Intro To The Endomembrane System Flashcards
What is the Endomembrane system
Also called the cytoplasmic membrane system
It’s made up of the cytoplasmic membranes (organelles) that are found in the eukaryotic cell and is a dynamic moving process
This means that the Endomembrane system isn’t in prokaryotes because they don’t have membrane bound organelles
What makes up the Endomembrane system
Groups of cytoplasmic organelle like
The ER
GOLGI
endosomes
Lysosomes
Vacuoles
What does the Endomembrane system
do in terms of transport
- It helps transport materials from a donor to recipient compartment (1 organelle to another)
- It helps transport things out of the cell through the secretory pathway
- It helps transport materials into the cell (endocytic pathway)
When transporting materials from donor compartment to recipient compartments, how are materials actually moving
Membrane bound vesicles contains the stuff bud from the donor compartment and shuttle the things between organelles or diff compartments of the same organelle
They move in a directional manner with the help of motor proteins and the cytoskeleton network
When transporting materials from donor compartment to recipient compartments, what happens once the vesicles bud off the donor compartment
They fuse with the membrane of the recipient and the the cargo is released
The membrane of the vesicle becomes part of the recipient compartments membrane.
Sometimes some resident protiens of the donor compartment also transported, but they can be brought back
When transporting materials from donor compartment to recipient compartments, what type of protiens are transported and how are they directed in their movement
Secreted protiens, lysosomal enzymes, and membrane protiens
Directed to the correct place because of the amino acid or oligosaccharide sorting signals on them
These signals on the proteins are recognized by receptors that are in the membranes of budding vesicles
What biomolcules are made in the ER
What happens in the golgi complex
Lipids/chilesterol
Steroid hormones
Secreted protiens
Integral membrane protiens
Glycosylation of protiens
Modifications of protiens occurs in the golgi complex
When transporting materials out of the cell (secretory pathway) what type of secretions are there
Constitutive
Regulated
What is constitutive secretion
Happens in most cells
The things to be transported are continually moved to secretory vesicles right when they are formed and then are secreted out of the cell
This helps form and build up the plasma membrane of the cell since the membrane of the vesicle fused with the plasma membrane
What is an example of constitutive secretion
Fibroblasts secreting collagen
What is regulated secretion
The materials from the er are stored in membrane bound compartments called secretory granules and only released on response to a stimulus
Examples:
Endocrine cells that release hormones
Pancreatic acinar cells that release digestive enzymes
Nerve cells that release neurotransmitters (in response to increasing ca due to arrival of a nerve impulse)
When transporting materials into the cell (endocytic pathway) what help do this
Endosomes
Lysosomes
What are endosomes
They include early and late endosomes
Early endosomes take up materials from the outside of the cell for sorting
Late endosomes are more acidic than early endosomes and fuse with the lysosomes to allow cargo to be degraded if needed
What are lysosomes
They contain hydrolytic (digestive) enzymes and are kept at an acidic ph
They play roles in breakdown of material coming into the cell and in organelle turnover
What are the two ways to study endo membranes
Autoradiography
Mutant phenotypes
What is auto radiography
The process of following radioactively labeled material in the cell
Includes the pulse chase experiment
What is the pulse chase experiment
It’s helps examine a proccess that occurs over time
Ex. We want to see the path that the enzymes in acinar cells of the pancreas take when being synthesized and secreted
What is step one of the pulse chase experiment
The pulse step:
Radio labelled amino acids are added into the digestive enzymes being made in the cell
But only expose to the amino acids for a SHORT time (hence pulse)
What is step 2 of the pulse chase experiment
Chase step:
The cells that had the radio labeled protiens are transferred to a media with only unlabelled (no radio) amino acids
So the enzymes made during this time are not radio labelled
What are the results of the pulse chase experiment
The labeled amino acids enzymes during the chase part began to move from er to golgi to the membrane surface
How to we study Endomembranes based on the mutant phenotype
First we characterize a phenotype that resulted from a mutation or deleted gene
This gives us info about how the protien would have normally functioned
Use yeast cells to test
Explain the results for protien 1 of the mutant phenotypes test
In the control (WT) we had the ER and the golgi
With mutant one, the golgi disappeared and the ER expanded,
this meant that the protien that was mutated played a role in the formation of vesicles in the ER. Since the ER expanded this show that the vesicles aren’t leaving.
Explain the results for protien 2 of the mutant phenotypes test
There was excess vesicles and lack of golgi
This means that the protien may have had a role in vesicle fusion to the golgi
The vesicle in the mutant aren’t able to bind to the golgi so they just form from the ER but don’t go anywhere
