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Flashcards in UWorld- Endo/Biochem Deck (64)
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1

what kind of transport is responsible for glucose movement through cell membranes

carrier-mediated transport (the membrane proteins change conformation, but don't use energy), which is a form of facilitated diffusion

2

what enantiomer of glucose is preferred by GLUT molecules

D-glucose

3

what is the most common cause of elevated AFP on triple test

dating error (underestimated gestational age, because AFP rises with gestational age)

4

list the three domains of proinsulin, and describe what has to happen to generate the mature form of insulin

proinsulin= N-terminal B chain, C peptide connects the two flanking chains, C-terminal A chain
beta cell peptidases cleave C peptide out to form mature insulin

5

what kind of drug is glyburide and what does it do

sulfonylureas
1st gen: tolbutamide and chlorpropamide
2nd gen: glyburide, glimepiride, glipizide

sulfonylureas increase insulin secretion (by closing beta cell K+ channel to depolarize membrane and increase Ca influx)

6

what kind of drug is risperidone and what specific side effect is it known for

risperidone is an atypical antipsychotic (D2 receptor antagonist)
side effect= increased prolactin

7

what's the difference between the kinds of proteins that are synthesized in ribosomes attached to the RER vs. free ribosomes

free ribosomes synthesize cytosolic proteins/ proteins for organelles

RER ribosomes synthesize secretory, membrane-bound and lysosomal proteins

8

where is the sodium-iodide symporter (NIS) found and what molecules compete with iodide to be taken up

NIS is found in the basolateral membrane of the thyroid follicular cell

anions like perchlorate, pertechnetate and thiocyanate compete with iodide for uptake by NIS from the blood

9

would giving exogenous T3 to a patient with primary hypothyroidism cause increased or decreased levels of rT3

decreased rT3:
normally TSH upregulates T4, which is converted either to T3 or rT3. T3 cannot be converted to T4 or to rT3. T3 is the active form, but it also negatively feeds back on TRH and TSH levels. This would decrease T4 and thereby decrease rT3

10

how does elevated estrogen cause an initial growth spurt, but short stature in adulthood

in childhood and during puberty estrogen increases linear bone growth, but also mediates closure of the epiphyseal plates so linear bone growth will end earlier leading to short stature in adulthood

11

what are the endocrine toxicities of amiodarone and why is this the case

amiodarone can cause hyperthyroidism/hypothyroidism because it is 40% iodine by weight

12

what amino acids are safe to be supplemented to a patient with pyruvate dehydrogenase deficiency and why

leucine and lysine are save to give a PDH deficiency patient because they are ketogenic and not glucogenic (meaning they produce only acetoacetate and its precursors, not pyruvate or any TCA cycle intermediates)

13

why do septic shock patients usually become acidotic

septic shock-related hypoperfusion leads to decreased oxidative phosphorylation and in the absence of oxidative phosphorylation pyruvate gets converted to lactate (by lactate dehydrogenase)

14

describe the polyol pathway that metabolizes glucose in the lens (include enzymes)

glucose gets taken up by cells in the lens and converted to sorbitol via aldose reductase; sorbitol is then converted to fructose via sorbitol dehydrogenase

15

how does hyperglycemia cause cataracts (explain the pathophysiology using the polyol pathway)

under normal conditions the limited forward reactivity of the sorbitol to fructose part of the pathway allows sorbitol to be cleared from the eye
in a hyperglycemic patient build up of glucose causes build up of sorbitol that overwhelms sorbitol dehydrogenase
increased sorbitol increases osmotic pressure leading to influx of fluid into lens and consequent hydropic fibers of lens that degenerate causing opacities

16

what is flutamide and how does it work

flutamide is a non-steroidal anti-androgen drug
it competitively inhibits androgen receptors by competing with testosterone and DHT to treat prostate cancer

17

what is finasteride and how does it work
what does it treat

finasteride is a 5-alpha reductase inhibitor used to block conversion of testosterone to DHT
used to treat BPH and male-patterned baldness

18

what does IGF-1 from the liver vs. from the hypothalamus do?

IGF-1 from the liver promotes bone growth
IGF-1 from the hypothalamus regulates CNS activity

19

what causes decreased potassium in a DKA patient and why does this sometimes result in normal net serum potassium balance

diuresis due to glycosuria wastes potassium;
acidosis causes outflux of potassium in order to shift H+ into of cells

20

why do you have to worry about exacerbating hypokalemia while giving insulin to treat

the DKA patient probably already has a decreased overall potassium content due to K+ wasting in the kidney; once the acidosis is fixed K+ will shift back into the cell and can cause hypokalemia as a result

21

a patient with Lynch syndrome has a defect in what cellular process

nucleotide mismatch repair

22

An older patient with atherosclerotic disease has cells with intracytoplasmic granules that are yellowish-brown in color. What is the molecule behind this pigment and what process causes it?

lipofuschin (natural result of aging and "wear and tear") results from lipid peroxidation and free radical injury

23

explain why a certain drug might reach higher serum levels when administered per rectum than when taken orally

a drug with high first-pass metabolism (metabolism by liver) would have low bioavailability (percent reaching the serum) because the gastric vessels drain through the portal system, but 2/3 of the rectal venous drainage goes straight to the systemic venous system via the internal iliacs

24

which amino acids and which other molecules are metabolized to form propionyl-CoA

valine, isoleucine, methionine, and threonine as well as odd-chain fatty acids and cholesterol side chains are metabolized to form propionyl-CoA

25

what do ApoE3 and ApoE4 do?

VLDL and chylomicron remnant uptake by hepatocytes

26

what vitamin would you want to give to a patient with measles

vitamin A

27

what enzyme converts norepinephrine to epinephrine

PNMT (phenylethanolamine-N-methyltransferase)

28

synthesis of ALA synthase is normally inhibited by what

heme

29

which amino acids have three titratable protons

histidine, arginine, lysine, glutamate, aspartate, tyrosine, cysteine

30

which monosaccharide (and in what form) has the highest rate of metabolism and why

F-1-P;
it bypasses the rate-limiting step of phosphofructokinase-catalyzed conversion of F-6-P to F-1,6-BP