Keratinocytes are primarily found in epidermis and its made up of 90% epidermal skin in man.
keratinocytes forms barrier that prevent us against environmental damage by heat, ultraviolet radiation, water loss from the skin, invasion of pathogenic bacteria, fungi, parasites, and viruses.
Keratinization is a form of the physical barrier formation where more keratinocytes is produced under terminal differentiation.
I mean, the basic answer would be the leaf of the cell. If you need to get more in depth than that, the palisade mesophyll layer of the leaf is where the majority of photosynthesis occurs.
When it reaches the duodenum, though, it assumes an inactive form as the pH rises above 6. Pepsins are secreted by Brunner's glands of the duodenum, and the crypts of Lieberkühn of the small intestine secrete an aqueous fluid.