Melanin

Question 1

Describe melanin

Answer 1

-produced by melanocytes in stratum basale

-has amino acid tyrosine; bonded by the enzyme tyrosinase; happens in special vesicle (melanosome)

Question 2

What is the primary function of melanin

Answer 2

Protects keratinocyte DNA from mutations induced by UV radiation

Question 3

What is the secondary function of melanin

Answer 3

It reduces vitamin D synthesis in response to UV radiation; less calcium ion absorption and maintenance of calcium ion homeostasis within narrow range

Question 4

What does skin color depend on

Answer 4

-number of melanocytes in particular body region

-differences lead to uneven distribution of melanin

-skin tone depends on tyrosinase activity and type of melanin produces

Question 5

What are the variations of pigmentation from melanin

Answer 5

Freckles - small area of increased pigmentation; increased melanin production in local spot

Mole or nevus - area of increased pigmentation; caused by proliferation of melanocytes, not an increase in melanin production

Albinism - melanocytes fail to create tyrosinase; lack of skin pigmentation and increased risk of keratinocyte DNA damage from UV radiation