Biochemistry

Front 1

Homocystinuria

Back 1

Homocystinuria results in mental retardation, marfanoid habitus, and lens subluxation (down & in). Increased risk of thromboembolic events in third decade.

3 forms:
1. Cystathionine synthase deficiency (requires vit B6 as a cofactor)
2. Decreased affinity of cystationine synthase for pyridoxal phosphate
3. Homocysteine methyltransferase deciciency

Front 2

Hypotensive infant at birth; elevated 17-hydroxyprogesterone

Physical exam: enlarged clitoris and partially fused labioscrotal folds

Back 2

21-hydroxylase deficiency; only congenital adrenal hyperplasia that causes HYPOtension & salt wasting

Decreased ACTH and cortisol

Masculinization, female pseudohermaphroditism

Front 3

Salt wasting

Back 3

Hyponatremia + hyperkalemia; can cause hypovolemia

Front 4

6-year-old boy is diagnosed with a worsening ataxic gait and a cardiac dysrhythmia

Back 4

Freidreich's Ataxia - trinucleotide repeat disease

Trinucleotide repeat expansion diseases typically demonstrate anticipation and resulr in earlier manifestation of the clinical disease in subsequent generations. The unstable repeates in the frataxin gene impede protein translation, causing Freidreich's ataxia

Front 5

A 6-month-old child develops failure to thrive, developmental delay, and recurrent respiratory tract infections. The child is diagnosed with an autosomal recessive disease caused by a deficiency in N-acetylglucosamine phosphotransferase, which phosphorylates mannose residues

Back 5

Failure to phosphorylate mannose residues results in targeting to lysosome instead of exocytosis

This is called I (inclusion) cell disease

Front 6

46-year-old patient who appears confused and is not oriented to time or place. The medical student notices the man's tense, distended abdomen, palmar erythema, and pronounced gynecomastia. The patient also has a hand tremor

Back 6

Hepatic encephalopathy from chronic alcoholism. Hyperammonemia may result in asterixis, cerebral edema, and encephalopathy. In hyperammonemia, alpha-ketogluturate is consumed to make glutumate. Causes cessation of the citric acid cycle, which is an important source of energy for the brain. Ammonia is also neurotoxic.

Front 7

Baby with ambigous genitalia, fused labia and hypotension.

Back 7

HYPOtension - think 21 hydroxylase deficiency

Front 8

2-year-old girl is brought to the clinic because she has recently developed muscle weakness and atrophy. Physical examination also reveals strabismus. A peripheral nerve biopsy reveals brown granules in Schwann cells and macrophages when stained with toluidine blue.

Back 8

Arylsulfatase A deficiency aka metachromatic leukodystrophy. Lysosomal enzyme that cleaves sulfate from sulfatides. Results in accumulation of cerebroside sulfate. Appears brown when stained with toluidine blue.

Front 9

A 3-week-old infant presents with failure to thrive, poor feeding, and lethargy. A physical examination reveals an enlarged liver and jaundice. Laboratory analysis reveals an elevated blood galactitol level and increased urinary reducing substance

Back 9

Patiens with galactosemia lack the enzyme galactose-1-phosphate uridyltransferase. Build up of galactose-1-phosphate and galactitol. Reducing substance in urine.

Front 10

Strabismus

Back 10

Strabismus or tropia are the medical terms for eye conditions commonly called by various names: eye turns, crossed eyes, cross-eyed, wall-eyes, wandering eyes, deviating eye, etc. Strabismus is not the same condition as "lazy eye" (amblyopia).

Front 11

Neurofibromatosis type 2

Back 11

Bilateral schwannomas, juvenile cataracts. Tinnitus. Assoc w other CNS tumors including ependymomas.

Front 12

Mechanism of angiotensin II signaling

Back 12

Angiotensin II acts on smooth muscle cells to cause them to contract. It does this through angiotensin receptor type I, which is a seven transmembrane G-protein (Gq) coupled receptor that activates phospholipase C. PLC cleaves PIP2 to form IP3 and DAG. IP3 opens calcium channels and DAG activates PLC. Lisinopril, and ACE inhibitor, thus causes decreased activity of PLC in vascular smooth muscle, relaxing efferent renal arterioles, decreasing GFR.

Front 13

Cystinuria

Back 13

Defect in amino acid reabsorption in the proximal tubule. Recurrent nephrolithiasis. Pelvic pain. Increased lysine, arginine, ornithine and cystine in the urine. Only cystine precipitates at acidic pH. Treat with acetazolamide to hydrate and alkalanize the urine.

Front 14

Seizure in a patient with 72 hours of vomiting and diarrhea.

Back 14

Most likely due to hyponatremia. In general, vomiting and diarrhea cause solute and water loss. Hypovolemia causes increased ADH secretion, leading to water conservation and hyponatremia. Hyponatremia results in neurologic dysfunction induced by cerebral edema. Nausea and malaise below 125 -130 mEq Na, followed by headaches, lethargy, and obtundation. Seizures, coma, and respiratory arrest below 115-120 mEq/L plasma Na.

Front 15

Hypocalcemia

Back 15

Distal paresthesias, Chvostek's sign (twitching of perioral muscles after tapping the facial nerve anterior to the ear) and Trousseaus sign (carpal spasm after inflation of blood pressure cuff above systolic pressure for three minutes). Severe hypocalcemia can cause seizure, bronchospams, and QT prolongation.

Front 16

Hyperkalemia

Back 16

Weakness that can progress to flaccid paralysis, metabolic acidosis, peaked T waves on EKG, cardiac arrest

Front 17

Arsenic poisoning

Back 17

Dysphagia, stomach pains, vomiting, diarrhea, and a metallic breath

Front 18

Acute intermittent porphyria

Back 18

Build up of delta ALA and porphobilinogen in urine, which can turn red in 30 minutes. No basophilic stippling as seen in lead poisoning. Abdominal pain, polyneuropathy, and psychiatric symptoms.

Front 19

Iron poisoning

Back 19

Vomiting, diarrhea, abdominal pain, GI bleeding.

Front 20

Porphyria cutanea tarda

Back 20

Accumulation of uroporphyrin in urine, which turns urine the color of tea. Photosensitive skin lesions.

Front 21

A patient presents to the clinic with a glycogen storage disease that is characterized by muscle pain and cramps after periods of intense exercise. Urinalysis indicates myoglobinuria.

Back 21

Deficiency in glycogen phosphorylase, which shortens the glycogen chains by removing glucose 1 phosphate.

Front 22

Pompe's disease

Back 22

Deficiency in acid maltase. Lysosomes cannot be degraded. Cardiomegaly and early death.

Front 23

Vitamin K deficiency in newborns

Back 23

Sterile gut. Vitamin K synthesized by intestinal flora.
Newborns are given a vitamin K shot shortly after birth in the US to prevent bleeding.

Front 24

Chronic alcoholic with neurologic signs. Blood finding.

Back 24

High serum lactate level. Chronic alcoholics have impaired intestinal absorption and often have thiamine deficiency. Thaimine is a cofactor for pyruvate dehydrogenase in the conversion of pyruvate to acetyl CoA. Thiamine deficiency results in shunting of pyruvate to lactate dehydrogenase instead.

Front 25

LFTs in viral hepatitis

Back 25

High serum ALT:AST ratio

Front 26

LFTs in alcoholic hepatitis

Back 26

High serum AST:ALT ratio

Front 27

Northern blot
Southern blot
Western blot

Back 27

Northern blot - mRNA
Southern blot - DNA
Western blot - protein

Front 28

Lead poisoning

Back 28

Blocks delta ALA dehydratase

Front 29

Bilirubin glucuronyl transferase

Back 29

Hepatic enzyme responsible for conjugation of bilirubin with glucuronide. Deficiency results in unconjugated bilirubinemia.

Front 30

Why does HbF have an increased affinity for oxygen?

Back 30

Has gamma chains in place of beta chains. Gamma chains have serine residues instead of charged histidine residues like beta chains. Beta chains binds to 2,3 DPG via histidine residues, decreasing the affinity of Hb for O2.

Front 31

HbA1C

Back 31

Formed by glycosylation of HbA

Front 32

Diagnosis of thiamine (B1) deficiency

Back 32

Erythrocyte transketolase activity

Front 33

Wernicke sydnrome

Back 33

Caused by deficiency of thiamine (B1) in alcoholics. Results in decreased glucose utilization which is especially apparent in the CNS.

Wernicke's traid:
1. Ophthalmoplegia
2. Ataxia
3. Confusion

Front 34

Enzymes for which thiamine is a cofactor

Back 34

Enzymes involved in glucose utilization

1. pyruvate dehydrogenase (converts pyruvate to acetyl CoA)
2. a-ketogluturate dehydrogenase
3. transketolase (enzyme in HMP shunt)

Front 35

Treatment of acute intermittent porphyria

Back 35

1. Intravenous heme preperations

2. glucose loading

These work by negative feedback on delta ALA synthase, decreasing production of urinary ALA and porphyrobilinogen

Front 36

Lactic acidosis

Back 36

High anion gap metabolic acidosis

Caused by a number of conditions that result in reduced tissue oxygenation. Impaired tissue oxygenation results decreases oxidative phosphorylation, resulting in shunting of pyruvate to lactate after glycolysis.

Front 37

Diabetic ketoacidosis

Back 37

Increased lipogenesis and ketogenesis

Front 38

Impaired renal tubule bicarbonate reabsorption

Back 38

Type II (proximal) renal tubular acidosis

Front 39

Cause of lactic acidosis and increased lung opacities in 87 yo nursing home resident with a history of dementia, stroke, and hemiparesis

Back 39

swallowing muscle dysfunction leading to aspiration pneumonia

Aspiration pneumonia - intoxication, neurological disorders

Front 40

Beta thalassemia minor

Back 40

Defective mRNA processing resulting in decreased beta globin production. Increased HbF. Mild. Iron is of no use in these patients.