What substance gives pigment to the skin and hair?

The substance that gives pigment to the skin and hair is melanin. Melanin is a complex polymer that is produced by cells called melanocytes found in the skin, hair follicles, and even in the eyes. It plays a crucial role in determining the color of a person's skin and hair, as well as providing some protection against the harmful effects of ultraviolet (UV) radiation from the sun.

There are different types of melanin, primarily eumelanin (which is brown or black) and pheomelanin (which is yellow or red), and the ratio of these types of melanin determines the overall pigmentation. The presence of melanin is also responsible for variations in skin tone among different individuals and populations.

The other substances mentioned function differently. Carotene contributes a yellow-orange hue and is primarily found in certain fruits and vegetables but is not the main determinant of skin and hair color. Collagen is a protein that provides structure and elasticity to the skin but does not impart color. Hemoglobin is the molecule in red blood cells responsible for carrying oxygen and gives blood its red color; while it can affect skin tone indirectly, it does not contribute to the pigmentation of skin and hair.