Biochem

Question 1

What is one of the main causes of Paresthesias?

Answer 1

• Parethesias is due to hypocalcemia
• CP: tickling/prickling from pressure/damage on peripheral nerves
• citrate (in stored blood) chelates calcium and magnesium and may decrease plasma levels

Question 2

Pyruvate kinase deficiency

Answer 2

causes hemolytic anemia because of failure of glycolysis and resultant failure to generate enough ATP to maintain erythrocyte structure

Question 3

What are the precursor proteins/peptides responsible for localized amyloidosis?

Answer 3

• cardiac atria-atrial natriuretic peptide (ANP)
• thyroid gland: calcitonin
• pancreatic islets: islet amyloid protein (aylin)
• cerebrum/cerebral blood vessels: beta-amyloid protein
• pituitary gland: prolactin

>>immune globulin light chain cuases multi-organ amyloid deposition in primary systemic amyloidosis

Question 4

What are the five cofactors needed by branched-chain alpha-ketoacid DH, pyruvated DH, and alpha-ketoglutarate DH?

Answer 4

(Tender Loving Care For Nancy)

• Thiamine pyrophosphate
• Lipoate
• Coenzyme A
• FAD
• NAD

Question 5

Kozak sequence

Answer 5

• plays a role in initiation of translation
• mut 3 bases upstream from start codon (AUG) in associated with thalassemia intermedia which leads to hypochromic, microcytic anemia
• mitochondria are needed for heme synthesis

Question 6

heterochromatin vs. euchromatin

Answer 6

• hetero:
  
  • condensed chromatin made of heaviy methylated DNA in tight association with deacetylated histones
  • LOW transcriptional activity
• [EU]chromatin:
  
  • loosely arranges
  • HIGH transciptional activity

Question 7

Maple Syrup Dz

Answer 7

• caused by defect in alpha-keto acid dehydrogenase
• leads to inability to degrade branched chain AA beyond their deaminated alpha-keto acid st
• results in dystonia, poor feeding, maple syrup scent of urine within first few days of life
• tx: dietary restrictions of branched-chain AA

Question 8

Vit B12

Answer 8

• only water-soluble vitamin that is NOT rapidly removed from body stores (without diet intake)
• b12 stores last for years

Question 9

Fabry disease

Answer 9

• (angiokeratoma corporis diffusum)
• cause: inherited deficiency of alpha-galactosidase A
• CP: globoside ceramide trihexoside accumulates in tissues
• early:
  
  • angiokeratomas
  • hypohidrosis
  • acroparesthesis
• tx: enzyme replacement
• prognosis: progressive renal failure

Question 10

Chronic granulomatous disease (XL)

Answer 10

• cause: deficiency of NADPH oxidase
  
  • NADPHox=enzyme responsible for formation of reactive oxygen species in phagosomes
  • affected neutrophils can NOT kill catalase-producing organisms
  • CP: recurrent bacterial and fungal infections
    
    • involves: lungs, skin LN

Question 11

A1AT (alpha-1 anti-trypsin) and A1AT deficiency

Answer 11

• made mostly by liver
• serum protein that decreases tissue damage caused by inflammation through the inhibition of neutrophil elastase
• Histo: reddish-pink, periodic acid-schiff (PAS) positive granules of unsecreted, polymerized leads to liver disease
  
  • A1AT in the peripheral hepatocytes
• A1AT deficiency-autosomal co-dominant
  
  • affects the lungs and liver
  • due to destruction of alveolar walls develop severe PANacinar emphysema
  • smoking plays synergistic role with disease

Question 12

xeroderma pigmentosum

Answer 12

• enzymatic d/o (AR)
• CP: photosensitivity, poikiloderma, hyperpigmentation in sun-exposed
• risk: increased risk of skin cancer (all forms of cutaneous malignancy)..get it EARLY in life!
• defect: nucleotide excision repair

Question 13

Homocystinuria

Answer 13

• most commonly caused by a defect in cystathionine synthase
• causes: inability to form cysteine from homocysteine

Question 14

3 stop codons

Answer 14

UAA

UGA

UAG

Question 15

Homocystinuria

Answer 15

• AR-deficiency of cystathionine beta-synthase (co-factor=Vit B6 {pyridoxine})
• Tx: high dose pyridoxine and restriction of methionine
• most common inborn error of methionine metabolism
• CP1: 3-10 yo with ectopia lensis (dislocated lens)
  
  • 50% pts have intellctual disability
• CP2: Marfanoid habitus
  
  • elongated limbs
  • arachnodactyly
  • scoliosis
• High risk for: thromboembolic occlusion (large vessel and small vessels)..*brain, heart, kidney

Question 16

Age-related changes

Answer 16

• presbyopia
  
  • denaturation of structural proteins within the lens which leads to a loss of lens elasticity
• skin wrinkles
  
  • decreased synthesis and increase breakdown of collagen and elastin

Question 17

Pyrimidine dimers

Answer 17

• formed in DNA as a result of UV light exposure
• recognized by a specific endonuclease complex that initiates the process of rapir by nicking the damaged strand on both sides of the pyrimidine dimer
  
  • damaged segment is excised, and replacement DNA is synthesized by DNA polymerase

Question 18

ribosomal RNA

Answer 18

all rRNA is transcribed in the nucleolus except for 5S rRNA

Question 19

Which non-glucose monosaccharide is metabolized fastest by the liver

Answer 19

• fructose
  
  • its the only one wose metabolites bypass phosphofructokinase (key enzyme involved in regulating the rate of glycolysis; rate-limiting enzyme)
  • fructose is metabolized faster than galatose and mannose, and is rapidly cleared form the bloodstream following dietary absorption

Question 21

Pyrimidine dimers

Answer 21

• formed in DNA as a result of UV light exposure
• recognized by a specific endonuclease complex that initiates the process of repair by nicking the damaged stran on both sides of the pyrimidine dimer
• damaged segment is excised, replacement DNA is synthesized by DNA polymerase

Question 22

Spliceosome

Answer 22

• small nuclear ribonucleoproteins (snRNPs) are important components of the spliceosome
• splice removes introns form pre-mRNA during processing within the nucleus
• spinal muscular atrophy is a d/o caused by mutations in the SMN1 gene=impaired assembly of snRNPs in LMN
• infants: flaccid paralysis due to degeneration of ant horn cells in the SC

Question 23

Peroxisomal dz

Answer 23

• rare inborn errors of metab where peroxisomes are either absent or nonfunctional
• v. long chain FA or FA with branch pts at odd-numbered carbons can NOT undergo mitochondrial beta-oxidation
• FA are metabolized by alpha and beta within peroxisomes:
  
  • a special form of beta oxidation-v. long chain FA
  • alpha oxidation: branched chain FA, like phytanic acid
• commonly lead to neurologic defects form improper CNS myelination

Question 24

common medical conditions with polygenic inheritance

Answer 24

• androgenetic alopecia
• epilepsy
• glaucoma
• HTN
• ischemic heart dz
• schizophrenia
• T2DM

Question 25

Vit A overuse

Answer 25

* can result in: * intracranial HTN * skin changes * HSM

Question 26

Hartnup dz

Answer 26

* can result in nicain deficiency due to an excess loss of dietary tryptophan resulting from defective intestinal and renal tubular absorption of the AA * niacin (nicotinamide/Vit B3) is synthesized from tryptophan (an essential AA)