Cytokinesis: Study with Video Lessons, Practice Problems & Examples

Cytokinesis is the process that follows mitosis, dividing the cytoplasm to form two identical daughter cells. In animal cells, this occurs through the formation of a cleavage furrow, created by actin and myosin filaments, which pinches the cell into two. In contrast, plant cells lack a cleavage furrow; instead, they form a cell plate from Golgi vesicles, which eventually develops into a cell wall. Understanding these mechanisms is crucial for grasping cell division and the differences between plant and animal cells.

Cytokinesis

In this video, we're going to begin our introduction to cytokinesis. Recall from our previous lesson videos that the M phase of the cell cycle consists of both mitosis and cytokinesis. Already in our previous lesson videos, we've covered the five phases of mitosis. Recall that mitosis ends up dividing the nucleus and at the end of mitosis, you still technically have a single cell with two nuclei. This means that mitosis needs to be followed up by another process called cytokinesis. Cytokinesis is technically the process that's going to produce two identical daughter cells, separating the two nuclei. Cytokinesis can be defined as the division of the cytoplasm, essentially separating one cell into two cells. It turns out that animal and plant cell cytokinesis actually differ in their mechanism. Moving forward, we're going to talk about animal cytokinesis, and plant cytokinesis in their own separate videos. So I'll see you all in our next video to talk about animal cell cytokinesis.

Animal Cell Cytokinesis

In this video, we're going to introduce animal cell cytokinesis. And so in animal cells, cytokinesis is characterized by the formation of what's known as a cleavage furrow. And so a cleavage furrow is really just a small indentation of actin filaments mainly and some myosin filaments as well at the center of a dividing cell. And so this cleavage furrow ultimately is going to result in the pinching of the cytoplasm and the separation of the 2 cells.

And so if we take a look at our image down below over here on the left-hand side notice we're showing you a cell right after mitosis, and recall that mitosis technically ends with a single cell that has 2 nuclei. And so notice that we still have a single cell here, this is a cell that is still a single cell because the cytoplasm is still connected here, And notice that there are 2 nuclei here. And so, what you'll notice is that mitosis technically does not end with 2 cells. And so mitosis needs to be followed up by the process of cytokinesis and cytokinesis is what's going to separate the cytoplasm, essentially separating this single cell to form 2 cells.

And so during animal cell cytokinesis, a structure referred to as the cleavage furrow is going to form. And really the cleavage furrow is just this indentation, that you can see that forms and the indentation is forming from the result of these contractile actin microfilaments and myosin filaments that form in the middle, or in the center of the dividing cell. And so ultimately this cleavage furrow is going to continue to pinch off the cytoplasm until the cytoplasm has been divided and the 2 cells have their own cytoplasm and their own nucleus. And so these here would represent the daughter cells that result.

And so technically, telophase which is the final phase of mitosis and cytokinesis are going to occur simultaneously, which is why mitosis is technically so highly linked to creating 2 daughter cells. But technically it's the process of mitosis and cytokinesis that leads to the 2 daughter cells. And so this here concludes our introduction to animal cell cytokinesis and how it's characterized by the formation of the cleavage furrow. And this is going to be different when we look at plant cell cytokinesis in our next video. So I'll see you all there.

Cytokinesis Example 1

Alright, so here we have an example problem that's asking why is cytokinesis an important part of cell division? And after reading through each of these four answer options down below, there are a few that we can eliminate right off the bat. Taking a look at option d, it says that cytokinesis is responsible for the growth and production of new organelles and other cytoplasmic contents. But of course, we know that this is not the role of cytokinesis; this option, option d, is more so the role of interphase. But interphase and cytokinesis are not the same thing. So we can go ahead and cross off answer option d. Answer option c says that cytokinesis is responsible for the linking of two sister chromatids, but of course, that's not going to be the case at all. That's not what we've discussed in our previous lesson videos. And now we're between answer option a and answer option b. Notice answer option a says that cytokinesis is responsible for the proper separation of genetic information. But technically, it's mitosis that is separating the genetic information, which is the DNA, and separating the single nucleus to form two nuclei. So really, it's mitosis that is responsible for the proper separation of the genetic information. Mitosis is slightly different from cytokinesis, and so option A is more so linked to mitosis not cytokinesis. This only leaves answer option b here as the correct answer. Cytokinesis is an important part of cell division because it is responsible for the proper separation of the cytoplasmic contents and that's really how cytokinesis is defined: as division of the cytoplasm. So, answer option b here is the correct answer for this example problem, and that concludes this example. I'll see you all in our next video.

In animal cell cytokinesis, a cleavage furrow is ________.

• A. A ring of vesicles forming a cell wall.
• B. The equatorial line which chromosomes align along during mitosis.
• C. A groove in the plasma membrane between daughter nuclei.
• D. The space that is created between two chromatids during anaphase.

Plant Cell Cytokinesis

In this video, we're going to introduce plant cell cytokinesis. And so plant cell cytokinesis is going to be different than animal cell cytokinesis because in plant cell cytokinesis, there is no cleavage furrow. And so what we need to recall from our previous lesson videos is that unlike animal cells, plant cells are actually surrounded by a cell wall. And so notice that in our image down below, the cell wall is color coordinated to this dark green color. And so what's important to note is that again in plant cell cytokinesis, there is no cleavage furrow that forms. Instead, vesicles from the Golgi apparatus are going to carry materials to generate what's known as a cell plate, and the cell plate is ultimately going to be responsible for helping to separate each of the daughter cells. And so instead of a cleavage furrow forming, like what happens in animal cells, in plant cells a cell plate will form instead of the cleavage furrow. And so the cell plate you can really just think of as the precursor structure to a fully developed cell wall. And so the cell plate forms first and ultimately the cell plate ends up developing into a fully mature cell wall.

And so if we take a look at our image down below, notice over here on the far left-hand side, we are showing you a plant cell here that has a cell wall. And notice that this plant cell is undergoing mitosis, and so you can see here that it's undergoing anaphase where the sister chromatids are being pulled apart from one another. And notice that right here in the middle of the cell instead of a cleavage furrow forming, we have Golgi vesicles or vesicles from the Golgi apparatus starting to accumulate and form here in the middle of the cell. And again, recall that these vesicles from the Golgi apparatus are carrying the materials to generate a cell plate. So ultimately, what we're going to see is that these Golgi vesicles are going to form a cell plate. And so notice that as mitosis continues here, there is a structure here forming in the middle of the cell referred to as the cell plate. And ultimately, this cell plate is going to continue to develop over time to form a fully mature cell wall, which is what we're labeling over here.

And so once the fully mature cell wall has been formed, then the plant cell has successfully undergone a full complete cell division. And so again, the biggest takeaway here is that in animal cells, it's the cleavage furrow that forms, but in plant cells, it's the cell plate that forms and ends up developing into a cell wall. And so this here concludes our introduction to plant cell cytokinesis, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.

Which of the following are primarily responsible for cytokinesis in plant cells?

• A. Kinetochores.
• B. Golgi-derived vesicles.
• C. Actin and myosin.
• D. Metaphase plate.
• E. Centrosomes.

FtsZ is a bacterial cytoskeletal protein that forms a contractile ring involved in binary fission. Its function is analogous to ________.

• A. the cleavage furrow of eukaryotic animal cells.
• B. the cell plate of eukaryotic plant cells.
• C. the mitotic spindle of eukaryotic cells.
• D. the microtubule-organizing center of eukaryotic cells.

Here’s what students ask on this topic:

What is cytokinesis and how does it differ between animal and plant cells?

Cytokinesis is the process that follows mitosis, dividing the cytoplasm to form two identical daughter cells. In animal cells, cytokinesis occurs through the formation of a cleavage furrow, created by actin and myosin filaments, which pinches the cell into two. In contrast, plant cells lack a cleavage furrow; instead, they form a cell plate from Golgi vesicles, which eventually develops into a cell wall. This difference is due to the presence of a rigid cell wall in plant cells, which necessitates a different mechanism for cell division.

What role do actin and myosin filaments play in animal cell cytokinesis?

In animal cell cytokinesis, actin and myosin filaments play a crucial role in forming the cleavage furrow. These filaments create a contractile ring at the center of the dividing cell. The contraction of this ring pinches the cytoplasm, leading to the separation of the cell into two daughter cells. This process ensures that each daughter cell receives an equal share of the cytoplasm and organelles, completing the cell division process.

How does the formation of the cell plate in plant cells lead to cytokinesis?

In plant cells, cytokinesis is achieved through the formation of a cell plate. Vesicles from the Golgi apparatus carry materials to the center of the dividing cell, where they coalesce to form the cell plate. This cell plate serves as a precursor to the new cell wall. Over time, the cell plate matures and develops into a fully formed cell wall, effectively separating the two daughter cells. This mechanism is necessary due to the rigid cell wall that surrounds plant cells, which prevents the formation of a cleavage furrow.

Why is cytokinesis important for cell division?

Cytokinesis is crucial for cell division because it ensures that the cytoplasm and organelles are evenly distributed between the two daughter cells. While mitosis divides the nucleus, cytokinesis completes the process by physically separating the cell into two distinct entities. This step is essential for maintaining cellular function and viability, as it ensures that each daughter cell has the necessary components to survive and function independently.

What happens if cytokinesis does not occur after mitosis?

If cytokinesis does not occur after mitosis, the result is a single cell with two nuclei, known as a binucleated cell. This can lead to various cellular dysfunctions, as the cell may struggle to manage two sets of genetic material and an uneven distribution of cytoplasmic components. In multicellular organisms, failed cytokinesis can contribute to developmental abnormalities and diseases, including cancer, where cells proliferate uncontrollably without proper division.