Question

which of the following describes a key difference among the 20 amino acids that are used to make proteins? a only some amino acids have an r - group. b only some amino acids have a carboxyl group (cooh). c some amino acids are hydrophobic. d some amino acids contain the element phosphorus

Explanation:

All 20 amino - acids have an amino group, a carboxyl group and an R - group. They are all made of carbon, hydrogen, oxygen and nitrogen, and none of the 20 standard amino - acids contain phosphorus. However, some amino - acids have non - polar R - groups making them hydrophobic, while others have polar or charged R - groups.

Answer:

C. Some amino acids are hydrophobic.