4.4a C: Essential vs. Nonessential

15

What differentiates EAAs from NEAAs?

• essential amino acids take additional steps to synthesize

• essential amino acids have a complex r group sidechain (see red above)

Essential amino acids (EAAs)

• Can not be synthesized by most metazoans, so they must come from the diet

• there is very low fractionation of EAAs between trophic positions

• The ∆C of EAAs will reflect the base source of C (e.g. zooplankton, algae, etc.)

• Can be used to assess pure routing of diet to consumer

Nonessential amino acids (NAAs)

• can be synthesized by metazoans by breaking up other AAs and restructuring them

• synthesized de novo from a bulk carbon pool

• huge amount of variability in NAAs

• Can be used to represent pure mixing of diet into consumer

Amino Acid C isotope fingerprinting

• every source that can synthesize EAAs leaves a specific fingerprint, or ratio, of the EAAs based on the biosynthetic pathways involved in making the EAAs

• Currently very broad - because most plants use the same pathways, we group them all together.

• End members will have very specific fingerprints that can be seen to segregate using a PCA