Cell Systems

Question 1

Function of the nuclear pore complex (NPC)?

Answer 1

regulate import/export (nuclear transport)

Question 2

Proteins that want to be imported into the cell need ___________ to enter.

Answer 2

nuclear localization sequence (NLS tag)

Question 3

Where is the NLS sequence located?

Answer 3

the C-terminus of the proteins that want to be imported

Question 4

The NLS can be compared to what?

Answer 4

a password… if the protein does not have the password, it can not enter the nucleus

Question 5

How does the endomembrane system function?

Answer 5

protein sorting, packaging, shipping, and recycling

Question 6

What can the endomembrane system be compared to?

Answer 6

a UPS store

Question 7

What is the order of organelles in the endomembrane system?

Answer 7

rough ER –> golgi apparatus (cis then trans) –> vesicles –> destination (organelles or plasma membrane)

Question 8

How are proteins ensured to reach their locations in the endomembrane system?

Answer 8

they have different tags/receptors that ensure they are packaged and shipped to correct locations (packing slip like UPS)

Question 9

Describe the secretory pathway.

Answer 9

1. protein enters the ER
2. proteins exit the ER
3. protein enters golgi
4. protein exits golgi
5. protein is secreted from cell

Question 10

What is the signal hypothesis?

Answer 10

how proteins are targeted to the rough ER

Question 11

Describe the steps of the signal hypothesis.

Answer 11

1. ER signal sequence is synthesized.
2. Er signal sequence binds to signal recognition particle (SRP)
3. SRP binds to a receptor
4. Protein enters ER through the translocon
5. Er signal sequence is removed

Question 12

What is the ER signal sequence?

Answer 12

short sequence located at the N terminus (password for the ER)

Question 13

What other things occur in the ER?

Answer 13

1. protein folding
2. protein “tagging”
3. folded and tagged proteins are sent to golgi

Question 14

protein folding is assisted by ______

Answer 14

chaperones

Question 15

proteins undergo _____ to become _______

Answer 15

glycosylation; glycoproteins

Question 16

What happens in the golgi?

Answer 16

1. proteins bound for different destinations carry distinct tags (tags are recognized by corrresponding receptors)
2. proteins are sorted
3. transport vesicles bud
4. cytosylic and membrane proteins cause transport vesicles to attach and fuse at destinations
5. vesicles deliver contents

Question 17

What is the mannose-6-phosphate?

Answer 17

• a type of tag
• lysosome password
• monomer w/ a phosphate attached

Question 18

What are examples of things containing the mannose phosphate tag?

Answer 18

hydrolases and proton pumps (acidify proteins)

Question 19

What are the types of recycling material in the lysosome?

Answer 19

1. receptor-mediated endocytosis
2. phagocytosis
3. autophagy

Question 20

What is phagocytosis?

Answer 20

“cell eating”

Question 21

What is autophagy?

Answer 21

“self-eating”

Question 22

What are the types of filaments in the cytoplasm?

Answer 22

• microfilaments
• microtubules
• intermediate filaments

Question 23

describe microfilaments

Answer 23

• aka actin filaments
• two coiled strands
• subunit: actin

Question 24

What is the specific function of microfilaments?

Answer 24

movement of cells via muscle contraction or cell crawling

Question 25

describe intermediate filaments

Answer 25

• fibers wound into thick cables
• subunits: keratin and lamins

Question 26

What is the specific function of intermediate filaments?

Answer 26

-maintain cell shape resisting tension (pull)
- anchor nucleus/other organelles

Question 27

describe microtubules

Answer 27

• hollow tubes
• subunits: alpha and beta tubulin dimers

Question 28

What is the specific function of microtubules?

Answer 28

• move cells via flagella or cilia
• move chromosomes during cell division
• provide tracks for intracellular transport

Question 29

Myosin is a ________

Answer 29

motor protein

Question 30

What does myosin do?

Answer 30

converts chemical energy to kinetic/mechanical energy

Question 31

Describe muscle contraction.

Answer 31

when myosin head attaches to actin and moves, the actin filaments slide

Question 32

What is involved in intracellular transport?

Answer 32

kinesin and microtubules; kinesin walks along microtubule track

Question 33

Describe the microtubule-organizing center (MTOC).

Answer 33

• plants: many throughout cells
• animals: centrosomes (two centrioles)