Cell Systems Flashcards
Function of the nuclear pore complex (NPC)?
regulate import/export (nuclear transport)
Proteins that want to be imported into the cell need ___________ to enter.
nuclear localization sequence (NLS tag)
Where is the NLS sequence located?
the C-terminus of the proteins that want to be imported
The NLS can be compared to what?
a password… if the protein does not have the password, it can not enter the nucleus
How does the endomembrane system function?
protein sorting, packaging, shipping, and recycling
What can the endomembrane system be compared to?
a UPS store
What is the order of organelles in the endomembrane system?
rough ER –> golgi apparatus (cis then trans) –> vesicles –> destination (organelles or plasma membrane)
How are proteins ensured to reach their locations in the endomembrane system?
they have different tags/receptors that ensure they are packaged and shipped to correct locations (packing slip like UPS)
Describe the secretory pathway.
- protein enters the ER
- proteins exit the ER
- protein enters golgi
- protein exits golgi
- protein is secreted from cell
What is the signal hypothesis?
how proteins are targeted to the rough ER
Describe the steps of the signal hypothesis.
- ER signal sequence is synthesized.
- Er signal sequence binds to signal recognition particle (SRP)
- SRP binds to a receptor
- Protein enters ER through the translocon
- Er signal sequence is removed
What is the ER signal sequence?
short sequence located at the N terminus (password for the ER)
What other things occur in the ER?
- protein folding
- protein “tagging”
- folded and tagged proteins are sent to golgi
protein folding is assisted by ______
chaperones
proteins undergo _____ to become _______
glycosylation; glycoproteins
What happens in the golgi?
- proteins bound for different destinations carry distinct tags (tags are recognized by corrresponding receptors)
- proteins are sorted
- transport vesicles bud
- cytosylic and membrane proteins cause transport vesicles to attach and fuse at destinations
- vesicles deliver contents
What is the mannose-6-phosphate?
- a type of tag
- lysosome password
- monomer w/ a phosphate attached
What are examples of things containing the mannose phosphate tag?
hydrolases and proton pumps (acidify proteins)
What are the types of recycling material in the lysosome?
- receptor-mediated endocytosis
- phagocytosis
- autophagy
What is phagocytosis?
“cell eating”
What is autophagy?
“self-eating”
What are the types of filaments in the cytoplasm?
- microfilaments
- microtubules
- intermediate filaments
describe microfilaments
- aka actin filaments
- two coiled strands
- subunit: actin
What is the specific function of microfilaments?
movement of cells via muscle contraction or cell crawling
describe intermediate filaments
- fibers wound into thick cables
- subunits: keratin and lamins
What is the specific function of intermediate filaments?
-maintain cell shape resisting tension (pull)
- anchor nucleus/other organelles
describe microtubules
- hollow tubes
- subunits: alpha and beta tubulin dimers
What is the specific function of microtubules?
- move cells via flagella or cilia
- move chromosomes during cell division
- provide tracks for intracellular transport
Myosin is a ________
motor protein
What does myosin do?
converts chemical energy to kinetic/mechanical energy
Describe muscle contraction.
when myosin head attaches to actin and moves, the actin filaments slide
What is involved in intracellular transport?
kinesin and microtubules; kinesin walks along microtubule track
Describe the microtubule-organizing center (MTOC).
- plants: many throughout cells
- animals: centrosomes (two centrioles)
