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Up to Embryology Flashcards

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0
Q

What three enzymes are required to break down glycogen?

A

1) glycogen phosphorylase
2) a debranching enzyme
3) phosphoglucomutase (converts glucose-1P into glucose-6P)

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1
Q

What types of linkages does glycogen phosphorylase cleave?

A

alpha 1,4-glycosidic linkages in glycogen

glycogen -> glucose 1-phosphate

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2
Q

What organ is responsible for maintaining glucose levels?

A

Liver (contains glucose-6-phosphatase, which muscle does not have)
can take glucose-6P to glucose

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3
Q

What is type 5 glycogen storage disease? Enzyme deficiency? Inheritance? Presentation?

A

McArdle’s syndrome - deficiency in skeletal muscle glycogen phosphorylase (myophosphorylase)

Autosomal recessive

increased glycogen in muscle but cannot break it down:
decreased exercise tolerance
painful muscle cramps
myoglobinuria (red urine) with strenuous exercise
arrhythmia from electrolyte abnormalities

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4
Q

What are the purely ketogenic amino acids?

A

Leucine and lysine

would not lead to increased formation of lactate in pts with PDH deficiency

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5
Q

Presentation of PDH deficiency?

A

multiple possible presentations ranging from neonatal death to mild episodic symptoms in adulthood

neurologic defects
lactic acidosis
increased serum alanine starting in infancy

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6
Q

What is essential fructosuria?

A

defect in fructokinase; autosomal recessive

benign and asymptomatic since fructose not trapped in cells
fructose in blood and urine
hexokinase takes over fructokinase function - turns into F6P (glycolysis or turned into G6P)

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7
Q

What is fructose intolerance?

A

deficiency of aldolase B; autosomal recessive
hereditary fructose intolerance - onset of vomiting and hypoglycemia

fructose 1-P accumulates, causes a decrease in available phosphate
phosphate loss results in inhibition of glycogenolysis and gluconeogenesis.

signs after consuming fruit, juice, honey
negative dipstick test (only glucose tested)
treatment to decrease fructose and sucrose intake

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8
Q

What type of cells make up a pheochromocytoma? What MEN syndromes is this associated with?

A

Chromaffin cells (derived form neural crest cells)

MEN 2A and 2B

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9
Q

What tissue is the adrenal cortex derived from? The adrenal medulla?

A

cortex derived from mesothelial cells

medulla derived from neural crest cells

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10
Q

What do high levels of fructose 2,6-bisphosphate promote? What enzymes does it regulate?

A

promotes glycolysis and inhibits gluconeogenesis
also decreases the gluconeogenic conversion of alanine to glucose

F2,6BP allosterically activates PFK1, the main regulatory step in glycolysis, which converts F6P to F1,6BP.

F2,6BP allosterically inhibits fructose 1,6-bisphosphatase, which converts F1,6BP to F6P.

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11
Q

What does inhibition of gluconeogenesis do to alanine conversion to glucose?

A

decreases the conversion of alanine to glucose
(alanine transaminated to pyruvate and then converted to glucose)

processes that inhibit gluconeogenesis also downregulate the production of gluconeogenic substrates (like pyruvate)

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12
Q

What is fructose 2,6-bisphosphate concentration regulated by?

A

bifunctional enzyme composed of:
phosphofructokinase-2
fructose 2,6-bisphosphatase

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13
Q

What is the function of smooth ER? In what cells is smooth ER abundant?

A

contains enzymes for steroid and phospholipid biosynthesis

steroid-producing cells in the adrenals, gonads, and liver all contain well-developed smooth ER

cholesterol-derived steroid hormones in the adrenals
detox of numerous drugs in hepatocytes
specialized SER is the sarcoplasmic reticulum in striated muscle cells

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14
Q

What is Keq if standard free energy change (deltaGo) is positive? Negative? Zero?

A

positive deltaGo: Keq is less than 1
negative deltaGo: Keq is more than 1
zero deltaGo: Keq equals 1

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15
Q

What is negative predictive value? Does pretest probability matter?

A

the probability of being free of a disease if the test result is negative

the NPV will vary with the pretest probability of a disease!!
pt with high pretest prob. will have low NPV with a negative test
pt with low pretest prob. will have high NPV with a negative test

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16
Q

TSH, LH, and FSH activate what type of receptors? Describe the transmembrane domain.

A

GPCRs

segments of the 7-tm alpha helices containing approximately 20 hydrophobic amino acids

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17
Q

Where does the thyroid migrate from? The GnRH-secreting neurons of the hypothalamus? The testes?
What does failure of each of these migrations lead to?

A

Thyroid migrates from tongue to lower anterior neck - failure leads to lingual thyroid or thyroid mass at any point along thyroglossal duct

GnRH-secreting neurons migrate from olfactory lobes to hypothalamus - failure is Kallman syndrome

Testes migrate from intra-abdominal location to scrotum - failure is called cryptorchidism

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18
Q

Where is epinephrine sythesized? Where is dopamine and NE synthesized?

A

Epinephrine - adrenal medulla

Dopamine and NE - CNS and PNS

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19
Q

What are cortisol’s effects on Epinephrine production?

A

Cortisol increases activity of phenylethanolamine-N-methyltransferase (PNMT) which converts NE to epinephrine.

High levels of cortisol in the adrenal medulla because venous drainage from the adrenal cortex runs through the medulla. Catecholamine contents of the adrenal medulla are 80% epinephrine, 20% NE.

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20
Q

What type of signaling pathway does insulin work by? Glucagon? Cortisol? Catecholamines? Growth hormone receptors?

A

Insulin and growth hormone receptors - act via an intrinsic tyrosine kinase (cell surface receptor with resultant activation of tyrosine kinase)
THINK GROWTH FACTORS = intrinsic cell surface RTK

Glucagon and catecholamines - acts via cAMP through binding/activation of GPCRs

Cortisol - acts as a steroid receptor

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21
Q

What are the signaling pathways of endocrine hormones that act as vasdilators? What are these hormones?

A

ANP, NO (EDRF) - vasodilators

Act through cGMP via GPCR binding/activation

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22
Q

Which endocrine hormones work through a receptor-associated tyrosine kinase? Name an example of this kind of pathway.

A

Prolactin, immunomodulators (cytokines), and GH
PIG

JAK/STAT pathway

think acidophiles and cytokines!!

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23
Q

Is the nucleolus membrane-bound/does it have a membrane?

A

Nope.

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24
How do you identify euchromatin in the nucleus on electron microscopy?
lighter "electron lucent" regions | DNA is unpackaged and is actively being transcribed
25
What is AFP and where is it synthesized? How does it change with gestational age?
alpha-fetoprotein synthesized by fetal liver, GI tract, and yolk sac (in early gestation only) Maternal serum AFP levels increase with gestational age.
26
What is the most common cause of elevated AFP levels in maternal serum? What is associated with decreased AFP levels?
Dating error (underestimation of gestational age) Increased AFP also associated with: - neural tube defects - anterior abdominal wall defects - multiple gestation Down syndrome associated with decreased AFP levels.
27
What is hCG and what is it synthesized by? What conditions are associated with elevated hCG?
human chorionic gonadatropin (hCG) is synthesized by trophoblastic tissue increased levels associated with: - multiple gestation - hyatidiform mole - choriocarcinoma
28
What are estriol level reflective of in pregnancy? What do decreased levels suggest?
placental and fetal function - both are necessary for its synthesis decreased levels suggestive of placental insufficiency
29
Mechanism of insulin activity?
insulin binds cell surface RTK phosphorylation of a number of proteins (insulin receptor substrates) leads to activation of protein phosphatase protein phosphatase dephosphorylates glycogen syntase glycogen synthase activated by dephosphorylation - promotes synth.
30
What is the end product of sorbitol metabolism? What does aldolase reductase do?
Fructose Aldolase reductase takes glucose to sorbitol using an NADPH
31
What organs contain significant amounts of sorbitol dehydrogenase? Which cells lack it? What is the relation to diabetes?
Seminal vesicles, ovaries, and liver Schwann cells, retina, and kidneys lack the enzyme - conversion of glucose to sorbitol in hyperglycemic states causes osmotic damage (peripheral neuropathy, retinopathy) Lens has significant amounts of sorbitol dehydrogenase, but it gets overwhelmed in hyperglycemia - cataract formation.
32
How does insulin promote glucose uptake in adipocytes and muscle cells? How does insulin resistance occur and in response to what factors?
Insulin moves cytoplasmic GLUT-4 to the PM in muscle and fat cells. Insulin resistance occurs via the activation of serine kinases, which aberrantly phosphorylate serine and threonine residues. TNFalpha, catecholamines, glucocorticoids, and glucagon all promote these aberrant phosphorylations.
33
Why does lactic acidosis occur in septic shock pts?
tissue hypoxia results in impaired ox-phos and shunting of pyruvate to lactate following glycolysis hepatic hypoperfusion also contributes to buildup of lactic acid, since liver is the primary site of lactate clearance
34
What are the most dependent locations in the lungs of supine individuals? What does dependent lung consolidation suggest?
superior regions of lower lobes and posterior regions of the upper lobes Dependent lung consolidation is commonly seen in aspiration pneumonia. Elderly pts with dementia or hemiparesis may also have dysphagis, which is a risk factor for aspiration pneumonia.
35
What is glucokinase? What do inactivating mutations result in?
glucose sensor in pancreatic beta cells (first enzyme in glycolytic pathway of beta cells - converts glucose to G6P) inactivating mutations result in mild hyperglycemia that can be exacerbated by pregnancy
36
How long do glycogen stores last during fasting? What maintains normal blood glucose levels after this point?
last 12-18 hours after fasting after liver glycogen depleted, gluconeogenesis is the primary process used by the body to keep blood glucose levels within normal range
37
What are the 4 irreversible enzymes and reactions in gluconeogenesis?
Getting pyruvate back to phosphoenolpyruvate (one step in glycolysis) accounts for 2 of these rxns: - pyruvate carboxylase in the mitochondria pyruvate converted to oxaloacetate (OAA), requires biotin, ATP - phosphoenolpyruvate carboxykinase in the cytosol OAA converted to PEP, requires GTP ``` Then final 2 dephosphorylations - fructose 1,6 bisphosphate in the cytosol fructose 1,6 BP converted to fructose 6P - glucose 6 phosphatase in the ER glucose 6P converted to glucose ```
38
What is protein kinase C activated by?
directly into DAG and by calcium released from the sarcoplasmic reticulum by IP3 both DAG and IP3 generated by phospholipase C activation from Gq GPCR
39
Through what channel does glucose enter pancreatic beta cells?
GLUT-2
40
What is the most effective preventive intervention in almost every pt?
Smoking cessation!!
41
What is the function of GLUT-4? GLUT-2?
GLUT-4 is the insulin-sensitive transporter found in skeletal muscle cells and adipocytes (stored in cytoplasmic vesicles and released to PM with insulin) GLUT-2 facilitates export of glucose from the liver, small intestine, and kidneys into the circulation and also helps to control insulin secretion in the pancreas.
42
What are neurophysins and what do they do?
proteins involved in the posttranslational processing of oxytocin and vasopressin (carrier proteins as they travel in axon from hypothal to post. pituitary) hormones and neurophysins produced in neuronal cell bodies of paraventricular (oxytocin) and supraoptic nuclei (ADH), and released into circulation from axon terminals in the posterior pituitary gland
43
Where does ADH production start? Oxytocin?
supraoptic nuclei; paraventricular nuclei
44
How do hormones from the posterior pituitary enter systemic circulation?
secreted from nerve terminal of the posterior pituitary into the hypophysial vein to ultimately enter systemic circulation
45
What are the functions of thyroid peroxidase?
- oxidation of inorganic iodine - formation of mono-iodotyrosine (MIT) and di-iodotyrosine (DIT) - coupling to form T4 (two DITs come together) and T3 (DIT+MIT) thyroid follicular cells engulf thyroglobulin (the scaffold for all these iodinated Tyrs) by pinocytosis and in the cytoplasm, iodinated Tyr resides are removed from the rest of the thyroglobulin to be secreted from the basolateral border of the thyroid follicular cells.
46
Describe Klinefelter syndrome: karyotype and presentation? | What is the defect due to?
47 XXY tall stature, gynecomastia
47
What is Chvostek sign? What does it indicate? What is another sign of this condition?
tapping of facial nerve (tap cheek) elicits contraction of facial muscles neuromuscular hyperexcitability due to hypocalcemia (possibly due to hypoparathyroidism) Trousseau sign - occlusion of brachial artery with BP cuff (cuff the Triceps) and get a carpal spasm
48
Pt with hypocalcemia, shortened 4th/5th digits, short stature?
Pseudohypoparathyroidism / Albright hereditary osteodystrophy autosomal dominant unresponsiveness of kidney to PTH
49
Permissive effect? Additive? Synergistic? What is tachyphylaxis?
Permissive - no action on its own but allows another drug to achieve its full potential Additive - two drugs with similar actions have combined effect equal to the sum of the effects expected from the individual drugs Synergistic - combined effect of two drugs EXCEEDS the sum of the individual drug effects Tachyphylaxis - decreased drug responsiveness with repeated administration
50
Cellular distribution of GLUT1, 2, 3, 4, 5? Which transporter is responsive to insulin (insulin-dependent)? Which are insulin-independent?
1: RBCs, CNS 2: hepatocytes, pancreatic beta-cells (regulation of insulin release) 3: placenta, brain, kidney (placental glucose transport) 4: muscle cells, adipocytes 5 (fructose transport): spermatocytes, GI tract GLUT-4 is the only insulin-dependent transporter.
51
What regulates chromaffin cell release of catecholamines from the adrenal medulla?
Preganglionic sympathetic fibers release ACh onto chromaffin cells; chromaffin cells release catecholamines directly into bloodstream Chromaffin cells are modified postganglionic sympathetic neurons derived from neural crest (neuroendocrine cells)
52
Hormone levels in Klinefelter's? FSH and LH? Testosterone? Estrogen?
Increased FSH (dysgenesis of seminiferous tubules, decreased inhibin from Sertoli cells, increased FSH) Increased LH and estrogen (abnormal Leydig function, decreased testosterone, increased LH and increased estrogen) Decreased testosterone
53
What are the three cardinal signs of diabetes mellitus?
polyuria, polydypsia, and polyphagia
54
How does DKA result? What are classic signs?
inadequate glucose transport into cells -> perceived hypoglycemia/starvation state -> increased glucagon production and adrenergic activation -> glucagon stimulates ketone body synthesis in adipose tissue as an alternate energy source, also increases glycogenolysis, gluconeogenesis, lipolysis, urea production fruity odor on breath (due to ketone bodies), nausea/vomiting, abdominal pain, psychosis/delirium, dehydration
55
Primary function of ADH? Mechanism of ADH effect?
serum osmolarity regulation regulation of aquaporin channel transcription in principal cells of renal collecting duct
56
What causes diabetes insipidus? Presentation? What are the two types? Treatment?
lack of ADH or ADH-sensing ability presents with intense thirst and polyuria with inability to concentrate urine Central (decreased ADH production) vs. nephrogenic (receptor defect) treatment is DDAVP in central; HCTZ, indomethacin, amiloride in nephrogenic
57
What processes can cause isoosmotic volume contraction? Hypoosmotic volume expansion? Hyperosmotic volume contraction?
Isoosmotic volume contraction: GI hemorrhage, diarrhea Hypoosmotic volume expansion: psychogenic polydipsia, SIADH Hyperosmotic volume contraction: diabetes insipidus, profuse sweating (hypotonic nature of sweat)
58
How is reverse T3 formed?
from T4 in the peripheral tissues!! T4 can be converted in the peripheral tissues to the more active T3 OR the inactive rT3. T3 cannot be converted to rT3 or T4.
59
What cells does FSH act on in males? Where are these cells located? What is the result of FSH stimulation in these cells?
FSH acts on Sertoli cells in the seminiferous tubules! FSH stimulation is responsible for: - spermatogenesis - inhibin B production (provides negative feedback to FSH production in the pituitary) FSH stimulates Sertoli cells to produce androgen-binding protein locally within seminiferous tubules -- this results in high local testosterone concentration necessary for spermatogenesis.
60
What is primary polydipsia and how is it diagnosed?
Psychogenic polydipsia - excessive/pathologic water drinking Water deprivation test will show: - steady, reliable, and prompt increase in urine osmolality - paltry response (<10% change) to vasopressin administration, due to acquired partial deficiency in aquaporin channels in collecting ducts

Endocrine (4 decks)

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