Cytoskeleton Flashcards
Which secretory pathway doesn’t need a signal? What types of stuff gets transported on this pathway?
Constitutive secretory pathway. Add receptors to plasma membrane / secreting proteins without special features
Which secretory pathway runs through a signal cascade? What goes through it?
regulated secretory pathway. Sends out secretory proteins (have signals on them).
What signal marker diverts proteins to lysosomes?
Mannose 6-phosphate.
Do receptors go to lysosomes too? check in book
What is another word for actin filaments?
microfilaments
How many strands to actin filaments have? What are the strands?
Two strands. Helical polymers of the protein actin.
What important thing does an actin monomer have in a central cleft?
ATP or ADP
What designates the minus and plus end of an actin filament?
The orientation of subunits. They all have the same orientation
What protein causes actin to pack tightly?
fimbrin. Forms parallel bundle (orientation of all filaments is the same in terms of + and -)
Why does fimbrin packing actin tightly matter?
Tight packing prevents myosin II from entering bundle
What protein loosens up actin?
a-actinin. Forms contractile bundle (orientation of actin filaments is opposite in terms of + and -)
If there is no actin at all, how fast will it form compared to growing pre-existing actin?
Slower (lag phase)
What is it called when actin filaments aren’t growing or contracting?
equilibrium phase, steady state. Happens at Cc (critical concentration)
What needs to happen for actin filaments to be elongated?
Subunits have to be above critical concentration
What is treadmilling?
Subunits are getting removed at - end
Subunits are getting added at + end
Both happens at the same rate
At what concentration of filaments does treadmilling happen?
Intermediate concentration
What types of subunits do actin filaments contain?
T form (soluble)
D form
T subunits are at their critical concentration
D subunits are at their critical concentration
Is there the same number of subunits?
No. Cc of T requires less subunits
Cc of D requires more subunits
Treadmilling happens when you’re both above the critical concentration of T and below the critical concentration of D
Why? (Read book on this)
Why must proteins released to extracellular space need to be soluble?
Where do these proteins come from? How are they transported?
Soluble because that way they can get through membrane
Come from trans golgi, transported in lipids which become part of plasma membrane.
Which pathway are neurotransmitters exocytosized through? Why?
Regulated secretory pathway.
They need to wait by the plasma membrane in secretory vesicles
Which pathway are most membrane lipids and membrane proteins added through?
Constitutive secretory pathway
Lipids come from the vesicles themselves, membrane proteins attached to vesicles during travel
Where in relation to the ER / cytoplasm are the cisternae of the trans golgi network?
Cis golgi network?
Trans is closer to the cytoplasm
Cis is by the ER
What makes up a single intermediate filament coiled-coil dimer?
Two dimers wrapped around each other
antiparallel (n-terminus next to c-terminus)
What makes up a single intermediate filament? How do they grow?
Two coiled-coil dimers form a tetramer by lining up (c-terminus next to c-terminus, staggered)
8 tetramers line up in parallel. 32 individual a-helical coilds per filament.
To grow, another circular set of 8 filaments adds on to the end
Where can a dense network of intermediate filaments be found? Why? What are they called?
Nuclear lamina (called nuclear lamins).
Anchorage site for chromosomes / nuclear pores
