Water Soluble Vitamins Flashcards
What are vitamins
Organic, essential molecules that are required in tiny amounts to maintain normal growth, development, and metabolism. We cannot synthesize them in good amounts so we supplement from our diets.
What is the water soluble non-B complex vitamin?
Ascorbic Acid (vitamin C)
What are the water soluble energy releasing vitamins?
Thiamine (vitamin B1), Riboflavin (vitamin B2), Niacin (vitamin B3), Biotin, Pantothenic acid.
What are the water soluble Hematopoietic vitamins?
Folic Acid, Vitamin B12.
What is the effect of acidity on B12 absorption?
Decreased acid production in the stomach decreases vitamin B12 availability since the acid helps release vitamin B12 from its bound protein.
Digesting and absorbing water soluble vitamins
1) Water soluble vitamins are usually bound to proteins.
2) Vitamins are hydrolyzed in the stomach from the protein complexes.
3) Most of the vitamins are absorbed in the upper small intestine with the exception of vitamin B12 which is absorbed in the ileum.
4) Most of the water soluble vitamins are excreted readily except for vitamin B12 and Pyridoxine (vitamin B6)
What are the two water soluble vitamins that are stored?
Vitamin B12 and Pyridoxine (vitamin B6)
Cofactors
accessory molecules that are important for protein or enzyme function. Could be inorganic (minerals) or organic (coenzymes)
Coenzymes
co-substrates for specific enzymes and are essential for the catalysis of metabolic reactions and they are recycled.
Prosthetic groups
Tightly bound to enzymes or proteins and they are not released from protein or enzymes even after reaction.
What is the active form of riboflavin
FAD
Mnemonic for B-vitamins
The rhythm nearly proved fully contagious
B1
Thiamine
B2
Riboflavin
B3
Niacin
B6
Pyridoxine
B9
Folate
B12
Cobalamin
Food rich in thiamin
Meat, sunflower and grains
Active form of thiamin
Thiamin pyrophosphate
What decreases thiamin absorption
Alcohol consumption and folate deficiency
Function of thiamin
coenzyme for:
- pyruvate dehydrogenase
- a-ketoglutarate dehydrogenase
- Branched chain a-ketoacid dehydrogenase
- Transketolase
Thiamin deficiency
Found in malnourished, homeless patients, alcoholics and weight loss diet. Symptoms: loss of appetite, irritability, apathy, confusion, and weight loss. In advanced stages, beriberi develops
Types of beriberi
Wet and dry. Wet affects the cardiovascular systems and dry beriberi affects the neurologic system.
Symptoms of dry beriberi
muscle wasting, pain, numbness, and tingling of the lower extremities making walking difficult.
Symptoms of wet beriberi
Edema
What food sources are rich in riboflavin
Milk, milk products (greek yogurt), liver, whole grains
Active forms of riboflavin
Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)
Function of riboflavin
prosthetic groups to many enzymes in oxidation reduction reactions
Deficiency of Vitamin B2
Inflammation of membranes (cheilosis, glossitis, stomatitis, seborrheic dermatitis), bloodshot eyes, sensitivity to bright light
Food sources rich in B3 (Niacin)
meat, fish, poultry, peanut butter, mushrooms, asparagus, and fortified foods
Forms of Niacin
Nicotinic Acid, Nicotinamide
Active forms of niacin
NAD and NADP
What can we use to make niacin?
Tryptophan
Symptoms of Niacin deficiency
4Ds (diarrhea, dermatitis, dementia, and death), Pellagra (rough skin)
Toxicity of Niacin
Can occur in patients taking high doses of Nicotinic acid for lowering LDL, triacylglycerols and increasing HDL. Symptoms: Niacin flush and itching
Food sources of Vitamin B6 (Pyridoxine)
Protein rich foods, starchy vegetables and non citrus fruits. Bananas!!
Forms of Pyridoxine
Pyridoxal, pyridoxine, pyridoxamine
Active form of Pyridoxine
Pyridoxal phosphate which is used for amino acid metabolism
Functions of Pyridoxine
Transamination reactions, deamination reactions, urea metabolism, conversion of tryptophan to niacin and synthesis of heme
What causes Pyridoxine deficiency
newborn infants fed formulas low in B6, women taking oral contraceptives, alcoholics
What is isoniazid used for? effect on vitamin B6?
Isoniazid is used for tuberculosis and binds to vitamin B6 causing deficiency
What is penicillamine used for? effect on vitamin B6?
Penicillamine is used for Rheumatoid arthritis and leads to pyridoxine deficiency
Toxicity of vitamin B6
Irreversible nerve damage
Food sources of Folate
Dark Leafy vegetables such as spinach, broccoli, legumes, citrus fruits.
Basic structure of a folate
Ring structure called pteridine, followed by PABA as a bridge molecule which in turn is connected to glutamate.
Methyltetrahydrofolate
Inactive form of floats which makes it a good form for circulation but not within the cell.
How is folate activated?
Vitamin B12 removes and keeps the methyl group which activates both folate and vitamin B12.
Function of Folate
Synthesis of DNA, RNA, some amino acids so its critical for embryos in development. Also important for regeneration of methionine from homocysteine.
Folate deficiency
weakness, fatigue, headache, palpitation and shortness of breath due to microcytic anemia. NEURAL TUBE DEFECTS!
Drawback of giving Folate supplements?
May mask the symptoms of vitamin B12 deficiency and lead to neurologic damage.
Methylmalonic acid Test
Its accumulation is an indication of vitamin B12 deficiency.
Food sources of vitamin B12
Animal products only so vegans are deficient
Active forms of cobalamin
methylcobalamin and deoxyadenosylcobalamin
Digestion and absorption of B12
1) In stomach, HCl and pepsin release vitamin B12 bound to protein in food. Free vitamin B12 binds to R protein. Intrinsic factor is released by parietal cells
2) In duodenum, pancreatic enzymes cleave R-protein allowing vitamin B12 to bind to IF.
3) In ileum, IF receptors allow internalization of vitamin B12.
4) Vitamin B12 is released from IF and released to hepatic circulation and is transported bound to transcobalamin II.
Where is R protein secreted from?
Salivary Gland
Deficiency of Vitamin B12 due to decreased Intake
Pure vegan diet, malnutrition
Deficiency of vitamin B12 due to malabsorption
Decreased intrinsic factor, decreased gastric acid, and removal of terminal ileum
What is Pernicious anemia?
Autoimmune inactivation of IF
Symptoms of vitamin B12 deficiency
megaloblastic anemia, nerve damage, painful swollen tongue
Biotin
Coenzyme that adds CO2 to compounds. Required for metabolism of carbs, fats, and proteins
ABC carboxylases
ATP, biotin, CO2 carboxylases
Biotinidase enzyme
Enzyme responsible for recycling active forms of biotin
Avidin
Molecule in egg whites that binds to biotin very tightly and causes a deficiency
Symptoms of biotin deficiency
Weak muscles, seizures, hair loss, inflammatory skin rash, developmental delays
Pantothenic Acid
Found in meat, milk and vegetables. Its a part of coenzyme A and is important for acetyl or acyl groups. It is essential of activation fatty acids and fat metabolism
Relationship between Riboflavin and B6
FMN is important for the conversion of pyridoxine to pyridoxal phosphate (PLP)
What other vitamin depends on FMN and PLP
Conversion of Trp into niacin
Scurvy
Disease associated with muscle weakness, joint pain, impaired wound healing, loose tooth, bleeding and swollen gums, bruised skin and fatigue. Due to vitamin C deficiency
Function of Ascorbic Acid
Formation of collagen water soluble antioxidant synthesis of neurotransmitter synthesis of carnitine enhances absorption of nonheme iron
Ascorbic acid on Collagen synthesis
Catalyzes prolyl hydroxylase and lysyl hydroxylase
Scorbutic gums
Common symptom of scurvy. Symmetrical appearance of lesions without infection in the gums of patients with vitamin C deficiency
Toxicity of vitamin C
Vitamin C is metabolized to oxalic acid and excess can lead to oxalate kidney stones.