15 – Energy Associated Vitamins Flashcards
1
Q
What are some energy associated vitamins? What do they act as?
A
- Thiamin, riboflavin, niacin, pantothenate, biotin
- Involved extensively in CHO, AA, and lipid metabolism as components of COENZYMES (or factors)
o Small organic molecules
o Required for catalytic activity of enzyme
2
Q
Where are all 5 energy releasing vitamins absorbed?
A
- Passive diffusion at high levels in the gut
- Na-coupled transport at low levels in the gut
3
Q
Energy associated vitamins: general principles
A
- Transported in blood dissolved in aqueous plasma
- Excesses are excreted in urine
- Toxicity is rarely a problem
- *storage limited and must be ingested regularly
o B2 (riboflavin) makes urine bright yellow
4
Q
Thiamin (or Thiamine)
A
- Vitamin B1
- Active thiamin is thiamin diphosphate (TPP)
- *TPP is a coenzyme in reactions involving removal of CO2
o w/o=difficult to make ATP and use macromolecules for energy
5
Q
Thiamine deficiency: neural disorders
A
- causes brain damage
o beriberi: humans
o star-gazing: chicks
o *loss of balance or seizures in non-humans
6
Q
Beriberi
A
- Common in SE Asia b/c of polished rice diets
- Rice brain contains thiamine and riboflavin
- *primary cause of infant mortality in some regions
- **causes cardiomyopathy in adult humans
7
Q
Thiamine deficiency in ruminants
A
- High sulfate water destroys thiamine causing POLIOENCEPHALOMALACIA
o Disorientation and wandering
o Blindness
o Opisthotonos
8
Q
Riboflavin
A
- Vitamin B2
- Functions as coenzyme to 2 electron transport reactions
o FAD TO FADH2 (complex 1)
o FMN to FMNH (complex 2) - *crucial for glucose and FA oxidation (TCA cycle)
9
Q
Riboflavin deficiency
A
- Relative common: low in cereals and legumes used for most monogastric diets
- Requirement increases with high fat diets
- Deficiency is NOT life threatening
10
Q
What are the symptoms of riboflavin deficiency?
A
- Stomatitis
- Glossitis
- Cheilosis
- Seborrhea
- Photophobia
- Chickens: curled-toe paralysis
- Other species: NO specific symptoms
11
Q
Niacin
A
- Vitamin B3
- Generic name for nicotinic acid and nicotinamide (both can act as a source)
- Tryptophan can be converted into nicotinamide and replace some of the requirement for niacin
o Pathway is very INEFFICIENT (60mg Trp=1mg niacin in humans)
o Very inefficient in POULTRY - Sometimes need to add it to ruminant diets (especially when using urea)
12
Q
Niacin deficiency
A
- Causes pellagra in humans
- *requires a diet low in niacin AND tryptophan
o Ex. corn based diets
13
Q
Pellagra in humans
A
- 4D’s: diarrhea, dermatitis, dementia and death
- *rough skin
- Through it was a bacterial disease
14
Q
Corn based diets and niacin deficiency
A
- Niacin in corn is bound in an UNAVAILABLE for niacytin
o Can be released by pre-treatment by alkali (lime) (used to make tacos=so no pellagra in Mexico) - Corn protein is low in tryptophan
15
Q
Niacin, cholesterol therapy and toxicity
A
- Megadoses of nicotinic acid have been shown to lower LDL cholesterol (bad cholesterol) and increase HDL (good cholesterol) in humans
- Need 2000mg/d for this effect in humans
o High doses cause FLUSHING and ORANGE SKIN - *higher doses can cause liver damage
16
Q
Pantothenic acid
A
- Vitamin B5
- Part of Coenzyme A
o Needed for protein catabolism to produce oxaloacetic acid
o Needed for Acetyl CoA production from either glucose or fats
o Needed for TCA cycle
17
Q
Pantothenic acid deficiency
A
- Results in impaired fat synthesis
- Dermatitis and goose-stepping (wider stance)
18
Q
Biotin
A
- Vitamin B7
- Functions as CO2 carrier in CO2 fixation and decarboxylation
- Required for
o Protein catabolism
o Fat synthesizing enzymes - *polyunsaturated fatty acids increase biotin requirements
- Wheat-based diets have low biotin availability
19
Q
Biotin and wheat
A
- Have low biotin availability
20
Q
Biotin and fat synthesizing enzymes
A
- Aids in adding a carbon
- Pyruvate carboxylase
o First reaction in pathway that converts 3C precursors to glucose - Acetyl-CoA carboxylase
o Commits acetyl-units to fatty acid synthesis by forming malonyl-CoA
21
Q
Biotin deficiency
A
- Hair-loss
- Dermatitis
- Foot cracking
- Depression
- Hallucinations
- Muscle pain
- *raw egg whites contain a protein (avidin) which binds biotin making it UNAVAILABLE TO THE HOST
22
Q
Choline
A
- B vitamin but does not entirely meet vitamin definition since most animals synthesize it
o Not a coenzyme or cofactor
o Requirements increase beyond synthetic capacity in some species/conditions - *most choline in diet present as lecithin (phosphatidyl choline), less as sphingomyelin
23
Q
Choline is important for synthesis of key signalling molecules in body
A
- Phosphatidyl CHOLINE in cell membrane
- Lipid transport
- NT acetylcholine
- Act as a methyl donor group in SAM pathway after conversion to betaine
24
Q
Choline deficiency
A
- Fatty liver (puppies, maybe more so in cats)
o If restricting diet to cats - Increased blood prothrombin times
- Thymic atrophy
- Decreased growth
- Anorexia
- Peritubular infiltration in liver (cats)
25
Q
Choline toxicity
A
- Found in most dietary fat, toxicity is rare unless accidental over-supplementation
- Egg yolks, glandular meals and fish=rich in choline
- Lecithin commonly used in food industry as an emulsifier
- *reports of anemia with only 3x dietary requirements in dogs
26
Q
Carnitine
A
- ‘quasi’ vitamin since animals can synthesis sufficient L-carnitine in most cases
- *L-carnitine important for FA shuttling across inner mitochondrial membrane and beta-oxidation
- *found in animal tissue and meat ingredients
27
Q
Synthesis of carnitine requires sufficient levels of what?
A
- Lysine, methionine
- Ascorbic acid
- Fe3+
- Vitamins B6 and niacin
28
Q
Carnitine deficiency
A
- Muscle weakness
- Fasting hypoglycemia
- Cardiomyopathy
- Hepatomegaly
- Dicarboxylic aciduria
- *or might be asymptomatic
- **toxicity is rare and not described
