structure and function of vesicles

Question 1

What are vesicles?

Answer 1

Vesicles are small, rounded sacs with a single layer membrane that contain various contents. They are dynamic structures that are continuously made, moved, and merged within cells.

Question 2

How are vesicles formed?

Answer 2

Vesicles are formed by pinching off a small area of membrane from a larger membrane, often in processes like endocytosis. This process is aided by the protein clathrin.

Question 3

What role does clathrin play in vesicle formation?

Answer 3

Clathrin is a three-legged protein that forms a lattice of pentagons and hexagons on the inner surface of the membrane. This helps the membrane indent and eventually form a clathrin-coated vesicle by pinching off to create a spherical structure.

Question 4

What are the two general reasons for vesicle transport?

Answer 4

Vesicles are used to transport materials within cells for two main reasons:

1. To move the contents of the vesicle, such as neurotransmitters to the presynaptic membrane in neurons.
2. To move the membrane or membrane proteins, such as increasing the cell membrane area or moving proteins between organelles.

Question 5

How do vesicles contribute to the growth of a cell membrane?

Answer 5

In a growing cell, vesicles help increase the cell membrane area by:

• Phospholipids being synthesized next to the RER and inserted into its membrane.
• Ribosomes on the RER synthesizing membrane proteins, which are inserted into the RER membrane.
• Vesicles bud off from the RER, move to the cell surface membrane, and fuse with it, adding a small amount of membrane each time.

Question 6

What is another example of vesicles increasing organelle size?

Answer 6

Vesicles can also be used to increase the size of other organelles, such as mitochondria, in the cytoplasm, by transporting membrane materials to them.