Chapter 9 Nutr 221

What is the primary function of vitamin D?

is to maintain levels of calcium and phosphorus in the blood that favor bone mineralization.

two sources of vitamin D in the diet.

liver; fatty fish such as salmon, mackerel, and sardines; cod liver oil; and egg yolks.

symptoms of vitamin K deficiency

Abnormal blood coagulation is the major symptom of vitamin K deficiency

two food sources of provitamin A

Plant foods containing provitamin A compounds include dark orange fruits and vegetables such as mangos, apricots, cantaloupe, carrots, red peppers, pumpkins, and sweet potatoes as well as in leafy greens.

rickets

Vitamin D deficiency in children characterized by bone deformities such as narrow rib cages known as pigeon breasts, and bowed legs.

symptoms of vitamin D deficiency in children

, bones are weak because they do not contain enough calcium and phosphorus

two food sources of preformed vitamin A

Animal foods such as liver, fish, egg yolks, and dairy

Why is beta-carotene not toxic, but preformed vitamin A

Carotenoids are not toxic because their absorption from the diet decreases at high doses, and once in the body, their conversion to retinoids is limited. Preformed Vitamin A is toxic because it is absorbed more efficiently than beta-carotene and does not need to be converted to an active form once inside the body.

How is vitamin A involved in the perception of light?

In the eye, the retinal form of the vitamin combines with the protein opsin to form the visual pigment rhodopsin. Rhodopsin helps transform the energy from light into a nerve impulse that is sent to the brain. This nerve impulse allows us to see.

Why is vitamin D called the "sunshine vitamin"

because it can be produced in the skin by exposure to ultraviolet light.

Why does a deficiency of vitamin A cause night blindness

because it causes a delay in the regeneration of rhodopsin, which causes difficulty in adapting to dim light after experiencing a bright light.

Why does a deficiency of vitamin A cause dry eyes?

because of its role in cell differentiation. When vitamin A is deficient the mucus-secreting cells on the surface of the eye are replaced by keratin secreting cells. This results in a lack of mucus and a buildup of keratin, causing the cornea to dry and leaving the eye open to infection.

What is the function of Vitamin E

functions primarily as a fat-soluble antioxidant.

Name two sources of vitamin E in the diet

vitamin E include nuts and peanuts; plant oils, such as soybean, corn, and sunflower oils; leafy green vegetables; and wheat germ