A melanosome is a type of organelle inside a cell. Organelles are specialized parts of cells that have particular functions; organelles behave in cells much like organs do in the body. In order for an organelle to be called a melanosome, it must contain something called melanin. Melanin is the natural pigment found in both humans and animals; it gives a living organism its natural coloring. For example, a person who has a darker skin tone has more melanin, while lighter-skinned people have less melanin.
Understanding what a melanosome is may be easier if a person first learns about organelles. Organelles are often compared to organs in a human’s or animal’s body. The body has organs that have important functions for keeping it alive and functioning. The same arrangement goes for cells. Organelles are like little organs that play a role in a cell's life and function.
There are different types of organelles, but those that contain melanin are called melanosomes. The presence of melanosomes actually affects what a cell is called. If a cell contains melanosomes, it is called a melanocyte. Melanocytes produce melanin, which not only gives the skin its color but also helps determine the color of a person’s eyes and hair.
Melanin doesn’t just affect a person’s appearance. It also influences a person’s vulnerability to skin damage caused by exposure to ultraviolet rays from the sun. Individuals with higher amounts of melanin are usually less vulnerable to these rays than those with less. Lighter-skinned people tend to be more vulnerable, which means they are more likely to develop a sunburn and skin cancer. No one is immune to the sun’s effects, however, no matter how much melanin he has in his skin.
The melanin-production process starts when deoxyribonucleic acid (DNA) sends instructions to a melanocyte that stimulates it to create enzymes capable of producing melanin. The melanocyte also creates an amino acid, which is an organic compound that helps build a protein called tyrosine as part of the process. The melanosomes take the enzymes and amino acid and begin the process of converting the tyrosine into melanin. The role of the enzymes is to act as catalysts and start the process of chemical reactions necessary for melanin production.
A melanosome can move around quite a bit in some types of animal cells, such as those found in some reptile species. This explains the ability some reptiles have to camouflage themselves or change color when necessary. In such a case, hormonal or nerve changes cause the mobility of the melanosomes and lead to changes in coloring.