I'm vegetarian and have been hearing that in addition to protein synthesis being more difficult for us, some amino-acids may be more difficult to acquire. Does anyone know of which vegetables have those aminos or know of a good source?
Many plant foods have all the essential amino acids, but the ratios may be far-off of what your body needs, meaning you'd have to eat a huge amount in order to get an adequate dose of the rarer amino acids.
Look at this answer which examines the Protein Digestibility Corrected Amino Acid Score (PDCAAS) demonstrating not only which foods are complete, but how well they correlate to our dietary needs when taking into account digestibility and ratios. As a quick summary, soy has a very good ratio, followed by chickpeas, fruits, vegetables, and legumes. Grains aren't so good.