Exam 2, biotin

Question 1

biotin structure

Answer 1

two pentoses together with a chain

Question 2

biocytin

Answer 2

biotin binds with lysine to form biocytin

Question 3

main function of biotin

Answer 3

CO2 carrier in macronutrient metabolism
*responsible for carboxylating

Question 4

biotin-dependent carboxylases

Answer 4

1. pyruvate carboxylase
2. acetyl co a carboxylase
3. propionyl co a carboxylase

Question 5

metabolic processes that require biotin

Answer 5

1. gluconeogenesis: pyruvate carboxylase
2. lipogenesis: ACoA carboxylase

Question 6

how does the biotin cycle work

Answer 6

-biotinidase frees biotin bound to protein
-biotin then attaches to apocarboxylases
-forms holocarboxylases, activate to participate in metabolism
-once they are used they go through proteolytic degradation -> biotin bound to peptides or free
-cycle repeats itself

Question 7

secondary function of biotin

Answer 7

binds to histones and affects gene expression

Question 8

how does biotin affect gene expression? * how prevalent is this effect?

Answer 8

> 2000 genes use biotin for expression of cell signaling & cell cycle
-Biotin binds to histones (proteins that package DNA); thus, altering DNA replication and transcription.

Question 9

deficiency of biotin

Answer 9

-alopecia (hair loss9
-inflammation of membrane covering eye
-nervous problems
-can be created by drinking raw egg white because avidin protein binds to biotin

Question 10

who is at risk of biotin deficiency

Answer 10

-alcoholics
-IBS
-lack of HCl
-pregnant women and infants (increased cell division)
-genetic disorders involving biotinidase
-certain drugs limit absorption

Question 11

deficiency symptoms

Answer 11

-brittle nails
-hair loss
-loss of appetite
-neurological symptoms
-conjuntivitis

Question 12

photo of a child with inflammation in eyelid/ looks dark

Answer 12

biotinidase deficiency