What part of a grain kernel is the largest and contains carbohydrates and some protein?

The endosperm is the largest part of the grain kernel and serves as the primary source of carbohydrates, making it crucial for energy. It also contains some protein, but its main composition is starch, which is essential for providing the energy needed by the plant during germination and growth. The endosperm is designed to support the developing seedling, containing the nutrients necessary for early growth.

In contrast, the bran is the outer layer of the grain and is rich in fiber, vitamins, and minerals, but it does not constitute the largest portion of the grain kernel. The germ, or seed, is the part that can develop into a new plant and is rich in nutrients, but it is the smallest part of the grain. The term 'kernel' refers to the entire grain structure, which includes the bran, endosperm, and germ. Therefore, when identifying the part of the grain kernel that is the largest and mainly contains carbohydrates and some protein, the endosperm is the correct answer.