Vit C

Question 1

Ascorbic Acid/Ascorbate

Answer 1

Water soluble vit
Required as an essential nutrient
Requirements increased during illnes, stress, injury, old age, smoking
Richest source are fruits and vegetables

Question 2

Metabolic Role of Ascorbate

Answer 2

Co-factor in the synthesis of collagen (connective tissue)

Proline +O2+ a-ketoglutarate –> [proline hydroxylase]+[Ascorbate] –> Hydroxyproline +CO2 +Succinate

Hydroxyproline stabilises the collagen triple helix and by forming intra-strand hydrogen bonds

Abnormal collagen fibers result when there is insufficient hydroxylation. These strands are unstable and contribute to skin lesions and blood vessel fragility seen in scuvy

Question 3

How is Ascorbate Working

Answer 3

Ascorbate reduce the Ferric iron (Fe3+) on Proline
Hydroxylase –> (Fe2+), activate the enzyme for Proline Hydroxylation

Ascorbate osidised to Dihydro- ascorbate

Question 4

Ascorbic Acid as an antioxidant

Answer 4

[reduction] Ascorbate –> Semi-dehydro-ascorbyl radical –> dehydroascorbate

Question 5

Ascorbate as a pro-oxidant

Answer 5

The Fenton Reaction

Question 6

Function of Folic Acid

Answer 6

One-carbon metabolism

Nucleic acid metabolism

Amino acid metabolism

Question 7

Folic Acid One-carbon metabolism

Answer 7

Folate coenzymes act as acceptors and donors of one-carbon units in a variety of reactions critical to the metabolism of nucleic acids and amino acids

Question 8

Folic Acid Nucleic acid metabolism

Answer 8

Folate coenzymes play a vital role in DNA metabolism through two different pathways:

1) The synthesis of DNA
2) required for the synthesis of Methionine (required for methylation of DNA

Question 9

Folic Acid Amino acid metabolism

Answer 9

Methionine synthesis from homocysteine requires a folate coenzyme as well as a vitamin B12 dependent enzyme

Question 10

significant of Homocysteine [sulfur amino acid] Metabolism

Answer 10

Important for the synthesis of sulphur containing amino
acids

remethylation of Homocysteine to methionine, requires folate, vitamin B12 & methionine synthase

Folic acid and Vitamin B12 function together to ensure the optimum activity of methionine synthase.

If absent can lead to an accumulation of homocysteine, which has been associated with increased risk of CVD

Question 11

Nutrient Interactions:

Folate, Riboflavin and Vitamin B12

Answer 11

slide 82

Question 12

Folic Acid Deficiency

Answer 12

Homocysteine increase
Megaloblastic anaemia (fewer but larger red blood cells)

Question 13

Folic Acid Deficiency risk factors

Answer 13

Alcoholism
Pregnancy
Cancer
Drugs

Question 14

Folic Acid and Disease

Answer 14

Neural tube defects
Birth defects, including certain heart defects and limb malformations
Cardiovascular diseases
Colorectal cancer
Breast cancer
Alzheimer’s disease and cognitive impairment

Question 15

Folic Acid and Neural Tube Defects

Answer 15

Adequate folate is critical because of its roles in DNA and RNA synthesis during rapid dell division

Neural tube defects (NTD) result in either anencephaly or spina bifida

Occur between the 21st and 27th days after conception

The risk of NTD in US prior to fortification of foods with folic acid was estimated to be 1: 1000 pregnancies

60% to 100% reductions in NTD cases when women consumed folic acid supplements in addition to a varied diet about 1 month before and 1 month after conception