Exocytosis and Endocytosis

Flashcards covering the processes of exocytosis and endocytosis, including their types, mechanisms, and examples.

What is endocytosis?

A cellular process where the plasma membrane folds inward to form a vesicle that brings substances or particles into the cell.

What are the three types of endocytosis?

Receptor-mediated endocytosis, pinocytosis, and phagocytosis.

What is receptor-mediated endocytosis?

A type of endocytosis where specific cargo binds to receptors in the plasma membrane, leading to the formation of a coated vesicle that internalizes the cargo.

Why is receptor-mediated endocytosis important for cells?

It allows cells to take up cargo that may not be very concentrated in the extracellular environment, such as cholesterol, lipids, and iron.

What is the role of coat proteins in receptor-mediated endocytosis?

They bind to the membrane around aggregated receptors, causing the plasma membrane to invaginate and form a vesicle.

What is pinocytosis?

A type of endocytosis, often called 'cell drinking,' where membrane vesicles internalize extracellular fluid, allowing cells to sample extracellular solutes.

What does the Greek term 'pinocytosis' mean?

Cell drinking.

What is phagocytosis?

A type of endocytosis, known as 'cell eating,' which involves the formation of a large membrane vesicle (phagosome) to engulf large particles like bacteria.

What does the Greek term 'phagocytosis' mean?

Cell eating.

Which specialized cells perform phagocytosis, and what is an example of their function?

Only certain cells called phagocytes, such as macrophages in the immune system, which engulf and destroy bacteria.

What happens to engulfed bacteria during phagocytosis by macrophages?

The phagosome fuses with a lysosome, and the lysosome's digestive enzymes destroy the bacterium.

How are nitrogen-fixing root nodules formed in certain plants like legumes?

Through the endocytosis of bacteria, which are then contained within a membrane-enclosed compartment in the root nodules.

What is exocytosis?

A process where material inside the cell is packaged into vesicles and then excreted into the extracellular environment.

From which organelle are vesicles usually derived during exocytosis?

The Golgi apparatus.

What is the final step in exocytosis?

The vesicle fuses with the plasma membrane and releases its cargo into the extracellular environment.

Provide two examples of substances secreted into the extracellular environment via exocytosis.

Hormones like insulin and digestive enzymes.