Exam 3 Flashcards
what are vitamins?
organic compounds that are required in small quantities for specific functions, such as the maintenance of regulatory and metabolic processes in the body.
what are organic compounds?
compounds that contain both carbon-carbon and carbon-hydrogen bonds.
why is it necessary for human to obtain vitamins through diet?
in most cases, human cells cannot synthesize vitamins; but in the few vitamins manufactured by the body (or by intestinal bacteria) are not produced in amounts sufficient to meets our needs
are vitamins an energy source?
no, but we need a number of them in order to extract energy from macronutrients as well as provide many regulatory and metabolic functions in the body and proper cell functioning, development, and growth.
what is bioavailability?
the degree to which nutrients can be absorbed and utilized by the body.
what can influence bioavailability, particularly for vitamins?
physiological and dietary condition; the presence of disease, chronic alcohol abuse, and age-related physiological changes can decrease bioavailability; it can also be affected by the presence of other nutrients or food components hat can enhance or reduce absorption or by food-handling practices such as whether you cook a food or eat it raw.
how are vitamins grouped?
according to their solubility: fat-soluble vitamins and water-soluble vitamins.
what is solubility?
the ability of a substance to dissolve in a solution.
what are fat-soluble vitamins?
require the presence of bile acids for absorption, and are stored in body tissue; vitamins A, D, E, and K.
what are water-soluble vitamins?
vitamins that disperse easily in water-based solutions; B vitamins, vitamin , and the vitamin-like nutrient choline.
what is the plant form of vitamin A?
betacarotene.
what are possible benefits of betacarotene?
provide benefits through their ability to function as antioxidants in the body.
what are antioxidants?
a substance that prevents damage to cells by inhibiting the oxidation caused by free radicals.
what are free radicals?
molecules that are naturally formed in the body or are present in the environment that have an unpaired electron; at high levels they damage cells, including DNA, through a process called oxidation.
what is oxidation?
a loss of electrons; in the bod, this results in damage to cells.
what are some results of oxidation in the body?
it can alter DNA, destabilize cell membranes, lead to chronic diseases such as cancer and heart disease.
what are some benefits of ample dietary intakes of carotenoids?
can provide some protection to the skin from the damaging effects of UV radiation from sunlight.
what is the vitamin A deficiency called?
hypovitaminosis A.
where is hypovitaminosis A most common/uncommon.
uncommon in the United States, common in developing countries due to a lack of access to preformed vitamin A and beta-carotene.
what are the effects of hypovitaminosis A?
mainly affect the eye, night blindness occurs due to problems in the synthesis of rhodopsin, decreased production of mucus in tears, which results in the cornea of the eye drying. if the deficiency continues, the affected cornea can become ulcerated and essentially melt away, causing scarring and permanent blindness; hypovitaminosis A is the leading cause of blindness in children worldwide; cornea ulcerations generally develop suddenly, occurring mostly in children aged 1-4 and typically causing blindness. this deficiency causes a high risk of death due to impaired immunity and an increased likelihood of infections; other symptoms include rough, dry, or scaly skin resulting from a loss of moisture in the mucous membranes; keratinization occurs in the epithelial cells that cover the surface of our bodies and line body cavities, epithelial cells cannot develop properly and they become filled with a fibrous structural protein called keratin.
what is vitamin A toxicity called?
hypervitaminosis A.
what is the UL for vitamin A?
3000 mcg.
what are the effects of hypervitaminosis A?
defects or weaknesses in bones, leading to osteoporosis or fractures; in pregnant women, intake of vitamin A above the UL can interfere with fetal development, increasing the risk of birth defects, excess provitamin A as beta-carotene from plant sources has not been demonstrated to cause toxicity but may only temporarily turn skin yellow or orange.
what are characteristics of fat soluble vitamins?
small amounts necessary for good health, absorption occurs in the small intestine, leave the small intestine in chylomicrons, often present in fatty portion of foods, stored in tissue; toxicity possible when consumed in excess, dissolves in lipid.
what are characteristics of water soluble vitamins?
small amounts necessary for good health, all except choline function as coenzymes, most circulate freely in blood, many are easily destroyed or removed during food storage or preparation, not stored in large amounts in tissues; toxicity generally does not occur, dissolve in water.
