Which of the following statements is a correct description o

Which of the following statements is a correct description of a microtubule? A microtubule is composed of only alpha-tubulin A microtubule is an polar structure During polymerization of a microtubule. GTP on both, alpha and beta-tubulin is hydrolyzed A microtubule is smaller than an intermediate filament A microtubule is made up of 13 protofilaments What is the function of gamma-tubulin? It is a critical component of the microtubule It nucleates microtubules at the centrosome It proteas the (+) end from dynamic instability it binds alongside the microtubule It is a critical component of the centriole Which statement below describes a feature that is shared between kinesin and dynein? Both proteins \"walk\" towards the (+) end of a microtubule Both proteins \"walk\" towards the (-) end of a microtubule Both proteins bind ATP and F-actin Both proteins function in the positioning of organelles inside a cell Both proteins associate with the same regulatory factors Which of the following statements best describes the GTP cap on a microtubule? a A microtubule binding protein that caps the (-) end of a microtubule A microtubule protein that caps the (+) end of a microtubule It promotes microtubule shrinkage at the (+) end It stabilizes the (-) end It is necessary for growth at the (+) end

Solution

Answers:

1. Correct Answer: e

A microfilament is made up of 13 protofilaments.It is true for eukaryotes. In the case of bacteria, it is 5. Regulated assembly of protofilaments forms the microtubules.

Wrong Options

option a. Microtubule is composed of both alpha and beta tubulin.

b. Microtubule is polar, it is composed of both - and + ends.

c. During polymerisation, GTP at beta-tubulin is only hydrolysed.

d. Microtubule is 20-25 nm in diameter cylindrical tubes whereas Intermediate filaments are only 10 nm diameter. So latter are smaller compared to microtubules.

2. Correct Answer: b It helps in nucleation of the microtubule, though it is not an integral component of the microtubule.

\'3. Correct Answer: d. Both function in positioning the organelles inside the cell.

Kinesins mostly move toward the plus end of the microtubule whereas dyneins travel toward the minus end of the microtubule (towards the center of the cell). Thus, kinesins help to carry cargoes to the periphery of the cell (for example Endoplasmic reticulum), while dyneins help to bring cargoes/vesicles to the center of the cell (for example golgi complex).

4. Correct answer: d. GTP cap stabilizes ( -) end protecting or preventing from disassembly of the microtubule.