Question

A.Microtubules can be assembled and disassembled quickly in response to the cellular changes is because:

Choose one answer

Answers:               

1. Cells synthesize tubulin proteins very fast.

2. Cells can turn other cytoskeletal filaments into microtubules

3. Microtubules have an instable plus end and microtubules are probably organized by weak non-covalent interactions

4. The motor proteins of microtubules can organize the microtubules in response to the cellular changes

B.Kinesin is the motor protein that coorporates with microtubules. It has the following functions:

Could be more than one answer

Answers:               

1. It uses GTP as energy source.

2. It can hydrolyze ATP and use the energy to drive cargo along microtubules from minus end to plus end.

3. It has a globular head that can act as GTPase

4. The tail of kinesin is more diverse and binds to cargo

C.During actin filament polymerization:

Choose one answer

Answers:               

1. GTP-actin monomers are required to incorporate in the growing polymer.

2. Both the plus end and minus end of actin filaments can grow at the same speed.

3. Both the plus end and minus end can grow, but at a different speed.

4. Actin filaments can only grow at its plus end.

Answer 1

A. GTP hydrolysis in microtubules brings "dynamic instability" resulting cycle of growth and shrinkage of the micro tubules. So, the right answer is: 3. Microtubules have an instable plus end and microtubules are probably organized by weak non-covalent interactions.

B. To drive cargo the power currency ATP is expensed and kinesin usually drive cargo along microtubules from minus end to plus end. So, the right answer is: 2. It can hydrolyze ATP and use the energy to drive cargo along microtubules from minus end to plus end.

C. Actin filament also called as microfilament. It is shown by electron micrograph that the barbed (+ve) end grows faster then pointed (-ve) end. So, the right answer is: 3. Both the plus end and minus end can grow, but at a different speed.