Chapter 8A The Endomembrane System

Biology 329 with Hoyle at University of Louisville

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Created: 2012-03-06
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Endomembrane System

Extensive network of membrane-bound organelles in cytoplasm

Endoplasmic reticulum (rough and smooth)

Golgi Complex

Secretory granules
Secretory Vesicles
Lyosomes, Endosomes, Vacuoles

What does the endomembrane system do?

Moves proteins to the final destination.

What are the two major shuttling pathways?

Secretory/biosynthetic
Endocytic

What do the secretory/biosynthetic pathways do?

They move proteins synthesized at rough ER through Golgi to final destination of:

extracellular space = secretion, exocytosis
plasma membrane (integral membrane proteins)
lysosome

A) constitutive by secretory vesicles
B) regulated secretory granules

What do the endocytic pathways do?

They bring materials in from

extracellular space
plasma membrane (bound to receptor)

Endosome

What is an organelle formed by endocytosis.

Transport Vesicles

Movement between compartments of the Endomembrane System

How are proteins directed to their proper destination?

By targeting signals/sorting signals

Targeting Signals/Sorting Signals

Sequences of amino acids in the proteins themselves or oligosaccharides attached to the proteins

signals are recognized by internal receptors in the membranes of transport vesicles

Name three techniques for visualizing proteins

Radioactive labeling
GFP fusion proteins
Antibodies to Proteins

Radioactive Labeling

Incubate tissue with radioactive amino acids
fix tissue
Cover with photographic emulsion

What is autoradiography?

When the protein is covered with phrgotographic emulsion. Radioactivity causes silver to precipitate into black granules visible by microscopy.

Explain the pulse-chase experiment?

Pulse = BRIEF incubation with radioactive amino acid

Chase = Longer incubation with UNLABELED amino acid

What is the drawback of radioactive labeling?

Have to label every protein that is being made.

What does GFP stand for?

Green Fluorescent Protein

What are the drawbacks of the GFP fusion proteins technique?

track one specific protein
must work with live cells

What is the procedure for injecting antibodies to proteins?

Purify Protein X
Inject into rabbit
Isolate antibodies to protein X from rabbit serum
Link antibody to molecules that can be visualized by electron mocroscopy

Why is immunofluorescent staining done?

To detect a protein in the rough ER

When cells are homogenized; membrane fragments of the endomembrane system (ER, Golgi) form smaller vesicles called?

Microsomes ( can be artifacts of lab experiments)

How do PURIFIED microsomes differ from "regular" microsomes?

They maintain some biological activity & thus provide a cell free system for experiments.
Can further purify proteins of ER or Golgi for identification, antibody production

What is RER?

Rough Endoplasmic Reticulum; ribosomes are attached on cytosolic surface;

What is SER?

Smooth Endoplasmic Reticulum; lacks ribosomes

Cisternae

Channels are flattened sacs on RER; channels are tubular on SER

What are the functions of the SER ( Smooth Endoplasmic Reticulum)?

Synthesis of steroid hormones in gonad and endocrine cells
Detoxification in liver of many compounds( ex... barbiturates & ethanol)

Oxygen-transferring enzymes convert these compounds into more hydrophilic derivatives that can be easily excreted.

Sequestering Ca²+ ions: Regulated release of Ca ²+ ions from SER triggers:

What two functions occur with respect to SER (Sarcoplasmic Reticulum)?

Skeletal and cardiac muscles contract..(Tissue in these muscles Sarcoplasmic Reticulum)
Fusion of secretory granules with the plasma membrane

What are the functions of the Rough Endoplasmic Reticulum-RER?

Site of synthesis ( and carbohydrate modifications) for proteins that are

secreted
integral membrane proteins
proteins localized to endomembrane organelles ( ex...lysosomes)

Site of synthesis for membrane phospholipids

In ______ _______, endomembrane structures are highly polarized, reflecting the flow of secretory products from synthesis at the RER to discharge into duct.

Secretory Cells

What is translation of all mRNAs into protein that starts on free ribosomes in the cytoplasm?

Protein Localization

see slide

What is the signal sequence function?

for docking a translating ribosome at the RER

What are the steps in the signal sequence function?

Signal Recognition Particle( SRP)

SRP binds SRP receptor on RER = docks ribosome at RER
Docked ribosomes binds transcolon = channel in RER membrane

Signal sequence is passed into transcolon, displacing plug

Growing polypeptide is co-translationally inserted into RER lumen

About this deck

By: Tommy Leveston
Created: 2012-03-06
Size: 31 flashcards
Views: 26

About StudyBlue

“Simply amazing. The flash cards are smooth, there are many different types of studying tools, and there is a great search engine. I praise you on the awesomeness.”
Dennis