Question

Which cytoskeletal element is being described? Answer with the letter corresponding to the element: M. Microtubules A. Actin filaments IF. Intermediate filaments 1. Formation requires nucleation at a centrosome 1 2. Forms the contractile ring during cytoplasmic division (cytokinesis) 2 3. Found organized in a characteristic 9+2 arrangement in cilia and flagella 3 4. Examples include keratin and neurofilaments, which are important in the mechanical strength of skin and axons 4 5. Involved cellular crawling such as seen with white blood cells (e.g., macrophages) 5 6. Forms the mitotic spindle 6 7. Interact with the motor proteins kinesin or dynein to move vesicles and organelles 7 8. Have polarity (that is, the two ends of the filament differ) 8

Answer 1

ANSWER:

1.Formation requires nucleation at a centrosome -  M.(microtubules)

Reason- Micrortubule nucleation is the event of de-novo formation

2.Forms the contractile ring during cytoplasmic division (cytokinesis)- A.(Actin filaments)

Reason- The contractile ring during cytokinesis at anaphase is done by formation of ring made up of actin microfilaments.

3. Found organised in characteristic 9+2 arrangement in cilia and flagella- M.(microtubules)

Reason- Cilia and flagella have a core composed of microtubules which is arranged as 9+2 pattern, which is connected by plasma membrane.

4.Examples include keratin and neurofilaments which are important in mechanical strength of skin and axons-( IF. Intermediate filaments)

Reason- Intermediate filaments are apolar , and composed of various proteins that are expressed in different types of cells. They are divided into six major groups - including keratin and neurofilaments.

5. Involved in cellular crawling such as seen in WBC (eg macrophages)-A.(Actin filaments)

Reason- The crawling of cells as seen in case of WBC( macrophages) is due to Actin Polymeristation as well as acto-myosin contractility.

6.Forms the mitotic spindle-  M.(microtubules)

Reason- Mitotic spindle is a typical structure that forms during cell division . It is constituted by microtubules.

7. Interact with motor protein kinesin or dynein to move vessicles and organelles- M.(microtubules)

Reason- Microtubules interacts with two motor proteins kinesins and dyneins ususlly to cargo organelles such as vessicles from the centre to the periphery of the cells.

8.Have polarity (that is the two ends of filament differ)-A.(Actin filaments) and M.(microtubules)

Reason- Both actin filaments and microtubules are with two different and distinct ends, called plus and minus ends and thus is called polar.