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UWorld Review > 5/4 Biochemistry/ Mixed > Flashcards

5/4 Biochemistry/ Mixed Flashcards

1
Q

Short non-coding RNA sequences (micro RNA and small interfering RNA) role in gene silencing

A

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

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2
Q

Hormone-sensitive lipase

A

Found in adipose tissue

Functions to drive the breakdown of stored triglycerides into free fatty acids and glycerol

During times of starvation, this enzyme provides substrated for hepatic gluconeogenesis and ketone body formation

Stimulated in response to stress hormone (catecholamines, glucagon, ACTH), inhibited by insulin

NOTE: brain can only use ketone bodies/glucose (FFA do not cross BBB), RBC only use glucose (no mitochondria

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3
Q

Hereditary fructose intolerance

A

Aldolase B deficiency

Failure to thrive, jaundice, hepatomegaly

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4
Q

Lynch syndrome (hereditary nonpolyposis colon cancer)

A

Autosomal Dominant

Defective DNA mismatch repair (MSH2, MLH1 mutations) > MutS and MutL homologs

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5
Q

Acetyl-CoA’s role in gluconeogenesis

A

Acts as an allosteric activator by increasing the activity of pyruvate carboxylase (pyruvate to oxaloacetate). Note, this only occurs when Acetyl-CoA levels are high. When Acetyl-CoA is low, pyruvate is shunted toward Acetyl-CoA production, preventing the cell from becoming energy depleted

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6
Q

Sucrose

A

Fructose + Glucose

Avoid in aldolase B deficiency (hereditary fructose intolerance)

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7
Q

Most common genetic cause of hyperhomocysteinemia (increased thrombotic events)

A

MTHFR deficiency (methylene tetrahydrofolate reductase)

also deficiencies of Vit B12, 6, and folate

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8
Q

More than one codon can code for a particular amino acid

A

Genetic code is degenerate

Wobble

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9
Q

Secondary lactate deficiency

A

Can occur after inflammatory (celiac disease) or infectious (giardiasis) processes damage the microvilli of the small intestines

Abdominal distension, cramping, flatulence, diarrhea

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10
Q

Conversion of norepinephrine to epinephrine

A

Phenylethanolamine-N-methyltransferase

Adrenal medulla

Cortisol increases converstion
(no pituitary= no ACTH= no cortisol)

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11
Q

Galactosemia

A

Impaired galactose-1-phosphate metabolism

Deficiency of galactose-1-phosphate uridyl transferase

Vomiting, lethagy, failure to thrive soon after breastfeeding

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12
Q

Scurvy (vit C deficiency)

A

perifollicular hemorrhages, myalgias, subperiosteal hematoma, gingivitis, hemarthrosis, petechial hemorrhages, impaired wound healing, weakened immune responses

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13
Q

Base excision repair

A

Repairs non-bulky DNA base alterations (depurination, alkylationmoxidation, deamination)

Excessive consumption of dietary nutrutes can promote deamination

Glycosylases, endonuclease, lyase DNA polymerase, ligase

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14
Q

Cofactor for oxaloacetate to phosphoenolpyruvate during gluconeogenesis

A

GTP (synthesized by succinyl-CoA synthetase during the conversion of succinyl-CoA to succinate in the Citric acid cycle)

During gluconeogenesis, phosphoenolpyruvate carboxykinases uses GTP to synthesize phosphoenolpyruvate from oxaloacetate

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15
Q

Wernicke encephalopathy

A

Opthalmoplegia, ataxia, confusion (coma, death)

Foci of hemorrhage/necrosis in mammillary bodies

Chronic thiamine (B1) deficiency

Dx: baseline erythrocyte tranketolast activity is low but increases with addition of thiamine pyrophosphate

Treat with thiamine supplementation and glucose infusion

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16
Q

Smooth ER

A

Contains enzymes for steroid and phopholipid biosynthesis

All steroid producing cells (e.g. cells in the adrenals, gonads, and liver) contains a well developed smooth ER

17
Q

Methylmalonic acidemia

A

AR, organic acidemia
Deficiency of methylmalonyl-CoA mutase

Metabolic acidosis, hypoglycemia, ketones, hyperammonemia

Elevated urine methylmalonic acid and propionic acid

Lethargy, vomiting, tachypnea

18
Q

Pompe disease

A

Deficiency of acid-a-glucosidase

Infancy, cardiomegaly, macroglossia, muscular hypotonia

19
Q

Glucose-6-phosphate dehydrogenase (G6PD deficiency)

A

Hemolytic anemia after infections (pneumonia, viral hepatitis), consumption of fava beans, meds (primaquine, sulfa drugs)

G6PD converts glucose 6-phosphate to ribulose-5-phosphate, 2 NADPH are produced (pentose phosphate pathway)

Major source for cellular NADPH
Necessary for reducing glutathione (preventing oxidative damage), biosynthesis of cholesterol, fatty acids, steroids

20
Q

Spinal muscular atrophy

A

Mutation in SMN1 gene

impaired assembly of snRNPs in lower motor neurons

Flaccid paralysis dye to degeneration of anterior horn cells

21
Q

Familial erythrocytosis

A

B-globin mutation > reduced binding of 2,3-BPG, results in loss of positive charge in pocket, causes hemoglobin A to resembled fetal hemoglobin (binds oxygen with a higher affinity, due to inability to interact with 2,3-BPG

22
Q

GLUT-4

A

Skeletal muscles, adipocytes

Insulin-sensitive

23
Q

What causes cataract formation in a patient with galactosemia

A

(Galactokinase deficiency)

Galactitol accumulates in lens of patients with galactosemia and causes osmotic damage leading to cataract formation.

Galactitol is formed from excess circulation galactose in galactosemia by aldose reductase

24
Q

Glucagon second messenger system mechanism

A

Exerts it effects via G-protein coupled receptors using adenylate cylase second messenger system, cAMP, protein kinase A

TSH, glucagon, PTH receptors all use this system!

25
Q

Lesch-Nyhan syndrome

A
  • deficiency of HGPRT
  • increases the demand for de novo purine synthesis
  • activity of PRPP aminotransferase must increase to supply a sufficient quantity of purine nucleotides
26
Q

Cofactor for transaminases

A

Pyridoxine (Vit B6)

Transamination reactions (N) typically occur between an amino acid and an a-keto acid

Amino group is transferred to a-keto acid from amino acid and the a-keto acid thereby becomes an amino acid

Glutamate reacts with oxaloacetate to form asparate and a-ketoglutarate

27
Q

Ataxia-telangiectasia

A

AR, defect in DNA-repair genes
DNA is hypersensitive to ionizing radiation

Cerebellar ataxia, oculocutaneous telangiectasias, repeated sinopulmonary infections, increased incidence of malignancy

28
Q

Rx of moderate-severe allergic asthma

A

Anti-IgE antibodies given as SQ injection (Omalizumab)

Helps to reduce dependency on both oral and inhaled steroids

29
Q

Most important mediator of sepsis

A

TNF-a (produced by activated macrophages), induces a systemic inflammatory response

(IL-1 and IL-6 are also involved)

30
Q

Theophylline intoxication

A

Seizures, tachyarrhythmias, nausea/vomiting, abdominal pain, diarrhea

Rx: activated charcoal, B-blockers, benzodiazepines/barbituates (seizures)

31
Q

Best indicator of severity of mitral regurgitation?

A

Presence of audible S3
Indicates a high regurgitant volume and severe mitral regurg, left ventricular volume overload (reflects increased rate of left ventricular filling due to a large volume of regurgitant flow-reentering the ventricle during mid diastole)

32
Q

Pulsus paradoxus

A

decrease in systolic blood pressure of >10 mm Hg with inspiration

seen in patients with cardiac tamponade (pericardial dx), severe asthma, COPD, constrictive pericarditis

Quanitified by the difference between systolic pressure at which Korotkoff sounds first become audible during expiration and the pressure at which they are head throughout all the phases of respiration

33
Q

How do beta-adrenergic agonists control acute asthma/COPD?

A

Cause bronchial smooth muscle relaxation via increased intracellular cAMP

34
Q

Drugs that have been shown to improve long-term survival in patients with heart failure due to left ventricular systolic dysfunction

A

Beta blockers, ACE inhibitors, angiotensin II receptor blockers, aldosterone antagonists

35
Q

Stop codons

A

UAA, UAG, UGA

Cause releasing factor proteins to bind the ribosome and stimulate release of the formed polypeptide chain

Note: START = AUG

36
Q

Colchicine

A

Inhibits tubulin polymerization into microtubules (cytoskeleton)

Used for acute Rx and prophylaxis of gout

SE: nausea, abdominal pain, diarrhea

37
Q

Which artery supplies Broca’s area and Wernicke’s area

A

Middle cerebral artery
Broca= superior division
Wernicke= inferior division

UWorld Review (28 decks)

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