q

Which molecule is required for fatty acid synthesis in the cytosol?

205
Q

How are fatty acids brought into the mitochondria for degradation?

A

Carnitine shuttle

206
Q

What are the symptoms of carnitine deficiency?

A

Fatty acid accumulation in cytosol, weakness, hypotonia, hypoketotic hypoglycemia

207
Q

What is the product of beta-oxidation in the mitochondria?

A

Acetyl-CoA, used for TCA cycle and ketone bodiess

208
Q

A fasting infant or child that presents with vomiting, lethargy, seizures, coma and liver dysfunction and has hypoketotic hypoglycemia likely is deficient in which enzyme?

A

medium-chain acyl-CoA dehydrogenase

209
Q

What’s a key feature of ketoacidosis (accumulation of ketones in blood)?

A

Breath with fruity odor

210
Q

Which ketone can urine test not detect?

A

beta-hydroxybutyrate (can detect acetoacetate)

211
Q

How does alchoholism lead to ketoacidosis?

A

Buildup of NADH shunts OAA to malate, which builds up Acetyl-CoA, shunting to favor ketone generation

212
Q

Why can RBCs not use ketones?

A

They lack mitochondria

213
Q

How soon after starvation does the body run out of its glycogen store?

A

12-18 hours

214
Q

After glycogenolysis is used up, how does body maintain glucose levels in state of starvation >24 hours?

A

Hepatic gluconeogenesis from lactate and alanine and adipose tissue glycerl and propionyl-coA

215
Q

After 3 days of starvation, what is the primary source of energy?

A

Ketone bodies, eventual protein breakdown and eventual death

216
Q

What are the four functions of cholesterol?

A
  1. Maintain cell membrane integrity 2. Synthesize bile acid 3. Synthesize steroids 4. Synthesize Vitamin D
217
Q

What is the rate-limiting step of cholesterol synthesis?

A

HMC-CoA reductase (induced by insulin)

218
Q

What are lipoproteins?

A

Transport molecules composed of varying amounts of cholesterol, TGs, phospholipids

219
Q

What are the two functions of chylomicrons?

A

Deliver dietary triglycerides to peripheral tissue and cholesterol to liver

220
Q

What is function of VLDL?

A

Deliver hepatic triglycerides to peripheral tissues

221
Q

What is the function of IDL?

A

Deliver TGs and cholesterol to liver

222
Q

What is the function of LDL? How is to formed?

A

Deliver hepatic cholesterol to peripheral tissues. Formed by hepatic modification of IDL

223
Q

What is the function of HDL?

A

Delivers cholesterol from peripheral tissues to liver, storage for apolipoproteins C and E (needed for chylomicron and VLDL metabolism); secreted by liver and intestine

224
Q

Why is it good to sip a glass of wine at dinner?

A

Increases HDL synthesis

225
Q

Which enzymes are deficient in Familal Hyperchylomicronemia?

A

Lipoprotein lipase or ApoCII

226
Q

Which lipids are elevated in Type I dyslipidemia (hyperchylomicronemia)?

A

Chylomicrons, TG and cholesterol

227
Q

Clinical findings of hyperchylomicronemia?

A

Pancreatitis, hepatosplenomegaly, and eruptive/pruritive xanthomas!!!
Creamy supernatant in blood draw

228
Q

How is hyperchylomicronemia inherited

229
Q

What is Type IIa familial dyslipidemia?

A

Familial hypercholesterolemia

230
Q

How is Familial Hypercholesterolemia inherited?

231
Q

Which enzyme is defective or absent in familial hypercholesterolemia?

A

LDL Receptor

232
Q

Which lipids are elevated in familal hypercholesterolemia?

A

LDL, cholesterol

233
Q

What are the three major findings and risks of patients with Familial Hypercholesterolemia?

A

Accelerated atherosclerosis (MI by 20s), corneal arcus (blue/grey ring around cornea), tendon (Achilles) xanthomas

234
Q

What is type IV familial dyslipidemia?

A

Hypertriglyceridemia

235
Q

How is Familial Triglyceridemia inherited

236
Q

What is the pathogenesis of Hypertriglyceridemia?

A

hepatic overproduction of VLDL

237
Q

Which lipids are increased in blood in Hypertriglyceridemia?

238
Q

How would a patient with hyper triglyceridemia likely present?

A

Triglycerides > 1000mg/dL; acute pancreatitis

239
Q

The Ras pathway uses ATP or GTP

240
Q

Where are medium chain fatty acids oxidized

A

Mitochondria

241
Q

Where are very long chain fatty acids oxidized

A

Peroxisomes

USMLE (36 decks)

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