What are tiny grains of pigment in the skin that determine skin color?

Melanin is the key pigment in the skin that is responsible for determining skin color. It is produced by specialized cells called melanocytes, which are predominantly located in the epidermis, the outer layer of the skin. The amount and type of melanin produced by these melanocytes vary among individuals and are influenced by genetic factors, sun exposure, and certain hormonal changes.

In essence, higher levels of melanin lead to darker skin tones, while lower levels result in lighter skin tones. It is also important to note that melanin provides some protection against the damaging effects of ultraviolet (UV) radiation from the sun, contributing to the skin's overall health.

The other choices represent different components with distinct functions. Keratin is a protein that helps form hair, nails, and the outer layer of skin, serving mainly a protective role. Collagen is a structural protein found in connective tissues that provides strength and elasticity to the skin but does not influence color. Hemoglobin, found in red blood cells, is responsible for transporting oxygen and can affect skin color but is not a pigment present in the skin itself.