Endocytosis Flashcards
what is the definition of endocytosis
How is endocytosis balanced by the process of exocytosis
If exocytosis doesn’t occur:
- less plasma membrane so cell would shrink
- exocytosis is increased if a cell needs to increase the size of the plasma membrane for cell division
Recall the 3 main types of endocytosis
Pinocytosis
Phagocytosis
Receptor mediated endocytosis
What is pinocytosis
Endocytosis of fluids and solutes
Most eukaryotic cells do it continuously (doesn’t require a signal to occur
Removes damaged membrane
Endocytosis vesicle around 100nm in size
Name the two types of pinocytic vesicle
Cathrin coated
Caveolae
What is Clathrin
A protein that arranges itself to form a basket of proteins which fits over the pinocytic vesicle
They help to distort the plasma membrane and pinch the vesicle off the membrane
How do Clathrin coated pinocytic vesicles work
Can take in extracellular fluid
The vesicle then gets rid of the clathrin coat since it hides what’s inside the vesicle
The vesicle then fuses with endosomes
What are caveolae pinocytic vesicles
Caveolins are in the plasma membranes of most cells
They form from lipid rafts
They are made up of caveolins and Calvin proteins (caveolins are embedded in the membrane of the pinocytic vesicle)
They don’t have a clathrin coat
How do caveolins pinch off the plasma membrane
Dynamin (protein) wraps around the neck of the vesicle and pinches it off the plasma membrane
It does this by making the lipids at the neck of the vesicle come close together, squeezing out the liquid so that the lipids fuse together to form the vesicle
Caveolins aren’t released
The vesicle then fuses with an endosome or transcytose
What is macropinocytosis and how are macropinosomes formed
• is induced (doesn’t happen continuously) - by receptor activation (requires a signal to occur)
• Formed from cell surface ruffles which collapse back into the cell surface and trap extracellular fluid
• Macropinosomes- large fluid filled endocytosis vesicles (they transport fluid)
• Macropinosomes acidify and then fuse with late endosomes
How is iron taken into a cell via receptor mediated endocytosis
Why may some cells take up cholesterol
What is the result of a cell not being able to take up cholesterol
What are some clinical relevances of endocytosis
Outline the process of endocytosis
• when an endocytosis vesicle is formed it fuses with the early endosome which sorts the contents of the vesicle
• Some of the contents are returned to the plasma membrane directly of via a recycling endosome
• Other contents of the endosome are degraded in a late endosome
• Late endosomes fuse with each other and then with a lysosome