Endoplasmic reticulum (ER)

Definition

The endoplasmic reticulum (ER) is a network of membranous tubules and sacs within eukaryotic cells that plays a key role in protein and lipid synthesis. It comes in two forms: rough ER, studded with ribosomes, and smooth ER, which lacks ribosomes.

5 Must Know Facts For Your Next Test

1. The rough ER is involved in the synthesis of proteins that are either secreted from the cell or inserted into cellular membranes.
2. Smooth ER functions in lipid synthesis, detoxification processes, and calcium ion storage.
3. Proteins synthesized in the rough ER are transported to the Golgi apparatus for further modification and sorting.
4. The smooth ER is abundant in liver cells due to its role in detoxifying harmful substances.
5. ER stress can lead to diseases such as diabetes and neurodegeneration because it affects protein folding and quality control.

Review Questions

• What are the main differences between the rough ER and smooth ER?
• How does the endoplasmic reticulum contribute to protein synthesis?
• What roles does smooth ER play in cellular metabolism?

Related terms

Golgi Apparatus:

An organelle that modifies, sorts, and packages proteins for secretion or use within the cell.

Ribosome:

A molecular machine responsible for synthesizing proteins by translating messenger RNA.

Lysosome: A membrane-bound organelle containing enzymes that break down waste materials and cellular debris.