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Free STEP1 Exam Braindumps (page: 40)

Page 39 of 213
PDF with 845 Questions

A 20-year-old woman admits herself to the emergency room with a yellow discoloration of the whites of her eyes. She says that she does not drink and that she has not experienced any changes in her stool. Her liver enzyme profile and direct serum bilirubin levels are normal, while total bilirubin is elevated.
What is the most likely cause for her jaundice?

  1. defect in hepatocytes
  2. defect in Kupffer cells
  3. gallstones
  4. hemolysis
  5. tumor obstructing bile duct

Answer(s): D

Explanation:

Rupture of large numbers of red blood cells can result in jaundice in the absence of any liver disease. The capacity of the liver to clear released heme metabolites such as bilirubin is temporarily exceeded. Since the liver will not perform its normal function to conjugate bilirubin before excretion in bile and urine, unconjugated bilirubin backs up in serum. This is the reason for the increase in total bilirubin, while conjugated bilirubin, also called direct bilirubin, is not affected. Direct bilirubin would be elevated with most defects of liver cells (choice A) and with obstruction of bile flow by gallstones (choice C) or by a tumor (choice E). All these would most likely also affect bile formation and consequently absorption of dietary fat and fat-soluble vitamins, with the consequence of developing oily, fatty stool. Kupffer cells (choice B) are macrophages within the liver and don't play a role in the production of bilirubin.



A 54-year-old insulin-dependent diabetic notes that her insulin requirements have gone up dramatically in the past year (from 50 U to nearly 200 U of recombinant human insulin) and her blood glucose is still poorly controlled. A possible explanation for the worsening of her diabetes includes which of the following?

  1. a high titer of anti-insulin antibodies
  2. an improved diet
  3. an improved exercise program
  4. progression of macrovascular disease
  5. weight loss

Answer(s): A

Explanation:

The patient clearly has an increase in her state of insulin resistance. Given the magnitude of her increased insulin requirements, she most likely developed a high titer of antiinsulin antibodies that are preventing the injected insulin from lowering blood glucose effectively. Agood choice of lifestyle, including an improved diet (choice B), an improved exercise program (choice C), or weight loss (choice E) each are shown to beneficially affect her insulin requirements. Progression of macrovascular disease (choice D) is largely irrelevant to her insulin requirements, except to the extent that it might decrease her ability to exercise.



A 55-year-old male diabetic has an accommodative power of the lens of 10 dioptres. His near point is located 5 cm (2 in), his far point 10 cm (3.9 in) in front of the eye. Which of the following statements are correct?

  1. his corrective lenses are convex
  2. his corrective lenses have a positive dioptric value
  3. the patient has hyperopia
  4. the patient is capable of driving a car without corrective glasses
  5. the patient is functionally blind

Answer(s): E

Explanation:

Functionally blind means that a person has a visual impairment, that does not qualify as "legally blind" but results in substantial impediment. With a near point of 5 cm and a far point of 10 cm, the man has a severe case of myopia, not hyperopia as stated in choice C. The total convergence power of the relaxed eye with normal vision is approximately 60 dioptres, and the cornea accounts for more than two-thirds of that (40 dioptres). The accommodative power of the lens is about 20 dioptres in the very young, about 10 dioptres at age 25, and would be around 1 dioptre at the patient's age, if he had normal vision. For young adults with normal vision, the near point is about 10 cm from the eye; the far point is at infinity. The corrective lenses for the myopic eye are concave, not convex (choice A). Concave lenses compensate for the excessive positive dioptres of the myopic eye. These lenses are thin in the middle and wide at the edges and have negative dioptric values, not positive ones (choice B). The patient definitely won't be able to drive a car or perform other activities that require fast accommodation without corrective glasses (choice D).



An advertisement promotes energy bars containing fructose as an ideal food to take on extreme mountain- climbing expeditions. Which of the following statements concerning fructose absorption is true?

  1. absorption of fructose into an intestinal epithelial cell is by facilitated transport and thus does not require energy
  2. metabolism of fructose generates more energy than glucose
  3. some fructose is already absorbed in the mouth and hence is the fastest way to get energy
  4. the presence of fructose aids in absorption of vitamin A, C, and D
  5. the presence of fructose inhibits reabsorption of glucose, which is then more readily available for muscle activity

Answer(s): A

Explanation:

Carbohydrate absorption occurs at enterocytes of the upper region of small intestinal villi. Fructose absorption is via the facilitated transporters GLUT5 across the apical enterocyte membrane and GLUT2 across the basolateral enterocyte. Glucose and galactose on the other hand are transported into enterocytes on carriers in combination with a sodium ion. The energy for this secondary active transport is provided by the electrochemical sodium gradient that is created by Na/K-ATPases. Experimental conditions that collapse the sodium electrochemical gradient, hypoxia, or poisoning of the Na-KATPase by ouabain inhibit glucose, but not fructose absorption. Nevertheless, the physiological importance of "saving energy" under extreme conditions such as mountain climbing through the use of fructose as energy source is questionable. For instance, fructose absorption is much slower than absorption of glucose and galactose.
The statements in choices B, C, D, and E are incorrect.






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