Biochemistry SHELF Revised Questions and
Correct Answers Graded A++
branched amino acids
Val, leu, ile
essential amino acids
PVT TIM HALL
-OH amino acids
Tyr, Ser, Thr
Maple syrup urine disease: deficiency of
Alpha-keto acid dehydrogenase
Lesch-Nyhan syndrome
Deficiency in hypoxanthine-guanine phosphoribosyl transferase. Defect in purine
salvage reactions. Orange sand urine, self-mutilation and mental retardation.
PKU
Phe hydroxylase deficiency. Need cofactor BH4; mental retardation; hypopigmentation
Trp is precursor for 3 molecules:
Serotonin, melatonin, and niacin
Tyr is precursor for 6 molecules:
Dopamine, norepinephrine, epinephrine, melanin, T3 and T4
Alkaptonuria
Homogentisate oxidase deficiency. Black pigmentation of cartilaginous tissues
(ochronosis) due to oxidized products of homogentisic acid.
Albinism
Tyrosinase deficiency. Hypopigmentation and photosensitivity
Secondary structure of proteins is determined by:
H-Bonds
Parkinson's disease
,Accumulation of misfolded proteins form aggregates called Lewy bodies
proximal histidine
His F8. Interacts with Fe2+
Distal Histidine
His E7. Interacts with O2
Fetal Hb (HbF)
Does not interact with 2,3-BPG, so it has more affinity for oxygen
Carboxyhemoglobin
CO binds to Fe2+ covalently and promotes the R(relaxed) state and increases affinity
for O2, so O2 cannot be released. Victims of
poisoning have pink skin.
Glycosylation of Hb
At N-terminal Valine; to monitor glucose levels in blood
sickle cell anemia
Glutamate exchange for Valine that leads to polymerization. Anemia is because of
constant hemolysis. Form calcium bilirubinate stones
alpha thalassemia
Deletion of 1,2,3 or 4 loci of alpha globin gene on chromosome 16
HbH
Hemoglobin with three loci deleted
Hydrops fetalis HbBarts
No synthesis of alpha chain, four gamma chains. Fatal because HbF needs alpha
chains. Very high affinity to O2, so no delivery.
beta thalassemia
Deletion of 1 (minor) or 2 (major) copies of the beta globin chain on chromosome 11.
Lead to chipmunk face.
iron deficiency anemia
Histology shows microcytic and hypochromic RBC
Methemoglobinemia
Oxidation of Fe+2 to Fe+3 ; unable to bind oxygen. Can be due to a deficiency in
NADPH-cytochrome b5 reductase.
, Alport syndrome
Mutations in collagen type IV
Ehlers-Danlos syndrome
Defect in collagen synthesis. Hypermobile joints, hyper-elastin skin, and easy
bruisability
osteogenesis imperfecta
"Brittle bones disease". Type I collagen defect. Substitution of Glycine for bulkier amino
acids. Presents blue sclera, multiple fractures, and opalescent teeth
Menkes disease
Decreased copper absorption. Decreased lysyl oxidase activity.
Scurvy
Deficiency of Vitamin C. Bleeding gums, bednails and hair follicles
Marfan syndrome
Mutation in fibrillin-1 gene. Defects in heart valves and aorta. Presents as long limbs,
dislocated lenses, pectus excavatum, and aortic dilatation.
Requirements of Carboxylases
ABC (ATP, Biotin, CO2 & Mg+2)
competitive inhibitor
Km increases, Vmax remains the same
non-competitive inhibitor
Km remains the same, Vmax decreases
Markers in myocardial infarction
Troponin, Creatine Kinase- MB (heart)
Kwashiorkor
Low protein intake with high carbohydrate diet
Marasmus
Low intake of proteins and calories
Dissacharidases
Sugars are osmotically active in intestinal lumen and cause diarrhea. Causes bacterial
fermentation
Galactose and glucose transport to enterocyte
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