BIOL130 Lecture Notes - Lecture 6: Nuclear Export Signal, Nuclear Localization Sequence, Signal Recognition Particle

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raspberryweasel693

27 Feb 2015

School

University of Waterloo

Department

Biology

Course

BIOL130

Professor

Engelheardt/ Holyoak

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UNIT 7: INTRACELLULAR COMPARTMENTS & PROTEIN SORTING

Glory Widjaja

Relative Volumes & Numbers of Organelles within Cell

Compartment % Compartment

Cytosol 54 1

Mitochondria 22 1700

ER 12 1

Nucleus 6 1

Golgi 3 1

Peroxisomes 1 400

Lysosomes 1 300

Endosomes (temporary

vesicles)

1 200

Organization of Eukaryotic Cell

-not random

Important:

- cell shape

- cell motility

- position/movement organelles

- movement materials within (chromosomes mitosis)

3 Ways to Import Proteins into Organelles

- protein sorting: transfer of proteins into compartments where they are needed

-***synthesis of all proteins starts in cytosol @ FREE RIBOSOMES

- all protein transport requires energy

Via Nuclear Pores - proteins pass through without unfolding

Features

- basketball net (nuclear basket)

- highly selective gate

- DNA & RNA nucleotides can get in (small proteins)

- enter and exit

- several subunits of proteins

- complexes form

-space between fibrils wide = not blocking pores

What moves in Nucleus?

- histones, ribosomal proteins, proteins for transcription

- dNTP, rNTP

What moves out?

- mature mRNA

- rRNA (made in nucleolus)

What is needed?

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- nuclear localization signal: amino acid sequence that tags a protein for import into the

nucleus by nuclear transport

- nuclear export signal: tags a protein for export

Via Across Memebrane (mitochondria & chloroplasts)

- both double membrane (chloroplast has third - thylakoid)

- own genomes & ribosomes, proteins need to be imported

Mitochondria

1) synthesis protein on free ribosome (cytosol)

2) signal sequence at N-terminus

3) bind to import receptor protein (outer membrane) laterally

4) proteins moved across both membranes & special sites (protein translocator - inner

membrane) & threads in

5) signal sequence cleaved off by signal peptidase

*PROTEIN UNFOLDED TO IMPORT, REFOLD & THEN SIGNAL SEQUENCE REMOVED*

*molecular chaperones: help refold

Endoplasmic Reticulum

- polyribosome (multiple ribosome on mRNA) = membrane bound (on ER with sequence

targeted for ER) OR free ribosome

- ER most extensive part of endomembrane system

- entry point for not only ER proteins themselves (also Golgi, lysosomes, endosomes, cell

surface, secretory, endomembrane system)

*ONCE IN ER, NEVER GO BACK OUT*

Types

a) water soluble (completely across ER)

b) partially across (plasma, ER, another organelle)

ER Signal Sequence & SRP (ribosome to ER)

1) protein with SRP (signal recognition particle) attached to end with signal sequence

2) attaches to SRP receptor in ER membrane

3) SRP thrown & recycled

4) protein put through translocation channel

5) thread to ER (cross membrane still being synthesized)

a) Soluble Protein Path (still starts on free ribosomes)

1) translocation channel binds to signal sequence and actively transfers polypeptide in

2) at some point of translocation, signal cleaved into bilayer & degraded

3) polypeptide released into ER lumen

4) pore of channel closes

b) Single Pass Protein Path

1) N-terminal ER signal initiates transfer, protein has a 2nd hydrophobic sequence= stop it

hits translocation channel & discharges protein sideways

2) N-terminal sequence cleaved off & transmembrane protein left anchored

3) translation occurs at cytosolic

Via Vesicles

- traffic flow = outward from ER --> Golgi --> plasma membrane

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Document Summary

Relative volumes & numbers of organelles within cell. Protein sorting: transfer of proteins into compartments where they are needed. ***synthesis of all proteins starts in cytosol @ free ribosomes. Via nuclear pores - proteins pass through without unfolding. Dna & rna nucleotides can get in (small proteins) Space between fibrils wide = not blocking pores. Nuclear localization signal: amino acid sequence that tags a protein for import into the nucleus by nuclear transport. Nuclear export signal: tags a protein for export. Both double membrane (chloroplast has third - thylakoid) Own genomes & ribosomes, proteins need to be imported. *protein unfolded to import, refold & then signal sequence removed* Polyribosome (multiple ribosome on mrna) = membrane bound (on er with sequence targeted for er) or free ribosome. Er most extensive part of endomembrane system. Entry point for not only er proteins themselves (also golgi, lysosomes, endosomes, cell surface, secretory, endomembrane system)

Related Questions

1. Name two similarities and two differences between thecellular processes of importing

protein into the ER and importing protein to the nucleus.

2. What proteins are directly involved in the transportation ofcargo in a clathrin-coated

vesicle?

a. Dynamin

b. Adaptins

c. Cargo receptors

d. t SNARES

3. Suppose a cell was treated with colchiine, a drug causingmicrotubule disassembly.

What would happen within the cell? Why?

Suppose there were a genetic defect in the genes that code forkinesins and dyneins.

What would happen within the cell? Why?

4. Which of the following are true about microtubules?

a. They are utilized by the disease causing bacteriaLysteria.

b. Instability in the minus-end of the microtubule is caused bythe hydrolization of GTP.

c. Centrosomes contain binding sites for microtubules composed atype of tubulin ring.

d. Cellular concentrations of tubulin are above the criticalconcentration for plus-end

polymerization.

e. Motor proteins can attach organelles to the microtubules.

5. Indicate which of the following statements are false:

a. Membrane fusion is energetically unfavorable and thusrequires ATP or similar high

energy molecule to occur

b. Clathrin is responsible for capturing specific molecules fortransport in coated vesicle

structures.

c. Receptor proteins that are incorporated into an endosome canbe retrieved back to the

membrane domain it originated from; can return to a new domainof the membrane; or

can enter the lysosome for digestion.

d. Transport vesicles occasionally bud from the trans Golginetwork to fuse with the

plasma membrane in a process called constitutive exocytosis.

e. Most components of the endocytic vesicle membrane eventuallyare returned to the

plasma membrane for reuse.

6. Match the following organelles with their function:

Organelle Bank:

a. Mitochondria

b. Endoplasmic reticulum

c. Nucleus

d. Lysosome

e. Endosome

f. Peroxisome

g. Golgi apparatus

_____ quality control of mRNA

_____ location of oxidative phosphorylation

_____ responsible for detoxifying organic molecules (livercells)

_____ houses and protects genetic material

_____ responsible for modification and sorting of proteins andlipids

_____ location of ATP synthesis

_____ responsible for sorting endocytosed materials

_____ site of degradation and digestion

_____ responsible for oxidizing toxic molecules

_____ location of lipid synthesis

_____ location of hormone synthesis (adrenal cells)

B. Which organelle(s) from the above list communicate(s) withother organelle(s)

through the use of vesicular transport? ________________

C. Which organelle(s) from the above list receive proteins madein the

cytosol?___________________

D. Through which organelle(s) must proteins pass to reach theorganelle(s) which do not

receive proteins made exclusively in thecytosol?______________

E. Entrance into which organelle(s) requires that proteinsunfold and snake through the

membrane? _________________

F. How do organelles maintain their position in the cytosol? Bespecific.

G. Give 2 advantages that eukaryotic cells gain by havingorganelles.

7. Which of the following statements are true regardingactin?

a. They are arranged in a

crimsonwalrus870

i need help with this homwork please choose the correct answers and just be claer to read and understand for the slect the apply qusestions too and it is important i realy need the right answers so please be claer not write randomly i really need the correct answers to study for my test so hop you can help me

Question 1

What is the smallest cell you could find?

Question 2

TEMs appear as 3D images

True

False

Question 3

Bacteria are what cell type? Write one word as the answer in lowercase and using no syntax.

Flag this Question

Question 42 pts

ALL eukaryotic cells have which of the following. Click all that apply.

membrane enclosed cell organelles

mitochondria

Question 5

Prokaryotes and eukaryotes both have which if the following cellular components. Click all that apply.

Question 6

I am made of one 60s and one 40s subunit, which organelle am I?

protein

lipid

bacterial ribosome

Question 9

The difference between the rough and smooth ER is

the rough produces lipids where as the smooth does not

the rough has many folds and convolutions where as the smooth does not

the rough has ribosome embedded and the smooth does not

the rough is closer to the cell membrane whereas the smooth is closer to the nucleus

Question 10

The site where many lipids, including cell membrane is produced.

Question 11

Name the organelle: In muscle cells in particular, I would increase in number and size in response to frequent exercise

Question 12

In animal cells, glucose would be mobilized from its storage molecule (glycogen) in this part of the cell.

Question 13

Which of these is associated with the rough ER

production of carbohydrates

production of steroid hormones

production of ATP

production of proteins that are secreted from the cell

Question 14

Which organelle sorts, modifies and stores substances produced on the rough ER. Write two words as the answer in lower case separated by a space.

Question 15

Which organelle is responsible for ATP production. Write one word in the singular as the answer.

Question 16

You inherit all of your mitochondria from your

father

half from your mother and half from your father

your siblings

mother

Question 17

An organelle that contains chlorophyll

Question 18

Microtubules have a variety of roles, which of the options below is NOT one of them?

separate chromosomes

cilia and flagellum movement

tracks for organelle movement

constrict the cell during cell division

Question 19

Made of tubulin subunits

microfilaments

chromosomes

intermediate filaments

microtubules

Question 20

Name the part of the cytoskeleton that is made of two twisted rods of actin. Write one word as the answer in lower case.

Question 21

Which part of the cytoskeleton is made of the same protein as your hair and nails?

microfilaments

microtubules

Intermediate filaments

Question 22

The extracellular matrix is found outside of, but attached to the cell membrane?

True

False

Question 23

Which of the options below is an important function of the extra cellular matrix?

connecting cells together

regulate the movement of substances into and out of the cell

helping cells divide into two cells

keeping the cell in a fixed and ridged shape

Question 24

Which part of the cell wall has a high pectin content?

Question 25

Plants have mitochondria, chloroplasts, a cell wall, and nuclei.

True

False

Question 27

What accounts for 40% of the protein in our bodies?

Question 28

Animal cells have cell walls

True

false

________30. If you are investigating the inner structure of a new cell and see that it has a significantly larger amount of RER than other cells. You would conclude the cell does a great deal of____?
A. ATP synthesis

B. protein synthesis
C. DNA synthesis
D. active transport
E. polysaccharide hydrolysis

________31. If a cell comes in contact with a toxic substance such as H2O2, it could survive as long as it has a ___ to digest it.
A. DNA
B. peroxisome

C. mitochondria
D. phospholipids
E. intermediate filaments

________32. Some cells have structures to help them withstand osmotic pressure. For example,
A. Plant cells due to their walls
B. Animal cells due to the sodium/potassium pumps

C. Bacterial cell due to their swimming

D. Viruses due to their protein coats

________33. Evolution occurs only as a cell ____.

A. They undergo mitosis
B. Change in their gene pool
C. They move from one habitat to another

D. They begin to eat different foods

________34. Ribosomes are produced in the

A. nucleoli.
B. chromatin.
C. nuclear envelopes.

D. Golgi complex. E. cisternae.

________35. Algae are often green, but there are red and brown species also. What accounts for this difference in color?
A. The chlorophyll of chloroplasts
B. The pigments in other plastids

C. The presence of a mitochondria
D. The accumulation of cellular wastes

________36. The chloroplast and other like prokaryotes have which of the following that helps with photosynthesis?
A. They live in water based environments
B. They have chloroplasts in their cytoplasm

C. Change color in the dark vs. the sun
D. They have photoreceptor proteins in their membranes or mesosomes.

________37. Located in the membrane, we see a set of proteins called receptors that only connect with or bind to specific substances. This is called __.
A. ligand specificity.
B. hormone selectivity.

C. cell tonicity.
D. water saturation. E. signal resolution.

________38. Of the following statements, we could say that ___ is false.
A. All organisms are composed of cells and cell products.
B. An organism's structure and all of its functions are due to the activities of cells.
C. The cellular organelles are the simplest structural and functional unit of life.
D. Cells come from preexisting cells.
E. Cells are made from nonliving components including the nucleus, cell membrane and cytoplasm.

________39. If it is really true that our cells are the smallest anatomical unit that meets all of the properties of life, then which of the following could imply otherwise?
A. vacuoles
B. centrioles

C. Golgi apparatus
D. mitochondria
E. endoplasmic reticulum

________40. Oxygen is an absolute need for animal and plant cells alike due to the ___.

A. RER
B. Mitochondria
C. Lysosomes

D. DNA

________41. In a plasma membrane, we expect to see the carb/protein structures to extend into the ___, but the secondary messengers to move within the __.
A. extracellular fluid; cytosol
B. cytosol; extracellular fluid

C. intracellular fluid; cytosol

D. cytosol; intracellular fluid

E. extracellular fluid; plasma

________42. Bacteria are found in all of the following habitats:

A. Caves
B. Oceans
C. Animals

D. Everywhere on Earth

________43. Two solutions are separated by a selectively permeable membrane. Solution A has a higher concentration of an impermeable solute compared to solution B. Which of the following do you expect would happen?
A. solute will move from solution A to solution B

B. solute will move from solution B to solution A

C. water will more from solution A to solution B

D. water will move from solution B to solution A E. no movement of solute or water will occur

________44. In the kidney, we notice that almost all of the cells involved in the production of urine have high concentrations of the Na+/K+ pump. Which typically works to push Na+ ___ its concentration gradient by using ___.
A. up; active transport

B. up; facilitated transport
C. up; cotransport
D. down; active transport
E. down; facilitated transport

________45. In the charts of a patient recently admitted to the hospital noted that he was taking a medication called lithium and high doses of calcium supplements. Given this, we would expect the patientâs liver to have a higher than normal amount of __ to purify out the lithium and calcium.

A. lysosomes.
B. centrosomes.
C. mitochondria.
D. peroxisomes.
E. rough endoplasmic reticulum.

________46. We have long observed that our neural cells in the brain cannot replicate or replace themselves due to the lack of ____.
A. produce ATP.
B. divide.

C. produce enzymes.
D. secrete material across their plasma membrane E. conduct electrical signals.

________47. An organismâs structure and function is ultimately due to the structure and function of itâs __.
A. Organs
B. Tissues

C. Cells

D. Nuclei

BIOL130 Lecture Notes - Lecture 6: Nuclear Export Signal, Nuclear Localization Sequence, Signal Recognition Particle

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