Biochemistry USMLE practice questions

thrombocytopenia - deficiency of platelets in the blood. This causes bleeding into the tissues, bruising, and slow blood clotting after injury. A 16 year old boy presented to a doctor by his mother for the injury which he had recently during cycle riding. On examination doctor noticed the loose, overly-flexible joints, smooth or stretchy, easily-bruised skin and abnormal wound healing and scar formation. This is the characteristic feature of the disorder known as - Ehlers-Danlos syndrome A 67-year-old man has a restricted diet that includes no fresh citrus fruits or leafy green vegetables. His teeth are loose and his gums bleed easily. This patient's disorder most likely results from a defect in collagen synthesis that involves which of the following amino acids? - Hydroxyproline N-terminal and C -terminal polypeptides of collagen are cleaved in - Extracellular space A 15 year old boy visited the physician with the complaints of joint pain, bleeding of the gums and loosening of the teeth. This is due to the defect in the post translational modification of collagen molecule. This problem is corrected by supplying which compound in the diet of the patient? - Ascorbic acid A 40 year old woman, cigarette smoker, complained about shortness of breath and chronic fatigue. Which one of the following most likely explains the patient's pulmonary symptoms? - Deficiency of α1- Antitrypsin Cross-linking of collagen to form mature collagen fibrils occurs at which of the following sites? - Extracellular space Individuals who are habitual and chronic smokers are likely to have a functional deficiency of alpha 1 antitrypsin. This can cause pulmonary emphysema based on accelerated degradation of - Elastin Some forms of Ehlers-Danlos syndrome are characterized by abnormally elastic skin. This is due to defective formation and function of - Collagen The enzyme that catalyzes the cross-linking of the side chains of four lysine residues to form desmosine is - Lysyl oxidase