Cytokinesis - Online Tutor, Practice Problems & Exam Prep

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 5 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 2 nuclei. Hence, mitosis needs to be followed by another process called cytokinesis.

Cytokinesis is technically the process that's going to produce 2 identical daughter cells by separating the 2 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 mechanisms. Moving forward, we will 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. This 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. This cleavage furrow ultimately results in the pinching of the cytoplasm and the separation of the two cells. If we take a look at our image down below 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 two nuclei.

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 two nuclei here. What you'll notice is that mitosis technically does not end with two cells and so mitosis needs to be followed up by the process of cytokinesis. Cytokinesis is what's going to separate the cytoplasm, essentially separating this single cell to form two cells. During animal cell cytokinesis, a structure, referred to as the cleavage furrow, is going to form. The cleavage furrow is just this indentation that you can see forms from the result of these contractile actin microfilaments and myosin filaments that form in the middle, or in the center of the dividing cell. Ultimately, this cleavage furrow is going to continue to pinch off the cytoplasm until the two, the cytoplasm has been divided and the two cells have their own cytoplasm and their own nucleus.

These here would represent the daughter cells that result. Telephase, which is the final phase of mitosis and cytokinesis, are going to occur simultaneously, which is why mitosis is so highly linked to creating two daughter cells. But technically, it's the process of mitosis and cytokinesis that leads to the two daughter cells. This here concludes our introduction to animal cell cytokinesis and how it's characterized by the formation of the cleavage furrow. 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 cytokinesis is an important part of cell division. 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 down below, 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 discussed in our previous lesson videos. And so now we're between answer option A and answer option B, and 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. And 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. And so, of course, this only leaves answer option B here as the correct answer and so 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 the division of the cytoplasm. And so, answer option B here is going to be the correct answer for this example problem and that concludes this example, so 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. Plant cell cytokinesis is different from animal cell cytokinesis because in plant cell cytokinesis there is no cleavage furrow. What we need to recall from our previous lesson videos is that unlike animal cells, plant cells are surrounded by a cell wall. Notice that in our image down below, the cell wall is color-coordinated to this dark green color. It's important to note that 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. The cell plate is ultimately responsible for helping to separate each of the daughter cells. Instead of a cleavage furrow forming, like what happens in animal cells, in plant cells, a cell plate will form. The cell plate can be thought of as the precursor structure to a fully developed cell wall. The cell plate forms first and ultimately develops into a fully mature cell wall.

If we take a look at our image down below, notice on the far left-hand side we are showing you a plant cell that has a cell wall and is undergoing mitosis. You can see here that it's undergoing anaphase where the sister chromatids are being pulled apart from one another. Notice that right here in the middle of the cell, instead of a cleavage furrow forming, we have vesicles from the Golgi apparatus starting to accumulate and form. Recall that these vesicles from the Golgi apparatus carry the materials to generate a cell plate. Ultimately, these Golgi vesicles form a cell plate.

Notice that as mitosis continues here, a structure forming in the middle of the cell, referred to as the cell plate, is going to continue to develop over time to form a fully mature cell wall, which we are labeling over here. Once the fully mature cell wall has been formed, the plant cell has successfully undergone a full, complete cell division. 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. This 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 plant and animal 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 actin filaments, along with myosin, generate the force needed to pinch the cytoplasm, leading to the separation of the cell into two daughter cells. This process ensures that each daughter cell receives its own nucleus and cytoplasm, completing cell division.

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 in the cell cycle?

Cytokinesis is a critical step in the cell cycle because it ensures the physical separation of the cytoplasm, resulting in two distinct daughter cells. While mitosis divides the nucleus, cytokinesis completes the process by dividing the cytoplasm and cellular organelles. This ensures that each daughter cell receives the necessary components to function independently. Without cytokinesis, cells would end up with multiple nuclei and an incomplete division, leading to potential cellular dysfunction and abnormal growth.

What is the cleavage furrow and how does it function in animal cell cytokinesis?

The cleavage furrow is an indentation that forms at the center of a dividing animal cell during cytokinesis. It is primarily composed of actin and myosin filaments, which create a contractile ring. This ring contracts, pinching the cytoplasm and leading to the separation of the cell into two daughter cells. The cleavage furrow ensures that each daughter cell receives its own nucleus and cytoplasm, completing the cell division process. This mechanism is unique to animal cells and differs from the cell plate formation seen in plant cells.