Vitamin B2 Flashcards by Udayan Ginjupalli

Q

What reactions does riboflavin participate in?

A

Cellular oxidation-reduction reactions

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Q

What is the coenzyme role of riboflavin?

A

Part of FMN and FAD in redox reactions

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Q

What is the ring structure in riboflavin called?

A

6,7-dimethyl isoalloxazine

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Q

What is isoalloxazine attached to in riboflavin?

A

D-ribitol by a nitrogen atom

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Q

What is ribitol derived from?

A

Ribose with aldehyde group reduced to alcohol

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Q

What is the chemical formula change from ribose to ribitol?

A

CHO to CH2OH

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Q

Is riboflavin heat stable?

A

Yes

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Q

Is riboflavin light stable?

A

No

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Q

What does riboflavin convert to under UV light?

A

Lumiflavin

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Q

What is a feature of lumiflavin?

A

Yellow fluorescence

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Q

What are lactoflavin, hepatoflavin and ovoflavin?

A

Structurally identical to riboflavin

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Q

What are the two coenzyme forms of riboflavin?

A

FMN and FAD

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Q

What is ribitol linked to in FMN?

A

Phosphate

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Q

How is FAD formed?

A

AMP moiety is transferred from ATP to FMN

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Q

What is the functional unit in FMN and FAD?

A

Isoalloxazine ring

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Q

What does isoalloxazine ring do?

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A

Accepts two hydrogen atoms with electrons

Q

What are the reduced forms of FMN and FAD?

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A

FMNH2 and FADH2

Q

What kind of reactions do FMN and FAD undergo?

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A

Identical reversible hydrogenation reactions

Q

What are enzymes using FMN or FAD called?

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A

Flavoproteins

Q

How do coenzymes bind to proteins in flavoproteins?

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A

Tightly by non-covalent or covalent bonds

Q

What is the name for flavoproteins with metal atoms?

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A

Metalloflavoproteins

Q

What metals can metalloflavoproteins contain?

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A

Iron, molybdenum

Q

What metabolic pathways involve FMN and FAD?

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A

Carbohydrate, lipid, protein and purine metabolism

Q

What chain do FMN and FAD play a role in?

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A

Electron transport chain

What are rich sources of riboflavin?

Milk, milk products, meat, eggs, liver, kidney

What are moderate sources of riboflavin?

Cereals, fruits, vegetables, fish

What is cheilosis?

Fissures at the corners of the mouth

What is glossitis?

Smooth and purplish tongue

What is a skin symptom of riboflavin deficiency?

Dermatitis

Is isolated riboflavin deficiency common?

No

Who is more susceptible to riboflavin deficiency?

Chronic alcoholics

How can riboflavin deficiency be assessed?

Assay of glutathione reductase in erythrocytes

What is glutathione reductase assay used for?

Assessing riboflavin deficiency

What is an antimetabolite of riboflavin?

Galactoflavin

What does galactoflavin act as?

Antimetabolite of riboflavin