Question 1

You are tending to a patient in the emergency room (ER) who presents with the following symptoms: nystagmus, organic toxic psychosis, and ataxia. You notice that the patient is dirty and appears not to have bathed in several days or weeks. There is an odor of vomit and alcohol on his clothing. Given the outward appearance and observed symptoms, your diagnosis is indicative of a deficiency in which of the following vitamins?

Accepted Answer

The symptoms described are indicative of Wernicke's encephalopathy, which is caused by a deficiency in thiamin (vitamin B1), often associated with chronic alcohol abuse.  The symptoms observed in this patient are typical of Wernicke-Korsakoff syndrome. This disease is most commonly found in chronic alcoholics due to their poor dietetic lifestyles. WernickeKorsakoff syndrome is characterized by the symptoms described as well as acute encephalopathy followed by chronic impairment of short-term memory. Persons afflicted with Wernicke-Korsakoff syndrome appear to have an inborn error of metabolism that is clinically important only when the diet is inadequate in thiamin.

Question 2

Wernicke encephalopathy results from a deficiency of vitamin B₁. Which of the following represents classical symptoms associated with this disorder?

Accepted Answer

Wernicke encephalopathy is characterized by a triad of symptoms: ophthalmoplegia (eye movement disorders), ataxia (lack of voluntary coordination of muscle movements), and confusion. Peripheral neuropathy and mental depression can also be associated with thiamine (vitamin B1) deficiency.

Question 3

A 60-year-old chronic smoker and alcoholic man
Suffering from odynophagia, insomnia, epigastric
Discomfort, and recurrent diarrhea presented to
The outpatient department. Clinical examination
Revealed memory disorientation, stomatitis, glossitis, esophagitis, and exfoliative dermatitis with some
Vesicles on erythematous bases on photoexposed
Sites such as his hands shown in the attached image.
These signs and symptoms are most likely the result
Of a deficiency in which of the following vitamins?

Accepted Answer

A diet deficient in niacin (as well as tryptophan) leads to glossitis of the tongue (inflammation of the tongue leading to purplish discoloration), dermatitis, weight loss, diarrhea, depression, and dementia. The severe symptoms, depression, dermatitis, and diarrhea, are associated with the condition known as pellagra and are sometimes referred to as the 3 Ds of niacin deficiency.

Question 4

Deficiency in which of the following vitamins is associated with progressive keratinization of the cornea?

Accepted Answer

Vitamin A deficiency can lead to xerophthalmia, which includes symptoms like progressive keratinization of the cornea, potentially leading to blindness.  The earliest symptoms of vitamin A deficiency are night blindness. Additional early symptoms include follicular hyperkeratosis, increased susceptibility to infection and cancer, and anemia equivalent to iron deficiency anemia. Prolonged lack of vitamin A leads to deterioration of the eye tissue through progressive keratinization of the cornea, a condition known as xerophthalmia

Question 5

The attached radiograph shows the typical bowed legs of an infant suffering from a deficiency in which of the following vitamins?

Accepted Answer

The main symptom of vitamin D deficiency in children is rickets. Rickets is characterized by improper mineralization during the development of the bones resulting in soft bones, muscle weakness (rickety myopathy or "floppy baby syndrome,"), and increased tendency for fractures (especially greenstick fractures). In toddlers with rickets, a common skeletal deformity is bowed legs as depicted in the radiograph

Question 6

Although α-lipoic acid is not truly a vitamin, it is an essential cofactor for several important enzymes. An inability to maintain adequate levels of this lipid-derived molecule would result in which of the following consequences?

Accepted Answer

α-lipoic acid is known to improve insulin sensitivity, so a deficiency would lead to decreased insulin sensitivity.  Lipoic acid (LA) is an essential cofactor for the E2 component of α-ketoacid dehydrogenase complexes, exclusively located in mitochondria. These include the PDH, α-ketoglutarate dehydrogenase (KGDH), and branched chain α-ketoacid dehydrogenase (BCKDH) complexes. Extensive evidence suggests that LA may have therapeutic usefulness in lowering blood glucose levels in diabetic conditions and that the intracellular redox status plays a role in the modulation of insulin resistance. Lipoic acid has been shown to stimulate glucose uptake by affecting components of the insulin-signaling pathway.

Question 7

Which of the following is associated with increased glucose uptake due to its ability to prevent phosphorylation of downstream effectors of the insulin-signaling cascade?

Accepted Answer

α-lipoic acid is known to enhance glucose uptake by improving insulin sensitivity and preventing the phosphorylation of downstream effectors in the insulin-signaling pathway.  Lipoic acid (LA) is an essential cofactor for the E2 component of α-ketoacid dehydrogenase complexes, exclusively located in mitochondria. These include the PDH, α-ketoglutarate dehydrogenase (KGDH), and branched chain α-ketoacid dehydrogenase (BCKDH) complexes. Extensive evidence suggests that LA may have therapeutic usefulness in lowering blood glucose levels in diabetic conditions and that the intracellular redox status plays a role in the modulation of insulin resistance. Lipoic acid has been shown to stimulate glucose uptake by affecting components of the insulin-signaling pathway

Question 8

A deficiency in which of the following vitamins would most likely be associated with prolonged clotting times, hemorrhaging, and anemia?

Accepted Answer

Vitamin K is essential for the synthesis of clotting factors, and its deficiency can lead to prolonged clotting times and hemorrhaging.  The major role of the K vitamins is in the maintenance of normal levels of the blood-clotting proteins, factors II, VII, IX, X, and protein C and protein S, which are synthesized in the liver as inactive precursor proteins. Conversion from inactive to active clotting factor requires a posttranslational modification of specific glutamate (E) residues. This modification is a carboxylation and the enzyme responsible requires vitamin K as a cofactor. The resultant modified E residues are g-carboxyglutamate (gla). Thus, a deficiency in vitamin K will result in prolonged bleeding and the potential for hemorrhage.

Question 9

A 45-year-old man, a known alcoholic for at least the past 10 years, reported to a physician for consultation. He complained of burning of eyes, a sore tongue, reduced appetite, and mild abdominal discomfort. Physical examination revealed cracks on the lips and in the corners of the mouth; a red, fissured, and inflamed tongue; dull hair, oily skin, and split nails. A deficiency in which of the following vitamins would best explain the observed symptoms?

Accepted Answer

Although riboflavin deficiencies are rare in the United States, the common symptoms associated with deficiency include itching and burning eyes, angular stomatitis and cheilosis (cracks and sores in the mouth and lips), bloodshot eyes, glossitis (inflammation of the tongue leading to purplish discoloration), seborrhea (dandruff, flaking skin on scalp and face), trembling, sluggishness, and photophobia (excessive light sensitivity).

Question 10

Not all water-soluble vitamins are strictly required in the diet since the human body has the capacity to synthesize at least one of this class of vitamin. However, the ability to do so is limiting and not of sufficient capacity to provide all the necessary coenzyme required for normal metabolic processes. Which of the following is this vitamin?

Accepted Answer

The human body can synthesize niacin from the amino acid tryptophan, but this synthesis is not sufficient to meet the body's full requirements, so dietary intake is still necessary. Niacin is not a true vitamin in the strictest definition since it can be derived from the amino acid tryptophan. However, the ability to utilize tryptophan for niacin synthesis is insufficient (60 mg of tryptophan are required to synthesize 1 mg of niacin). Also, synthesis of niacin from tryptophan requires vitamins B₁, B₂, and B₆ which would also likely be limiting on a marginal diet.

Question 11

A 58-year-old male stumbles into a local soup kitchen mumbling about aliens and space craft. He is dirty, unshaven, wearing tattered clothing, and reeking of alcohol. He is discovered to have died in the alleyway during the night. At autopsy, a sagittal section through the brain shows severe pigmentation of the mammillary bodies due to apparent hemorrhage. A deficiency in which of the following vitamins would be expected to cause hemorrhaging in this brain structure?

Accepted Answer

Thiamin deficiency can lead to Wernicke's encephalopathy, which is characterized by hemorrhagic lesions in the mammillary bodies. This condition is often associated with chronic alcoholism.  The mammillary bodies are a pair of small round bodies, located on the undersurface of the brain, and, as part of the diencephalon, form part of the limbic system. Damage to the mammillary bodies due to thiamine deficiency is implied in the pathogenesis of Wernicke-Korsakoff syndrome. Symptoms include impaired memory, also called anterograde amnesia, suggesting that the mammillary bodies may be important for memory.

Question 12

A smear of your patients' blood is shown in the following picture demonstrating that the person suffers from a form of anemia. A deficiency in which of the following vitamins would lead to the anemia shown in the slide?

Accepted Answer

The answer of A smear of your patients' blood is...

Question 13

A patient presents with pale skin, sunken eyes, sore gums, muscle pain, loose teeth, and corkscrew-shaped hair. A deficiency in which of the following vitamins would result in the observed symptoms?

Accepted Answer

The symptoms described are indicative of scurvy, which is caused by a deficiency in vitamin C, also known as ascorbic acid. Vitamin C is essential for collagen synthesis, and its deficiency leads to the symptoms mentioned.  Deficiency in vitamin C leads to the disease scurvy due to the role of the vitamin in the posttranslational modification of collagens. Scurvy is characterized by easily bruised skin, muscle fatigue, soft swollen gums, decreased wound healing and hemorrhaging, osteoporosis, and anemia.

Question 14

The vitamin involved in biochemical reactions concerned with the transfer of methyl, methylene, or formyl groups is a derivative of which of the following vitamins?

Accepted Answer

Folic acid is involved in the transfer of one-carbon units such as methyl, methylene, or formyl groups in various biochemical reactions. The function of THF (synthesized from folic acid) derivatives is to carry and transfer various forms of one-carbon units during biosynthetic reactions. The one-carbon units are methyl, methylene, methenyl, formyl, or formimino groups.

Question 15

Wernicke encephalopathy syndrome is caused by a deficiency of which of the following?

Accepted Answer

Wernicke encephalopathy is caused by a deficiency of thiamine (vitamin B1).  Wernicke encephalopathy results from a dietary deficiency in thiamin. The disorder is most commonly found in chronic alcoholics due to their poor dietetic lifestyles. Wernicke encephalopathy is a syndrome characterized by ataxia, ophthalmoplegia, nystagmus, confusion, and impairment of short-term memory.

Question 16

Scurvy is due to a dietary deficiency of which vitamin?

Accepted Answer

Scurvy is caused by a deficiency of vitamin C, which is essential for the synthesis of collagen in humans.

Question 17

A deficiency of vitamin B12 in humans results in anemia primarily because it is which of the following?

Accepted Answer

Vitamin B12 is involved in the conversion of N5-methyl-THF to THF, which is crucial for DNA synthesis and red blood cell formation.

Question 18

Which of the following represents a significant biochemical role of vitamin C?

Accepted Answer

Vitamin C is crucial for the synthesis of collagen, an essential component of connective tissue. The active form of vitamin C is ascorbic acid itself. The main function of ascorbate is as a reducing agent in a number of different reactions. Ascorbate is the cofactor for Cu+-dependent monooxygenases and Fe2S1U1P1+S1S1P0-dependent dioxygenases. Ascorbate has the potential to reduce cytochromes a and c of the respiratory chain as well as molecular oxygen. The most important reaction requiring ascorbate as a cofactor is the hydroxylation of proline residues in collagen. Vitamin C is, therefore, required for the maintenance of normal connective tissue as well as for wound healing since synthesis of connective tissue is the first event in wound tissue remodeling

Question 19

When vitamin D is deficient, what 2 disorders occur most readily?

Accepted Answer

Vitamin D deficiency most readily leads to rickets in children and osteomalacia in adults, both of which are disorders related to bone health.  The main symptom of vitamin D deficiency in children is rickets and in adults is osteomalacia. Rickets is characterized by improper mineralization during the development of the bones resulting in soft bones. Osteomalacia is characterized by demineralization of previously formed bone leading to increased softness and susceptibility to fracture.

Question 20

The ability of rod cells in the eye to respond to light and transmit that response to the optic nerve requires that the 11-cis form of vitamin A be attached to which of the following proteins?

Accepted Answer

Photoreception in the eye is the function of 2 specialized cell types located in the retina; the rod and cone cells. Both rod and cone cells contain a photoreceptor pigment in their membranes. The photosensitive compound of most mammalian eyes is a protein called opsin to which is covalently coupled an aldehyde of vitamin A. The opsin of rod cells is called scotopsin. The photoreceptor of rod cells is specifically called rhodopsin or visual purple. This compound is a complex between scotopsin and the 11-cis-retinal (also called 11-cis-retinene) form of vitamin A. Rhodopsin is a serpentine receptor imbedded in the membrane of the rod cell. Coupling of 11-cisretinal occurs at 3 of the transmembrane domains of rhodopsin. Intracellularly, rhodopsin is coupled to a specific G-protein called transducin.

Quiz 8: Vitamins and Minerals

Wernicke encephalopathy results from a deficiency of vitamin B1. Which of the following represents classical symptoms associated with this disorder?