AP BIOLOGY

Detailed explanation-1: -Basal cells expressing 1 integrin at a lower level can also divide-indeed, they divide more frequently-but only for a limited number of division cycles, after which they leave the basal layer and differentiate.

Detailed explanation-2: -Answer 1: Our skin cells divide rapidly in order to maintain a protective barrier against infection. The outer skin layer is called the epidermis and contains mostly dead cells that contain keratin. Keratin is a tough fibrous protein found in hair, skin, and calluses, and acts as a protective coating.

Detailed explanation-3: -During the growth and repair of human skin the skin cells reproduce asexually through the process of mitosis to produce new skin cells.

Detailed explanation-4: -Epithelial and and blood cells are the two of the main types of cells that need to be constantly replaced in developed organisms. As far as I know cells lining the gut epithelium are fastest to divide.

Detailed explanation-5: -It takes a new cell about a month to reach the top most layer and being finally shed off. Thus a faster form of cell cycle regulation operates in skin epithelium. In an adult liver regular cell replacement is not needed (as physical growth has stopped), and cell cycle is generally in G0 stage.