6/20 UWorld

Question 1

Describe defect and presentation of Abetalipoproteinemia

Answer 1

• Lack of apoprotein B
  
  • B48 needed for chylomicron secretion from the intestinal cells
    
    • Enterocytes fill with chylomicrons that cannot pass into circulation
    • Fat malabsorption, steatorrhea, failure to thrive
    • Night blindness (Vitamin A deficiency)
    • Ataxia
  • B100 needed for LDL reuptake in the liver

Question 2

Histology and treatment of abetalipoproteinemia

Answer 2

• Will see abnormal star-shaped RBCs called acanthocytes (spur cells)
• Treatment:
  
  • Vitamin E – will restore apolipoprotiens

Question 3

Defect and presentation in familial hypercholesterolemia

Answer 3

• Increased LDL due to defective or absent LDL receptor
• Presentation:
  
  • Accelerated atherosclerosis (early MI), tendon xanthomas, corneal areus

Question 4

Starting substrate and rate limiting enzyme of cholesterol synthesis

Answer 4

Starting substrate = acetyl CoA

Rate-limiting step = HMG CoA Reductase (vs. ketogenesis which is HMG CoA synthase)

Question 5

Where does fatty acid synthesis occur and what is the rate limiting enzyme

Answer 5

Occurs in the cytoplasm

Acetyl CoA carboxylase

Question 6

Location and rate limiting enzyme of Fatty acid degradation

Answer 6

Occurs in the mitochondria

Carnitine palmitoyl transferase

Question 7

Deficiencies in what 2 enzymes can lead to hypoketotic hypoglycemia

Answer 7

Carnitine palmitoyl transferase deficiency (cannot transport fatty acids into mitochondria for degradation)

Medium chain acyl-CaO dehydrogenase deficiency (no beta-oxidation = cannot break down fatty acids)

Question 8

What is the amino acid derivative of serotonin

Answer 8

Tryptophan

Question 9

AA derivative of nitric oxide

Answer 9

Arginine

Question 10

AA derivative of norepinephrine

Answer 10

Phenylalanine (to tyrosine)

Question 11

AA derivated of Niacin

Answer 11

Tryptophan (remember Hartnup disease)

Question 12

What organ does Urea cycle take place in?

Answer 12

Liver

Question 13

Rate limiting enzyme for urea cycle

Answer 13

carbamoyl phosphate synthetase I (CPSI)

Found in mitochondria

Question 14

AA derivative of porphyrin

Answer 14

Glycine

Question 15

Defective enzyme in PKU

Answer 15

o Deficiency in phenylalanine hydroxylase, or

o Deficiency in tetrahydrobiopterin cofactor (BH4)

Question 16

Treament of PKU

Answer 16

• Decreased phenylalanine intake (proteins, aspartame in artificial sweeteners)
• Increased tyrosine intake (deficient enzyme was supposed to convert phenylalanine to tyrosine)
• BH4 supplementation

Question 17

Causes of homocysteinuria

Answer 17

o Cystathionine synthase deficiency

o Decreased affinity of cystathionine synthase for B6

o Methionine synthase deficiency

Question 18

What type of receptor does glucagon use?

Answer 18

Gs (not part of FLAT ChAMP though)

Question 19

Cause and presentation of Hartnup disease

Answer 19

o Autosomal recessive deficiency of neutral amino acid transporters

o Leads to decreased absorption of tryptophan, which is the source of niacin (B3)

o Can lead to pellagra-like symptoms

o Treat with high-protein diet and nicotinic acid

Question 20

What vitamin (deficiency or toxicity) is associated with pseudotumor cerebri (idiopathic ICP)

Answer 20

Vitamin A toxicity

Question 21

Function of Vitamin E

Answer 21

Antioxidant - protects RBC from free radical damage

Question 22

Describe the 3 major diseases caused by thiamine deficiency

Answer 22

Thiamine = B1

• Wernicke-Korsakoff syndrome
  
  • Triad: confusion, ophthalmoplegia, ataxia
  • Confabulation, personality change, memory loss (permanent)
• Beriberi = THINK: Ber1Ber1 to remember B1
  
  • Dry beriberi
    
    • THINK: nerves
    • Polyneuritis, symmetrical muscle wasting
  • Wet beriberi
    
    • THINK: heart
    • High-output cardiac failure (dilated cardiomyopathy), edema

Question 23

What vitamin deficiency will cause corneal vascularization

Answer 23

B2 Riboflavin

THINK: things are flavorful when you get high (red eyes)

Question 24

Function of Pyridoxine

Answer 24

Vitamin B6

• Converted to pyridoxal phosphate (PLP) and used as a cofactor for transamination (e.g. ALT and AST)
• Needed for synthesis of cystathionine, heme, niacin (B3), histamine, NTs (serotonin, epinephrine, norepinephrine, dopamine, GABA)

Question 25

Presentation of Vitamin B6 deficiency

Answer 25

Convulsions, hyperirritability, peripheral neuropathy Due to GABA deficiency

Question 26

With what drug should Vitamin B6 be co-administered

Answer 26

Isoniazid

Question 27

What type of reactions is Vitamin B7 necessary for

Answer 27

Cofactor for carboxylase reactions: o Pyruvate to oxaloacetate (gluconeogenesis) o Acetyl CoA to malonyl CoA (fatty acid synthesis) o Propionyl-CoA to methylmalonyl CoA (fatty acid oxidation)

Question 28

How do you determine the probability of a child being affected by an autosomal recessive disorder if you don't know the genotype of one of the parents, but are given the allele frequency in the population

Answer 28

§ P(affected child) = ¼ § P(carrier mother) = usually given that the mother is a carrier = 1 § P(carrier father) = use Hardy-Weinberg

Question 29

PAH is used to estimate what renal value?

Answer 29

Renal plasma flow

Question 30

What are the bones of the wrist

Answer 30

* Wrist bones = So Long To Pinky, Here Comes The Thumb * Scaphoid, Lunate, Triquetrum, Pisiform, Hamate, Capitate, Trapezoid, Trapezium

Question 31

Differentiate type I from type 2 muscle fibers

Answer 31

* Type 1: * Slow twitch * Red fibers due to increased mitochondria and myoglobin concentration à increased oxidative phosphorylation à sustained contraction * Muscle involving low-level sustained force (e.g. postural maintenance) * Proportion increases after endurance training * THINK: One slow red ox * Type 2: * Fast twitch * White fibers due to decreased mitochondria and myoglobin concentration à increased anaerobic glycolysis * Muscle involved in rapid forceful pulses (e.g. biceps) * Proportion increases after weight/resistance training

Question 32

What is the cause and presentation of Osgood-Schlatter disease (OSD)

Answer 32

Due to repetitive quadricep contraction (e.g. jumping) * Quadricep attached to proximal/superior patella * Patellar tenden is attached to distal/inferior patella and inserts at the tibial tuberositiy * Reptitive quad contraction (leg extension) causes the proximal patellar tendon to separate from the tibial tubercle, leading to focal pain and swelling at the tibial tuberosity

Question 33

Dynein vs. Kinesin

Answer 33

§ Dynein: * · Transports from (+) to (-) end of microtubule * · Retrograde transport towards the nucleus * o THINK: Negative end Near Nucleus * · Defective in Kartagener syndrome § Kinesin: * · Transports from (-) to (+) end of microtubule * · Anterograde transport away from nucleus * o THINK: Positive end Points to Periphery

Question 34

What is the antibody specific for rheumatoid arthritis (not RF)

Answer 34

Anti-CCP (anti-cyclic citrullinated peptide) antibodies

Question 35

Major effect of second hand smoke on children (pre- and post-natal)

Answer 35

SIDS

Question 36

Effects of opioid toxicity on BP and HR

Answer 36

Bradycardia and hypotension

Question 37

Is Gardnerella vaginalis aerobic/anaerobic gram+/-

Answer 37

Anaerobic gram-variable rod

Question 38

MOA of DKA

Answer 38

No insulin so no glucose in cells Cells undergo ketogenesis for energy since there is no glucose

Question 39

Possible hormones secreted by small cell lung cancer

Answer 39

* ADH = SIADH * ACTH = Cushing’s * Antibodies against pre-synaptic Ca2+ channels = Lambert-Eaton

Question 40

Possible hormones secreted by squamous cell carcinoma of the lung

Answer 40

PTH = hypercalcemia

Question 41

Describe bronchoalveolar pneumonia (XR and histology)

Answer 41

* Subtype of adenocarcinoma * X-ray shows hazy infiltrates similar to pneumonia * Columnar cells grow along pre-existing alveolar septa = apparent “thickening” of alveolar walls

Question 42

Risk factors associated with mesothelioma

Answer 42

* Malignancy of pleura * Associated with asbestos * No associated with smoking * Psammoma bodies

Question 43

Most common locations for lung cancer to mestastasize to

Answer 43

* Adrenals, brain, bone, liver

Question 44

What will you see on CXR in the 3 types of pnuemonia: Lobar Bronchopneumonia Interstitial

Answer 44

Lobar = consolidation of an entire lobe Broncho = scattered, patchy consolidation centered around bronchioles Interstitial = diffuse infiltrate with increaed lung markings

Question 45

Differentiate between transudative and exudative pleural effusion

Answer 45

* (1) Transudate * Low protein content * THINK: **_Trans_**udate is more **_trans_**parent * Due to increased hydrostatic pressure (e.g. CHF or fluid overload) or decreased oncotic pressure (e.g. cirrhosis, nephrotic syndrome) * (2) Exudate * High protein content, cloudy * Due to malignancy, pneumonia, trauma, connective tissue disease * Must be drained due to risk of infection

Question 46

Content and caue of lymphatic pleural effusion

Answer 46

* Aka “chylothorax” – milky fluid high in triglycerides * Due to thoracic duct rupture or occlusion

Question 47

What is and isn't drained by the thoracic duct

Answer 47

R lymphatic duct drains R side of the body above the diaphragm Thoracic duct drains everything else into the junction of the L subclavian and internal jugular vein

Question 48

What part of the bone (diaphysis, metaphysis, or epiphysis), do the following tumors occur: * Osteochondroma * Giant cell tumr * Osteosarcoma * Ewing sarcoma

Answer 48

* Diaphysis: * Osteoid osteoma * Ewing sarcoma * Metaphysis: * Osteosarcoma * Osteochondroma * Epiphysis: * Giant cell tumor

Question 49

What translocation is associated with Ewing sarcoma

Answer 49

t(11;22) THINK: 11 + 22 = 33 (Ewing's jersey number) * Ewing Sarcoma * Malignant proliferation of poorly differentiated cells derived from neuroectoderm * Arises in the diaphysis of long bones * Biopsy reveals small round blue cells resembling lymphocytes * XR = onion skin

Question 50

Describe defect and cause of osteopetrosis

Answer 50

* Disorder of bone resorption (osteoclasts) = dense, thickened bones that fracture easily * Often due to mutation in carbonic anhydrase II = cannot create acidic environment necessary for bone resorption