EK 3 - actin vs microtubule

[lostnconfused]

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Can somebody please explain why C would be incorrect? I thought actins were responsible for cytokinesis.

 

[lostnconfused]

Bumpp

 

[Gulliver Dark]

It has to do with this, basically. https://en.wikipedia.org/wiki/Mitotic_inhibitor ... honestly, this is one of those in the weeds questions, which might be better to not obsess over it. Know the basics of mitosis. How microtubules and microfilaments function, etc. At least, thats what I've gleaned.. MCAT is still upcoming for me.

 

[theonlytycrane]

admittedly, I always get too bored to study the microtubules / 9+2 arrangement. I would love a high-yield short summary of what to know based on / related to this question posted.

 

[David513]

This question is very easy. You can rule out C by asking the following...
In what part of mitosis does actin act?

The answer is ... no part. Actin does not play a significant role. Actin has a big role in cytokinesis, which is technically not a part of mitosis.

Meanwhile, choice D describes a method that Taxol could employ to very much break down the process of mitosis (without microtubules you can't form the mitotic spindle/centrosomes).

(Choices A and B would help mitosis happen, so Taxol would not be doing those things since Taxol disrupts mitosis.)

 

[theonlytycrane]

This question is very easy. You can rule out C by asking the following...
In what part of mitosis does actin act?

The answer is ... no part. Actin does not play a significant role. Actin has a big role in cytokinesis, which is technically not a part of mitosis.

Meanwhile, choice D describes a method that Taxol could employ to very much break down the process of mitosis (without microtubules you can't form the mitotic spindle/centrosomes).

(Choices A and B would help mitosis happen, so Taxol would not be doing those things since Taxol disrupts mitosis.)

Choice A is the correct answer.

 

[yeasureyoubetcha]

Microtubule function relies on the dynamic instability of them. Stabilizing the microtubules would essentially freeze the growth and collapse of them, preventing the mitotic cell process from continuing. This is what taxol is doing.

Actin is involved in amoeboid movement, and in telophase/cytokinesis the formation of the contractile ring and cleavage furrow.

There are some questions that are just bad questions.

 

[David513]

Microtubule function relies on the dynamic instability of them. Stabilizing the microtubules would essentially freeze the growth and collapse of them, preventing the mitotic cell process from continuing. This is what taxol is doing.

Actin is involved in amoeboid movement, and in telophase/cytokinesis the formation of the contractile ring and cleavage furrow.

There are some questions that are just bad questions.

Wow, you're tellin me. I can't believe stabilizing microtubules would actually hinder their ability to assist in mitosis. I guess choice D isn't the right answer (unlike what I said above) because 9+2 is used in flagella and cilia but not mitosis microtubule formation? *shrug* This is pretty low yield for me at this point.

 

[yeasureyoubetcha]

I can't believe stabilizing microtubules would actually hinder their ability to assist in mitosis.

The dynamic instability of microtubules is related to how quickly the αβ-tubulin herterodimers hydrolyze their bound GTP

 

[lostnconfused]

It has to do with this, basically. https://en.wikipedia.org/wiki/Mitotic_inhibitor ... honestly, this is one of those in the weeds questions, which might be better to not obsess over it. Know the basics of mitosis. How microtubules and microfilaments function, etc. At least, thats what I've gleaned.. MCAT is still upcoming for me.

Interesting... I didn't know mitotic inhibitors were specifically substances that disrupted microtubule polymerization. I guess I was too focused on "mitotic division" and overthought the question. Thank you everyone for your help!

 

[theonlytycrane]

noobie microtubule question: Are microtubules deemed + or - depending on which MTOC they are located at in the cell? Are there multiple MTOCs near the nucleus?

 

[NextStepTutor_2]

Can somebody please explain why C would be incorrect? I thought actins were responsible for cytokinesis.

This is a good example of AAMC reasoning. Does actin play NO role in mitosis? No way. Cables of actin stretch from pole to pole of the mitotic spindle, and, with myosin, help control spindle length and shape. Microtubules and their motors are indispensable for mitotic spindle formation, but whether actin filaments and actin-based myosin motors are also part of the spindle apparatus is not quite as clear. This is a case where the AMC would likely come back to you and say that A is simply the better, more accurate answer, not necessarily that choice C is flat out wrong.

You would not need to know the exact function of Taxol for the MCAT, so do not go off an a tangent into the intricacies of their various roles. Focus on the thinking employed by the AAMC. These kinds of questions will be few and far between, but knowing how they think will help you get more of them correct.

Hope this helps, good luck!

 

[lostnconfused]

This is a good example of AAMC reasoning. Does actin play NO role in mitosis? No way. Cables of actin stretch from pole to pole of the mitotic spindle, and, with myosin, help control spindle length and shape. Microtubules and their motors are indispensable for mitotic spindle formation, but whether actin filaments and actin-based myosin motors are also part of the spindle apparatus is not quite as clear. This is a case where the AMC would likely come back to you and say that A is simply the better, more accurate answer, not necessarily that choice C is flat out wrong.

You would not need to know the exact function of Taxol for the MCAT, so do not go off an a tangent into the intricacies of their various roles. Focus on the thinking employed by the AAMC. These kinds of questions will be few and far between, but knowing how they think will help you get more of them correct.

Hope this helps, good luck!

Thank you, that was very helpful!

A follow up question though... Is cytokinesis technically not part of mitosis then? That was my line of reasoning for the question - it asked about mitotic DIVISION, so it made me think of cytokinesis and therefore actin more than microtubules separating the chromosomes.