Vitamins Flashcards
history of vitamins
Purified diets of carbohydrate, protein, fat, minerals and water were not capable of normal growth
“Accessory growth factors”
Casimir Funk, a Polish biochemist, isolated an antiberberi substance from rice polishings
Named it vitamine
An amine
Vital for life
what are vitamins?
Essential organic compounds required in very small amounts involved in fundamental functions of the body
Not metabolic fuels or structural nutrients
Regulators (catalysts) of reactions, some of which are involved in energy metabolism
All vitamins are metabolically essential but not all required in the diet
Most mammals can synthesize vitamin C; not humans and primates
Most B vitamins cannot be synthesized by animals but bacteria do make them
Some function as vitamins after undergoing a chemical change
classification of vitamins
Based on solubility in the laboratory Solubility greatly influences how the body absorbs, transports and stores vitamins Fat-soluble Vitamins A, D, E and K Water-soluble B vitamins and vitamin C
bioavailability
Rate and extent to which a nutrient is absorbed from the gastrointestinal tract
Influenced by genetics, aging, nutritional status & other food compounds
Extent to which nutrient is available to cells for metabolic purposes
Poor bioavailability can negate higher abundance in foods
regulation and body stores
Absorption
Small intestine & large intestine
Regulation
Kidneys & small intestine
increasing intake
Increase diet availability
Fortification
Genetic modification
water soluble vitamins
B1
B2
B3
B5
B6
B7
B12
vitamin B2- riboflavin
Riboflavin is easily destroyed by light so milk is packaged in cardboard or cloudy plastic containers so little riboflavin is lost before consumption.
vitamin B3- Niacin
Forms
Nicotinic acid
Nicotinamide
Body uses both forms to make:
NAD+
NADP
bioavailability of niacin/b3
Treating grain products with alkaline substances cleaves protein from niacin
Not limes, lime water (Ca(OH)2)
Destroys other vitamins
1 mg niacin = 60 mg tryptophan
vitamin b5- pantothenic acid
Bioavailability
Pantos = everywhere
Not stored in body
Coenzyme form high in liver, kidney, heart, adrenal glands, & brain
vitamin B6
Forms Pyridoxine Pyridoxal Pyridoxamine Forms pyridoxal phosphate (PLP) Coenzyme form of B6 Stored in muscle & liver
functions of biotin
Catalyzes carboxylation reactions
Use of amino acids & fatty acids in citric acid cycle for synthesis of fatty acids
Function of Folate: Single-Carbon Transfers
Coenzyme involved in transfer of single-carbon groups to form organic substances
Homocysteine to methionine
Coenzyme involved in transfer of single-carbon groups to form organic substances
Homocysteine to methionine
Purines & pyrimidines
Normal growth & development
dietary sources of folate
Since 1998, all cereal products in U.S. fortified with folic acid
Heat, light, & oxygen destroy folate
functions of b12
Coenzyme that catalyzes:
Production of succinyl CoA
Uses amino acids & fatty acids for ATP production
Key for ruminants!!
Conversion of homocysteine to methionine
Allows use of folate
functions of vitamin c
Antioxidant
Recharges enzymes
Involved in a variety of redox reactions
Vitamin C & Protection from Free Radical Damage
Free radicals
Charged substances that have unpaired electrons in their outer shells
Break DNA & oxidize fatty acids found in cell membranes
Regulation of Choline in the Body
Unbound choline absorbed in small intestine
Lecithin
Cleaved from glycerol backbone by pancreatic enzymes
Taken up by intestinal cells & reconstituted into lecithin molecules
Released into lymph
Becomes LDL
Made in body by methionine
Assists FA in crossing membranes
water soluble vitamins
Absorbed at the small intestine
Absorption often highly regulated by either other vitamins or binding proteins in the small intestine
Transported away from small intestine in blood
Typically not stored; instead, kidney filters excess into urine
Thus, more important to get these vitamins daily
Toxicities almost unheard of
fat soluble vitamins
A, D2, D3, E, K
Stored in body
Key players in:
Cell growth
Maturation
Gene regulation
basics of fat soluble vitamins
Absorbed in small intestine
Requires lipids & bile
Circulated in lymph via chylomicrons
Become part of lipoproteins or bound to transport proteins
vitamin A
Retinoids (preformed) Retinol Most potent form Retinal Retinoic acid Carotenoids Provitamin A β-carotein Nonprovitamin A Lycopene, lutein, etc. Phytochemicals
Retinol activity equivalent (RAE)
1 RAE = 12 micrograms beta-carotene & 1 microgram retinol
Sensitivity
NO3
Rumen
night blindness
Inadequate amounts of retinal to re-form rhodopsin
Compound in retina that consists of the protein opsin & vitamin cis-retinal that is needed for night vision
Night vision becomes difficult
vitamin K
Phylloquinone (K1) Food & supplements Menaquinone (K2) Produced by bacteria in large intestine Menadione (K3) Produced commercially
Packaged into lipoproteins in liver
functions of vitamin K
coagulation
