Riboflavin (Vitamin B2) Flashcards
(23 cards)
what are the sources of riboflavin?
found especially in products of animal origin (milk, cheese, yogurt)
how can riboflavin be destroyed in foods?
because of exposure to sunlight
what is riboflavin fairly resistant too?
heat, oxidation, and acid
what is another source of riboflavin (specifically in the body)?
bacterial synthesis in the large intestine
what form of riboflavin is most commonly found in food?
free and protein-bound (milk, eggs, and enriched breads and cereals)
what form of riboflavin must be released prior to absorption?
riboflavin that is found in foods attached non-covalently to proteins, FAD, FMN and riboflavin phosphate
how is the protein from riboflavin released?
accomplished by hydrochloric acid secreted within the stomach and proteases secreted by the stomach , pancreas and small intestine
how is FAD converted to free riboflavin?
FAD pyrophosphatase converts FAD to FMN, and FMN, in turn, is converted to free riboflavin by FMN phosphatase
how is free riboflavin absorbed?
across the intestinal brush border membrane by energy-dependent riboflavin vitamin transporters (RFVT)
what is the function of RFVT3?
transports riboflavin across the brush border membrane of the SI
what is the function of RFVT1?
carries riboflavin across the basolateral membrane of he intestinal cell
what are examples of riboflavin transporter deficiency disorders?
brown-vialetto-van-laere syndrome and Fazio-Londe syndrome
what impairs both riboflavin digestion and absorption?
alcohol
where is riboflavin found?
small quantities in a variety of tissues and the greatest concentration in the liver, kidneys and heart
following uptake into cell - what is riboflavin converted too?
FMN coenzyme by flavokinase/riboflavin kinase and then to FAD by FAD synthase
what is the major enzyme form?
FMN
what accelerates the conversion of riboflavin into its coenzyme forms?
ACTH, aldosterone, and thyroid hormone
what is the function of flavin coenzymes?
oxidizing agents
what is required in the conversion of both PMP and PNP to PLP?
FMN
how is riboflavin excreted from the body?
to a small extent in the feces, but primarily via the urine
what is oculo-orogenital syndrome?
condition that affects areas of the skin containing high concentration of sebaceous glands, including the external ear, the nasolabial fold, eyelids, and scrotum (males)
what can severe riboflavin deficiency also diminish?
the riboflavin-dependent synthesis of the co-enzyme form of vitamin B6 and synthesis of niacin from tryptophan
how do you determine riboflavin nutriture?
measure the activity of the FAD-dependent enzyme erythrocyte glutathione reductase
