Which part of the grain serves as the main starch and protein supply?

The endosperm is the part of the grain that serves as the primary source of starch and protein. It is the largest component of the grain and provides the energy necessary for the growth of the plant. The starch content in the endosperm is essential for energy, making it a staple in many diets. Additionally, the endosperm contains proteins that are vital for maintaining overall nutrition.

In contrast, the husk is the protective outer layer that primarily serves to protect the grain from environmental elements and pests. The bran is the outer layer beneath the husk, rich in fiber, vitamins, and minerals, but it is not the main source of starch or protein. The germ is the part of the grain that can sprout into a new plant and contains healthy fats, vitamins, and minerals, but it comprises a smaller portion of the grain compared to the endosperm and is not the main source of starch.

Therefore, the endosperm is fundamental in providing the necessary nutrients, specifically starch and protein, that support growth and energy requirements.