Question

Amino acids are classified as essential or nonessential. What does this mean and is the classification the same for all organisms?​

Answer 1

The essential amino acids, which are also referred to as indispensable, are the ones you must get through the foods you eat because your body can’t make them. Nine out of the 20 amino acids are essential, but adults only need to obtain eight of them: valine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine and tryptophan. The ninth amino acid -- histidine -- is only essential for infants. Your body doesn’t store amino acids, so it needs a regular daily supply of these essential building blocks.

Nonessential is a slightly misleading label because these amino acids actually fill essential roles, but since they’re synthesized by your body, they’re not an essential part of your diet. Of the 11 nonessential amino acids, eight are called conditional amino acids. When you’re sick or under significant stress, your body may not be able to produce enough of these amino acids to meet your needs. The list of conditional amino acids includes arginine, glutamine, tyrosine, cysteine, glycine, proline, serine and ornithine. The remaining three -- alanine, asparagine and aspartate -- are nonessential.

No the classification is not same for all organisms, it's different for different organisms, depending upon their requirements and their ability to produce them.