Energy-associated vitamins Flashcards
What are the energy associated vitamins?
-thiamin
-riboflavin
-niacin
-pantothenate
-biotin
Function of energy associated vitamins
Involved in carbohydrate, AA, lipid metabolism as coenzymes (small organic molecules, needed for catalytic activity of enzyme)
How are the energy associated vitamins absorbed?
- Passive diffusion at high levels in the gut
- Na-coupled transport at low levels in the gut
Energy associated vitamin transport, storage, and excretion
Transport: in blood dissolved in aqueous plasma
Storage: Limited. must be ingested regularly.
Excretion: Urine (toxicity rare). Riboflavin turns urine bright yellow
Thiamin
Vit B1
-used to make thiamin diphosphate (TPP) which is needed as a coenzyme in reactions involved in removal of CO2
eg. formation of acetyl-CoA, and in the TCA cycle
Thiamin deficiency
Neural disorders
-brain damage (beriberi in humans, star gazing in chickens, loss of balance.seizures)
Beriberi
Common in SE asia because polished rice diets
-rice bran contains thiamine and riboflavin but is often removed
-infant mortality, and cardiomyopathy in humans
Thiamin deficiency in ruminants
High sulfate water destroys thiamin in water
resulting in Polioencephalomalacia
-disorientation, wandering, blindness, opisthotonos (head retraction)
Riboflavin
Vit B2
-needed as coenzymes to two ETC rxns (FAD to FADH2, and FMN to FMNH), and glucose and fatty acid oxidation
Riboflavin deficiency
-Relatively common (when cereals and legumes used in most monogastric diets)
-Need more if high fat diets
-not life threatening
Symptoms of riboflavin deficiency
-stomatitis
-cheilosis
-glossitis
-seborrhea
-photophobia
-curled toe paralysis in chickens
Niacin
Vit B3; same as nicotinic acid and nicotinamide
-tryptophan can be converted to nicatinamide to meet some demands; but pathway inefficient so need in diet
What animals are most inefficient in niacin?
-poultry
-sometimes add to ruminant diets especially when using urea
Niacin deficiency in humans
Pellagra (rough skin)
-4 ds: diarrhea, dermatitis, dementia, death
-highest cause of mental illness in 1900s
Which diets result in niacin deficiency?
Corn diets
-niacin in corn is bound un unavailable form niacytin
-corn protein is also low in tryptophan
**lime or alkali can be added to free niacin from corn for use
Niacin toxicity
Megadoses= lower LDL cholesterol and increase HDL in humans
High doses=flushing and orange skin
Higher doses= liver damage
Pantothenic Acid
Vit B5
-part of coenzyme A
-needed for protein catabolism to produce oxaloacetic acid
-needed for acetyl coA production from either glucose and fats
-needed for TCA cycle
Pantothenic Acid deficiency
Results in impaired fat synthesis
-Symptoms: dermatitis and goose stepping
Biotin
Vit B7
Important for:
-CO2 carrier in carbon dioxide fixation and decarboxylation
-protein catabolism
-the function of fat synthesizing enzymes
What role does biotin play in helping fat synthesizing enzymes?
-aids in adding a carbon
-pyruvate carboxylase- first rxn in pathway that converts 3-carbon precursors to glucose
-Acetyl CoA Carboxylase- commits acetyl units to fatty acid synthesis by forming malonyl-CoA
What increases the biotin requirements?
Polyunsaturated fatty acids
Are wheat based diets high or low in biotin?
Low
Biotin deficiency symptoms
-hair loss
-dermatitis
-foot cracking
-depression
-hallucinations
-muscle pain
Egg whites and biotin
Raw eggs whites contain a protein called avidin which binds biotin making it unavailable to the host
Choline
Classified as B vit, but not a true vit because most animals can synthesize it
*not a cofactor or coenzyme
*requirements are greater than synthetic capacity in some species/conditions
Functions of choline
Important in the synthesis of:
-phosphatidyl choline in cell membrane
-lipid transport
-NT acetylcholine
-Acts as a methyl donor group in SAM pathway after conversion to betaine
What form is choline often in in the diet?
Present as lecithin (phosphatidyl choline), and sometimes as sphingomyelin
Choline deficiency
-fatty liver (puppies)
-peritubular infiltration in liver (cats)
-increased blood prothrombin times
-thymic atrophy
-decreased growth
-anorexia
Choline toxicity
Rare unless over supplementation
-egg yolks, glandular meals and fish are high in choline
-lecithin used as emulsifier in foods
Choline toxicity in dogs
Reports of anemia with only 3x dietary requirement
Carnitine
-not a true vit because animals synthesize it in L form
-found in animal tissue, meat ingredients
What is needed for carnitine synthesis?
-lysine, methionine
-Ascorbic acid
-Fe3+
Vit B6 and niacin
Function of Carnitine
-Needed for fatty acid shuttling across inner mitochondrial membrane and beta-oxidation
Carnitine deficiency
-muscle weakness
-fasting hypoglycemia
-cardiomyopathy
-hepatomegaly
-dicarboxulic aciduria
*can sometimes be asymptomatic
Carnitine toxicity
Rare, not described
