Water Soluble Vitamins - Gropper Ch 9

Question 1

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Answer 1

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Question 2

B vitamins are divided into which two functional groups?

Answer 2

1. energy releasing
   (thiamin, riboflavin, niacin, pantothenic acid, biotin, pyridoxine)
2. Hemtopoietic
   (folate, B12, B6, pantothenic acid)

Question 3

Which B vitamins are required for energy releasing activities? (6)

Answer 3

Thiamin
Riboflavin (FAD)
Niacin (NAD)
Pantothenic acid (acetyl-CoA)
biotin
B6 Pyridoxine

Question 4

What B vitamins are hematopoietic?

Answer 4

folate
B12
B6
pantothenic acid

Question 5

What is the main coenzyme form of thiamin?

Answer 5

thiamin diphosphate (TDP, which is also called thiamin pyrophosphate TPP)

Question 6

What is the main coenzyme form of riboflavin?

Answer 6

flavin adenine dinucleotide (FAD)

and

flavin mononucleotide (FMN)

Question 7

What is the main coenzyme form of niacin?

Answer 7

nicotinamide adenine dinucleotide (NAD)

and

nicotinamide adenine dinucleotide phosphate (NADP)

Question 8

What is the main coenzyme form of pantothenic acid?

Answer 8

Coenzyme A

Question 9

What is the main coenzyme form of biotin?

Answer 9

carboxybiotinyl lysine

Question 10

What is the main coenzyme form of B6?

Answer 10

pyridoxal phosphate (PLP)

Question 11

What are the main coenzyme forms of folate?

Answer 11

tetahydrofolate derivitives

5,10-methylene THF
10-formyl THF
5-formimino THF
5,10-methylenyl THF
5-methyl THF (folate trap - gets stuck in this form if B12 deficient)

Question 12

What are the coenzyme forms of B12?

Answer 12

methylcobalamin

adenosylcobalamin

Question 13

What are the main biochemical reaction that requires thiamin?

Answer 13

1. oxidative decarboxylation of alpha-ketoacids

(pyruvate dehydrogenase, branched chain keto acid dehydrogenase, alpha-ketoglutarate dehydrogenase

Question 14

What are the main physiological functions of thaimin? (2 as a coenzyme, 1 non-coenzyme)

Answer 14

1. energy transformation (oxidative decarboxylation of pyruvate, alpha-ketoglutarate, branched chain amino acids)
2. Synthesis of NADPH and pentoses in the Pentose Phosphate Pathway
3. membrane and nerve conduction (in a noncoenzyme capacity)

Question 15

What is the main biochemical function of riboflavin?

Answer 15

Flavins act as oxidizing agents because of their ability to accept hydrogen atoms

Their main biochemical function is in electron (hydrogen) transfer reactions

Question 16

Flavoproteins are required for synthesis or metabolism of which nutrients? (3)

Answer 16

1. B6 (synthesis of the coenzyme form PLP)
2. folate (synthesis 5-methyl THF)
3. choline catabolism

Question 17

What is the main biochemical function of niacin?

Answer 17

the coenzymes NAD and NADP act as hydrogen donors or acceptors (in redox reactions)

Question 18

What energy producing pathways require NAD as a cofactor? (5)

Answer 18

1. glycolysis
2. TCA cycle (oxidation of acetyl-CoA)
3. beta-oxidation of fatty acids
4. oxidation of ethanol
5. oxidative decarboxylation of pyruvate to acetyl-CoA (pyruvate dehydrogenase)

Question 19

What biosynthetic pathways require NADPH as a cofactor? (6)

Answer 19

1. fatty acid synthesis
2. cholesterol and steroid hormone synthesis
3. deoxyribonucleotide synthesis (precursors to DNA)
4. glutathione, vitamin C, and thioredoxin regeneration
5. folate coenzyme synthesis
6. proline synthesis

Question 20

What is the main biochemical function of pantothenic acid?

Answer 20

acyl transfer reactions

Question 21

What are the main functions of pantothenic acid as Coenzyme A? (5)

Answer 21

1. as acetyl-CoA holds the central position in the transformation of energy
2. pyruvate dehydrogenase requires CoA for the production of acetyl-CoA
3. Synthesis of cholesterol, bile salts, ketone bodies, fatty acids and steroid hormones requires CoA (HMG-CoA is the key intermediate in these pathways)
4. phospholipid and sphingomyelin production require CoA
5. acetylation of some proteins, sugars, and drugs (choline is acetylated to form the neurotransmitter acetylcholine)

Question 22

What is the biochemical function of biotin?

Answer 22

CO2 transfer / carboxylation reactions

Question 23

What enzymes (4) require biotin as a cofactor?

Answer 23

1. pyruvate carboxylase (converts pyruvate to oxaloacetate. Replenishes oxaloacetate for TCA cycle and needed for gluconeogenesis)
2. acetyl-CoA carboxylase (forms malonyl-CoA from acetate. Commits acetate for fatty acid synthesis.)
3. propionyl-CoA carboxylase (converts propionyl-CoA to methmalonyl-CoA. Metabolism of some amino acids and odd chain fatty acids.)
4. beta-methlcrotonyl-CoA carboxylase

Question 24

What non-coenzyme roles does biotin play?

Answer 24

biotinylation of proteins involved in gene expression (nonhistone and histone proteins)

Question 25

What is the biochemical role of B6?

Answer 25

1. transamination reactions 2. decarboxylation reactions - formation of GABA from glutamate - production of serotonin from 5-hydroxy-tryptophan - synthesis of histamine from histidine - synthesis of dopamine from tyrosine (phenylalanine) The PLP coenzyme form of B6, PLP, is associated with >100 enzymes, the majority of which are involved in amino acid metabolism

Question 26

What is the main storage site for B6?

Answer 26

muscle 75-80% of vitamin B6 stores are found in muscle 5% to 10% are found in the liver

Question 27

Vitamin B6 functions importantly in all of the following except? ``` transamination of amino acids modulation of gene expression synthesis of fatty acids glycogen breakdown heme synthesis ```

Answer 27

fatty acid synthesis

Question 28

What is the biochemical role of folate?

Answer 28

one-carbon transfer reactions

Question 29

What is the dietary folate equivalent (DFE) of folate from food and folic acid from supplement or enriched foods consumed with a meal?

Answer 29

folic acid from supplements is more easily absorbed than natural folate from food. 1 DFE folate = 0.5 DFE from folate taken with meals

Question 30

What are the physiological functions of B12?

Answer 30

1. methylation of homocysteine to methionine 2. conversion of methlmalonyl-CoA to succinyl-CoA (metabolism of methionine, isoleucine, threonine, and odd chain fatty acids)

Question 31

Intakes of about _________ of vitamin C per day have been shown to maximize the body pool?

Answer 31

100 to 200 mg

Question 32

Vitamin C has positive effects on? frequency of colds cardiovascular disease eye health prevention of skin cancer

Answer 32

prevention of skin cancer