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I'm wondering whether a cell can start a mitosis if it lack molecules or energy to fully complete it. From what I'm reading on wikipedia the cell passes most of its time in the interphase in which the DNA is replicated and then there's the G2 checkpoint to make sure mitosis can start.

However I'm not sure all of this is enough to ensure that the cell has sufficient energy to fully complete the mitosis (is the cell "fueled" in energy and molecules during the mitosis or does it has everything needed before starting it?).

Edit: I'm considering this question for humans in particular, or animals in general if the answer is the same.

When I speak about "molecules" I mean any atom or molecule. In other words, whether the cell needs some material intake from the external environment during the mitosis or not. If not, I consider that it has all the necessary atoms/molecules to fully complete the mitosis without any external need.

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  • $\begingroup$ When all checkpoints are working, then the most critical is the G1-S. The reason is that once the cell passes this checkpoint, it is committed to either replicate and divide or it will trigger apoptosis. The reason for this is that once DNA replication starts, there is no way for the cell to undo this, so it has to have everything it needs before it commits to DNA replication. There are other checkpoints, however these are to make sure that replication has proceeded properly, or that the daughter cells will receive the exact copies of the genome. AleksandrH's answer provides the basics. $\endgroup$ – AMR Jan 20 '16 at 20:01
  • $\begingroup$ Which organism are you considering? Free-living organisms such as yeast have a variety of mechanisms for sensing nutrients, and regulate proliferation depending on nutrient availability. In animal cells it's very different, as growth factors are the dominant driving forces, and here the role of nutrients as signals is more uncertain / controversial. $\endgroup$ – Roland Jan 21 '16 at 15:23
  • $\begingroup$ I've edited my question to make it clearer (humans basically). $\endgroup$ – thermomagnetic condensed boson Jan 21 '16 at 16:06
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The short answer: no. First, let's get an understanding of the cell cycle control system, as there are some important molecules involved in this system that regulate mitosis. Think of the control system as a series of stoplights: as you mention, there is one stoplight at the G2 phase. There are two additional checkpoints: one at G1 and one in the M (mitotic) phase, just before Anaphase. Why before anaphase? At this stage in mitosis, the cell checks to determine if all of the kinetochores of the duplicated sister chromatids have microtubules attached to them. This is to ensure proper distribution of chromatids in anaphase.

Ok, so back to your question: what are some of the molecules involved, or what are some molecules that the cell might need before it proceeds?

  • Cyclins - these are proteins that are produced in the late S-G2 phases of Interphase. They activate cyclin dependent kinases (Cdks)

  • Cyclin Dependent Kinases - as the name suggests, these proteins (kinases) are dependent on cyclin in order to operate. The best known Cdk is called MPF, short for maturation promoting factor.

Throughout the cell cycle, these Cdks, together with their bound cyclins, are able to phosphorylate various proteins in the cell as it undergoes mitosis. For instance, the MPF would phosphorylate lamins, which are proteins on the nuclear envelope that can initiate degradation of the laminar matrix. This is essential in Prophase, when the nucleus is disassembling. There are many other things it can phosphorylate. For a more complete list, look under "Targets of MPF" in the above link for MPF. Take a look at this diagram, taken from Campbell's Biology (9th Ed):

enter image description here

There is one other molecule worth mentioning:

  • Growth factors - these are proteins specifically released by neighboring cells (relative to the cell that is preparing to undergo mitosis). These are crucial for mitosis to even initiate. A great example of a growth factor is PDGF, which stands for "Platelet Derived Growth Factor". These PDGFs are released by platelets at sites of injury, such as a cut on your knee. The PDGFs stimulate cell division and help your skin to reheal!

There are many other essential nutrients that cells require before they can initiate mitosis; not all have been listed here. Also, I know I didn't necessarily answer the "energy" part of your question, but I hope this helps for your first part.

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  • $\begingroup$ This isn't the whole story, but it is representative of what would be taught in introductory college level biology. $\endgroup$ – AMR Jan 20 '16 at 19:56
  • $\begingroup$ This answer doesn't really concern energy or nutrients. Cyclins, CDKs and growth factors are all signalling proteins, they merely relay information. $\endgroup$ – Roland Jan 21 '16 at 15:19
  • $\begingroup$ @Roland But the OP didn't ask about nutrients, they asked about energy and molecules, and I covered the molecule part (I mention near the end that I don't know the answer to the "energy" part). $\endgroup$ – AleksandrH Jan 21 '16 at 15:38
  • $\begingroup$ Okay, I guess "molecules" is ambiguous, I would guess in this context it means material / building blocks, not signalling molecules. Perhaps the OP can clarify? $\endgroup$ – Roland Jan 21 '16 at 15:52
  • $\begingroup$ Sure, I wasn't too clear myself because molecules is indeed a very broad term. $\endgroup$ – AleksandrH Jan 21 '16 at 15:58

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