Cisternae

Definition

Cisternae are flattened, membrane-enclosed sacs that are part of the endoplasmic reticulum (ER) and Golgi apparatus in eukaryotic cells. They serve as storage and transport hubs for proteins and other cellular materials.

5 Must Know Facts For Your Next Test

1. Cisternae are the flattened, disc-like compartments that make up the Golgi apparatus, providing a surface area for the processing and sorting of cellular cargo.
2. In the endoplasmic reticulum, cisternae are the sites where newly synthesized proteins are folded and modified before being transported to the Golgi apparatus.
3. The curvature and arrangement of cisternae within the Golgi apparatus create a directional flow of materials, allowing for the sequential processing and sorting of proteins and other molecules.
4. Vesicles bud off from the rims of Golgi cisternae, carrying their cargo to their final destinations within the cell or for secretion outside the cell.
5. Disruptions in the structure or function of cisternae can lead to cellular dysfunction and have been implicated in various diseases, such as neurodegenerative disorders and cancer.

Review Questions

• Explain the role of cisternae in the endoplasmic reticulum (ER) and their relationship to protein synthesis and processing.
  • In the endoplasmic reticulum, cisternae are the sites where newly synthesized proteins are folded and modified. Ribosomes attached to the ER membrane translate mRNA into polypeptide chains, which are then transported into the lumen of the ER cisternae. Within the cisternae, chaperone proteins assist in the proper folding of these polypeptides, and enzymes perform post-translational modifications, such as the addition of carbohydrates or lipids. This processing prepares the proteins for their eventual transport to the Golgi apparatus for further sorting and distribution throughout the cell.
• Describe the organization and function of cisternae within the Golgi apparatus.
  • The Golgi apparatus is composed of stacks of flattened, membrane-enclosed sacs called cisternae. These cisternae are arranged in a specific orientation, with the cis-face receiving materials from the endoplasmic reticulum and the trans-face responsible for sorting and packaging the processed materials into vesicles for transport to their final destinations. As the materials move through the successive cisternae, they undergo further modifications, such as the addition of carbohydrates or the removal of specific tags. This sequential processing and sorting within the Golgi cisternae is crucial for the proper distribution of cellular components and the maintenance of cellular homeostasis.
• Analyze the importance of the structural and functional integrity of cisternae in cellular processes and its implications for human health.
  • The proper structure and function of cisternae within the endoplasmic reticulum and Golgi apparatus are essential for the efficient synthesis, processing, and transport of proteins and other cellular materials. Disruptions in the organization or dynamics of cisternae can lead to a breakdown in these critical cellular processes, contributing to various disease states. For example, alterations in the structure or function of Golgi cisternae have been linked to neurodegenerative disorders, as the improper sorting and trafficking of proteins can result in the accumulation of misfolded or aggregated proteins that can damage neuronal cells. Similarly, changes in the ER cisternae and their role in protein folding have been associated with conditions like cancer, where the uncontrolled proliferation of cells is often driven by the misregulation of signaling pathways that depend on properly processed and trafficked proteins. Understanding the fundamental importance of cisternae in cellular homeostasis is, therefore, crucial for developing targeted therapies and interventions to address these complex, multifactorial diseases.

Related terms

Endoplasmic Reticulum (ER): The endoplasmic reticulum is an extensive network of interconnected, membrane-bound tubes and flattened sacs (cisternae) that play a crucial role in protein synthesis, folding, and transport within the cell.

Golgi Apparatus:

The Golgi apparatus is a organelle composed of stacks of cisternae that receives, modifies, and sorts proteins and other molecules for distribution to their intended destinations within or outside the cell.

Vesicle: Vesicles are small, membrane-bound sacs that transport materials, such as proteins and other molecules, between different organelles or to the cell membrane for secretion.