B-Complex Vitamins

Question 1

Most B vitamins are ________ in ________ ___________ __________

Answer 1

coenzymes; cellular enzyme metabolism

Question 2

General B-complex deficiency symptoms

Answer 2

-loss of appetite (anorexia)
-poor growth
-emaciation
-nerve related disorders
-dermatitis
-anemia

Question 3

Vitamin B1

Answer 3

Thiamine

Question 4

What is the principle role of Thiamine?

Answer 4

part of the coenzyme cocarboxylase (TPP)
-TPP is the coenzyme for at least 24 enzyme systems

Question 5

Thiamine is closely related to _______ ________

Answer 5

Lipoic acid

Question 6

Lipoic acid

Answer 6

an essential component of a “multienzyme” system which is involved in the oxidative decarboxylation of keto acids

Question 7

What occurs with pyruvic acid before its entrance into the TCA cycle?

Answer 7

it must be decarboxylated and then combined with coenzyme A to form acetyl CoA

Question 8

What happens in the absence of Thiamine?

Answer 8

reactions do not proceed at a normal rate so pyruvic acid and lactic acid accumulate in the blood and tissues
-this increase in acids is responsible for deficiency symptoms in metabolically active tissue like muscle and nerve

Question 9

Beriberi

Answer 9

-thiamine deficiency disease in humans
-extensive damage to nervous and cardiovascular systems
-severe muscle wasting (dry beriberi
-edema (wet beriberi)

Question 10

Polyneuritis

Answer 10

-Thiamine deficiency disease
-in birds
-accumulation of intermediates of CHO metabolism
-a peripheral nerve degeneration as evidenced by the breakdown of the myelin sheaths of the nerve fibers

Question 11

Thiamine deficiency symptoms

Answer 11

-beriberi
-polyneuritis
-soft muscles
-anorexia or loss of appetite
-weight loss
-bradycardia (reduced heart rate) and enlargement of heart

Question 12

Thiamine requirements are influenced by

Answer 12

carbohydrate intake and caloric intake

Question 13

Thiamine is readily destroyed by ________ in the presence of moisture

Answer 13

heat (cooking)

Question 14

Thiamin deficiency in North America is largely associated with…

Answer 14

chronic alcoholism

Question 15

Where is Thiamine absorbed?

Answer 15

small intestine

Question 16

What happens to thiamine after it is absorbed?

Answer 16

carried to the liver and phosphorylated to form TPP

Question 17

Where is thiamine stored?

Answer 17

it is not stored and must have a daily intake (except for in the pig)

Question 18

What is thiamine’s role in ruminants and horses?

Answer 18

-in a functional rumen bacterial synthesis of B1 is adequate
-in the cecum and LI of the horse bacterial synthesis occurs
-synthesis is not adequate for nutritional needs alone, dietary intake is still necessary

Question 19

Pyrithiamine

Answer 19

-antivitamin of thiamine
-competes with thiamine for incorporation into the enzymes thus rendering the enzyme inactive

Question 20

Chastek paralysis

Answer 20

-in foxes
-due to an antagonistic action of thiaminase
-similar to “bracken fern poisoning” in horses

Question 21

Thiamine sources

Answer 21

-mainly from plants
-yeasts (richest)
-molds
-leaves of grasses
-germ of cereal grains
-seed coats of grains
-pork has 100x the amount in beef

Question 22

Vitamin B2

Answer 22

riboflavin

Question 23

What 2 coenzymes does riboflavin act as

Answer 23

-FMN - flavin mononucleotide (1 phosphate group)
-FAD - flavin adenine dinucleotide (2 phosphate groups)

Question 24

What are the flavin coenzymes concerned with?

Answer 24

donating and accepting H atoms
-FAD function with the enzyme succinic dehydrogenase

Question 25

What other enzymes is FAD a constituent of?

Answer 25

-D-amino acid oxidase -glycine oxidase -xanthine oxidase (purine to uric acid)

Question 26

What is different about the symptoms of riboflavin deficiency to thiamine deficiency?

Answer 26

it is not possible to relate the symptoms to the biochemical roles of riboflavin

Question 27

Riboflavin deficiency symptoms

Answer 27

-decrease growth -alopecia or hair loss in rats -opaque cornea or cataracts in humans -curled toe paralysis in chicks -low egg production and hatchability -skin and eye symptoms in man

Question 28

What are the skin and eye symptoms of riboflavin deficiency in humans?

Answer 28

-cheilosis = roughened skin and furrows around the mouth -dermatitis = due to overactivity of sebaceous or oil glands and results in waxy dermatitis of eyes, ear lobes, and mouth -corneal vascularization = due to increase blood vessels in the eye

Question 29

Where is riboflavin phosphorylated?

Answer 29

in the intestinal wall

Question 30

After phosphorylation what happens to riboflavin?

Answer 30

it is carried by the blood to the cells of the tissues where it occurs as the phosphate or as a flavoprotein

Question 31

Where is riboflavin stored?

Answer 31

storage is small and excessive intakes are rapidly excreted in urine

Question 32

Sources of riboflavin

Answer 32

-yeast (richest) -milk -leafy portions of plants like alfalfa -eggs, liver, heart, kidney, and meat muscle (richest animal products) -whey and distiller's solubles

Question 33

What/Who synthesizes riboflavin?

Answer 33

-higher plants -yeasts -fungi -some bacteria -ruminants synthesize inadequate amounts -horses synthesize inadequate amounts in cecum

Question 34

Vitamin B6

Answer 34

pyridoxine

Question 35

What results in substantial loss of the 3 pyridoxine compounds?

Answer 35

sterilization of milk

Question 36

Three forms of vitamin B6

Answer 36

-pyridoxine -pyridoxal -pyridoxamine

Question 37

What are the active forms of vitamin B6

Answer 37

pyridoxal phosphate and pyridoxamine phosphate (pyridoxal is the most active)

Question 38

Where are the forms of B6 phosphorylated?

Answer 38

in the liver after absorption (once phosphorylated, interconversion is possible)

Question 39

What does pyridoxal phosphate mainly function as?

Answer 39

a coenzyme in several enzyme systems concerned with protein/amino acid metabolism

Question 40

Pyridoxal phosphate is necessary in the process of ___________

Answer 40

transamination

Question 41

Transimination

Answer 41

a process that involves the transfer of the amino group to keto acids -most abundant catalyze transamination of glutamic acid to oxaloacetic and pyruvic acids

Question 42

Pyridoxal phosphate is involved in ______________ reactions

Answer 42

decarboxylation -serves as a coenzyme (codecarboxylase) which decarboxylates several amino acids -more abundant in microorganisms than animal tissues

Question 43

B6 is involved in the synthesis of ________ from ___________

Answer 43

niacin from tryptophan

Question 44

In the absence of B6 what forms instead of niacin?

Answer 44

xanthurenic acid is formed and excreted in the urine -level of this metabolite in urine can be used as an indicator of B6 nutrition

Question 45

What are the two antivitamins of B6?

Answer 45

-desoxypyridoxine -isoniazid (drug used in the treatment of tuberculosis) -compete with B6 for the active site on the apoenzyme

Question 46

Vitamin B6 deficiency symptoms

Answer 46

-growth failure -acrodynia (dermatitis) in rats -urinary calculi (especially in cattle) -anemia in dogs, pigs, and rats -convulsions or epileptic seizures -slow growth and suppressed appetite

Question 47

Acrodynia

Answer 47

-dermatitis of tails, ears, mouth, and paws accompanied by an edema -the edema distinguishes acrodynia from dermatitis of essential fatty acid deficiency

Question 48

Urinary calculi

Answer 48

-due to defect in glycine metabolism -high insoluble Ca oxalate precipitates out as "stones" in kidney and urinary tract

Question 49

What causes the anemia caused by vitamin B6?

Answer 49

inability to condense glycine with succinyl CoA to form a-amino-B-ketoadipic acid which is the initial step in heme synthesis so microcytic hypochromic anemia results

Question 50

Sources of B6

Answer 50

-yeast -liver -muscle meat -milk -cereal grains -food supply is usually so rich in B6 that practical rations are very unlikely to cause deficiency