What is the difference between complete and incomplete proteins?

The distinction between complete and incomplete proteins is fundamentally based on the amino acid content they provide. Complete proteins are defined as those that contain all nine essential amino acids that the human body cannot synthesize on its own. These essential amino acids must be obtained through diet, making complete proteins an important source for overall nutritional needs.

Animal-based foods, such as meat, fish, eggs, and dairy products, are typically considered complete proteins as they provide all these necessary components. On the other hand, most plant-based proteins are categorized as incomplete because they usually lack one or more of the essential amino acids. However, there are exceptions among certain plant sources, such as quinoa and soy, which can also be complete proteins.

Understanding this classification helps in dietary planning, especially for vegetarians or vegans who may rely on a mix of various plant sources to ensure they receive a full amino acid profile. Hence, the correct answer effectively captures the key distinction in protein classification based on essential amino acids.