0521

Question 1

how does acetyl CoA act as an allosteric activator of gluconeogenesis?

Answer 1

increases activity of pyruvate carboxylase (pyruvate to oxaloacetate)

Question 2

homocysteine is elevated in?

Answer 2

both folic acid and B12 defs.

whereas only methylmalonyl CoA is elevated in B12 def.

Question 3

how does TNF-a induce insulin resistance?

Answer 3

activate serine kinases to phosphorylate insulin receptor substrate-1 serine residues (thus preventing normal tyrosine phosphorylation by insulin)

Question 4

insulin tyrosine kinase activity

Answer 4

causes phosphorylation of “insulin receptor substrates” that then activate PROTEIN PHOSPHATASE, which dephosphorylates (activates) glycogen synthase to promote glycogen synth.

Question 5

heme inhibits what step of its synthesis?

Answer 5

ALA synthase, which forms aminolevulinic acid from glycine and succinyl CoA.

*glucose also inhibits this step

Question 6

what step of TCA cycle generates GTP?

Answer 6

succinyl CoA synthetase (succinyl CoA to succinate)

Question 7

what step in gluconeogenesis requires GTP?

Answer 7

PEPCK (oxaloacetate to PEP)

Question 8

repressor protein of Lac operon binds where?

Answer 8

to operator.

*allolactose prevents repressor protein from binding here

Question 9

how does glucose inhibit activator of Lac operon?

Answer 9

decrease adenylyl cyclase
= decrease cAMP
= decrease catabolite activator protein (CAP) that normally positively regulates operon

Question 10

why is proline important in collagen formation?

Answer 10

ring structure introduces bends in alpha helix

Question 11

cause of wrinkles with aging

Answer 11

decreased synth and net loss of dermal collagen and elastin

Question 12

why is ketogenic diet recommended in pyruvate dehydrogenase deficiency?

Answer 12

carbohydrates may aggravate lactic acidosis (pyruvate already being shunted to lactate since it can’t be converted to acetyl CoA).

ketogenic AAs: lysine, leucine.

Question 13

full mutation of FMR1 gene

Answer 13

> 200 CGG repeats causing hypermethylation leading to gene inactivation.

manifests as Fragile X syndrome.
vs. premutation (< 200 repeats).

Question 14

what bases are hypermethylated in fragile X syndrome?

Answer 14

cytosine

Question 15

androgenetic alopecia

Answer 15

most common cause of hair loss in both males and females.

aka male pattern baldness.
POLYGENIC inheritance w/variable penetrance.

Question 16

pathogenesis of polycythemia in COPD

Answer 16

COPD can cause hypoxia sufficient enough to stimulate EPO production by renal cortical cells

Question 17

rubella (German measles)

Answer 17

febrile maculopapular rash starting on face, spread to trunk and extremities (also seen in rubeola).

rubella rash spread faster.
does not darken or coalesce.

PLUS postauricular, occipital lymphadenopathy

Question 18

rubella is part of what virus family?

Answer 18

toga virus

Question 19

how does a naked RNA molecule induce viral protein synth in host cell?

Answer 19

directly acts as mRNA using host’s intracellular machinery for translation-
only works for naked viruses with ss (+) RNA

Question 20

TX of CF malabsorption

Answer 20

secondary to panc insuff-

treat with panc enz supp

Question 21

where are receptors for thyroid hormones?

Answer 21

nucleus

Question 22

initial skin lesion of Lyme disease?

Answer 22

erythema migrans-
at the site of tick bite.
begins as erythematous macule.
enlarges with red border as bacteria migrate slowly through skin.
may see central clearing within patch.

Question 23

what causes green discoloration of pus or sputum during bact infx?

Answer 23

release of myeloperoxidase (MPO) from neutrophil azurophilic granules.

MPO is a blue green heme-containing pigmented molecule

Question 24

sunlight catalyzes what step in vit D synth?

Answer 24

7-dehydrocholesterol to cholecalciferol (D3)

Question 25

Langerhans cells are derived from…?

Answer 25

myeloid cell line.

dendritic cells that act as APCs.

Question 26

hot tub folliculitis

Answer 26

superficial, self-limited P.aeruginosa infx of hair follicles.

culture of pustule:
Gram neg.
oxidase pos.
non-lactose fermenting.
motile rod.
produce blue-green pigment.

Question 27

what two carpal bones articulate with radius?

Answer 27

scaphoid (more lateral) and

lunate (more medial)

Question 28

glycogen degradation is coupled with skel muscle contraction via?

Answer 28

calcium-mediated myophosphorylase activation…

increased cytosol Ca allosterically activates phosphorylase kinase, which then activates muscle phosphorylase for glycogenolysis

Question 29

main toxin produced by C.perfringens

Answer 29

LECITHINASE (aka alpha toxin, phospholipase C)-

degrades lecithin in phospholipid membranes, leading to cell death and widespread necrosis/hemolysis

Question 30

TX against spirochetes, including syphilis

Answer 30

PENICILLIN

Question 31

penicillins are structural analogs of?

Answer 31

D-Ala-D-Ala.

inhibit transpeptidase to stop peptidoglycan cell wall synthesis.

Question 32

antimuscarinic agents for asthma only fix…

Answer 32

vagally-mediated bronchoconstriction.

ex: ipratropium.

Question 33

snRNP

Answer 33

small nuclear ribonucleoproteins.
synth by RNA pol II in nucleus.
help remove introns from RNA transcript.
necessary for synth of mRNA.

Question 34

four major causes of hypoxemia (low PaO2)

Answer 34

1. alv hypoventilation*
2. V/Q mismatch.
3. diffusion impairment.
4. R-L shunting.

*ONLY hypoventilation has normal A-a gradient