Which is a complete plant protein source?

Which is a complete plant protein source?

• A. Legumes
• B. Cereals or Grains
• C. Vegetables
• D. Soy Protein

Answer: (D)

The key idea is protein quality: a complete plant protein provides all nine essential amino acids in amounts adequate for human needs. Soy protein fits this, even though it comes from a legume, because its essential amino acid profile is well balanced and includes sufficient methionine and other amino acids. That makes it a complete plant protein source. Legumes are typically high in lysine but limited in methionine, cereals or grains are often low in lysine, and vegetables vary with many not providing all essential amino acids in adequate amounts. So, among the options, soy protein uniquely meets the full amino acid requirements on its own.

The key idea is protein quality: a complete plant protein provides all nine essential amino acids in amounts adequate for human needs. Soy protein fits this, even though it comes from a legume, because its essential amino acid profile is well balanced and includes sufficient methionine and other amino acids. That makes it a complete plant protein source.

Legumes are typically high in lysine but limited in methionine, cereals or grains are often low in lysine, and vegetables vary with many not providing all essential amino acids in adequate amounts. So, among the options, soy protein uniquely meets the full amino acid requirements on its own.