The Inner Life of the Cell: Biovisions Video/Explanations

[Lynseyann]

Just wanted to say that this is a great video - it covers a module I'm currently revising for - thank you so much!

La xx

[megachristo]

Thanks for the education Bio. Truly amazing! I love how it seemed like that small motor protein dragging a vacuole looked like it was just out for a walk dragging it's tools needed to do his job.
AWSOME!!!

[olgaka]

I have a question.
Can we say that a cell actually doesn't die, but it lives until it is divided? And if so, the number of cells should be increasing continuously!

[Lynseyann]

cells don't "live" forever - they all meet a death at some point
I hope this link helps?

http://users.rcn.com/jkimball.ma.ultran ... tosis.html

La xx

[olgaka]

Thank you for the link. It is very helpful.

[BioWizard]

cells don't "live" forever - they all meet a death at some point
I hope this link helps?

That is true, but to elaborate a little, in multicellular organisms, that is generally correct for differentiated cells. However, the germ cell line is practically immortal, unless killed or rendered a genetic dead end. As for unicellular organisms, sometimes the division is not symmetrical, and the two daughter cells are of different "initial age", that is, one cell is more chemically aged than the other. It's as if the cells concentrate the "aged components" in one of the two daughter cells, and after several divisions, they accumulate more than the cell can survive, and it dies off, while it's sisters propagate an immortal line.

[glycin30]

Wow it is amazing.

Its really a great video. Thanks for posting it.

[BioWizard]

I've seen it a bazillion times, and I still get goose bumps every time I watch it. The music makes it all that much nicer.

I heard that the budget for its making was in the viscinity of $ 1/4 million, but I'm not very sure about the source.

[goingtothedogs]

And then what I actually came to the thread for.....

WOW! What a movie. I've tried to get it to play before and couldn't manage it, but it seems my PC has now taken to it it's heart.

Can't truly say I've followed all of it, but I keep watching it and going back to the screenshots.

I think I'll have things to ask on this.

Who says science and art are incompatible................


Edit: having watched the narrated version it helps a lot with the understanding. But I still love the "hairs on the back of the neck" musical version

[BioWizard]

Can you please link to the narrated version?

[goingtothedogs]

Sure. It's the link Olgaka gave earlier in the thread.



http://multimedia.mcb.harvard.edu/anim_ ... fe_hi.html

[BioWizard]

Oh I must have missed it. I just wanted to check my captions against the narration of the authors :)

[goingtothedogs]

It's quite a bit longer than the musical version. You may want to do more screenshots

[BioWizard]

Yeah I liked the extra scenes with cross sections of membranes showing the integral parts of proteins and so on. I don't think that any captions are needed for the narrated version though. It more than clearifies everything.

My initial post in this thread has been extensively referenced over the internet, and I just wanted to make sure that I didn't get anything significantly wrong :)

[Neonate]

Hello,
I read your commentary and explanation on each of the clips for this video and I had a question...

The scene showing the motor protein that was moving vesicles along the cytoskeleton of the cell, can you tell me how that molecule is related to myosin?

Its abit overwhelming for me and I want to get a better sense of it.
Thank you.

[BioWizard]

The motor protein is a kinesin. You can find more information about it here: http://en.wikipedia.org/wiki/Kinesin

[MrMistery]

About that, just a random fact: I met Robert Lue (the person who thought up that animation) a couple of days ago. I'll have him next semester in cellular biology. He is well-known around here for the aminations he shows in class.

[Deftil]

Whoa...

That video is freakin rad!

[Neonate]

Thank you for that site info. Ill check it out.

[erythrophyte]

That's amazing. But I wonder, how did they get cameras that small?!

[MrMistery]

Hehe, Harvard awesome nanotechnology..

[Paralith]

That video is definitely awesome, but I would like to point people to this Pharyngula post discussing it and an error the creators of the video made:

http://scienceblogs.com/pharyngula/2008 ... _chanc.php

Here is a quote from the entry:

Here's the central problem: molecules don't behave that way. What is portrayed is wonderfully precise movement; it looks like the molecules are all directed, purposeful, and smooth. Take for instance the behavior of kinesin, that stalk-like molecule seen marching in a stately way down a tubule, with two "feet" in alternating step, towing a large vesicle. That's not how it moves! We have experiments in which kinesin is tagged — it's towing a fluorescent sphere — and far from a steady march, what it does is take one step forward, two steps forward, one step back, two steps forward, one back, one forward … it jitters. On average it progresses in one direction, but moment by moment it's a shivery little dance.

[BioWizard]

Yeah I remember that criticism, and I remember the authors responded to it by saying that a lot of things were taken out of the video for the sake of practicality. For example, if they were to show the stochastic behavior of molecules, the video would have to run for days. What they did was the equivalent of taking out frames of motion that do not lead to the final destination, and in that made the video shorter and more practically watchable. They also took out molecules of water and represented them by a space of blueish tint, because it would be difficult to see what's going on if they were to include them even as dots. I respect pharyngula, but I honestly don't think the authors are ignorant enough to not know that molecules behave stochastically, and their justification does make sense. I've seen the video of fluorescently tagged kinesin, and if I recall correctly, it takes it several minutes to move just a few angsrtroms. Imagine the whole video like that. Although it would have been useful if the authors included a disclaimer or pointed it out before or after the video for those who might take it at face value.

[Paralith]

I'm sure the authors had good reason for doing what they did, but for the purposes of accuracy I think it's good to at least be made aware of the stochasticity of molecular behavior so you can keep it in mind while you watch the video. That's why I like to post that link, not because I don't like the video.

[BioWizard]

I'm sure the authors had good reason for doing what they did, but for the purposes of accuracy I think it's good to at least be made aware of the stochasticity of molecular behavior so you can keep it in mind while you watch the video. That's why I like to post that link, not because I don't like the video.

I agree with that. What I was commenting on is that the choice was more a matter of convenience rather than getting things wrong. Pointing it out for the sake of accuracy is definitely a good thing to do, and I think the authors should have included that at the beginning or end of the video.

[BioWizard]

Take for instance the behavior of kinesin, that stalk-like molecule seen marching in a stately way down a tubule, with two "feet" in alternating step, towing a large vesicle. That's not how it moves! We have experiments in which kinesin is tagged — it's towing a fluorescent sphere — and far from a steady march, what it does is take one step forward, two steps forward, one step back, two steps forward, one back, one forward … it jitters. On average it progresses in one direction, but moment by moment it's a shivery little dance.

I'm trying to remember the videos of motor proteins I saw in class many years ago, and I can't recall whether or not the kinesin actually jitters. I do recall many videos on DNA binding proteins that do jitter, especially those that move along the DNA without being ATP driven. Those you expect to be stochastic and only as move as result of net jittering in one direction. But I'm less inclined to think that an ATP driven protein behaves in the same way. For example, the contraction of muscles is carried out by similar movement of myosin heads over actin filaments, and that's completely polarized.



Although perhaps in the case of kinesin, there might be some slippage, so it might appear like it's jittering (unlike with actin/myosin, where other myosin heads hold the actin filament from sliding back while the myosin head leaps to its next position). For some reason I can't find a real-time video for kinesin like the above, but I'll keep looking.

[MrMistery]

i would say kinesin-1 doesn't jitter, because it is a processive motor. How it works is that it never lets go of the tubulin protofilament it's walking on, and can only move forward (by hydrolyzing ATP) or stand still (if it's not hydrolyzing ATP). Now I don't pretend to be an expert on motor proteins nor do I have time to dissect the problem in detail now, but in this figure it seems to me that this is what happens - it does go back sometimes, but very rarely, and this could be accounted by the rare situations when the kinesin lets go of the microtubule, which of course will inevitably happen. The figure is from Grigoriev et al. 2007, Dev Cell 13(2) - figure 3 in the article.

[BioWizard]

i would say kinesin-1 doesn't jitter, because it is a processive motor. How it works is that it never lets go of the tubulin protofilament it's walking on, and can only move forward (by hydrolyzing ATP) or stand still (if it's not hydrolyzing ATP). Now I don't pretend to be an expert on motor proteins nor do I have time to dissect the problem in detail now, but in this figure it seems to me that this is what happens - it does go back sometimes, but very rarely, and this could be accounted by the rare situations when the kinesin lets go of the microtubule, which of course will inevitably happen. The figure is from Grigoriev et al. 2007, Dev Cell 13(2) - figure 3 in the article.

That's how I remember it as well.

[genemachine]

I thought this video of a walking myosin-5 mollecule might belong here.

"Atomic Force Microscopy Shows Myosin Walking On Actin"
http://kambiz.wordpress.com/2010/11/10/ ... -on-actin/

[BioWizard]

I thought this video of a walking myosin-5 mollecule might belong here.

"Atomic Force Microscopy Shows Myosin Walking On Actin"
http://kambiz.wordpress.com/2010/11/10/ ... -on-actin/

Very cool video. I didn't know you can do this sort of thing with AFM.