*BIO* How are chemical and physical properties of amino acids different?

The R groups of the amino acid are different.
Some amino acids do not have a central carbon atom.
Some amino acids have a carbonyl group.
Some amino acids do not have an amino group.

the major parts of the digestive system:

salivary glands.

pharynx.

esophagus.

stomach.

small intestine.

large intestine.

rectum.

accessory digestive organs: liver, gallbladder, pancreas.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.