question

Name two reactions catalized by aldose reductase.

answer

Galactose → galactitol; glucose → sorbitol

question

4 cell types without sorbitol dehydrogenase:

answer

Schwann cells, lens, retina, kidneys

question

Reaction catalyzed by sorbitol dehydrogenase:

answer

sorbitol → fructose

question

What energy source does the urea cycle require?

answer

2ATP

question

Name the basic amino acids:

answer

Arginine, lysine, histadine (Arg, Lys are abundant in histones, histine is neutral at physiologic pH)

question

Hereditary pattern of ornithine transcarbamolyase deficiency:

answer

X-linked recessive

question

Serotonin is derived from what precursor?

answer

Tryptophan -(BH2)→ serotonin → melatonin

question

Dopa decarboxylase is inhibited in the treatment of what disease?

answer

Parkinsons; decreases peripheral dopamine synthesis → increases peripheral DOPA which can cross the BBB

question

Cofactor in dopamine -(Dopamine beta-hydroxylase)→ norepinephrine reaction

answer

vitamin C

question

What substance regulates phenylethoanolamine N-methyl transferase?

answer

Cortisol (more norepinephrine → epinephrine during stress)

question

Where is epinephrine synthesized?

answer

Adrenal gland

question

2 metabolic diseases that demonstrate locus heterogeneity:

answer

albinism (tyrosinase defect, tyrosine transport defect, lack of neural crest migration), homocystinuria (cystathionine synthase deficiency, decrased affinity of cystathionine synthase for pyridoxial phosphate (B6), Homocysteine methyltransferase deficiency (B12))

question

Inheritance pattern of cystinuria:

answer

autosomal recessive (defect in PCT amino acid transport)

question

Pathway of glucagon (liver) and epinephrine (liver and muscle) signaling:

answer

bind receptor → increased cAMP → increased protein kinase A → phosphorylation of glycogen phosphorylase kinase → phosphorylation of glycogen kinase → breakdown of glycogen (think phosphorylation)

question

Pathway of insulin signaling:

answer

bind receptor → receptor tyrosine kinase dimerizes → activation of protein phosphatases → dephosphorylation of glycogen phosphorylase kinase and glycogen kinase → decreased breakdown of glycogen (think dephosphorylation)

question

Name a lysosomal storage disease that is not autosomal recessive.

answer

Fabry's disease and Hunter's disease are X-linked recessive (Fabry's: deficient alpha-glactosidease A, accumulation of ceramide trihexoside; Hunters: deficient iduronate sulfatase, accumulation of heparan sulfate, dermatan sulfate)

question

Most common lysosomal storage disease:

answer

Gaucher's disease; deficiency of glucocerebrosidase, accumulation of glucocerebroside

question

Findings in Gaucher's disease:

answer

Aseptic necrosis of femur, bone crisis, Gaucher's cells: macrophages that appear as crumpled paper, hepatosplenomegaly (crying skeleton riding skeleton horse pointing to a crow with a femur)

question

Findings in Krabbe's disease:

answer

Peripheral neuropathy, developmental delay, optic atrophy, globoid cells (crab on top of the world with sunglasses and axon arms)

question

Deficency in Krabbe disease:

answer

Galactocerebrosidase (accumulation of glalactocerebroside)

question

Findings in metachromatic leukodystophy:

answer

central and peripheral demyelination with ataxia, dementia (Metal Luke shooting an arrow and getting in a taxi with a confused driver) (deficiency of arylsufatase A, build up of cerebroside sulfate)

question

Findings in Hurlers syndrome:

answer

gargoylism, corneal clouding, developmental delay, airway obstruction, hepatosplenomegaly (Hurling gargoyl with corn in his eyes) (Hunter's syndrome less severe, no corneal clouding and X-linked recessive)

question

Enzyme deficiency and substance that accumulates in Hurler's and Hunter syndrome:

answer

alpha-L-iduronidase deficiency, accumulation of heparan sulfate and dermatan sulfate (deer pulling hurling gargoyl with corn in his eyes; no corneal clouding in Hunters)

question

How does fatty acid synthesis begin?

answer

Transport of citrate out of the mitochondrial matrix into the cytoplasm via the citrate shuttle (produces and NADPH, which is used in fatty acid synthesis, citrate is then broken down into acetyl-CoA)

question

How would carnitine deficiency affect ketone and glucose levels?

answer

Decrease; increased acyl-CoA would inhibit gluconeogenesis

question

How would acyl-CoA dehydrongenase deficiency affect ketone and glucose levels:

answer

decrease; cannot make ketone bodies and lack energy for gluconeogenesis

question

Ketones have the same starting substrate as:

answer

cholesterol (HMG-CoA)

question

What reactions need to occur in order for cholesterol to be packaged into VLDL, IDL, LDL?

answer

Esterfication catalized by lecithin-cholesterol acyltransferase (allows cholesterol to be stored in vesicles rather than imbedded in the membrane) and then transfer from mature HDL to VLDL, IDL or LDL by a transfer protein

question

What lipoprotein is Apo-E not present on?

answer

LDL

question

What enzyme does ApoA-1 activate?

answer

Lethicin-cholesterol acyltransferase, LCAT (present on HDL and chylomicrons)

question

What apolipoprotein is a cofactor of lipoprotein lipase?

answer

ApoC-II (present on Chylomicrons and VLDL, mediates transfer of TG to adipose tissue)

question

What apolipoprotein binds the LDL receptor?

answer

B-100 (present on VLDL, IDL, LDL)

question

What is the function of ApoB-48?

answer

Mediates chylomicron secretion (present on chylomicron and chylomicron remnant)

question

Describe the life of a chylomicron.

answer

Secreted by intestinal epithelial cells, delivers dietary TGs to peripheral tissue, delivers cholesterol to live in the form of chylomicron remnant

question

Name the apoprotein that activates the enzyme necessary to make a mature HDL molecule.

answer

ApoA-1 activates LCAT

question

What is the cause of hyperchylomicronemia?

answer

LPL deficiency or altered ApoC-II

question

Does LPL deficiency or altered ApoC-II seen in hyperchylomicronemia increase the risk for atherosclerosis?

answer

No; causes pancreatitis, hepatosplenomegaly, and eruptive/pruritic xanthomas

question

Name an ocular manifestation of familial hypercholesterolemia.

answer

Corneal arcus

question

Inheritance pattern of familial hypercholesterolemia:

answer

Autosomal dominant

question

Abetalipoproteinemia is due to hereditary inability to synthesize apoB-100 and apoB-48. What is the main cause of symptoms?

answer

Inability to export absorbed lipid as chylomicrons leads to steatorrhea, failure to thrive, night blindiness, acanthocytosis and ataxia

question

What can be seen on peripheral blood smear in patients with abetalipoproteinemia?

answer

Acanthocytes due to imbalance of membrane components

question

Activity of what enzyme is increased in Lesch-Nyhan syndrome?

answer

PRPP amidotransferase

question

Name a treatment for cyanide poisoning.

answer

Nitrates cause methemoglobin which binds tightly to CN and helps to prevent it from damaging mitochondrial enzymes

question

In the cells of the respiratory tract, viral proteins from the influenza virus are degraded and attached to major MHC I molecules that are then expressed on the cell surface for presentation to cytotoxic CD8+ lymphocytes. What enzyme is most likely involved in this process?

answer

Ubiquitin ligase, which catalyzes ubiquitin attachment

question

What is the main cause of fine skin wrinkles in aging?

answer

Decreased synthesis and net loss of dermal collagen and elastin

question

Name a metabolic process inhibited by fructose 2,6-bisphosphate.

answer

Gluconeogenesis

question

Insulin-mediated glucose uptake is primarily present in:

answer

skeletal muscle cells and adipocytes

question

Where are thyroid hormone receptors located?

answer

Nucleus

question

Why does HbS sickle?

answer

Hydrophobic interaction among hemoglobin molecules; normally all of the hydrophobic amino acids are in the interior

question

How does iRNA work?

answer

Posttranscriptional gene silencing by base-pairing with complementary sequences within target mRNA molecules

question

An infant who fails to gain weight has no enteropeptidase activity on the surface of her duodenal epithelium. What substance is most likely impaired as a result?

answer

Trypsin

question

What type of reaction does methylmalonyl CoA undergo to produce succinyl CoA?

answer

Isomerization

question

Where is the cortisol receptor located?

answer

Cytoplasm; translocates to the nucleus after binding

question

How does cortisol affect glucose metabolism?

answer

Enhances hepatic glucose production and limits peripheral glucose utilization through altering gene transcription (contributes to glucose homeostasis during prolonged fasting along with GH; glucagon with epinephrine as a major backup, is the primary hormone secreted in response to a rapid drop in blood glucose levels

question

3 examples of steroid producing cells that have a prominent smooth ER:

answer

adrenal, gonadal, liver

question

Name 4 example of factors that utilize the tyrosine kinase-associated receptors and the JAK/STAT signaling pathway:

answer

colony-stimulating factors, prolactin, growth hormones, cytokines

question

Deletion of a single nucleotide from a DNA sequence results in what type of mutation?

answer

Frameshift

question

Name an allosteric activator of pyruvate carboxylase.

answer

Acetyl-CoA; pyruvate carboxylase catalyses the first step in gluconeogenesis; high acetyl-CoA levels indicate energy excess

question

Citrate is an allosteric activator of:

answer

acetyl-CoA carboxylase (fatty acid synthesis) and fructose-1,6-bispohsphatase

question

What type of disorders tends to have a mutation in the cytoplasmic tyrosine kinase, Janus kinase 2 (JAK2)?

answer

Chronic myeloproliferative disorders including polycythemia vera, essential thrombocytosis and primary myelofibrosis; constitutive tyrosine kinase activity results in cytokine-independent activation of STAT transcription factors

question

A 67-year-old man has pallor, early satiety, severe fatigue, 20lbs weight loss over the past 6 months, hepatomegaly and massive splenomegaly. A cytosolic protein in his WBCs has constitutive tyrosine phosphorylation activity. There is persisten activation of STAT protein. What condition does he likely have?

answer

Primary myelofibrosis

question

Most enchancers are located where, with respect to the transcription start site?

answer

Variable locations

question

What serum autoantibodies have a high specificity for rheumatoid arthritis?

answer

Anti-cyclic citrullinated peptides (anti-CCP)

question

Monoamine oxidase normally metabolizes:

answer

Tyramine

question

Tyramine is present in:

answer

aged cheeses, cured meats, draft beer

question

Mechanism of action of tyramine:

answer

indirect sympathomimetic that is usually metabolized in the intestine by monoamine oxidase (MAO); excess amounts displace norepineprine from vesicles in the presenaptic neuron

question

A patient on a monoamine oxidase (MAO) inhibitor who consumes beer and cheese is at risk for developing a:

answer

hypertensive emergency (sever hypertension, headache, blurry vision) and excessive sympathetic activity (tachycardia, diaphoresis, tremors)

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