Intro To The Endomembrane System

Question 1

What is the Endomembrane system

Answer 1

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

Question 2

What makes up the Endomembrane system

Answer 2

Groups of cytoplasmic organelle like

The ER
GOLGI
endosomes
Lysosomes
Vacuoles

Question 3

What does the Endomembrane system
do in terms of transport

Answer 3

1. It helps transport materials from a donor to recipient compartment (1 organelle to another)
2. It helps transport things out of the cell through the secretory pathway
3. It helps transport materials into the cell (endocytic pathway)

Question 4

When transporting materials from donor compartment to recipient compartments, how are materials actually moving

Answer 4

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

Question 5

When transporting materials from donor compartment to recipient compartments, what happens once the vesicles bud off the donor compartment

Answer 5

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

Question 6

When transporting materials from donor compartment to recipient compartments, what type of protiens are transported and how are they directed in their movement

Answer 6

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

Question 7

What biomolcules are made in the ER

What happens in the golgi complex

Answer 7

Lipids/chilesterol
Steroid hormones
Secreted protiens
Integral membrane protiens
Glycosylation of protiens

Modifications of protiens occurs in the golgi complex

Question 8

When transporting materials out of the cell (secretory pathway) what type of secretions are there

Answer 8

Constitutive

Regulated

Question 9

What is constitutive secretion

Answer 9

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

Question 10

What is an example of constitutive secretion

Answer 10

Fibroblasts secreting collagen

Question 11

What is regulated secretion

Answer 11

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)

Question 12

When transporting materials into the cell (endocytic pathway) what help do this

Answer 12

Endosomes

Lysosomes

Question 13

What are endosomes

Answer 13

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

Question 14

What are lysosomes

Answer 14

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

Question 15

What are the two ways to study endo membranes

Answer 15

Autoradiography

Mutant phenotypes

Question 16

What is auto radiography

Answer 16

The process of following radioactively labeled material in the cell

Includes the pulse chase experiment

Question 17

What is the pulse chase experiment

Answer 17

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

Question 18

What is step one of the pulse chase experiment

Answer 18

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)

Question 19

What is step 2 of the pulse chase experiment

Answer 19

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

Question 20

What are the results of the pulse chase experiment

Answer 20

The labeled amino acids enzymes during the chase part began to move from er to golgi to the membrane surface

Question 21

How to we study Endomembranes based on the mutant phenotype

Answer 21

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

Question 22

Explain the results for protien 1 of the mutant phenotypes test

Answer 22

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.

Question 23

Explain the results for protien 2 of the mutant phenotypes test

Answer 23

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