12. Biochem Flashcards
What is the rate-limiting enzyme in purine synthesis? In pyrimidine synthesis?
purine: glutamine PRPP amidotransferase
pyrimidine: CPS2 (carbamoyl phosphate synthetase 2)
What are the sources of carbon in the synthesis of purines? (3) in pyrimidine synthesis? (2)
- purines: CO2, glycine, tetrahydrofolate
- pyrimidines: aspartate, CO2
Which medication inhibits each of the following enzymes?
- ribonucleotide reductase
hydroxyurea
Which medication inhibits each of the following enzymes? (2)
- dihydrofolate reductase
TMP, methotrexate
Which medication inhibits each of the following enzymes?
- thymidylate synthase
5-FU
Which medication inhibits each of the following enzymes?
- inosine monophosphate (IMP) dehydrogenase
mycophenolate
Which medication inhibits each of the following enzymes?
- PRPP amidotransferase
6-MP
- note this is the rate-limiting enzyme
What accounts for the positive charge of histones? What accounts for the negative charge of DNA?
histones: b/c made of lysine and arginine
DNA: negative b/c of phosphate groups
How does UV radiation damage DNA?
makes pyrimidine dimers (usually T-T) on the same strand of DNA –> makes “bulky” helix-distorting lesion
need repair via nucleotide excision repair
What amino acid is encoded by the most common start codon?
AUG –> methionine
What is the diff. b/w an intron and exon?
Intron: non-coding segment of DNA
Exon: coding sequences for specific protein products
Production of what enzyme is regulated by the lac operon?
b-galactosidase
What two proteins regulate the lac operon?
- CAP
- lac repressor
What 2 substrate conditions must be met for the lac genes to be transcribed?
- abundant lactose (removes repressor)
- low glucose (allows CAP to bind)
What enzyme matches amino acids to tRNA?
aminoacyl tRNA synthetase
What antibiotics are inhibitors of prokaryotic protein synthesis at the 30S ribosomal subunit?
- aminoglycoside
- tetracyclines
What antibiotics are inhibitors of prokaryotic protein synthesis at the 50S ribosomal subunit?
- chloramphenicol
- clindamycin
- macrolides
- linezolid
What enzymes convert glucose to glucose-6-phosphate?
hexokinase or glucokinase (only in liver and b-cells of pancreas)
What is the clinical consequence of a glycolytic enzyme deficiency?
hemolytic anemia
What enzymes are responsible for increasing and dereasing the intracellular levels of fructose-2,6-bisphosphate?
PFK-2 (fed): increase level of fructose 2,6-BP
FBPase-2 (fasting): decrease level of fructose 2,6-BP
What is the rate limiting enzyme in the glycolytic pathway?
phosphofructokinase-1
What irreversible enzymes are involved in gluconeogenesis (4)
- pyruvate carboxylase (with biotin)
- PEP carboxylase
- fructose-1,6-bisphosphatase
- glucose-6-phosphatase
What enzyme catalyzes the rate-limiting step in gluconeogenesis?
fructose-1,6-bisphosphatase
What is the rate limiting enzyme for glycogen synthesis? For glycogenolysis?
- glycogen synthase
- glycogen phosphorylase
Which enzyme converts G-6-P to glucose?
glucose-6-phosphatase
Which glycogen storage disease matches each of the following phrases?
- glycogen phosphorylase deficiency
McArdle
Which glycogen storage disease matches each of the following phrases?
- glucose-6-phosphatase
Von Gierke
Which glycogen storage disease matches each of the following phrases?
- lactic acidosis, hyperlipidemia, hyperuricemia (gout)
Von Gierke
Which glycogen storage disease matches each of the following phrases?
- a-1,6-glucosidase deficiency
cori
Which glycogen storage disease matches each of the following phrases?
- a-1,4-glucosidase deficiency
Pompe
Which glycogen storage disease matches each of the following phrases?
- cardiomegaly
pompe (infantile type)
Which glycogen storage disease matches each of the following phrases?
- diaphragm weakness leading to resp failure
pompe (adult type)
Which glycogen storage disease matches each of the following phrases?
- increased glycogen in liver, severe fasting hypoglycemia
Von Gierke
Which glycogen storage disease matches each of the following phrases?
- hepatomegaly, hypoglycemia, hyperlipidemia (normal kidneys, lactate, uric acid)
cori
Which glycogen storage disease matches each of the following phrases?
- painful muscle cramps, myoglobinuria with strenous exercise
McArdle
Which glycogen storage disease matches each of the following phrases?
- severe hepatosplenomegaly, enlarged kidneys
von gierke
What are the possible products of pyruvate? (4)
- acetyl-coa
- oxaloacetate
- lactate
- alanine
What are the two main nitrogen transporters in the blood?
- alanine
- glutamine
What are the major regulatory enzymes of the TCA cycle? (3)
- citrate synthase
- isocitrate dehydrogenase
- a-ketoglutarate dehydrogenase
What substances are known to inhibit the complexes of the electron transport chain?
- amytal
- rotenone
- MPP
- antimycin A
- cyanide (CN)
- azide (N3-)
- carbon monoxide (CO)
- hydrogen sulfide (H2S)
What substances can increase the permeability of the inner mitochondrial membrane, thereby decreasing ATP synthesis but increasing heat generation? (3)
uncoupling agents
- aspirin (high dose)
- thermogenin (in brown fat)
- 2,4-dinitrophenol
What is the rate-limiting step of the pentose phosphate pathway?
G6PD
Which tissues of the body use the pentose phosphate pathway? (4)
- RBCs
- liver
- adrenal cortex
- mammary glands
Explain why a deficiency of the enzyme that is the rate limiter for the HMP shunt can result in hemolytic anemia
G6PD deficiency
- decreased NADPH –> decreased reduced glutathione
- RBCs more susceptible to oxidative damage –> hemolysis
What are the symptoms of classic galactosemia?
- failure to thrive
- intellectual disability
- hepatomegaly
- jaundice
- infantile cataracts
What disorder is caused by a deficiency of each of the following enzymes?
- galactokinase
galactokinase deficiency
What disorder is caused by a deficiency of each of the following enzymes?
- aldolase B
fructose intolerance
What disorder is caused by a deficiency of each of the following enzymes?
- lactase
lactose intolerance
What disorder is caused by a deficiency of each of the following enzymes?
- galactose-1-phosphate uridyltransferase
classic galactosemia
What disorder is caused by a deficiency of each of the following enzymes?
- fructokinase
essential fructosuria
What is the primary energy source in a patient that has not eaten in 2 days?
fatty acids
What is the rate-limiting enzyme in ketone body synthesis?
HMG-CoA synthase
How does ethanol leads to hypoglycemia?
- increase NADH when you metabolize ethanol
- shunts pyruvate towards production of lactate, and oxaloacetate –> malate
- thus, pyruvate and oxaloacetate no longer available for gluconeogenesis
What are some of the hallmark features of kwashiorkor?
FLAMES
- fatty liver
- anemia
- malnutrition
- edema
- skin lesions
What deficiency causes familial hypercholesterolemia?
deficiency in LDL receptor
which apolipoprotein matches each of the following statements?
- activates LCAT
ApoA-1
which apolipoprotein matches each of the following statements?
- mediates chylomicron secretion
ApoB-48
which apolipoprotein matches each of the following statements?
- mediates VLDL secretion
ApoB-100
which apolipoprotein matches each of the following statements?
- cofactor for lipoprotein lipase
ApoC-II
which apolipoprotein matches each of the following statements?
- mediates uptake of remnant particles
ApoE
What is the rate-limiting enzyme for fatty acid synthesis
acetyl CoA carboxylase
What is the rate-limiting enzyme for beta-oxidation of fatty acids
carnitine acyl transferase 1
What is the rate-limiting enzyme for ketone body synthesis
HMG CoA synthase
What is the rate-limiting enzyme for cholesterol synthesis
HMG CoA reductase
What are the essential amino acids?
Private (PVT) TIM HaLL
- phenylalanine
- valine
- threonine
- tryptophan
- isoleucine
- methionine
- histidine
- leucine
- lysine
What amino acid is the precursor to the following?
- histamine
histidine
What amino acid is the precursor to the following?
- porphyrin, heme
glycine
What amino acid is the precursor to the following?
- NO
arginine
What amino acid is the precursor to the following?
- GABA
glutamate
What amino acid is the precursor to the following?
- S-adenosyl-methionine (SAM)
methionine
What amino acid is the precursor to the following?
- creatinine
arginine
A full-term neonate feeds poorly, is hyperactive, and has musty odor. What is the diagnosis?
PKU
- deficiency in phenylalanine hydroxylase or BH4
A patient with PKU should have a diet low in phenylalanine. What other dietary modification should a pt with PKU make? (2)
- high tyrosine diet
- BH4 supplementation
A middle-aged man has dark spots on his sclera, and has noted that his urine turns black when left sitting for a period of time. What is the diagnosis?
Alkaptonuria
- defect with homogentisate oxidase
What is the underlying cause of maple syrup urine disease?
deficiency of branched chain a-ketoacid dehydrogenase complex
What has been the most common clinical scenario of excess iron ingestion in the last 3 decades?
infant consuming iron-fortified vitamins (prenatal vitamins)
What are some of the clinical effects of zinc deficiency?
- delayed wound healing
- impaired immune response
- rash around eyes, mouth, nose, anus (acrodermatitis enteropathica)
What are some of the signs of hypocalcemia?
- tetany and neuromuscular irritability
- Chvostek sign
- Trousseau sign
What organs are primarily affected by excess of mercury?
kidney and brain
What vitamin in excess can cause hypercalcemia?
vitamin D
What are the symptoms of vitamin A toxicity
- visual impairment
- fatigue
- ataxia
- headache
- increased ICP (pseudotumor cerebri)
- alopecia
What clinical features would lead you to suspect that a patient has scurvy?
- sore spongy gums
- loose teeth
- hemorrhage (b/c fragile vessels)
- swollen joints (hemarthrosis)
- impaired wound healing
Vitamin C is necessary for the hydroxylation of which amino acids in collagen synthesis? (2)
- proline
- lysine
Which enzymes are used to convert cholecalciferol to calcitriol?
- 25-hydroxylase (liver)
2. 1a-hydroxylase (kidney)
A patient presents with convulsions and irritability. What vitamin deficiency is causing these symptoms in this patient?
B6 (remember, B6 required for synthesis of GABA)
What type of anemia can be caused by folate or B12 deficiency?
megaloblastic anemia
Where is B12 absorbed into the circulation?
Terminal ileum
Which vitamin deficiency matches?
- peripheral neuropathy, glossitis
B12, B6
Which vitamin deficiency matches?
- neural tube defects
B9 (folate)
Which vitamin deficiency matches?
- dermatitis, diarrhea, dementia
B3 (niacin)
Which vitamin deficiency matches?
- megaloblastic anemia
B9 (folate), B12
Which vitamin deficiency matches?
- Pernicious anemia
B12
Which vitamin matches each of the following?
- used in oxidation/reduction reactions
B2 (FAD)
B3 (NAD, NADP)
Which vitamin matches each of the following?
- used in carboxylation reactions
Biotin (B7)
note: also vit K for gamma-carboxylation of glutamic acid
Which vitamin matches each of the following?
- used by pyruvate dehydrogenase and a-ketoglutarate dehydrogenase
B1 (thiamine)
Which vitamin matches each of the following?
- can be used to elevated HDL and lower LDL
B3 (niacin)
Which vitamin matches each of the following?
- deficiency can be caused by isoniazid use
B6
Which vitamin matches each of the following?
- cobalt is found within this vitamin
B12 (cobalamin)
Which vitamin matches each of the following?
- critical for DNA synthesis
B9 (folate), B12
