B-Complex Vitamins Flashcards
Vitamin C types
-pantothenic acid
-niacin
-choline
-biotin
-folic acid
Nicotinamide
niacin
Nicotinic acid is a component of what two coenzymes?
-NAD
-NADP
What is the substance of acid and amide?
colorless crystalline
What are the niacin acid and amide soluble in?
water and alcohol
What is niacin resistant to?
heat, air, light, and alkali
(stable in foods)
Man, dog, rat, and pig metabolism leads to the excretion of _______ __________
methylated compounds
What is the nicotinic acid and nicotinamide excreted in ruminants?
unchanged
What does poultry conjugate 2 molecules of nicotinamide with?
ornithine
What is niacin present as in animal tissues?
pyridine nucleotides (free niacin is not present in the tissues)
What does NAD serve as in the TCA cycle?
the electron acceptor in 3 of the 4 dehydrogenation steps
NAD and NADP function in biological oxidation-reduction systems via their ability to serve as _______ _______ _______
hydrogen transfer agents
Niacin deficiency symptoms
-black tongue in dogs
-pellegra in humans
-casal’s necklace
Black tongue
-deficiency symptom of niacin in dogs
-black colorization of tongue
-loss of appetite
-diffuse inflammation of gums
-tissues become neurotic and eroded
-bloody diarrhea caused by GI mucosa infammation
Pellegra
-deficiency symptom of niacin in humans
-dermatitis of skin exposed to light
-loss of appetite
-nausea
-fiery red tongue caused by inflammation of mucous membranes
-delirium and hallucinations
Casal’s necklace
-deficiency symptom of niacin
-reddened area around the neck when sunlight hits it
Where does adequate synthesis of niacin occur?
in ruminants in the rumen
Niacin relationship with corn
-corn is low in the amino acid tryptophan
-niacin in corn is in a bound form that is unavailable to the rat, pig, or poultry without alkali treatment
What is needed for niacin synthesis?
tryptophan
-60 mg TRP required for synthesis of 1 mg of niacin
Niacin assay
microbiological because tryptophan does not interfere with it
Sources of niacin
-animal and fish by-products
-distiller’s grains
-yeast
-alfalfa
-present in cereals but low availability
-widespread in feeds
Pantothenic acid is a constituent of _______
coenzyme A (coenzyme for acetylation)
Coenzyme A contains
-pantothenic acid
-adenosine-3 phosphate
-pyrophosphate
-B-mercaptoethylamine
Pantothenic acid exists in the tissues as:
-free pantothenic acid
-coenzyme A (bound form)
-pantothenyl phosphate
-pantotheine phosphate
What is pantothenic acid normally sold as?
Ca pantothenate salt
Pantothenic acid is sensitive to _____, ______, and _______
acid, base, and heat
As a constituent of coenzyme A what is pantothenic acids function?
necessary in various acetylations of the 2 carbon fragments that arise from metabolism of fats, CHO, and amino acids to form acetyl CoA
Functions of pantothenic acid
-serves in fatty acid synthesis
-functions in steroid synthesis
-acetylation of choline
(choline + Acetyl CoA —> acetylcholine)
-1st step in heme porphyrin synthesis is the condensation of glycine and succinyl CoA
General deficiency symptoms of pantothenic acid
-nervous disorders
-dermatitis (especially in poultry around eyes and mouth)
-graying of black hair in rats, dogs, and foxes (achromotrichia)
Metabolic deficiency symptoms of pantothenic acid?
-reduced pyruvate utilization
-decreased cholesterol synthesis
-altered energy conversion and CHO utilization
-reduced antibody production
-nerve involvement (due to acetylcholine)
Two antimetabolites of pantothenic acid
-pantoyltaurine
-methylpantothenic acid
(normally only have a deficiency if antimetabolites are present)
Pantothenic acid assay’s
no suitable chemical methods
-general bioassays carried out on depleted rats and chicks
Sources of pantothenic acid
-yeast
-liver
-eggs
-alfalfa hay
-molasses
-wheat bran
What/who synthesizes pantothenic acid?
-green plants
-some microbes
-practical diet deficiency is rare
What can be substituted as biotin in nutrition?
oxybiotin
What form in nature and natural products does biotin usually occur in?
bound form (biocytin)
What does a mammalian enzyme do to the bound form of biotin?
cleaves it into equimolar amounts of biotin and lysine
-most biotin is bound to protein or high molecular weight peptides
Primary function of biotin
it serves as the prosthetic group for a series of enzymes that incorporate CO2 into organic linkage
Biotin is very important in _________ ________
propionate metabolism (especially in ruminants)
What synthesis does biotin play a role in?
fatty acid synthesis
What causes deficiency symptoms of biotin?
-feeding raw egg white
-use of biotin-free diets plus a sulfa drug (prevents intestinal synthesis)
Deficiency symptoms of biotin
-dermatitis (due to overactivity of sebaceous glands)
-loss of hair
-poor growth
-spectacled eye factor (loss of hair around eyes specifically)
-problems in normal hoof growth
Antagonist of biotin
Avidin
Avidin
a protein in egg white, combines with biotin to prevent its absorption
-biotin is released by denaturation of the protein with steam, heat (frying eggs), or UV irridation
Which assay is best for biotin?
rat bioassay
-can use chicks but they have a higher biotin requirement
What synthesizes biotin?
intestinal microflora in substantial qualities
-rumen synthesis supplies needs of cattle and sheep
What diet usually causes a biotin deficiency?
synthetic diet
Sources of biotin
-yeast
-organ meats
-seeds of plants
-molasses
-milk
Does choline qualify as a vitamin?
No, because it is a structural component of fat and nerve tissue and is not known to participate in any enzyme system
Function of choline
functions as a part of acetylcholine - it is involved in nerve transmission
What is choline a donor of?
methyl groups-mediated through its role in forming S-adenosylmethionine (methyl donor for various reactions)
What is choline a constituent of?
-lecithin - promotes mobilization of fat from the liver
-sphingomyelin
-found in abundance in the myelin sheaths of nerves
-examples of phospholipids
How does the function of choline differ from that of the other B vitamins?
it is essential as a structural component of tissues rather than as a metabolic catalyst
Deficiency symptoms of choline
-perosis
-fatty livers
-hemorrhagic kidney
-
Perosis
slipped tendons in chicks
Fatty livers
-mobilization of fat from the liver is somehow impaired and abnormal accumulations of fat occurs
-fats are routinely mobilized from the liver as lipoproteins containing: free fatty acids, fatty acids esterified to glycerol, fatty acids esterified to cholesterol, choline-containing phospholipids
What material is capable of contributing methyl groups for choline synthesis?
-lipotropic materials = capable of preventing or correcting fatty livers or a choline deficiency
Hemorrhagic kidney
-blood fails to leave the kidney at a normal rate
-hypertension may happen due to constriction in kidney blood vessels
-deficiency in choline in early life may result in inadequate phospholipids necessary to build the structure of the kidneys and/or their blood vessels
What can synthesize choline?
the body can synthesize some choline endogenously from phosphatidyl serine + S-adenosylmethionine —> lecithin
Sources of choline
-all naturally occurring fats
-all feeds that have a source of fat supply
What greatly influences the choline needed?
dietary level of methionine
Folic acid
folacin
Folic acid structure
tetrahydrofolic acid which serves as the biological carrier for C1
What is the biochemical role that folic acid plays?
a role in the transfer of one carbon units similar to the role of pantothenic acid plays in 2 carbon unit transfer
-THFA interconversion of glycine to serine
-THFA interconversion of homocysteine and methionine
What is folic acid necessary for the formations of?
it furnishes methyl groups necessary for the formation of purines (DNA synthesis)
Folic acid functions in ________ degeneration
histidine
What is found in large amounts in the urine of folic acid deficient animals?
formiminoglutamic acid
What is folic acid deficiency due to?
intestinal synthesis
To be deficient in folic acid usually an _____________ must be added
antagonist
What drugs will produce a folic acid deficiency because they compete with parminobenzoic acid
sulfa drugs (because parminoenzoic acid is necessary for folic acid synthesis)
Deficiency symptoms of folic acid
-pernicious anemia (Addison’s anemia)
-sprue - sore mouth, raw tongue, diarrhea, frothy fatty feces
-chicks have retarted growth, poor feathering, depigmentation of colored feathers
What is folic acid effective in treating?
-anemia of pernicious anemia (but not nervous symptoms only B12 can fix this)
-preventing megaloblastic anemias of pregnancy, infancy, and sprue
Sources of folic acid
-green, leafy material
-organ meats
-cereals
-animal by-products
What synthesizes folic acid?
intestines
-usually adequate for most farm animals
-poultry requires dietary source
What form and pH is folic acid stable at?
-dry form
-at a pH of 6 and above
-pH of 6 and below results in complete destruction
What is the preferred assay?
-bioassay (chicks)
-microbiology methods can be used
Primary source of B12 in nature
from microbes
Who synthesizes B12
neither animals or plants
Sources of B12
-microbes
-meats
-eggs
-cheese
-milk
Where is B12 produced?
microbial synthesis in the GI tract
Is B12 absorbed in nonruminants?
No it is available only as coprophagy
Plant products are devoid of B12 unless subject to a __________ _________
microbial fermentation
Functions of B12
-coenzyme in several metabolic reactions
-participates in propionic metabolism in the rearrangement step from methylmalonyl CoA to succinyl CoA
-conversion of homocysteine to methionine
-role in protein synthesis and purine metabolism
-role in the impaired rate of RNA and DNA synthesis in deficiency situations
Deficiency symptoms of B12
-pernicious anemia in humans
-due to the failure of absoprtion of the vitamin at the gut tissue level
-usually due to insufficient secretion of the intrinsic factor by the gastric mucosal cells
-slow growth
-nervousness
-irritability
What is the intrinsic factor necessary for?
B12 absorption
What can deficiency of B12 in sheep be solved with?
injection of Co
Vitamin B12 works _________ or ________
injected or fed
Assay for B12
biological or microbiological
