Final answer:
Fruits are the source of carbohydrates that affect blood sugar and are essential for cell membrane structure, as they provide glucose and help in forming glycoproteins and glycolipids.
Step-by-step explanation:
The question asks about a source of carbohydrates that not only affects blood sugar but is also essential for cell membrane structure. Carbohydrates are a major component of our diet and play a key role in cellular functions. They are the third major component of plasma membranes, found on the exterior surface of cells and are bound either to proteins (forming glycoproteins) or to lipids (forming glycolipids).
These carbohydrates form specialized sites on the cell surface that allow for cell recognition, which is important for immune response. While grains, fruits, and vegetables are all natural sources of carbohydrates, the one that affects blood sugar and is involved in cell membrane structure is fruits, as they can provide glucose and contain the necessary components for the formation of glycoproteins and glycolipids on cell membranes.