UWORLD facts 2 Flashcards
Enterococci are ______hemolytic, while GAS is ___ hemolytic
enterococci: gamma hemolytic (non-hemolytic)
GAS: beta-hemolytic
Which bacteria has a positive Quellung reaction?
Strep pneumo (swelling of bacterial capsule when exposed to antibodies)
What is the only coagulase positive Gram positive coccus?
S aureus
Which is catalase positive? Staph or Strep?
Staph is atalase positive
80% of patients with reactive arthritis are positive for HLA-B27. They develop rehumatic symptoms 2-6 weeks after GU infxn/diarrhea caused by which organisms?
chlamydia, campylobacter, salmonella, shigella, or Yersinia
Neutrophil recruitment resulting in the creation of small microabscesses at the dermal papillary tips, also known as dermatitis herpetiformia (on extensor surfaces), is associated with what intestinal pathology?
Celiac disease
Deficiency of adenosine deaminase causes what?
SCID (autosomal recessive)
Definciency of purine nucleoside phosphorylases (PNP) leads to what?
isolated T-lymphocyte defect
Deficiency of HGPRT results in Lesch Nyhan syndrome. What does it result in increased buildup of?
increased purine syntehsis (decreased purine salvage); hyperuricemia, hyperuricuria
Which antibiotics inhibit prokaryotic protein syntehsis at the 30s ribosomal subunit?
tetracyclines and aminoglycosides
How doe macrolide antibiotics work?
bind to the 50s prokaryotic ribosomal subunit and prevent tRNA release from donor site AFTER peptide bond formation (chloramphenicol binds at the same spot but prevents new peptide bond formation)
How does rifampin work?
blocks prokaryotic mRNA synthesis by bacterial RNA polymerase
How does diptheheria toxin work?
prohibits protein syntehsis in eukaryoticcells through ADP ribosylation of EF2
Trace progression of cell from zygote to dermal cell.
Zygote –> morula –> embryoblast –> epiblast –> mesoderm –> dermal cell
What are the direct cholinergic agonists (don’t require release of AcH to work)?
pilocarpine, bethanechol, carbachol
What are the indirect cholinergic agonists (require release of AcH, because they are acetycholinesterase inhibitors)?
physostigmine, neostigmine, edrophonium
In pernicious anemia, which hormone builds up?
Gastrin (usually inhibited by hydrochloric acid).
Levles of IF, gastric acid, and secretin are low.
What is flutamide?
androgen receptor antagonist on target cells
What abnormalities are seen in DiGeorge syndrome?
C: cardiac abnormalities (ToF, truncus arteriosus, interrupted aortic arch) A: abnormal facies T: thymic aplasia C: cleft palate H: hypocalcemia, hypoparathyroidism 22 (22q11.2 deletion)
What are the two steps for antibody isotype to switch?
1) activation of transcritpion at region in the Ig locus
2) CD40 on B cells, causing DNA switch recombination
defect of CD40 leads to low levels of IgA, IgG, and IgE form original IgM/IgD antibodies
How does DNA methylation affect the transcription of genes? Which repeat sequences are preferentially methylated?
DNA methylation = silences gene transcription
methylated regions are typically rich in cytosine-guanine dinucleotide repeat sequences
Macrophages that look like wrinkled tissue paper:
Hepatosplenomegaly, aseptic necrosis of femur, bone crises
Gaucher cells, seen in deficiency of glucocerebrosidase = Gaucher’s disease (most common lysosomal storage disease). Glucocerebroside builds up
Severe extremity pain, decreased ability to sweat, corneal and lenticular changes, GI dysfunction, angiokeratomas:
Fabry disease, X linked R (all other lysosomal storage diseases are AR), deficiency of a-galactosidase (increased ceramide triheoside)
Progressive neurodegeneration, cherry red spot on macula, foam cells, HEPATOSPLENOMEGALY:
Niemann-Pick disease; deficiency of sphingomyelinase (increased sphingomyelin)
Progressive neurodegeneration, developmental delay, cherry red spot on macula, lysosomes with onion skin, NO HEPATOSPLENOMEGALY
Tay-Sach’s disease; deficiency of hexosaminidase A, accumulation of GM2 ganglioside
What is the signaling pathway of a-1 adrenergic receptor?
Gq –> phospholipase C –> IP3 (liberates stored intracellular calcium) and DAG (actives protein kinase c)
gnrh, oxytocin, adh (vasopressin), trh, histamine, angiotensin II, gastrin
What is the signaling pathway used by beta-adrenergic receptors, glucagon, fsh, lh acth, tsh, crh, hcg, adh (v2 receptor), histamine, epinephrine?
Gs –> adenylate cyclase –> cAMP (activates protein kinase A for intracellular effects)
Cyclic GMP is the second messenger for which hormones?
atrial natriuetic peptide and NO
guanylate cyclase –> cGMP –> protein kinase G (intracellular effects)
______ is a monoclonal antibody to TNF-a, while _______ is a recombinant TNF receptor fusion protein
infliximab = monoclonal antibody
etanercept: recombinant receptor fusion protein
What is the mechanism of action of aspirin with regards to platelets?
Aspirin inhibits cox-1 in platelets, which inhibits formation of prostaglandin H2 and preventing the synthesis of thromboxane A2, a potent stimulator of platelet aggregation and vasoconstriction.
From where does the azygous vein draw blood?
from the posterior walls of the thorax and abdomen into the SVC
What is teh ductus venosus?
In the fetus, the ductus venosus drains blood from the gut/liver directlyi nto the IVC, bypassing the sinusoids.
What is bacterial transformation?
when bacteria take up naked DNA from the environment and incorporate it into their genomes
What is bacterial transduction?
Bacteriophage-mediated transfer of genetic information.
What is bacterial conjugation?
Conjugation is a process where DNA is passed from one bacterium to another by direct cell-cell interaction, as awith a sex pilus
Graunular deposits of IgG and/or C3 are seen in what renal disease?
membranoproliferative glomerulonephritis
Glomerular capillary wall thickenign with spiky subepithelial IgG deposits is seen in
membranous glomerulonephritis
linear deposits of IgG and often C3 is seen in
anti-GBM disease, a form of rapidly progressive glomerulonephritis
p53 is a tumor suppressor gene mutated in which syndrome?
Li Fraumeni
The darkest line on an electron micrograph represents:
the Z line = where thin filmaents, composed of actin/tropomyosin/troponin anchor
What is the I band?
The Z line and only the thin (actin) filaments that do not overlap with thick (myosin) filaments
What is the H band? What lies at the center?
the section of the sarcomere containing only thick (myosin) filametns that do not overlap with actin.
At the center is the M line, wher ethe myosin filaments anchor in the center of the sarcomere
What is the A band?
The A band is the only named band in teh sarcomere containing an overlap of thick and thin filaments
When the sarcomere contracts, which bands will narrow?
H, I
A band DOES NOT contract
What is the virulence factor of Aspergillus?
vascular invasion (infections can disseminate to distant organs by hematogenous spread)
A polysaccharide capsule is the virulence factor of
strep pneumo, h flu, neisseria meningitidis
A lipid-rich cell wall is the virulence factor of
mycobacteria
Many organisms avoid the immune system by residing in an intracytoplasmic location; examples include:
m pneumonaie, penicillium marneffei, neisseria gonorrhea and others
What is the definition of ARDS?
PaO2/FiO2 ratio less than 300
Less than 100 is severe
How does the conduction velocity through the atrium, ventricles, Purkinje system, and AV node compare?
Fastest: Purkinge > SA node/atrial tissue > ventricular muscle > AV node (slowest)
What bone tumor is most often associated with Paget’s disease?
osteosarcoma (look for mixed radiodense and radiolucent areas, periosteal new bone formation, lifting of cortex, and Codman’s traingle–adjacetn soft tisseu showing ossification in a sunburst pattern)
DNA electrophoresis that shows DNA in fragmetns that are multiples of 180 base pairs spaced on the gel and appearing like a ladder suggests:
cell apoptosis
What is pralidoxime and how does it work?
An antidote to organophosphorus cholinesterases. Antihcolinesterases phosphorylate cholinesterates and prevent them from degrading AcH. Pralidoxime removes that phosphate group so they can work again.
What happens when a ligand binds to a cytoplasmic steroid, thyroxine, or retinoid receptor?
translocation to the nucleus to bind to DNA and modify transcription
What happens when an LDL receptor is bound?
internalization of the ligand receptor complex into a vesicle from clathrin-coated regions, or “pits”
What happens when a ligand binds toa tyrosine kinase receptor?
formation of receptor dimers and a conformational change exposing tyrosine kinase active sites
The long thoracic nerve is derived from which spinal nerves? What muscle does it innervate? What happens when this erve is damaged?
LTN = C5 - C7
Innervates serratus anterior
inability to raise arm over head and protrusion (“winging”) of the medial border of the scapula when the outstreched arm is pushed forward against resistance
Bicarbonate secretion in the pancreas and the epithelial cells of the biliary tract is mediated predominantly by
secretin
What viruses do the paramyxoviridae include?
measels, mumbs, RSV, parainfluenza
Acute intermittent porphyria is caused by a deficiency of what?
What are the manifestations?
deficiency of hydromethylbilane (HMB) synthase, which causes increased levels of porphobilinogen deaminase and uroporphyrinogen I synthetase
Characterized by intermittent episodes of abdominal pain with neurological manifesatoins after exposure to an offending medication. Urine from patients during attacks will classically darken upon standing in sunlight. Skin photosensitivity is characteristically absent.
The last enzyme in the heme sythensis pathway is
ferrochelatase
What is the most common form of porphyria and which enzyme is deficient?
porphyria cutanea tarda (PCT); deficiency of URO decarboxylase
What is the third heart sound and what does it indicate?
low-pitched sound heard during rapid filling of the ventricle in mid-diastole; normal in children but typically indcates ventricular fialure in adults (heard because there is increased end-sytolic volumes in and pressures present in patients with heart failure
What is Light’s criteria?
exudates demonstrate:
pleural fluid protein/serum protein > 0.5
pleural fluid LDH / serum LDH > 0.6
pleural fluid LDH > 2/3 normal upper limit LDH
While MG affects the eyes/bulbar musculature, Eaton-Lambert syndrome tends to present with
weakness of the extremities
If the second brachial cleft is not obliterated as expected during the 7th week of embryonic development, what can arise?
a branchial cleft cyst can arise on the lateral neck
DiGeorge syndrome results from failed development of what?
The third and fourth pharyngeal pouches (the predecessors of the thymus, parathyroid glands, and ultimobranchial body)
What is syringobulbia?
fluid-filled cavities within the medulla oblongata
What is phenoxybenzamine?
long acting alpha receptors (lasts 3-4 days)
Name risk factors for intraventricular hemorrhage of an infant?
birth before 32 weeks of gestation; birth weight
Side effect of etoposide:
alopecia, GI irritation, yelosuprresion
Side effect of doxorubicin:
alopecia, myocardial damage, myelosuppression
Side effect of methotrexate:
myelosuppression, fatty change in liver
Side effect of cisplatin:
hearing loss
How can procainamide affect the lungs?
procainamide (class Ia antiarrhtyhmic, Na channel block) can cause a delayed onset pleuritis associated with drug-induced lupus
Through which receptors do acetylcholine, histamine, and gastrin stimulate parietal cells to produce gastric acid?
Ach –> M3 R
histamine –> AChR
gastrin –> CCK2
(of note, PPIs work directly on the luminal membrane H+ pump of the parietal cell itself)
What is palmitoylation?
A process in which fatty acids are covalently anchored to plasma membrane cysteine residues, increasing the hydrophobicity of ap rotein. G protein coupled receptors often have carboxyl tails palmitoylatedo n cysteine resideus (ie the vasopressin receptor)
How do CFTRs function differently in skin vs respiratory and intestinal epithelium?
In skin: CFTR reabsorbs luminal chloride ions and enhances sodium resorption (mutations result in greater sweat tonicity)
In lungs/gut: CFTR allows for active chloride secretion (mutated CFTR depletes water content of surface fluid layer)
What is Albright hereditary osteodyrtrophy?
Classic phenotype of pseudohypoparathyroidism. Characterized by skeeltal and developmetnal defects (Short stature, short metacarpal and metatarsal bones) and endo-organ resistance to PTH.
Though both S. aureus and Group A Streptococcus can cause impetigo, those cases with bullae are caused by
S. aureus only
Achondroplasia is characterized by a point mutation on the gene for what?
fibroblast growth factor receptor 3 (FGFR-3) on chromosome band 4p16.3
Bone fragility is characteristic of osteogenesis imperfecta, which is caused by a mutation of gene…
COL1A1 or COL1A2 (code for type I collagen)
Lens ectopy is a hallmark of Marfan syndrome, caused by mutation of which gene?
FBN1 gene
What is the hydrophobic core in the signal sequences of prohormone peptides?
signal sequences that target protein to RER. Without it, SRP (signal recognition particles) can’t bind and won’t translocate proteins into the RER, so they will remain in the cytosol
What is maple syrup urine disease (branched-chain ketoaciduria)?
a defect in the branched-chain alpha-keto acid dehydrogenase complex (which requires thiamine s a coenzyme, B1), resulting in an inability to degrade branched chain alpha-amino acids (leucine, isoleucine, and valine) and their alpha ketoacid metabolites.
If a guy has a low testosterone concentraion in his seminiferous tubules and epididymis, but normal blood testosterone, what is going on?
Sertoli cells are dysfunctioning, not making/secreting ABP. ABP bind sto testosterone in the seminiferous tubule and makes the hormones less lipophilic, concentrating them in the luminal fluid. ABP maintains the high local concetration of testosterone necessary for normal sperm production and maturation
Surgical sympathectomy for axillary hyperhidrosis targets which ganglion?
T2 sympathetic ganglion
In the synthesis of dopamine/norepinephrine/epinephrine, which steps require methylation?
NE –> E
and E –> VMA
What is the rate limiting step of dopamine metabolism?
conversion of tyrosine to DOPA (by tyrosine hydroxylase)
Hypoglycemia after prolonged fasting with inappropriately low ketone bodies suggests:
impaired B-oxidation (medium chian acyl CoA dehydrogenase deficiency is the most common genetic defect in beta-oxidation)
**HYPERketosis with hypoglycemia might indicate glycogen storage disease (ie type 5, mcardle, and type 6, hers) GSDs are autosomal recessive
What happens in glucose-6-phosphatase deficiency?
von Gierke’s disease = accumulation of glycogen in the liver and kidneys
This enzyme dephosphorylates glucose-6-phosphate to free glucose, enabling it to be released into the circulation during glycogenolysis and gluconeogenesis
What enzyme catalyzes the first step in fatty acid synthesis? What happens to the enzyme during fasting?
Acetyl CoA carboxylase (ACC) catalyzes the first step in fatty acid synthesis and is the major site of regulation for fatty acid synthesis. It is naturally inhibited during fasting to decrease synthesis of fatty acids
What is the role of glycogen phosphorylase? What does its deficiency result in?
Glycogen phosphorylase cleaves the alpha 1,4 glycosidic linkage between glucose residues in glycogen, thereby liberating glucose-1-phosphate. Deficiency results in glycogen storage disease type V (muscle phosphorylase deficiency, McArdle) or 6 (liver phosphorylase deficiency, HERS). Both are characterized by hypoglycemia and hyperketosis.
What is Pompe’s disase?
deficiency of lysosomal a-1,4 glucosidase, resulting in cardiomegaly and systemic findings leading to early death
What is Cori’s disase?
A milder form of Von Gierke’s disae, resulting from debranching enzyme a-1,6-glucosidase. Like von Gierke’s (tyep 1, deficiency of glucose-6-pohosphatase), there is fasting hypoglycemia, increased glycogen in liver, but NORMAL blood lactate (not increased)
Up to 20% of all human tumors contain mutated Ras proteins that have reduced GTPase activity. What does this result in?
Mutated Ras proteins remain in an excited GTP-containing state, stimulating neoplastic growth through continuous activation of the mitogenic signaling pathway
What does BRCA-1 encode?
DNA repair enzyme associated with breast and ovarian cancer when mutated
What is cyclin D1?
promoter of G1 to Sphase transition during the cell cycle
What is Rb?
a nuclear phosphoprotien that regulates the G1 –> S checkpoint
What is c-myc?
creates a nuclear phosphoprotein that functions as a transcription activator controlling cell proliferation, differentiation, and apoptosis
On a lineweaver-burke plot, what is the y-intercept? What is the x-intercept? What is the slope?
y intercept = 1/vmax
x intercept = (-1/km)
slope = km/vmax
if km is small, only a small amount of substrate is needed to act. usually enzyme with smallest km thought to be natural enzyme
What are P450 inhibitors?
MAGIC RACKS IN GQ
macrolides, amiodarone, grapefruit juice, isoniazid, cimetidine, ritonavir, acute alcohol, ciprofloxacin, ketoconazole, sulfonamides, gemfibrozil, quinidine
What are p450 INDUCERS?
Momma barb steals phen-phen and reduces greasy carbs chronically
modafinil, barbiturates, st. john’s wort, phenytoin, rifampin, griseofulvin, carbamazepine, chronic alc
MEN 1 results from an abnormality in ___ gene, while MEN 2 has a mutation in ___ gene
MEN 1 = MEN1 (deactivating)
MEN 2 = RET (activating)
How are poxviruses unique among DNA viruses?
they do not replicate in the host cell nucleus (whereas all other DNA viruses due. RNA viruses, however, all replicate in the cytoplasm EXCEPT influenza and retroviruses)
How do you increase renal plasma flow (RPF)?
RPF = MAP/TVR
If you increase the pressure of afferent or efferent arterioles, and MAP constant, RPF will decrease
How do you increase GRF?
constrict efferent arteriole or dilate afferent arteriole
Name unmyelinated axons:
postganglionic ANS axons, afferent neurons conducting heat; afferent neurons transmitting slow-onset dull, burning, or visceral pain. First order bipolar neurons of olfaction are also unmyelinated. These are known as group C fibers
How do you calculate standard error?
std dev/ (sq root of n)
The enterovirus belongs to which family of viruses?
Picornavirus, which also includes rhinovirus
What family of viruses does rotavirus belong to?
reoviridae
What family of viruses does RSV belong to?
paramyxoviridae (mumps, measles, and parainfluenza also are, along with RSV)
How do itraconazole and other triazole antifungals function?
by inhibiting ergosterol syntehsis. Resistance is acquired by mutations in 14-alpha-sterol demthylase enzyme or decreased drug efflux pumping
How does flucytosine work?
an antifungal agent that disrupts nucleic acid synthesis (specifically thymidylase synthetase)
Which meds impair peptidoglycan synthesis?
beta-lactam antibiotics; vancomycin
What are potential sequelae of untreated lichen sclerosus?
genital squamous cell carcinoma; genital disfigurement
What is leukoplakia? What is its most classic cause?
leukoplakia = white thickening of mucosal surgace, of which there are many potential causes. Most classic is EBV inefction in setting of immunosuppression
