Block 2: Vitamin Intro + Vitamin C Flashcards
Night blindness is caused by a deficiency in what vitamin?
A
What is a vitamin?
An essential organic compound required in small amounts important for the functions of the body
Not metabolic fuels or structural nutrients but rather regulators for energy metabolism
What vitamin is synthesized by most mammals except for humans?
C
What vitamin is synthesized by rumen bacteria?
B
Vitamins undergo a chemical change from ____?
Provitamins
What are some of the functions of vitamins?
- Hormones
- Antioxidants
- Mediators of cell signalling and regulators of cell and tissue growth and differentiation
Chemical name: Vitamin A
Deficiency?
Retinoid (retinol, retinoids, carotenoids)
Night blindness and keratomalacia
Chemical name: Vitamin B1
Thiamine
Beriberi
Chemical name: Vitamin B2
Riboflavin
Chemical name: Vitamin B3
Deficiency
Niacin
Pellagra
Chemical name: Vitamin B5
Deficiency?
Pantothenic acid
Paresthesia
Chemical name: Vitamin B6
Deficiency?
Pyridoxine, pyridoxamine, pyridoxal
Anemia
Chemical name: Vitamin B7
Deficiency?
Biotin
Dermatitis
Chemical name: Vitamin B9
Deficiency
Folic acid
Neural tube defect
Chemical name: Vitamin B12
Deficiency
Cyanocobalamin, Hydroxycobalamin, methylcobalamin
Megaloblastic anemia
Chemical name: Vitamin C
Deficiency?
Ascorbic acid
Scurvy
Chemical name: Vitamin D
Deficiency
Ergocalciferol, cholecalciferol
Rickets and osteomalacia
Chemical name: Vitamin E
Tocopherols, tocotrienols
Chemical name: Vitamin K
Deficiency?
Phylloquinone, menaquinones
Bleeding diathesis
What is the differnce between a primary and secondary vit def?
Primary: Occurs when an organism doesn’t get enough vitamins from food
Secondary: Due to an underlying disorder that prevents or limits absorption and use of vitamins
What are the general ADRs of vitamin OD?
N/D/V
How is vitamin manufacturing regulated?
FDA label them as Dietary Supplements not intended to treat only to supplement diet
Why are mammals more susceptible to scurvy?
The liver’s inability to produce the active enzyme L-gulonolactone oxidase an enzyme required for Vit C synthesis
What are the sx of scurvy?
- Liver spots on skin
- Spongy gums
- Bleeding
- Suppurating wounds
- Loss of teeth
- Death
Body soon depletes itself (20-40 days)
How is vitmain C mass synthesized?
Redoxon: D-sorbitol undergoes several redox reactions (reichstein process) to become ascorbic acid
What is the MOA of scurvey?
The liver’s inability to produce the active enzyme L-gulonolactone oxidase inhibiting the progresion of Vitamin C biosynthesis
What is the active form of Vitamin C? How does this affect metals?
L-ascorbic acid is a stron reducing agent that reverses oxidation (anti-oxidant)
L-ascorbic can reduce metals to their pro-oxidant form for coenzymatic activity
Why are free radicals and ROS bad? How are they resolved?
Attack phospholipids and proteins in the cell membrane via lipid peroxidation
Ascorbic acid reduces and deactivated ROS
How can Vitamin C cause kidney stones?
Exccesive Vitamin C produces the metabolite Oxalic acid that promotes the formation of kidney stones
Describe how the vitamin C contributes to collagen formation?
- Vit C requires to 2 hydroxylation reactions of proline or lysine (amino acids important for scurvy protection)
- Proline residue on collagen a-chains is hydrolyzed to aggregate into triple helix
- Fe3+ reduces to Fe2+ when converting ascorbate to dehydroascobate
Why is hydroxylation reactions of proline and lysine important?
Hydroxylation stabilizes the exo-conformation for collagen structure enhancing H-bond stabilizing the triple helix
What is carnitine synthesis?
Significant in fat metabolism where vitamin C undergoes 2 hydrolysis reactions:
1. tri-methyl lysine is catalyzed by iron containing TML dioxygenase to 3-hydroxyl TML
2. 4-butyrobetaine catalyzed by iron-containing 4BB hydroxylase to carnitine
Vitamin C maintains the enzymes iron reduced, active form
Describe the mechanism of tyrosine biosynthesis and metabolism?
Vitamin C catalyzes the following reactions:
1. Tyrosine is formed from phenylalanine hydroxylation by phenylalanine monooxygenase
2. Used for Cu++ dependent p-hydroxyphenyl pyruvate hydroxylase metabolizing tyrosine
What neurotransmitter and hormon is catalyzed by Vit C?
Vitamin C enhances the activity of 2 Cu2+ requiring enzymes for the biosynthesis of NE and adrenal hormone
1Tyrosine -> Dopamine -> NE
How does vitamin C assist with serotonin synthesis?
Vit C, folic acid, and O2 assist with the hydroxylation of tryptophan for synthesizing serotonin in the brain
Vitmain C enhances the absorption of what elements?
- Iron
- Copper
- Chromium
How does vitamin C assist bile synthesis?
Hydroxylation/degradation of cholesterol steroid nucleus by cholesterol 7a hydroxylase (diminished action with vit C def)
How is Vit C absorbed into the body?
Absorbed in the distal small intestine via active transport by a glucose transport protein
Where is the highest concentration of vitamin C found?
Adrenal gland (30-40 mg/100g wet tissue)
How can Vit C prevent cancer?
Vit C has antineoplastic properties against stomach and esophagus cancers when ingested with nitrates and nitrites preventing the formation of carcinogenic nitrosamines
What are the sx of vitamin C toxicity?
- Kidney stones and gout due to increased uric acid
- Osmotic diarrhea
- Iron poisoning due to increased absoprtion
What are the important functions of vitamin C?
- Antioxidant
- Amino acid hydroxylation
- Tyrosine biosynthesis
- Biosynthesis of NE, adrenal hormone, serotonin
