Explanation:An aminoacid is composed by an amino group, an acid or carbonyl group and a side chain or R group, all bonded to a central carbon atom. Aminoacids are different between them for the R group and can be classified as: 1) Non-polarNeutral if the side chain is uncharged and non-polar (aliphatic or cyclic). 2) Polar Neutral if the side chain contains amida, sulfur or hydroxyl groups. 3) Basic if the side chain contains other amino groups. 4) Acid if the side chain contains other carboxyl groups.
A closed circuit doesn't allow the flow of electrons. an open circuit does. example: if you turn off a switch in your house. you 'broke the circuit it is closed.
