The Endomembrane System

These flashcards cover key concepts and processes related to the endomembrane system, focusing on mechanisms of transport, secretion, and cellular functions.

What are the two methods unique to eukaryotes for transporting materials across the plasma membrane?

Exocytosis and Endocytosis.

What is exocytosis?

The process by which secretory vesicles release their contents outside the cell.

What is endocytosis?

The process by which cells internalize external materials.

What does the secretory pathway do?

Moves proteins from the ER through the Golgi complex to secretory vesicles and then to the exterior of the cell.

What is constitutive secretion?

The process where vesicles bud from the TGN and move directly to the cell surface, fusing with the plasma membrane.

What is an example of constitutive secretion?

Mucus secretion by the intestinal lining.

What is regulated secretion?

A process where secretory vesicles accumulate in the cell and fuse with the plasma membrane in response to specific signals.

What is an important example of regulated secretion?

Neurotransmitter release.

What is polarized secretion?

Exocytosis of specific proteins limited to a specific surface of the cell.

What triggers the fusion of regulated secretory vesicles?

Extracellular signals, such as hormones or neurotransmitters.

What process imports extracellular molecules by forming vesicles from the plasma membrane?

Endocytosis.

What are endocytic vesicles?

Vesicles that develop into early endosomes and fuse with vesicles from the TGN.

What is phagocytosis?

The ingestion of large particles, up to whole cells or microorganisms.

Which white blood cells use phagocytosis for defense?

Neutrophils and macrophages.

What is receptor-mediated endocytosis?

A process by which cells use receptors on the outer surface to internalize macromolecules.

What proteins are involved in receptor-mediated endocytosis?

Clathrin, adaptor proteins, and dynamin.

What happens in the early endosomes during receptor-mediated endocytosis?

They sort and recycle materials brought into the cell.

What facilitates the uncoating of the vesicle?

An uncoating ATPase.

What are SNARE proteins responsible for?

Mediating fusion between vesicles and target membranes.

What role do Rab GTPases play in vesicular transport?

They lock complementary SNARE proteins together, facilitating membrane fusion.

What do lysosomes contain?

Digestive enzymes capable of degrading all major classes of biological macromolecules.

How do lysosomes develop?

From endosomes that mature over time and acquire hydrolytic enzymes.

What are peroxisomes characterized by?

Presence of catalase for degrading hydrogen peroxide (H2O2).

What are some essential roles of peroxisomes?

Hydrogen peroxide metabolism, detoxification, oxidation of fatty acids, and catabolism of unusual substances.