Final answer:
The endosperm of a grain contains the stored starch, serving as a food source for the growing plant and for human consumption when processed into products like white flour.
Step-by-step explanation:
The anatomical part of the grain that contains the stored starch is the endosperm. The endosperm is the tissue within the seeds of most flowering plants following fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it also contains oils and protein. This tissue is used during germination as a food source for the growing plant. Starch itself is a polysaccharide composed of glucose units and serves as an energy reserve in plants, particularly in seeds and tubers. Starch is a mixture of two polymers: amylose and amylopectin. In the processing of grains such as wheat, the endosperm is separated and used to create white flour, while the bran and germ are often removed.