#Question id: 2586
#Unit 2. Cellular Organization
Intermediate filaments are the only nonpolar fibrous component of the cytoskeleton and are not associated with motor proteins. Intermediate filaments are built from coiled coil dimers that associate in an antiparallel fashion into tetramers and then into protofilaments, 16 of which make up the filament. There are five major classes of intermediate filament proteins. Match the following proteins (Column I) with their class (Column II).
|
Column I |
Column II |
|
A. Lamins |
a. Class I |
|
B. Keratins |
b. Class II |
|
C. Desmin |
c. Class III |
|
D. Neurofilaments |
d. Class IV |
|
e. Class V |
Which of the following is correct?
#Question id: 2588
#Unit 2. Cellular Organization
Which of the following statement is correct regarding attachment of microtubule to the kinetochore?
#Question id: 2589
#Unit 2. Cellular Organization
Following statements are regarding to the mechanism of thick filament regulation.
A. In vertebrate smooth muscle, phosphorylation of the myosin regulatory light chain (LC) activates contraction.
B. At Ca2+ concentrations of more than 10−6 M, the regulatory light chain is not phosphorylated, and the myosin adopts a folded conformation.
C. When the Ca2+ level rises, Ca2+ binds calmodulin (CaM), which undergoes a conformational change (CaM*). The CaM*-Ca2+ complex binds and activates myosin light chain kinase (MLC kinase), which then phosphorylates the myosin LC. This phosphorylation event unfolds the myosin II, which is now active and can assemble into bipolar filaments to participate in contraction.
D. When the Ca2+ levels drop, the myosin LC is dephosphorylated by myosin light-chain (MLC) phosphatase, which is dependent on Ca2+ for activity, causing muscle relaxation.
Which of the following combination is correct?
#Question id: 2590
#Unit 2. Cellular Organization
Following graph represents dynamic instability of microtubules in vitro. Identify the correct activity at A, B, C and D.
#Question id: 2591
#Unit 2. Cellular Organization
What kind of information can be obtained by injecting cells with fragments of heavy meromyosin (HMM) or S1 subfragments of HMM?
#Question id: 2592
#Unit 2. Cellular Organization
What function do kinetochore-bound motor proteins perform during anaphase A?