Question 1

The active hormonal form of vitamin D is synthesized by the combined action of the:

Accepted Answer

The active hormonal form of vitamin D, known as calcitriol, is synthesized through a multi-step process involving the skin, liver, and kidney. When skin is exposed to ultraviolet B radiation (UVB), a precursor molecule called 7-dehydrocholesterol is converted into previtamin D3, which is then transported to the liver where it is modified into 25-hydroxyvitamin D. Finally, the kidney converts 25-hydroxyvitamin D into its active form, calcitriol.

Question 2

The Recommended Dietary Allowance (RDA) for vitamin A is expressed in:

Accepted Answer

The RDA for vitamin A is expressed in micrograms (mcg). This is because vitamin A is a micronutrient that is needed in relatively small amounts in the body. The RDA for vitamin A ranges from 600-900 mcg depending on age and gender.

Question 3

An example of a meal high in vitamin A is:

Accepted Answer

Good sources of vitamin A include cheese and egg yolks. These would be found in a cheese omelet. Meat and poultry, grains, legumes, and potatoes are not good sources of vitamin A or precursor carotenoids.

Question 4

Liver stores of vitamin A are usually sufficient to last approximately:

Accepted Answer

Liver stores of vitamin A can last for 6 to 12 months. However, it is important to consume vitamin A regularly in your diet as excessive amounts can be toxic and cause harm to the body.

Question 5

A vitamin that is essential to bone growth is vitamin:

Accepted Answer

Vitamin D is essential for the absorption of calcium and phosphorus in the body, which are necessary for bone growth and maintenance.

Question 6

A factor that has significantly contributed to elimination of rickets in developed countries is:

Accepted Answer

The wide use of vitamin D-fortified milk has significantly contributed to the elimination of rickets in developed countries, as it helps to provide a reliable source of vitamin D, which is essential for bone health. While outdoor activities and access to fresh produce can support overall health, they may not provide a consistent source of vitamin D. The use of sunscreens also reduces the amount of vitamin D that the body can produce from sunlight.

Question 7

The condition resulting from hypovitaminosis A that can cause blindness is known as:

Accepted Answer

Xerophthalmia is the condition resulting from hypovitaminosis A that can cause blindness. Cheilosis is a condition of cracked lips, pellagra is the result of niacin (vitamin B3) deficiency, and keratinization is the thickening of the skin due to vitamin A deficiency.

Question 8

Vitamin A deficiency causes abnormal cell differentiation and results in:

Accepted Answer

Vitamin A deficiency leads to abnormal cell differentiation in various tissues, including skin, eyes, and respiratory and gastrointestinal epithelia. Keratinization occurs as a result of this abnormal differentiation, leading to thickening and hardening of the skin and mucous membranes. Beriberi is caused by thiamine deficiency, pellagra is caused by niacin deficiency, and kwashiorkor is a severe form of protein-energy malnutrition. None of these are caused by vitamin A deficiency.

Question 9

The type of tissue that is most vulnerable to a vitamin A deficiency is:

Accepted Answer

Vitamin A is essential for the maintenance of epithelial tissue, including skin, which makes it the most vulnerable tissue to a deficiency of this vitamin. Without adequate amounts of vitamin A, the skin may become dry, rough, and scaly, and susceptible to infections. In severe cases, a deficiency can cause blindness due to the damage to the cornea.

Question 10

The primary function of vitamin D is to regulate absorption and metabolism of:

Accepted Answer

Vitamin D is essential for the regulation of calcium and phosphorus absorption and metabolism. Calcium is important for bone health, muscle function, blood clotting, and nerve signaling, while phosphorus is necessary for cell membrane structure and energy metabolism. Vitamin D helps the body absorb these minerals and maintain proper levels in the blood.

Question 11

One reason it is difficult to establish recommended requirements for vitamin D is because:

Accepted Answer

Individual exposure to sunlight varies greatly, making it difficult to establish a recommended requirement for vitamin D. Sunlight is the primary source of vitamin D, and the amount of vitamin D produced in the body from sunlight exposure depends on many factors such as location, time of day, skin color, and use of sunscreen. As a result, it is difficult to determine a specific amount of vitamin D that would be beneficial for everyone.

Question 12

Spinach, carrots, and sweet potatoes are good sources of:

Accepted Answer

Spinach, carrots, and sweet potatoes are all rich sources of beta carotene, which is converted to vitamin A in the body.

Question 13

The adult form of rickets is called:

Accepted Answer

Rickets is a condition caused by vitamin D deficiency or impaired vitamin D metabolism, leading to inadequate mineralization of bones in children. In adults, this condition is called osteomalacia, which can result in weak bones, bone pain, and muscle weakness. Osteoporosis and osteopenia are also conditions related to bone density, but they are caused by different factors such as hormonal changes, aging, or lack of physical activity. Osteomyelitis is a bone infection and not related to vitamin D deficiency.

Question 14

The chemical name for preformed vitamin A is:

Accepted Answer

Preformed vitamin A refers to the active form of vitamin A, which is retinol. Beta carotene is a precursor to vitamin A, not the active form. Rhodopsin is a protein found in the retina that contains retinaldehyde. While retinaldehyde is a precursor to retinol, it is not the same as preformed vitamin A.

Question 15

The major provitamin form of vitamin A found in plant pigments is known as:

Accepted Answer

Beta carotene is a major provitamin form of vitamin A found in plant pigments.

Question 16

A deficiency of vitamin A in the body may result in:

Accepted Answer

A deficiency of vitamin A can lead to night blindness, which is a condition where a person cannot see properly in low light conditions or at night. Vitamin A is essential for the health of the retina, which is responsible for vision in low light conditions.

Question 17

A toxic level of vitamin D can result in:

Accepted Answer

A toxic level of vitamin D can lead to calcification of soft tissues, which can cause damage to organs such as the heart and kidneys. This is because vitamin D helps the body absorb calcium, and excess levels of vitamin D can cause too much calcium to be deposited in soft tissues. While excessive vitamin D intake can also cause other health issues such as nausea, vomiting, and constipation, none of the other answer choices are directly related to vitamin D toxicity.

Question 18

Vitamin D deficiency is most likely to occur in a child who is involved in:

Accepted Answer

Gymnastics is an indoor sport, so the child would have less sun exposure. This would result in less vitamin D production in his or her skin.

Question 19

Rickets is caused by a deficiency of:

Accepted Answer

Rickets is caused by a deficiency of vitamin D. This vitamin is needed for the body to absorb calcium and phosphorus, which are necessary for the development and maintenance of healthy bones. Without sufficient vitamin D, bones become weak and soft, leading to skeletal deformities and other symptoms associated with rickets. Vitamin A, cobalamin, and niacin deficiencies do not cause rickets.

Question 20

Foods that are commonly fortified with vitamin D are:

Accepted Answer

Milk and margarine are commonly fortified with vitamin D. Cereal and pasta may also be fortified, but are not as reliable sources as they vary by brand. Flour and sugar are not commonly fortified with vitamin D. Cheese and canned tuna may contain some vitamin D naturally, but are not typically fortified.

Quiz 6: Vitamins