Vitamin B7

Question 1

What type of vitamin is biotin?

Answer 1

Sulfur-containing B-complex vitamin

Question 2

What is another name for biotin?

Answer 2

Anti-egg white injury factor or vitamin H or vitamin B7

Question 3

Biotin functions as a coenzyme in what type of reactions?

Answer 3

Carboxylation reactions

Question 4

Who observed the egg-white injury in rats?

Answer 4

Boas in 1927

Question 5

What symptoms were observed in rats fed raw egg white?

Answer 5

Dermatitis, nervous manifestations, growth retardation

Question 6

Did cooked egg white cause the same symptoms as raw?

Answer 6

No

Question 7

What causes egg-white injury in rats and chicks?

Answer 7

Presence of anti-vitamin in egg white

Question 8

What is the anti-vitamin in raw egg white called?

Answer 8

Avidin

Question 9

What does avidin bind with to cause biotin deficiency?

Answer 9

Biotin

Question 10

What is biotin�s role in relation to avidin?

Answer 10

Anti-egg white injury factor

Question 11

What type of compound is biotin chemically?

Answer 11

Heterocyclic sulfur-containing monocarboxylic acid

Question 12

What rings are fused in the biotin structure?

Answer 12

Imidazole and thiophene

Question 13

What side chain is present in biotin?

Answer 13

Valeric acid side chain

Question 14

To what amino acid is biotin covalently bound in enzymes?

Answer 14

Lysine

Question 15

What compound is formed by biotin bound to lysine?

Answer 15

Biocytin(biotin-enzyme complex)

Question 16

What is biocytin regarded as?

Answer 16

Coenzyme form of biotin

Question 17

What is biotin a carrier of in reactions?

Answer 17

CO2

Question 18

In what reaction is biotin’s role studied in detail?

Answer 18

Pyruvate to oxaloacetate by pyruvate carboxylase

Question 19

What group is biotin linked to in the enzyme?

Answer 19

E-amino group of lysine

Question 20

What is the active form of the enzyme with biotin called?

Answer 20

Holoenzyme

Question 21

What does ATP provide in the biotin reaction?

Answer 21

Energy

Question 22

What high-energy complex is formed in biotin-dependent carboxylation?

Answer 22

Carboxybiotin-enzyme complex

Question 23

What does the carboxybiotin-enzyme complex do?

Answer 23

Transfers CO2 to pyruvate

Question 24

What is formed from pyruvate after carboxylation?

Answer 24

Oxaloacetate

Question 25

What are two metabolic pathways biotin is involved in?

Answer 25

Gluconeogenesis and citric acid cycle

Question 26

Which enzyme converts pyruvate to oxaloacetate?

Answer 26

Biotin-dependent pyruvate carboxylase

Question 27

Why is oxaloacetate essential?

Answer 27

For glucose synthesis and citric acid cycle operation

Question 28

What is the first step in fatty acid synthesis?

Answer 28

Carboxylation of acetyl CoA

Question 29

What enzyme carboxylates acetyl CoA?

Answer 29

Acetyl CoA carboxylase

Question 30

What is the product of acetyl CoA carboxylation?

Answer 30

Malonyl CoA

Question 31

Where is propionyl CoA produced from?

Answer 31

Metabolism of valine, isoleucine, threonine and odd-chain fatty acids

Question 32

What is needed for metabolism of propionyl CoA?

Answer 32

Biotin

Question 33

What is propionyl CoA converted to?

Answer 33

Methylmalonyl CoA

Question 34

What enzyme converts propionyl CoA to methylmalonyl CoA?

Answer 34

Propionyl CoA carboxylase

Question 35

In which amino acid�s metabolism is biotin involved?

Answer 35

Leucine

Question 36

What compound is formed in leucine metabolism with biotin?

Answer 36

Beta Methylglutaconyl CoA

Question 37

What is the precursor of ?-Methylglutaconyl CoA?

Answer 37

?-Methylcrotonyl CoA

Question 38

Do all carboxylation reactions require biotin?

Answer 38

No

Question 39

Name a carboxylation reaction that doesn�t require biotin

Answer 39

Formation of carbamoyl phosphate in urea cycle

Question 40

Name another biotin-independent CO2 incorporation

Answer 40

CO2 incorporation in purine synthesis

Question 41

What is the recommended dietary allowance of biotin?

Answer 41

100�300 �g per day for adults

Question 42

Where is biotin synthesized in the body?

Answer 42

By intestinal bacteria

Question 43

Is the extent of biotin synthesis contribution known?

Answer 43

No, it is not clearly known

Question 44

Is biotin widely distributed in food?

Answer 44

Yes

Question 45

Name rich sources of biotin

Answer 45

Liver, kidney, egg yolk, milk, tomatoes, grains

Question 46

List symptoms of biotin deficiency

Answer 46

Anemia, appetite loss, nausea, dermatitis, glossitis

Question 47

Name other symptoms of biotin deficiency

Answer 47

Depression, hallucinations, muscle pain

Question 48

Why is biotin deficiency uncommon?

Answer 48

Due to wide food distribution and intestinal synthesis

Question 49

What drug class can destroy gut flora and cause deficiency?

Answer 49

Sulfonamides

Question 50

What food in excess can cause biotin deficiency?

Answer 50

Raw egg whites

Question 51

What protein in raw egg whites causes deficiency?

Answer 51

Avidin

Question 52

How does avidin cause deficiency?

Answer 52

Binds biotin and blocks absorption

Question 53

How many raw eggs daily can cause deficiency in humans?

Answer 53

About 20

Question 54

Can occasional raw egg intake cause deficiency?

Answer 54

No

Question 55

Name two biotin antagonists

Answer 55

Desthiobiotin and biotin sulfonic acid