Biotin - Vitamin B7

Biotinidase

Which enzyme is responsible for liberating free biotin from biocytin?

Carboxylation reactions

Biotin functions as a coenzyme for which type of biochemical reactions?

Sodium-dependent multivitamin transporter (SMVT)

Which transporter is primarily responsible for biotin uptake in the small intestine?

Co2

In biotin-dependent enzymatic reactions, what molecule serves as the donor of the carboxyl group?

Gluconeogenesis

A genetic deficiency in holocarboxylase synthetase would directly impair which metabolic pathway?

Propionic acidemia

Which of the following metabolic disorders is most commonly associated with biotin deficiency?

High-fat ketogenic diet

Which of the following conditions is most likely to increase biotin requirements?

Alopecia and dermatitis

Which symptom is most characteristic of biotin deficiency?

Gene silencing and chromatin remodeling

Biotinylation of histones is associated with:

They contain avidin, which binds biotin and prevents absorption

Why do raw egg whites lead to biotin deficiency when consumed in large amounts?

Pyruvate dehydrogenase

A 30-year-old man presents with chronic fatigue, muscle weakness, and elevated levels of propionyl-CoA and methylcrotonyl-CoA in his bloodwork. Which enzyme is most likely impaired?

Inhibition of holocarboxylase synthetase

A 35-year-old woman on long-term anticonvulsant therapy develops hair loss,
depression, and dermatitis. Which mechanism best explains her symptoms?

Biotin attachment to carboxylases

A newborn presents with metabolic acidosis, hypoglycemia, and organic aciduria. A mutation in the HLCS gene is identified. Which biochemical function is most likely impaired?

Impaired biotin recycling and functional deficiency

A 60-year-old man with chronic kidney disease is found to have elevated levels of 3-hydroxyisovaleric acid (3-HIA) in his urine. This suggests:

Biotin deficiency due to inadequate dietary intake

A critically ill patient in the ICU is receiving total parenteral nutrition (TPN) without biotin supplementation. After several weeks, the patient develops muscle weakness, fatigue, and a red rash around the eyes. What is the most likely explanation?

False

Biotin deficiency commonly presents with megaloblastic anemia

True

Biotin is required for the metabolism of odd-chain fatty acids and branched-chain amino acids.

True

Avidin in raw egg whites is a competitive inhibitor of the sodium-dependent multivitamin transporter (SMVT).

Biotinylation of histones is an epigenetic modification that influences gene
expression.

False

Biotin deficiency can lead to disruptions in fatty acid metabolism, resulting in an accumulation of odd-chain fatty acids and branched-chain amino acid metabolites.