Protein Sorting and Transport

Question 1

List 4 organelles that play roles in protein sorting and transport

Answer 1

The Endoplasmic Reticulum (ER)
The Golgi Apparatus
Endosomes
Lysosomes

Question 2

What do eukaryotic cells have that seperate them from prokaryotes?

Answer 2

Membrane-enclosred organelles.
Ex. the nucleus
Organelles are just floating around in the cytoplasm in prokaryotic cells.

Question 3

What is the purpose of the membrane enclosed organelles in eukaryotes?

Answer 3

Subdividing the cytoplasm into sections allow cells to function efficiently.
Normally the larger size of these cells would make things much more difficult otherwise

Question 4

How much larger are eukaryotes than prokaryotes?

Answer 4

Approximately 1000 times the volume

Question 5

What is the endoplasmic reticulum?

Answer 5

A network of membrane-enclosure tubules and sacs

Question 6

Where is the endoplasmic reticulum located in a cell?

Answer 6

Extending out of the nuclear membrane, throughout the cytoplasm

Question 7

What is the largest organelle of most eukaryotic cells?

Answer 7

The endoplasmic reticulum!

Question 8

What are the two domains of the endoplasmic rediculum?

Answer 8

The rough endoplasmic reticulum
and
The smooth endoplasmic rediculum

Question 9

Describe the form and function of the rough endoplasmic reticulum

Answer 9

Covered by ribosomes on the outer surface

-

Question 10

Describe the form and function of the smooth endoplasmic reticulum

Answer 10

No ribosomes

Involced in lipid metabolism

Question 11

What are ribosomes?

Answer 11

A cell structure found in th cytoplasm that is involved in the synthesis of proteins

Question 12

When was the role of the endoplasmic reticulum in protein processing and sorting discovered and by who?

Answer 12

1960s

by Palade and colleagues

Question 13

How was the endoplasmic reticulums function discovered?

Answer 13

When studying pancreatic acinar cells that secrete digestive enzymes in the small intestine.
Proteins were radiolabeled and were tracked through the endoplasmic reticulum, golgi apparatus, secretory vesicles, and then outside the cells.

Question 14

What is autoradiography?

Answer 14

A technique that uses x-ray to view the radioactive decay of cells that have been labelled as radioisotopes

Question 15

List all the sections of the SECRETORY PATHWAY

Answer 15

rough ER -> Golgi -> secretory vesicles -> cell exterrior

Question 16

When does sorting take place in eukayotic cells?

Answer 16

During translation

Question 17

What happens to proteins synthesized on free ribosomes?

Answer 17

They remain in the cytosol OR are transported to the nucleus and other organelles

Question 18

What happens to proteins synthesized on membrane bound ribosomes?

Answer 18

They are translocated directly to the endoplasmic reticulum

Question 19

What targets ribosomes to the endoplasmic reticulum?

Answer 19

A signal sequence at the amino terminus (N terminus)

Question 20

What is the amino terminus?

Answer 20

A sequence of amino acids that signals the beginning of a protein chain

Question 21

What happens when a polypeptide chain enters the endoplasmic reticulum?

Answer 21

The N terminal is removed from the chain

Question 22

How was the role of signal sequences discovered?

Answer 22

By studying in vitro preparations of the rough endoplasmic reticulum

Question 23

What happens when cells are cells are disrupted?

Answer 23

The endoplasmic reticulum breaks up into small vesicles called microsomes

Question 24

Of the two types of endoplasmic reticulum, which form microsomes when broken apart?

Answer 24

Both of them!

The form smooth and rough microsomes respectively.

Question 25

How can a density gradient be used to isolate organelles?

Answer 25

Different organelles of a cell can be separated according to its density.

The cells are added to a test tube with a substrate such as sucrose, and the tub is then turned on it’s side and spun. The cylindrical force causes the more dense molecules to sink to the bottom and separates all organelles in order of density.

Question 26

ASK QUESTION ABOUT HOW EXPERIMENT WAS DONE AND WHAT WAS LEARNED sLIDE 19

Answer 26

1975
Blobel and Sabatini
WATCH VIDEO OF EXPERIMENT