15.2 - Endocytosis

Question 1

What is Endocytosis?

Answer 1

Process by which cells ingest external substances including fluids, molecules, particles, and other cells

Question 2

What occurs in Endocytosis?

Answer 2

• Plasma membrane pinches inward, forming endocytic vesicles.
• Contents are transported to lysosomes for digestion.

Question 3

What are the types of Endocytosis?

Answer 3

-Pinocytosis
-Phagocytosis

Question 4

What is Pinocytosis?

Answer 4

The continuous uptake of fluid and small macromolecules by cells.

Question 5

What is Phagocytosis?

Answer 5

Ingestion of large vesicles (phagosomes).

Question 6

What are Specialized Phagocytic Cells?

Answer 6

Cells like macrophages and neutrophils that engulf large particles via phagocytosis.

Question 7

How do Specialized Phagocytic Cells work?

Answer 7

• Extend pseudopods to engulf the target.
• Form a phagosome by pinching off the engulfed material.
• Fuse the phagosome with a lysosome to create a phagolysosome for digestion.

Question 8

What are the roles of Specialized Phagocytic Cells?

Answer 8

• Defense against pathogens.
• Recycling of cellular debris.

Question 9

How much volume do macrophages ingest during Pinocytosis?

Answer 9

Macrophages ingest fluid equivalent to 25% of their cell volume per hour.

Question 10

How much of their cell membrane do macrophages recycle during Pinocytosis?

Answer 10

About 200% of their cell membrane per hour.

Question 11

What is Receptor-Mediated Endocytosis?

Answer 11

A selective uptake mechanism for specific macromolecules via plasma membrane receptors.

Question 12

What happens to Endocytosed Macromolecules?

Answer 12

They are transported to endosomes for sorting, where they may be degraded in lysosomes, recycled, or sent elsewhere in the cell.

Question 13

What are Endosomes?

Answer 13

Sorting compartments for endocytosed materials.

Question 14

What are Lysosomes?

Answer 14

Organelles that serve as the primary sites for intracellular digestion.

Question 15

What is the function of Endocytic Vesicles?

Answer 15

They transport ingested material during endocytosis

Question 16

What are Pseudopods?

Answer 16

Extensions of a cell’s plasma membrane that engulf targets during phagocytosis.

Question 17

What is a Phagosome?

Answer 17

A vesicle containing material engulfed by phagocytosis.

Question 18

What is a Phagolysosome?

Answer 18

A fused structure of a phagosome and lysosome where degradation occurs.

Question 19

What are Macrophages?

Answer 19

Immune cells involved in phagocytosis and recycling cellular debris.

Question 20

What are Neutrophils?

Answer 20

Immune cells that engulf pathogens during the immune response.

Question 21

What is Receptor-Mediated Endocytosis?

Answer 21

Selective uptake of molecules via plasma membrane receptors.

Question 22

What is Mycoplasma tuberculosis?

Answer 22

A pathogen targeted by phagocytic activity.

Question 23

Mechanism of Phagocytosis (4 steps)

Answer 23

1. Pseudopod Formation
2. Engulfment
3. Fusion
4. Degradation

Question 24

Explain the process of Pseudopod formation during Phagocytosis.

Answer 24

Specialized phagocytic cells (macrophages, neutrophils) extend their plasma membrane around a target particle (bacterium, etc.)

Question 25

Explain the process of Engulfment during Phagocytosis.

Answer 25

Pseudopods encircle the target, enclosing it in a membrane-bound compartment known as “Phagosome”

Question 26

Explain the process of Fusion during Phagocytosis.

Answer 26

Phagosome moves toward and fuses with a lysosome;
forms Phagolysosome

Question 27

Explain the process of Degradation during Phagocytosis.

Answer 27

Digestive enzymes in the lysosome break down the engulfed material into simpler components; which the cell can either reuse or expel.

Question 28

Vesicles formed during pinocytosis are recycled back where and why?

Answer 28

Back to the cell surface to maintain membrane balance and to ensure the plasma membrane does not deplete ; supports constant uptake.

Question 29

What are the 3 steps in the mechanism of Receptor-Mediated Endocytosis?

Answer 29

1. Receptor-Binding
2. Vesicle Formation
3. Transport to Endosomes

Question 30

Explain Sorting Pathways in Endosomes.

Answer 30

Once Macromolecules are internalized, they are transported to endosomes; which act as sorting stations.

Question 31

What are the Pathways (destination) in Endosomes?

Answer 31

1. Recycling: some materials are sent back to the plasma membrane to be reused.
2. Degradation: other materials are transported to lysosomes for breakdown into usable components
3. Alternatives: some are directed to specific cellular location, like golgi apparatus for further processes.