HNF 462 1st Edition Lecture 1 Outline of Current Lecture I. Definition of VitaminsII. Discovery and ChemistryIII. BiosynthesisIV. Food SourcesV. Absorption, Transport, and Tissue DistributionVI. Function in the Synthesis of Collagen, Carnitine, etc.Current Lecture: 1. What are vitamins?a. Organic compoundsb. Essential for normal function of the bodyc. Must be supplied by the diet—can’t be synthesized by the body 2. Discovery and Chemistry a. Scurvy: Disease caused by Vitamin C deficiencyi. Symptoms (4 Hs): hemorrhagic signs, hyperkeratosis of hair folliclesii. Hypochondriasisiii. Hematologic Abnormalitiesb. 1747: James Lind’s Clinical Trial determined that oranges/lemons cured scurvydiscovery of Vitamin Cc. Molecular structure is similar to that of glucosei. Two forms: Ascorbic Acid (AA) and Dehydroascorbic Acid (DHAA—oxidized form)d. Solubility and Stability: Water soluble; sensitive to heat/light/oxygenThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.3. Synthesis of Ascorbic Acida. Humans (and all higher species) are unable to make vitamin C due to the lack of gulonolactone oxidase (the last enzyme in the vitamin C synthetic pathway)4. Food Sourcesa. Natural Sources: fruits and vegetables (ex. asparagus, broccoli, cauliflower, oranges, cantaloupe, strawberries)b. Supplements: in forms of free ascorbic acid, calcium ascorbate, sodium ascorbate, and ascorbyl palmitate5. Absorption, Transport, and Tissue Distributiona. Absorptioni. Digestion is not required: AA and DHAA are absorbed throughout the small intestineii. Absorption efficiency decreases with increased vitamin C intake (at very high intakes, unabsorbed vitamin C is metabolized by intestinal flora)iii. AA enhances the intestinal absorption of nonheme iron. Excess iron will reduce the availability of AAb. Transporti. AA is transported by SVCT1 and SVCT2 Na-dependent transporters to peripheral cellsii. DHAA is transported by facilitated diffusion with glucose transporters (GLUT 1 & 3) to peripheral cells. DHAA is then absorbed into the cells by GLUT 1, 3, and 4. c. Tissue Distributioni. High Level of AA: Pituitary and adrenal glandsii. Intermediate Level of AA: Leukocytes, lungs, heart, liver, spleen, pancreas,and kidneys6. Functions (Generally acts as a reducing agent to maintain reduced states of iron and copper atoms)a. Collagen Synthesis: (structural protein, most abundant protein in mammals)i. Hydroxylation reactions requiring vitamin C are necessary for synthesis: hydroxylation provides the hydrogen bonds between three chains in collagenii. Vitamin C acts as a reducing agent, reducing the iron back to its ferrous state in the hydroxylases in the synthesis reactionb. Carnitine Synthesis: (compound essential for the transport of long-chain fatty acids) i. Vitamin C acts as a reducing agent, reducing the iron atom from the ferric to ferrous statec. Tyrosine Synthesis and Catabolismi. Functions as the preferred reductant for copperd. Neurotransmitter Synthesisi. Serves as a reducing agent to reduce molecules that get oxidized in some of the
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