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Questions and Answers
What is the ring structure attached to ribitol in the riboflavin molecule?
What is the ring structure attached to ribitol in the riboflavin molecule?
What is the energy source required for the conversion of riboflavin to its active co-enzyme forms?
What is the energy source required for the conversion of riboflavin to its active co-enzyme forms?
What is the product formed when FMN is reoxidized by molecular oxygen?
What is the product formed when FMN is reoxidized by molecular oxygen?
What is the name of the enzyme that contains FMN in the respiratory chain?
What is the name of the enzyme that contains FMN in the respiratory chain?
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How many ATP molecules are generated when FADH2 is oxidized in the electron transport chain?
How many ATP molecules are generated when FADH2 is oxidized in the electron transport chain?
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What is the cause of riboflavin deficiency in humans?
What is the cause of riboflavin deficiency in humans?
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What is the earliest sign of riboflavin deficiency?
What is the earliest sign of riboflavin deficiency?
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What is the color of the tongue in riboflavin deficiency?
What is the color of the tongue in riboflavin deficiency?
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What is the daily requirement of riboflavin for adults on sedentary work?
What is the daily requirement of riboflavin for adults on sedentary work?
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Which of the following is not a rich source of riboflavin?
Which of the following is not a rich source of riboflavin?
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What is the additional requirement of riboflavin during pregnancy, lactation and old age?
What is the additional requirement of riboflavin during pregnancy, lactation and old age?
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Which enzyme is involved in the conversion of succinate to fumarate?
Which enzyme is involved in the conversion of succinate to fumarate?
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What is the role of riboflavin in the body?
What is the role of riboflavin in the body?
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Study Notes
Structure of Riboflavin
- Riboflavin has a dimethyl isoalloxazine ring attached to a ribitol, which is the alcohol of ribose sugar.
- Riboflavin is heat stable.
Co-enzyme Activity of Riboflavin
- Riboflavin exists in tissues tightly bound to enzymes, forming flavoproteins.
- The two coenzymes of riboflavin are FMN (flavin mono nucleotide) and FAD (flavin adenine dinucleotide).
- FAD accepts two hydrogen atoms from substrate during oxidation, reducing it to FADH2.
- The two nitrogen atoms of the isoalloxazine nucleus accept the hydrogen atoms.
FAD-dependent Enzymes
- FAD-dependent enzymes are involved in various reactions, including succinate to fumarate, acyl CoA to alpha-beta unsaturated acyl CoA, xanthine to uric acid, pyruvate to acetyl CoA, and alpha ketoglutarate to succinyl CoA.
FMN-dependent Enzymes
- FMN-dependent enzymes are involved in amino acid oxidation, where FMN is reduced and then reoxidized by molecular oxygen to produce hydrogen peroxide.
- In the respiratory chain, NADH dehydrogenase contains FMN, transporting electrons in the following manner: NAD+ → FMN → CoQ.
Riboflavin Deficiency
- Riboflavin deficiency is uncommon in humans due to synthesis by intestinal flora.
- Deficiency usually accompanies other deficiency diseases, such as beriberi, pellagra, and kwashiorkor.
- Symptoms of riboflavin deficiency are confined to skin and mucous membranes, including glossitis, magenta-colored tongue, cheilosis, angular stomatitis, circumcorneal vascularization, and proliferation of bulbar conjunctival capillaries.
Dietary Sources and Daily Requirement
- Rich sources of riboflavin include liver, dried yeast, egg, and whole milk.
- Good sources include fish, whole cereals, legumes, and green leafy vegetables.
- The daily requirement of riboflavin is related to calorie intake, with adults on sedentary work requiring about 1.5 mg per day.
- Additional 0.2 to 0.4 mg/day are required during pregnancy, lactation, and old age.
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Description
Learn about the structure of riboflavin, its co-enzyme forms FMN and FAD, and its role in flavoproteins. Understand how riboflavin is converted to its active forms with the help of ATP.
