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STEP1 2015 > BIOCHEM > Flashcards

BIOCHEM Flashcards

1
Q

5 substances required for purine synthesis

A

tetrahydrofolate, HCO3 > Co2,
glutamine
aspartate
glycine

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2
Q

nucleotide versus nucleoside

A

nucleotide is phosphorylated

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3
Q

4 substances required to make pyrimidines

A

aspartate
CO2
glutamine
ATP

CO2, ATP, and glutamine go into carbamoyl phosphate (requires energy)

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4
Q

Carbamoyl phosphate synthetase 2

A

rate limiting step of pyrimidine synthesis, which makes carbamoyl phosphate

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5
Q

CPS1

A

urea cycle, mitochondria, n from ammonia

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6
Q

CPS2

A

pyrimidine synthesis, cytosol, n from glutamine

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7
Q

deficiency of UMP synthase of pyrimidine synthesis pathway

A

orotic aciduria
AR
increased orotic acid in urine
uncommon cause of megaloblastic anemia that cannot be corrected with B12 of folic acid supplements
does not cause hyperammonemia (unlike ornithine transcarbamylase deficiency of urea cycle)

Tx: supplement uridine

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8
Q

purines can be salvaged rather than made de novo

A

GMP to guanosine to guanine to xanthine to uric acid

IMP to inosine to hyoxanthine to xanthine to uric acid

AMP to adenosine to inosine to hypoxanthine to xanthine to uric acid

HGPRT is a phosphoribosyltransgerase that converts guanine and inosine back to GMP and IMP respectively

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9
Q

Lesch- Nyhan

A 
deficient HGPRT
gout
intellectual disability
aggressive behavior
self- mutilation- lip biting
movement disorders- dystonia
x- linked

Tx: allopurinol, febuxostat to prevent formation of uric acid

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10
Q

Adenosine deaminase deificiency

A

SCID

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11
Q

rate limiting enzyme in purine synthesis

A

glutamine PRPP amidotransferase

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12
Q

sources of carbon in purine synthesis

A

CO2, glycine, tetrahydrofolate

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13
Q

sources of nitrogen in purine synth

A

glycine, aspartate and glutamine (GAG)

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14
Q

carbon in pyrimidine synthesis

A

HCO3, aspartate

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15
Q

nitrogen in pyrimidine synth

A

glutamine

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16
Q

inhibits ribonucleotide reductase

A

hydroxyurea

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17
Q

inhibits dihydrofolate reductase

A

methotrexate, trimethoprim

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18
Q

inhbits thymidylate synthase

A

5FU

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19
Q

inhibits inosine monophosphate dehydrogenase

A

mycophenolate

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20
Q

inhibits PRPP amidotransferase

A

6 mercaptopurine

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21
Q

aa’s accounting for positive charge in histones

A

lysine and arginine

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22
Q

Southern blot

A

DNA probe, DNA sample

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23
Q

Northern blot

A

DNA probe, RNA sample

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24
Q

Western blot

A

ab probe, protein sample

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25
Q

SW blot

A

DNA- binding protein sample, Oligonucleotide probe

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26
Q

ELISA

enzyme-linked immunosorbent assay

A

direct: tests for ag in patient’s blood
abs on the well, add ample to see if it contains antigen
then add antibodies to illuminate
(sandwich)

Indirect ELISA: tests for antibodies in the patient’s blood
wells coated with ag.
abs from pt sample bind the well
add signal antibodies that bind the antibodies

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27
Q

FISH

A

known segment of DNA
hybridize with fluorescent DNA or RNA probe

fluorescence indicates that the gene is present
If absent, the gene has been deleted

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28
Q

knock-in constitutive insertion

A

gene randomly inserted

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29
Q

knock-in conditional insertion

A

targeted insertion

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30
Q

karyotyping

A

metaphase chromosomes, paired
stain the bands
are there obvious changes in the chromosome?

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31
Q

rate limiting enzyme in de novo pyrimidine synthesis

A

CPS2

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32
Q

rate limiting enzyme in de novo purine synthesis

A

glutamine PRPP amidotransferase

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33
Q

rate limiting enzyme in glycolysis

A

PFK1

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34
Q

rate limiting enzyme in gluconeogenesis

A

fructose 1,6 bisphosphatase

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35
Q

rate limiting enzyme in glycogen synthesis

A

glycogen synthase

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36
Q

rate limiting enzyme in glycogenolysis

A

glycogen phosphorylase

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37
Q

rate limiting enzyme in TCA cycle

A

isocitrate dehydrogenase

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38
Q

rate limiting enzyme in hexose monophosphate shunt

A

glucose 6 phosphate dehydrogenase (G6PD)

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39
Q

gibbs free energy

A

Delta G= Delta H- T*DeltaS

Gibbs free energy=
change in enthalpy minus Temperature times change in Entropy

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40
Q

glycogen phosphorylase deficiency in skeletal muscle (myophosphorylase)

A

McArdle disease

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41
Q

Glucose-6-phosphatase deficiency

A

von Gierke disease

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42
Q

increased glycogen storage, lactic acidosis, hyperlipidemia, hyperuricemia (gout), glucose 6 phosphatase deficiency, affecting liver and kidney, leading to severe hypoglycemia, progressive renal disease, growth retardation, delayed puberty

A

von Gierke disease

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43
Q

alpha 1-6 glucosidase deficiency

A

Cori disease

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44
Q

alpha 1-4 glucosidase deficiency in lysosomes

A

Pompe disease

infantile- cardiomegaly, infantile onset, less than one year life expectancy
adult- diaphragm weakness leading to respiratory failure

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45
Q

increased glycogen in liver, severe fasting hypoglycemia

A

von Gierke disease

46
Q

hepatomeglay, hypoglycemia, hyperlipidemia (normal kidneys, lactate, uric acid)

A

Cori disease

47
Q

painful muscle cramps, myoglobinuria with strenuous exercise

A

McArdle disease

48
Q

severe hepatosplenomegaly, enlarged kidneys

A

von gierke disease

49
Q

vitamin deficiency resulting from Hartnup disease

A

lack of tryptophan leads to niacin deficiency, leading to pellagra

50
Q

TLC For Nobody

A 
pyruvate dehydrogenase complex cofactors
1. pyrophosphate (B1, thiamine)
2. FAD (B2, riboflavin)
3. NAD (B3, niacin)
4, CoA (B5, pantothenic acid)
5. Lipoic acid
51
Q

GI problems (vomiting, rice- water stools) plus garlic breath , and blocked lipoic acid

A

arsenic poisoning, leading to pyruvate dehydrogenase deficiency (lactic acidosis, neurological defects)

52
Q

what 4 end products can be made from pyruvate

A

OAA, Acetyl CoA, alanine, lactate

53
Q

Galactokinase deficiency

A

galactitol accumulates (via aldose reductase), relatively mild, AR, infantile cataracts, failure to track objects or develop social smile

54
Q

Aldolase B deficiency

A

AR, fructose-1-phosphate accumulates with a decrease in available phosphate, resulting in inhibition of glycogenolysis and gluconeogenesis. Sx: hypoglycemia, jaundice, cirrhosis, vomiting. Treatment: reduce fructose and sucrose intake.

55
Q

sucrose

A

glucose and fructose

56
Q

lactose

A

galactose and glucose

57
Q

galactose-1-phosphate uridyltransferase deficiency

A

Classic galactosemia. AR, accumulation of galactitol.

Sx: FTT

58
Q

FAB GUT

A

fructose is to Aldolase B as Galactose is to UridylTransferase
The more serious defects lead to PO43- depletion

59
Q

fructokinase deficiency

A

essential fructosuria

60
Q

pancreatic insufficiency- symptoms

A 
diarrhea
steatorrhea
malabsorption
weightloss
ADEK fat- soluble vitamin deficiency
61
Q

serotonin syndrome

A

muscle rigidity, hyperthermia, CV collapse due to autonomic instability

62
Q

chylomicrons

A

deliver Tgs to peripheral tissue, deliver cholesterol to liver

63
Q

VLDL

A

deliver TGs to peripheral tissue

64
Q

IDL

A

deliver TGs and cholesterol to liver

65
Q

ApoB48

A

chylomicron secretion from enterocyte to lymphatic system

66
Q

ApoB100

A

found on VLDL, IDL, LDL

binds LDL receptor

67
Q

ApoE

A

mediates extra remnant uptake

68
Q

ApoA1

A

activates LCAT, found on HDL

HDLs help scoop up extra cholesteral by moving it from cells to fat particles

69
Q

ApoCII

A

cofactor for lipoprotein lipase

70
Q

Abetalipoproteinemia

A

AR
defective ApoB48 and ApoB100

without these lipoproteins, enterocytes are never getting rid of their chylomicrons

2/2 mutation in microsomal transfer protein (MTP)

as a result there is decreased chylomicron and VLDL synthesis and secretion.

presents in the first few months of life, with steatorrhea (ADEK)

on intestinal biopsy, the enterocytes will be swollen with TGs

you will also see acanthocytosis of RBCs on peripheral smear (plasma membrane looks spiky due to altered membrane lipids)

Sx: ataxia, night blindness (no VitA)

Treat with Vit E which helps to restore the lipoproteins

71
Q

Type I hyperchylomicronemia

A

AR, lipoprotein lipase deficiency or defective ApoCII (cofactor for lipoprotein lipase)

in the blood you will find increased chylomicrons, TGs, cholesterol

presents with pancreatitis 2/2 increased TG, hepatosplenomegaly, pruritic xanthomas

no increased risk for atherosclerosis

72
Q

Type IIA familial hypercholesterolemia

A

AD, with absent of decreased LDL receptors, resulting in increased LDL in blood

tedinous xanthomas
corneal arcus
accelerated atherosclerosis
myocardial infarction

73
Q

type IV hypertriglyceridemia

A

AD.
overproduction of VLDL in the liver

pancreatitis

74
Q

where does cholesterol come from?

A

Acetyl CoA

75
Q

What is the rate limiting enzyme in cholesterol synthesis

A

HMG-CoA reductase (as opposed to synthase which is involved in ketone synthesis)

76
Q

what drugs inhibit HMG CoA reductase

A

statins

77
Q

where does fatty acid synthesis take place

A

cytoplasm of hepatocytes

78
Q

what is the precursor molecule for fatty acids?

A

acetyl coA

79
Q

what is the rate limiting enzyme for fatty acid synthesis

A

acetyl- coA carboxylase

80
Q

where does fatty acid degradation occur?

A

mitochondria

81
Q

what is the rate-limiting enzyme in fatty acid degredation?

A

carnitine acyltransferase 1 (Carnitine palmityoltransferase 1)

82
Q

what happens if you don’t have CAT1?

A

unable to transport LCFAs to mitochondria
accumulation of LCFAs in cytoplasm
presentation:
weakness, hypotonia, hypoketotic hypoglycemia

83
Q

rate limiting enzyme for ketone body synthesis

A

HMG-CoA synthase

84
Q

rate-limiting enzyme for cholesterol synthesis

A

HMG- CoA reductase

85
Q

Where is excess iron stored (after hemaglobin and myoglobin are satisfied)

A

liver, spleen, bone marrow

86
Q

ABG change 6-72 hrs into iron OD

A

metabolic acidosis

87
Q

Ferritin

A

iron protein complex (ferric acid and apoferritin)
cellular storage protein for iron
acute phase reactant

88
Q

Transferrin (transport)

A

protein that binds ferric molecules and transports them through plasma.
synthesized in the liver.
Half- life of 8 days
Transferrin increased in iron deficiency when cells are hungry for iron

89
Q

zinc functions

A

zinc finger motif, important in healing, during transcription. important in healing, immune system, carbonic anhydrase.
lactate dehydrogenase also requres zinc

90
Q

zinc deficiency

A

delayed wound healing, decreased body and facial hair, hypogonadism, anosmia, dysgeusia

decreased immune response

rash around eyes, mouth, nose anus (acrodermatitis enteropathica)

anorexia and diarrhea
growth retardation
decreased mental function
impaired night vision
infertility
91
Q

lead poisoning

A

inhibited ferrochelatase and ALA dehydratase lead to decreased heme synthesis and increased RBC protoporphyrin

basophilic stippling (rRNA retainged in RBCs)
ringed sideroblasts (RBC precursors) in bone marrow
anemia
abd pain
neuropathy leading to wrist and goot drop
Burton lines on gingivae
encephalopathy, drop in IQ

succimer or EDTA

if severe, use dimercaprol and succimer

92
Q

mercury poisoning

A

accumulates in kidney and brain

enlarged kidneys, neuro symptoms
acrodynia: peeling of the fingertips
abdominal pain
common sources: shark, swardfish, tilefish, king mackeral, old thermometers, batteries

93
Q

hypocalcemia

A

tetany and neuromuscular irritability
Chvostek sign (tap the cheek)
Trousseau (tighten blood pressure cuff)

94
Q

Common causes of ARDS

A 
shock
infection
toxic gas inhalation
acute pancreatitis
aspiration
heroin overdose
high concentrations of O2
95
Q

Vitamin K role in clotting factor formation

A

cofactor for gamma carboxylation of glutamic acid residues on various proteins required for blood clotting. (2, 7, 9. 10, C, S)

96
Q

drugs that lead to Vit K deficiency

A

warfarin, phenytoin, antibiotics that wipe out gut flora

97
Q

What vitamin B deficiency causes seizures, irritability

A

B6, which is involved in producing GABA

98
Q

vitamins involved in megaloblastic anemia

A

B12, folate

99
Q

where is B12 absorbed in the gut

A

terminal ileum

100
Q

Which vitamin deficiency is associated with peripheral neuropathy, glossitis?

A

B12, B6

101
Q

Which vitamin deficiency is associated with NTD?

A

folic acid

102
Q

Which vitamin deficiency is associated with dermatitis, diarrhea, dementia

A

B3 (niacin), pellagra

103
Q

Which vitamin deficiency is associated with megaloblastic anemia

A

folic acid, B12

104
Q

Which vitamin deficiency is associated with pernicious anemia

A

B12

105
Q

Which vitamin is used in redox reactions

A

B2 (riboflavin FMN FAD), B3 (niacin) NAD, NADP

106
Q

Which vitamin is used in carboxylation reactions

A

B7 biotin (gamma glutamate carboxylation)

107
Q

Which vitamin requires IF for absorption

A

B12

108
Q

Which vitamin is used by pyruvate dehydrogenase in alpha KG

A

B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (CoA, pantothenic acid), lipoic acid

109
Q

deficiency can be 2/2 INH use

A

B6, B3

110
Q

Cobalt is found within this vitamin

A

B12 (cobalamin)

111
Q

Critical for DNA synthesis

A

folate, B12

STEP1 2015 (30 decks)

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