Week 12 / Cellular Process 2 cont.. Flashcards
Q: What is exocytosis?
A: Exocytosis is the movement of molecules out of the cell via vesicles.
Q: What are the functions of exocytosis?
Replaces portions of the plasma membrane that were removed by endocytosis.
Adds new membrane components to the membrane.
Provides a route by which membrane-impermeable molecules (such as protein hormones) synthesized by the cell can be secreted into the extracellular fluid.
Q: What is the process of exocytosis?
A: The process of exocytosis involves the following steps:
The membrane-bound vesicle migrates to the plasma membrane.
Proteins at the vesicle surface (v-SNAREs) bind with t-SNAREs (plasma membrane proteins).
The vesicle and plasma membrane fuse, opening a pore.
The vesicle contents are released to the cell exterior.
Q: What are the key features of exocytosis?
A: Exocytosis involves the cytoplasmic vesicle merging with the plasma membrane to release its contents. It requires energy (ATP) and Ca²⁺ ions.
Q: Can you give examples of exocytosis?
A: Examples of exocytosis include:
Golgi body vesicles merging with the plasma membrane to release their contents.
Nerve cells releasing neurotransmitters, such as acetylcholine (ACh) and noradrenaline (NA), stored in vesicles.
Hormones, such as insulin, being released from storage vesicles in β-cells of the pancreas.
Q: How do nerve cells communicate with other cells?
A: Nerve cells communicate with other cells by releasing chemicals via exocytosis at the synaptic terminal.
Q: What is transcytosis?
A: Transcytosis is the process used to move a substance into, across, and out of a cell. It involves vesicles undergoing endocytosis on one side of the cell, moving across the cell, and then undergoing exocytosis on the opposite side.
Q: Is transcytosis an active process?
A: Yes, transcytosis is an active process.
Q: Where does transcytosis most often occur?
A: Transcytosis most often occurs across endothelial cells that line blood vessels.
Q: Can you provide an example of transcytosis?
A: During pregnancy, some of the mother’s antibodies cross the placenta into the fetal circulation via transcytosis.
