Exam 1

Question 1

Magnesium enhances which reaction?

Answer 1

Flavin mononucleotide production (FMN) from riboflavin

Question 2

1.1 mg is the adult female RDA for which nutrient?

Answer 2

Thiamin

Question 3

What is the measured by the tryptophan load test?

Answer 3

B6 deficiency

Question 4

The vitamin C UL was based on which condition?

Answer 4

Osmotic diarrhea

Question 5

Tea ingestion impacts the absorption of which vitamin?

Answer 5

Thiamin

Question 6

Define NE (niacin equivalent)

Answer 6

1 mg niacin = 60 mg tryptophan

Question 7

Discuss how niacin status is impacted by pregnancy.

Answer 7

Niacin is involved with ADP-ribosylation reactions such as DNA replcation.

Question 8

Explain why antacids alter riboflavin absorption rates.

Answer 8

Riboflavin enters the stomach bound to protein in its phosphorylated form and must be freed. HCl in the stomach helps denature the protein thus freeing riboflavin. Antacids create a less acidic environment, which reduces absorption.

Question 9

Explain the polymorphism thats linked to low vitamin C status?

Answer 9

Mutation that occurs on the SVCT1 (binding site for vit C). Or lack of gulonolactone oxidase.

Question 10

Discuss likely reason why (1) vitamin C and (2) vitamin B6 have high deficiency rates (6%-10% of americans)?

Answer 10

Vitamin C - easily oxidized; lower status in smokers; inverse relationship between weight and absorption; more processed foods, polymorphism in SVCT1; saturation kinetics (mega dosing C or too much glucose);
Vitamin B6 - large elderly population; poor diet; processed foods; relatively low bioavailability (Zn deficient, caught up in fibers, not high in diet); Mg, Zn or B2 deficient

Question 11

Discuss two populations that may benefit from vitamin “megadosing”. Use two different vitamins for your examples and provide the scientific evidence for these benefits.

Answer 11

Diabetics and Vitamin C - vitamin C and glucose use the same transporter for absorption. Uncontrolled diabetes results in high levels of glucose in the blood. Glucose wins out over vitamin C in terms of absorption and can lead to a vitamin C deficiency. Therefore, diabetics would benefit from a vit c supplement. Individuals w/ an unhealthy mucosa (Chrons, GI issues, IBS) and niacin: Niacin is passively diffused so an unhealthy mucosa can disrupt absorption and lead to a deficiency.
Chemo drugs interfere with B-vitamin integrity. Cancer Pt may benefit from supplements
Niacin helps reduce LDL, TG, and increases HDL BUT increases blood glucose and could lead to diabetes.

Question 12

Explain the nutrient deficiency linked to elevated lactic acid concentrations. You must discuss chemical reactions in your answer.

Answer 12

Thiamin is necessary in the decarboxylation of pyruvate to make acetyl-CoA. Without thiamin, pyruvate gets converted to lactic acid. Lactic acid build up can be dangerous to ones health in ways such as damage to the brain. Shorter periods of lactic acid conversion may result in feeling tired.

Question 13

identify the vitamin deficiency for each symptom below. Connect the symptom, with a vitamin function in each instance

Answer 13

Muscle weakness and neuropathy: Thiamin (Dry Beriberi) -> -Muscle weakness and wasting: ATP production in Kreb cycle is slowed down because pyruvate cannot be converted to acetyl-CoA. Peripheral neuropathy: not enough energy for brain, lactic acid killing brain cell
GI tract changes leading to vomiting and diarrhea: Niacin (Pellagra) -> NADPH -> biosynthetic pathways (important for growth and maintenance of tissues)
Inflamed tongue: Riboflavin (Cheilosis) -> cofactor for many rxns; FAD and FMN are coenzymes in many important metabolic pathways (TCA); also help metabolize other vitamins - Important for optimal efficiency of lots of micronutrients -> can lead to a hodgepodge of issues

Question 14

In general, what is the function of the nutrients listed below ( you need to discuss chemical reactions)

Answer 14

Vitamin C: reducing agent -> donates electrons
Niacin (B1): decarboxylation - removes -COOH group
Vitamin B6: Attached to an enzyme, shift base (breaks N=N bond to allow aa to attach) allows it to move and attach to an amino acid. Enzyme in the presence of the amino acid will determine reaction type.

Question 15

Discuss the excretion process for clearing excess vitamin from blood for each nutrient below

Answer 15

Vitamin C: excreted in urine as oxalate (stone former)
Niacin: methylated NMN and then excreted in urine; liver tests blood for excess
Vitamin B6: liver will test blood for B6 levels. If excess then will excrete in urine as 4-PA. If megadosing will be excreted as PN or 5-PA.
Thiamin: excreted in urine

Question 16

Compare/contrast the cofactor/coenzyme function of these 3 vitamins. Be very clear on how the vitamin promotes enzyme action.

Answer 16

Vitamin B6: PLP decarboxylating amino acid to make Niacin using schiff bridge, PLP connect with amino acid and destabilize the amino acid structure.
Vitamin C: ascorbic acid–reducing agents like to give out Hydrogen in collagen synthesis, ascorbic acid gave it Hydrogen to Fe3+ to make Fe2+ which is what we need for enzyme action.
Riboflavin: FAD convert to pyruvate to make acetyl coA by oxidizing the reduced form of trans-acetylase in order to create ATP

Question 17

How are glucose and ascorbic acid linked? How are glucose and dehydroascorbic acid linked? why are diabetics often low in Vitamin C?

Answer 17

derived from glucose

Question 18

What is the role of RCP? When are concentration high- and when are they low?

Answer 18

RCP is used to transfer riboflavin during times of high metabolic need or growth. Concentrations are typically high during pregnancy. If you’re not growing or under stress, then RCP will not be high.