What are saccules?

Saccules are indeed flattened vesicles that form part of the endoplasmic reticulum and the Golgi apparatus in eukaryotic cells. They play a crucial role in the processing and transport of cellular materials. The structure of saccules allows them to facilitate various functions, such as the modification of proteins and lipids received from the endoplasmic reticulum before they are transported to their final destinations in the cell.

In contrast, large vacuoles generally serve as storage structures and are not typically classified as saccules. Organelles found in the nucleus have different functions related to DNA and RNA synthesis, and while components of ribosomes are critical for protein synthesis, they are distinct from saccules due to their role and structural characteristics.