<span>Amino acids are the basic structural unit of all proteins. A 'free' amino acid (a single amino acid) always has:
an amino group -NH2,
a carboxyl group -COOH
a hydrogen -H
a chemical group or side chain -"R".
Since the amino acids (except glycine) have 4 different groups attached to the a-carbon, they are optically active stereoisomers (recall 23.101 Organic Chemistry) although only L-isomers are found in proteins.
At a neutral pH, both the amino and the carboxyl groups are ionised, giving what is termed the zwitterionic</span>
Answer: the Earth's spheres interact with other planets in the universe
Explanation: the Earth has different layers and its atmosphere and then when it is in contact with the outer space it can rotate around other planets
Atmosphere.
Hydrosphere.
Biosphere.
Cryosphere.
Lithosphere(also referred to as the Geosphere).
