Question

4. Tara is learning about how her vegetarian friend gets enough protein without eating meat. Her friend explains that she eats foods like beans, lentils, rice, and corn tortillas. Tara is surprised because she’s heard that meat is the only food that gives you “complete protein.” When Tara looks it up, she learns that animal-based foods like chicken, eggs, and milk contain all nine essential amino acids. However, many plant-based foods are incomplete proteins, they are missing one or more of these essential amino acids.

In her science class, she discovers that when people combine different plant-based foods, like beans with rice or peanut butter on whole wheat bread, the amino acids in one food fill in what’s missing in another, to make sure their bodies have all the building blocks needed to make new proteins.

Which of the following statements correctly explain how people can build all the body proteins they need from their food choices? (Select all that apply.)

Responses

A. Our bodies can make all 20 amino acids if we eat enough of any one plant food.
A. Our bodies can make all 20 amino acids if we eat enough of any one plant food.

B. Combining different plant foods can supply all 9 essential amino acids our bodies cannot make.
B. Combining different plant foods can supply all 9 essential amino acids our bodies cannot make.

C. Animal-based foods like meat and eggs are complete proteins because they contain all essential amino acids.
C. Animal-based foods like meat and eggs are complete proteins because they contain all essential amino acids.

D. Amino acids from food must be rearranged and reassembled into new proteins inside our cells.
D. Amino acids from food must be rearranged and reassembled into new proteins inside our cells.

E. Protein molecules in food are absorbed whole and used directly by the body’s muscles.

Answer 1

Correct answers: B, C, and D.

- B is true: combining plant foods with different amino‑acid profiles (e.g., beans + rice) can provide all nine essential amino acids humans cannot synthesize.
- C is true: many animal foods (meat, eggs, milk) are considered “complete” proteins because they contain all the essential amino acids in adequate amounts.
- D is true: dietary proteins are digested to amino acids and small peptides, which cells then use to synthesize (rearrange and reassemble) the body’s own proteins.

A is false — humans cannot make the nine essential amino acids no matter how much of one plant food you eat. E is false — whole protein molecules are generally not absorbed intact and are not used directly by muscles; they are broken down first.