Keratins is the plural form
No. Carotene is a pigment. Beta-carotene is a form of Vitamin A. Keratin is a protein which makes up hair and fingernails. http://en.wikipedia.org/wiki/Keratin
The plural form of "do" is "do" and the plural form of "don't" is "don't." These words do not change in the plural form when used in a sentence.
yes your hair is made of keratin unlike your nails and other body parts
The plural form of him, her, or it is them. (objective pronouns)
Bridges is the plural form of bridge.
The plural form of "I" is "we."
The plural form of "was" is "were."
The plural form of "is" is "are."
There are similarities in Keratin and Insulin, they are used differently. Insulin and Keratin are both made inside the human body and they are also both made synthetically. Insulin stays in liquid form while Keratin is a hardened form which an be has hard as finger nails or as soft as hair. Insulin in made synthetically and used for medical purposes where Keratin is made synthetically and used for beauty purposes.
The plural form of mouth is mouths. The plural form of month is months. The Mounth is a range of hills in Scotland and does not have a plural form.
"Groceries" is the plural form of "grocery."
"Beliefs" does not have a plural form, as it is already plural. Beliefs is the plural form of belief.