Vitamin C Quiz

Vitamin C toxicity causes dose dependent [blank_start]diarrhea and bloating[blank_end] in gram doses, false negative [blank_start]occult blood in stool,[blank_end] iron [blank_start]overabsorption[blank_end], hyperoxaluria, [blank_start]hyperoxalemia[blank_end] in dialysis patients, and hemolysis in patients with [blank_start]glucose-6-phosphate dehydrogenase[blank_end] deficiency

The Recommended Daily Allowance of Vitamin C is:

The four H's of vitamin C deficiency are [blank_start]Hemorrhage[blank_end], [blank_start]Hyperkeratosis[blank_end], [blank_start]Hyperchondriasis[blank_end], and [blank_start]Hematologic[blank_end] Abnormalities

Vitamin C is a cofactor for conversion of [blank_start]dopamine[blank_end] to norepinephrine via the enzyme [blank_start]dopamine monooxygenase[blank_end]. Vitamin C helps keep [blank_start]Copper[blank_end] in the reduced form so the reaction can continue.

[blank_start]Vitamin C[blank_end] is a cofactor for the creation of serotonin. [blank_start]Tryptophan[blank_end] is first converted to [blank_start]hydroxytryptophan[blank_end] via the enzyme [blank_start]tryptophan monooxygenase[blank_end]. [blank_start]vitamin C[blank_end] is a cofactor and it helps keep [blank_start]folate[blank_end] in the reduced form. [blank_start]Iron[blank_end] is also a cofactor for this reaction. [blank_start]Hydroxytryptophan[blank_end] is then changed to serotonin.

Vitamin C is a key component of amino acid metabolism. Vitamin C is a cofactor in the [blank_start]hydroxylation[blank_end] of phenylalanine. The enzyme that catalyzes this conversion is [blank_start]phenylalanine monooxygenase[blank_end]. This enzyme is also dependent on [blank_start]Iron[blank_end] and [blank_start]folate[blank_end]. It is thought that vitamin C keeps [blank_start]folate[blank_end] in the reduced form for the reaction to continue. The product of this reaction is [blank_start]tyrosine[blank_end], another amino acid. [blank_start]Tyrosine[blank_end] can then go on to form [blank_start]L-dopa[blank_end], which is converted to [blank_start]dopamine[blank_end]. [blank_start]Dopamine[blank_end] is then converted to [blank_start]Norepinephrine[blank_end] by [blank_start]dopamine monooxygenase[blank_end]. This reaction also uses vitamin C as a cofactor and is dependent on [blank_start]Copper[blank_end]. Vitamin C is thought to keep [blank_start]copper[blank_end] in the reduced form so the reaction can continue. [blank_start]Tyrosine[blank_end] can also go on to form [blank_start]homogentisate[blank_end], which is a precursor to acetyl CoA. Vitamin C is necessary for the conversion of [blank_start]homogentisate[blank_end] to acetyl CoA, as well as [blank_start]Iron[blank_end].

Vitamin C is important for the formation of carnitine, an important component of [blank_start]fat[blank_end] metabolism. The precursor to carnitine is [blank_start]trimethyllysine[blank_end], which is [blank_start]hydroxylated[blank_end] with the help of Vitamin C and [blank_start]Iron[blank_end]. Again, it is thought that Vitamin C helps keep [blank_start]Iron[blank_end] in the reduced form in order for the reaction to continue. [blank_start]Trimethyllysine[blank_end] is hydroxylated to [blank_start]3-OH trimethyllysine[blank_end], and in the process [blank_start]CO2[blank_end] is created and alpha-keto-glutarate is converted to [blank_start]succinate[blank_end]. The enzyme that catalyzes this reaction is [blank_start]trimethyllysine hydroxylase[blank_end]. [blank_start]3-OH trimethyllysine[blank_end] can then continue on to make carnitine through several other steps. Vitamin C is also a cofactor for [blank_start]4-butyrobetaine hydroxylase[blank_end], another enzyme needed for the final steps of carnitine synthesis.

Vitamin C is an important cofactor in the [blank_start]hydroxylation[blank_end] of various amino acids, especially [blank_start]lysine[blank_end] and [blank_start]proline[blank_end] in the synthesis of collagen.

The hydroxylation of proline and [blank_start]lysine[blank_end] is catalyzed by the enzyme [blank_start]prolyl[blank_end] or [blank_start]lysyl[blank_end] 3 or 4-OH [blank_start]hydroxylase[blank_end]. The product of this reaction is 3- or 4- [blank_start]hydroxyproline[blank_end] or [blank_start]hydroxylysine[blank_end]. The overall category of this type of enzyme is a [blank_start]dioxygenase[blank_end]. Vitamin C is a cofactor in this reaction and it keeps [blank_start]Iron[blank_end] in the reduced form so the reaction can continue.

Vitamin C is a cofactor for: 1. [blank_start]collagen[blank_end] synthesis, 2. car[blank_start]nitine[blank_end] synthesis, 3. cate[blank_start]cholamine[blank_end] synthesis, 4. peptide [blank_start]amidation[blank_end], 5. [blank_start]tyrosine[blank_end] metabolism

Vitamin C [blank_start]enhances[blank_end] the absorption of [blank_start]non-heme[blank_end] iron. It also reduced itraluminal iron from Fe [blank_start](III)[blank_end] to Fe [blank_start](II)[blank_end] which is absorbed more easily. Vitamin C helps form [blank_start]soluble iron complexes[blank_end] in the [blank_start]duodenum[blank_end] which are absorbed easily. Vitamin C counteracts [blank_start]phytates[blank_end] and [blank_start]tannins[blank_end] which form [blank_start]insoluble[blank_end] iron complexes.

Vitamin C donates two [blank_start]electrons[blank_end] and two protons in reactions, which is why it is an [blank_start]antioxidant.[blank_end] Vitamin C reacts with [blank_start]peroxyl[blank_end] radicals which can oxidize LDL and RBCs.

Large doses of Vitamin C are excreted [blank_start]unmetabolized[blank_end] in the urine.

L-ascorbic acid is reduced to L-[blank_start]dehydroascorbic[blank_end] acid by [blank_start]dehydroascorbate reductase[blank_end]. L-dehydroascorbate can be converted to 2,3 [blank_start]diketogulonic acid[blank_end], which can then be broken down into [blank_start]oxalic acid[blank_end] and [blank_start]threonic acid[blank_end], or converted to 5 carbon sugars such as [blank_start]xylose[blank_end] which can go onto other metabolic pathways.

The vitamin C pool varies from 1.4 to [blank_start]5[blank_end] grams. The [blank_start]adrenal[blank_end] gland has the highest concentration of Vitamin C, with 30-40 mg/ 100 grams of tissue. The [blank_start]pituitary[blank_end] and [blank_start]retina[blank_end] are also high in vitamin C. Some is found in the [blank_start]liver[blank_end], [blank_start]lungs[blank_end], [blank_start]pancreas[blank_end] and [blank_start]leukocytes[blank_end]. A small amount is found in the [blank_start]kidney[blank_end], [blank_start]muscle[blank_end], and [blank_start]RBC[blank_end]s. The tissue level of vitamin C is much greater than the plasma level of vitamin C. Both amounts are very dependent on vitamin C intake.

Vitamin C is primarily absorbed through [blank_start]active[blank_end] transport. Some is absorbed by [blank_start]simple diffusion[blank_end]. it occurs in the [blank_start]distal[blank_end] part of the [blank_start]small[blank_end] intestines. Absorption decreased with [blank_start]increased[blank_end] intake. An average of [blank_start]90[blank_end]% of vitamin C is absorbed from the diet. Vitamin C is transported in the plasma as a [blank_start]free anion[blank_end].

The enzyme that humans lack that plants and animals use to convert glucose to vitamin C is [blank_start]gulonolactone oxidase[blank_end].