Endoplasmic Reticulum Quiz

Endoplasmic Reticulum Overview

• Composed of interconnected tubular and microsomal vesicular structures.
• Surrounded by a membrane made of proteins and bilayered lipids.
• The lumen (endoplasmic matrix) diameter is approximately 400 to 700 Å.
• Connects the nucleus to the cell membrane, establishing a communication pathway.

Types of Endoplasmic Reticulum

• Divided into two main types: rough and smooth.
• Both types are interconnected and can transform into one another based on cellular activity.

Rough Endoplasmic Reticulum (RER)

• Characterized by a bumpy appearance due to attached ribosomes; also known as granule endoplasmic reticulum.
• Structure is tubular or vesicular.
• Main functions include:
  • Protein Synthesis: Primarily synthesizes secreted proteins, such as insulin and antibodies. Ribosomes facilitate amino acid assembly into proteins, which are then glycosylated (carbohydrates added) to form glycoproteins.
  • Transport: Vesicles containing proteins are transported to the Golgi apparatus for modification; some vesicles go to other organelles.
  • Degradation: Involved in degrading worn-out organelles by wrapping around them to form autophagosomes, which are digested by lysosomal enzymes.

Smooth Endoplasmic Reticulum (SER)

• Appears smooth and is also referred to as agranular reticulum; consists of interconnected tubules.
• Functions include:
  • Synthesis of Non-Protein Substances: Produces cholesterol, steroids, lipids, phospholipids, and lipoproteins, especially in cells responsible for lipid synthesis.
  • Cellular Metabolism: Contains enzymes on its outer surface that perform various metabolic processes.
  • Storage and Metabolism of Calcium: Major reservoir for calcium; releases calcium ions in skeletal muscles to trigger contractions.
  • Catabolism and Detoxification: Engaged in the breakdown and detoxification of toxic substances, including drugs and carcinogens, particularly in liver cells.