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Biochemistry

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Vitamins, Harmones and Hemoglobin

Question
43 out of 82
 

An adolescent female develops hemiballismus after anesthesia for a routine operation. She is tall and lanky, and it is noted that she and her sister both had previous operations for dislocated lenses of the eyes. The symptoms are suspicious for the disease homocystinuria. Which of the following statements is descriptive of this disease?



A Patients may be treated with dietary supplements of vitamin B12

B Patients may be treated with dietary supplements of vitamin C

C There is deficient excretion of homocysteine

D There is a defect in the ability to form cystathionine from homocysteine and serine

Ans. D There is a defect in the ability of form cystathionine from homocysteine and serine

a. In the synthesis of cysteine, the following sequence of steps occurs, where SAM is S-adenosylmethionine, cys is cysteine, and a-KG is a-ketoglutarate:

a.Methionine SAM homocysteine + adenosine

b. Homocysteine + serine cystathionine cys + α-KG + NH4+Cystathionine synthetase, a pyridoxal phosphate (vitamin B enzyme, catalyzes the condensation of serine and homocysteine to form cystathionine.

c. A deficiency of this enzyme leads to a buildup of homocysteine, which oxidizes to form homocystine.

d. This may result in mental retardation, but sometimes causes dislocated lenses and a tall, asthenic build reminiscent of Marfan’s syndrome.

e. Patients with homocystinuria also have a clotting diathesis, requiring care to avoid dehydration during anesthesia.

f. Their cysteine deficiency must be made up from dietary sources. In some cases, dietary intake of vitamin B (Pyridoxal phosphate) may alleviate symptoms because of its requirement by the crucial enzymes.

Vitamins, Harmones and Hemoglobin Flashcard List

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