The "How Does Melanin Protect Cells?" content opens below the video.
HOW DOES MELANIN PROTECT CELLS?
Where Are Melanosomes Found in Skin Cells?
Melanosomes mature within melanocytes. Melanin-containing melanosomes are then transported through the melanocytes’ projections and into the skin’s keratinocytes. What happens to them there? Find out by clicking the labels in the illustration below.
Test Your Knowledge
What Kinds of DNA Damage Does UV Radiation Cause?
UV photons of different energies have different effects on DNA. Some of the most significant DNA damage occurs with exposure to UVB radiation. Exposure to UVB radiation causes pyrimidine dimers to form. In a pyrimidine dimer, two adjacent pyrimidine bases become linked in an abnormal structure that causes a kink in the DNA double helix.
If pyrimidine dimers are not repaired, the cell would die because it cannot replicate or transcribe its DNA. But cells have mechanisms for repairing DNA damage. The cell’s repair machinery can remove the pyrimidine dimers and replace them with the appropriate nucleotides. Sometimes, though, this repair process results in errors—for example, the wrong nucleotide is introduced, resulting in a mutation in the surviving cell. When mutations occur in genes that are critical to regulating cell division and growth, they can lead to unregulated cell reproduction and possibly cancer. These mutations are one cause of skin cancer; other causes include other types of mutations, such as ones resulting from UVA damage or inherited mutations.
What Are Other Effects of UV Radiation?
Too much UVB radiation also destroys folate, an important vitamin circulating in blood. Folate deficiency can result in decreased fertility, and in a pregnant woman it can result in severe birth defects.
Folate is a B vitamin present in certain foods. Unlike vitamin D, our bodies cannot synthesize folate. The best sources of folate are leafy green vegetables and fruits. Folate is necessary for DNA synthesis and repair, as well as in reproduction and fetal growth and development.