Rough endoplasmic reticulum

Definition

The rough endoplasmic reticulum (RER) is a type of endoplasmic reticulum characterized by the presence of ribosomes on its cytoplasmic surface, giving it a 'rough' appearance. It plays a crucial role in the synthesis and processing of proteins, particularly those that are secreted from the cell or integrated into cellular membranes. The RER also facilitates the initial steps of protein folding and modification, making it essential for proper protein functionality and cellular communication.

5 Must Know Facts For Your Next Test

1. The rough endoplasmic reticulum is particularly abundant in cells that produce large amounts of proteins for export, such as pancreatic cells secreting insulin.
2. Ribosomes attached to the RER are responsible for translating mRNA into polypeptides, which enter the lumen of the RER for processing.
3. Proteins synthesized in the RER can undergo post-translational modifications, including glycosylation, which is important for their stability and function.
4. The rough endoplasmic reticulum is connected to the nuclear envelope, allowing for efficient transport of newly synthesized mRNA from the nucleus to ribosomes on the RER.
5. Defects in the rough endoplasmic reticulum can lead to diseases such as cystic fibrosis, where improper protein folding and trafficking occur.

Review Questions

• How does the presence of ribosomes on the rough endoplasmic reticulum influence its function in protein synthesis?
  • The presence of ribosomes on the rough endoplasmic reticulum is critical because these ribosomes are the sites where protein synthesis occurs. As ribosomes translate mRNA into polypeptide chains, these nascent proteins are directly translocated into the lumen of the RER. This arrangement allows for immediate folding and post-translational modifications, which are essential for producing functional proteins that can be secreted or incorporated into membranes.
• Discuss how the rough endoplasmic reticulum interacts with other organelles in the secretory pathway.
  • The rough endoplasmic reticulum plays a pivotal role in the secretory pathway by synthesizing proteins that will eventually be modified and sorted by the Golgi apparatus. After proteins are synthesized in the RER, they are packaged into vesicles that bud off from its surface and travel to the Golgi apparatus. The Golgi then further processes these proteins before sending them to their final destinations, which may include secretion outside of the cell or incorporation into cellular membranes.
• Evaluate the implications of dysfunctional rough endoplasmic reticulum on cellular health and its potential link to diseases.
  • Dysfunctional rough endoplasmic reticulum can have severe implications for cellular health as it disrupts normal protein synthesis and processing. When the RER is unable to properly fold proteins or conduct necessary modifications, misfolded proteins accumulate, leading to cellular stress responses. This dysfunction is linked to various diseases, including neurodegenerative disorders like Alzheimer's and genetic conditions such as cystic fibrosis, highlighting the importance of RER function in maintaining overall cellular homeostasis.

Related terms

Ribosomes:

Molecular machines found in all living cells that synthesize proteins by translating messenger RNA (mRNA) into polypeptide chains.

Smooth endoplasmic reticulum: A type of endoplasmic reticulum that lacks ribosomes and is involved in lipid synthesis, detoxification, and calcium storage.

Golgi apparatus: An organelle that modifies, sorts, and packages proteins and lipids received from the endoplasmic reticulum for secretion or delivery to other organelles.