BIO MODULE 3:Set 5 — Bulk Transport, Exocytosis & Endocytosis

What is bulk transport?

Movement of large molecules or materials across the plasma membrane using vesicles.

What types of molecules commonly require bulk transport?

Large molecules such as proteins and polysaccharides.

What are the two main mechanisms of bulk transport?

Exocytosis and endocytosis.

What is exocytosis?

The process of releasing materials outside the cell when a vesicle fuses with the plasma membrane.

What is another name for exocytosis?

Secretion.

What is the role of the Golgi complex in exocytosis?

It sorts and tags proteins for delivery to their final destinations.

What are secretory vesicles?

Membrane-bound sacs that transport materials to the plasma membrane for release.

What happens to the vesicle membrane during exocytosis?

It fuses with and becomes part of the plasma membrane.

What is endocytosis?

The process of bringing materials into the cell by forming vesicles from the plasma membrane.

What is another name for endocytosis?

Uptake.

How does the plasma membrane form a vesicle during endocytosis?

It folds inward, surrounds material, and pinches off into the cytoplasm.

Where can endocytic vesicles deliver materials?

To the Golgi complex or other destinations such as lysosomes in animal cells.

What are the two main forms of endocytosis discussed in the lecture?

Bulk-phase endocytosis (pinocytosis) and receptor-mediated endocytosis.

What is pinocytosis?

A form of endocytosis in which extracellular water and dissolved substances are taken into the cell.

Does pinocytosis require substances to bind to surface receptors?

No.

What is receptor-mediated endocytosis?

A process in which specific molecules bind to cell-surface receptors before being brought into the cell.

Why is receptor-mediated endocytosis selective?

Only molecules that bind to the appropriate receptors are taken up through this mechanism.

What is a coated pit?

A region of the plasma membrane containing receptor-bound molecules and a protein coat involved in vesicle formation.

What protein coat is shown in the receptor-mediated endocytosis diagrams?

Clathrin.

What is the main difference between pinocytosis and receptor-mediated endocytosis?

Pinocytosis takes up extracellular fluid without receptor binding; receptor-mediated endocytosis uses specific receptors to select molecules.