[Biology]Orientation of microtubules

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In summary, it is likely that both orientations of microtubules exist in the axon of a nerve cell due to their dynamic nature and the presence of both positive and negative ends.
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Homework Statement


1. Because cytoplasmic vesicles are seen to move in both directions in the axon of a nerve cell, can you conclude that some of the microtubules are orientated with their plus-end facing the axon terminus and others orientated with the opposite polarity? Why or why not?

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The Attempt at a Solution


The positive end is designated for the addition of actin subunits, where the ATP-binding cleft of the terminal actin subunit contacts the neighboring subunit (barbed). The negative end is favored for dissociation, where the cleft is exposed to the surrounding solution. Since the cleft is exposed, ATP will bind, hydrolysis of the bound nucleotide reduces the affinity of the subunit for neighboring subunit, and therefore the negative end is favored for dissociation.
 
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Given this information, it is reasonable to conclude that some microtubules are oriented with their plus end facing the axon terminus and others orientated with the opposite polarity. This is because microtubules are dynamic structures with the ability to grow and shrink in either direction. Therefore, it is possible for microtubules to be orientated in both directions depending on the environment and energy input.
 
  • #3


I cannot conclusively determine the orientation of microtubules based solely on the observation of cytoplasmic vesicle movement in a nerve cell. While it is possible that some microtubules may be oriented with their plus-end facing the axon terminus and others with the opposite polarity, there are other factors that could also influence the direction of vesicle movement, such as motor proteins and cellular signaling. Further experiments, such as labeling and tracking individual microtubules, would be necessary to accurately determine their orientation.
 

1. What is the role of microtubules in cell orientation?

Microtubules are responsible for determining the overall shape and orientation of a cell. They act as a scaffold for other cellular components and help maintain the cell's structure and organization.

2. How are microtubules oriented within a cell?

Microtubules are typically arranged in a radial pattern, with their plus ends facing outward and their minus ends facing towards the center of the cell. They can also be organized in parallel arrays or as part of a larger network.

3. What factors influence the orientation of microtubules?

The orientation of microtubules can be influenced by a variety of factors, including the cell's internal cytoskeleton, external mechanical forces, and chemical signals from other cells.

4. What is the significance of microtubule orientation in cell division?

During cell division, microtubules play a crucial role in organizing and separating the genetic material. They form the spindle apparatus, which helps guide the movement of chromosomes during mitosis and meiosis.

5. Can the orientation of microtubules be disrupted?

Yes, the orientation of microtubules can be disrupted by various factors, such as mutations in genes that regulate their formation or by certain drugs that interfere with their function. This can lead to abnormal cell division, which can contribute to diseases such as cancer.

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