Question 1

Free radicals are molecular terrorists that attack molecular targets indiscriminately.Their formation in the body cannot be prevented, because they are unavoidable byproducts of oxidative metabolism, but physicians can try to intercept them before they hit a sensitive target-for example, by an extra good supply of:

Accepted Answer

Vitamin E belongs to a large collection of antioxidants that function as scavengers of free radicals.Other examples are ascorbic acid, carotenoids, diverse phytochemicals, uric acid, and bilirubin.When one of these molecules reacts with a free radical, it destroys the free radical and becomes a free radical itself.However, the free radical formed by the scavenger is not sufficiently reactive to cause damage to ordinary molecules.It can react only with another free radical, which it destroys in the ensuing reaction.

Question 2

You look over the laboratory reports of 500 medical students to determine the frequency of iron deficiency in this population.The best way to identify iron deficiency from laboratory reports would be to define as iron-deficient all those with:

Accepted Answer

Measurements of transferrin saturation and serum ferritin are the most useful laboratory tests for determination of the iron status.

Question 3

Sunlight is good for your bones because:

Accepted Answer

Cholecalciferol (vitamin D₃) is made with the help of sunlight in the skin.It is subsequently processed to calcitriol by two successive hydroxylations, one in the liver and the other in the kidneys.

Question 4

Vitamin deficiencies are rarely seen in newborns.However, one vitamin that should be given shortly after birth to prevent any risk of deficiency is:

Accepted Answer

Vitamin K deficiency can cause hemorrhagic disease of the newborn.

Question 5

A medical student is brought to the student health center in a confused state.His friends report that he is a heavy drinker and that he subsisted mainly on cola fortified with gin during the past 2 years.However, he does not seem acutely drunk when seen by the doctor.It would be prudent to give this student immediately a high dose of:

Accepted Answer

He might have Wernicke encephalopathy.You have to make sure that he does not develop Korsakoff psychosis, because with the anterograde amnesia of Korsakoff psychosis, he would not be able to pass his examinations!

Question 6

After developing mild jaundice, a teenage boy is found to have an alanine transaminase level eight times higher than the upper limit of normal.A low level of serum ceruloplasmin is subsequently found.There is no fever.This boy most likely has:

Accepted Answer

Wilson disease is a defect of biliary copper excretion that leads to abnormal copper deposits in the liver and the basal ganglia of the brain.Some patients present initially with liver damage, and others with a central nervous system disorder.The copper-containing plasma protein ceruloplasmin is reduced, and copper appears in the urine.

Question 7

The iron overload disease hemochromatosis is caused by a mutation in the HFE gene that originated only recently and that is now most common in:

Accepted Answer

This mutation is believed to be about 2000 to 4000 years old, and it appeared in either a Celtic or a Viking population.Because of its recent origin, the mutation still has a rather restricted geographic distribution.

Question 8

Patients in renal failure require dietary restriction of all the following nutrients except:

Accepted Answer

Everything that needs to be excreted by the kidneys accumulates.However, calcium does not accumulate.Affected patients cannot make calcitriol, and without calcitriol, they cannot absorb dietary calcium from the intestine.

Question 9

A woman in her early 30s is found to be a hemochromatosis homozygote, but her serum ferritin level and transferrin saturation are only slightly increased.Which of the following is most likely to further increase her serum iron?

Accepted Answer

Women of reproductive age do not usually get iron overload because they dispose of excess iron in menstrual blood.

Question 10

Acute severe fat malabsorption can cause deficiencies of fat-soluble vitamins.The fat-soluble vitamin that becomes deficient first, after only 1 or 2 weeks of fat malabsorption, is:

Accepted Answer

All other fat-soluble vitamins are stored in liver or adipose tissue and therefore become deficient only after several weeks or months of malabsorption or dietary deficiency.

Question 11

On your arrival in a refugee camp in a nation undergoing civil war, you notice that many people in the camp have severe skin lesions on parts of the body that are exposed to the sun.The residents of the camp have to subsist on maize and cassava, everything else having been confiscated by the military.The vitamin deficiency that is the most likely cause of these skin lesions is:

Accepted Answer

Dermatitis is a prominent sign of pellagra, which is caused by a lack of Niacin, Maize and cassava are low in both niacin and tryptophan.

Question 12

Niacin deficiency causes pellagra.This disease is seen only in patients with a diet that is low in both niacin and:

Accepted Answer

Maize is the classical example of a food that is low both in tryptophan and in absorbable niacin.

Question 13

What is true about scurvy?

Accepted Answer

Abnormalities of connective tissue in skin and blood vessels account for these signs.

Question 14

Cholecalciferol, formed by the action of sunlight on 7-dehydrocholesterol in the skin, has to be converted to the fully active calcitriol before it can induce its physiological actions.The rate-limiting step in this process is catalyzed by an enzyme in:

Accepted Answer

This is the reason why signs of vitamin D deficiency are common in patients with kidney failure but not in patients with liver cirrhosis.

Question 15

A 28-year-old man who saw the doctor because of numbness of the feet is found to have a hematocrit of 26%.Except for frequent bouts of gastritis for which he self-medicated with antacids, there is nothing unusual in his medical history.A blood test shows unusually large erythrocytes, and a metabolic screen reveals methylmalonic acid in his urine.This is most likely a case of:

Accepted Answer

The co-occurrence of peripheral neuropathy (numb feet) and megaloblastic anemia, and especially the urinary methylmalonic acid, indicate the diagnosis.The patient's gastritis is most likely caused by the autoimmune process that has destroyed his parietal cells.

Question 16

Retinoic acid is a form of vitamin A that is most important as a:

Accepted Answer

Retinoic acid regulates gene expression by binding to nuclear zinc finger proteins, similar to the mechanism of action for steroid hormones, thyroid hormones, and calcitriol.

Quiz 29: Vitamins and Minerals