Prokaryotic & Eukaryotic Cells - Online Tutor, Practice Problems & Exam Prep

Prokaryotic cells, including bacteria and archaea, lack a nucleus and membrane-bound organelles, featuring circular DNA located in a nucleoid. They are unicellular and smaller, with 70S ribosomes, dividing through binary fission. In contrast, eukaryotic cells possess a nucleus, linear DNA, and various organelles, can be unicellular or multicellular, and utilize larger 80S ribosomes, dividing via mitosis and cytokinesis. Both cell types share a cell membrane and essential biomolecules like carbohydrates and proteins, highlighting their fundamental biological roles.

Prokaryotic & Eukaryotic Cells

In this video, we're going to talk about prokaryotic and eukaryotic cells. Prokaryotic and eukaryotic are the broadest and most distinct groupings of all life. The reason for this is because prokaryotic cells include two different domains of life. It includes both domain Bacteria and domain Archaea as well. Both bacteria and archaea are considered prokaryotic.

Prokaryotic cells specifically do not have an organelle called a nucleus, so prokaryotic cells do not have a nucleus. Whereas, eukaryotic cells, on the other hand, are cells that do have a nucleus along with other membrane-bound organelles. What you'll notice, comparing the words prokaryotic and eukaryotic, they both have this karyo root, which refers to the kernel of the cell, which is the nucleus. So, both words are referring to the nucleus.

What's different are the roots here pro and eu. Pro is a root that means before. If you put it together, you get 'before the kernel' or the nucleus, so 'before the nucleus'. 'Before the nucleus' essentially refers to not having a nucleus because it is before the development of a nucleus. The eu prefix means good. Putting this together with karyote, you get 'good nucleus', which means that it does have a good nucleus or just a nucleus. Hopefully, this can help you distinguish between prokaryotic and eukaryotic a little bit better.

Notice that the table has these column headers: the domains of life, the cell type, the nucleus, organelles, cell size, and cellularity. There are three domains of life: domain Bacteria, domain Archaea, and domain Eukarya. Both bacteria and archaea are collectively going to be the same cell type of prokaryotic. This is because, in terms of the nucleus, both bacteria and archaea do not have a nucleus, which means that the nucleus is absent.

On the other hand, eukaryotic cells, specifically those in domain Eukarya, do have a nucleus. In terms of other membrane-bound organelles, prokaryotic cells, including bacteria and archaea, do not have membrane-bound organelles, so they will be both absent. But, of course, in eukaryotic cells, organelles are going to be present. Moving forward in our course, we'll talk about a lot of these different types of organelles found in eukaryotic cells.

In terms of cell size, it's important to note that prokaryotic cells are significantly smaller than eukaryotic cells, which are significantly larger. Prokaryotic cells can range in size, but they're going to be about 1 micrometer in diameter, whereas eukaryotic cells, which can also range in their sizes, are going to be much larger on average. Here we have a 100 micrometers. Eukaryotic cells can be up to a hundred times larger than prokaryotic cells in some cases. In terms of cellularity, it's important to note that prokaryotic cells, including bacteria and archaea, are unicellular, meaning that they're only made up of one single cell since uni means one or singular.

Eukaryotic cells can either be unicellular or single-celled or they can be multicellular. The multicellular organisms that you're aware of are all going to be eukaryotic, and this is where humans fall. Humans are multicellular. This concludes our introduction to prokaryotic and eukaryotic cells, and we'll be able to continue to talk more about the differences between the two as we move forward in our course. I'll see you all in our next video.

Which domains of life are classified as prokaryotes?

• A. Bacteria & Eukarya.
• B. Archaea & Fungi.
• C. Bacteria & Archaea.
• D. Bacteria & Protista.

Features of Bacterial Cells

In this video, we're going to talk about some features of bacterial cells, which we know are prokaryotic cells that do not have a nucleus. Now, bacteria are actually the most abundant and the most diverse organisms on Earth, and that's because bacteria are the most ancient organisms on Earth. They're the ones that have been around the longest. Now, bacterial DNA is specifically circular in its shape, and again because bacteria are prokaryotic and they do not have a nucleus, the circular DNA is going to be found in a region that's called the nucleoid. And so the nucleoid is just the name of the specific region where the bacteria's circular DNA can be found.

Now bacteria, like all cells, have structures that are called ribosomes. And ribosomes, we'll get to talk more about these later in our course, but really what you need to know is that ribosomes are found in every single cell and ribosomes are specifically used for building proteins. Now once again, all cells have ribosomes including bacteria, but bacteria, specifically have really, really small ribosomes that we call 70S ribosomes. And the "s" here, is something that we're not going to worry about in our course. It's just a unit, that's referring to the size here of the ribosome, and the 70 here is just the number that goes along with the unit.

Now, bacteria have really small ribosomes, and when bacteria divide or multiply into more cells, they divide by a process that's known as binary fission. And so binary fission is a simple process in, with respect to how eukaryotic cells divide, which is a much more complex process. So let's take a look at our image down below so that we can clear some of these things up. So notice that we're showing you the bacterial cell here, and notice that the DNA that we see, right here, this blue circle, represents the circular DNA in the nucleoid. And so once again, the nucleoid is just the region where the circular DNA can be found within bacteria.

Also, notice that throughout the cell we have all of these orange dots, and these orange dots represent ribosomes. So notice that we're zooming in here to one of these orange dots. And ribosomes, again, we'll talk more about them later in our course, but basically they are specific for building proteins, and so all cells have ribosomes. But once again, bacteria, they have really really small ribosomes that we call 70S ribosomes. And so this here is representing a 70S ribosome, a small ribosome that bacteria cells have. And so this here concludes our introduction to the features of bacterial cells, and we'll be able to compare this to features of eukaryotic cells as we move forward in our course.

So I'll see you all in our next video.

In bacteria, DNA will be found in _______________.

• A. A membrane-enclosed nucleus.
• B. Mitochondria.
• C. The nucleoid.
• D. Ribosomes.

Features of Eukaryotic Cells

So now that we've talked about some features of prokaryotic cells in our last lesson video, in this video we're going to talk about some features of eukaryotic cells. Now, eukaryotic cells, unlike prokaryotic cells, actually contain several membrane-bound organelles that includes a nucleus. And so eukaryotic cells do have a nucleus, unlike prokaryotic cells that do not have a nucleus. Now, eukaryotic DNA is actually linear in its shape, unlike prokaryotic DNA, which is circular in its shape. Eukaryotic DNA is actually going to be found on the inside of the nucleus that it contains.

Whereas, once again, prokaryotic cells do not have a nucleus, so their DNA is not found inside of the nucleus. Instead, recall that prokaryotic cells, their DNA is found inside of the nucleoid. And so, don't confuse the nucleus with the nucleoid. Now also recall from our last lesson video that all cells have these structures called ribosomes that make proteins, and we'll get to talk more about ribosomes later in our course, but we know all cells have ribosomes. Recall from our last lesson video, prokaryotic cells have really small 70 S ribosomes, but eukaryotic cells, on the other hand or eukaryotes, have really large ribosomes that we call 80 S ribosomes, and so, they are larger.

And also, eukaryotic cells or eukaryotes, instead of dividing by binary fission like prokaryotic cells, eukaryotic cells, when they divide, they divide by a process called mitosis and cytokinesis, which we'll get to talk more about mitosis and cytokinesis later in our course. But we should know that eukaryotic cells divide by a more complicated process called mitosis and cytokinesis. And so if we take a look at our image down below at this eukaryotic cell, one thing to note is that, there are lots of membrane-bound organelles on the inside of the eukaryotic cells. There's a lot more going on inside a eukaryotic cell than a prokaryotic cell. And eukaryotic cells, we know, are much larger.

So because they're much larger, they can fit so many more organelles, membrane-bound organelles. Now notice that eukaryotic cells, they do have a nucleus which is represented by this circle that you see here. And on the inside of the nucleus, that's where you'll find the DNA of the cell. And recall, eukaryotic cells, they specifically have DNA that is linear in its shape, and so, it's linear, like what we see here. So we can label this as linear DNA.

And notice that these little blue circles that we see throughout represent ribosomes. And so, zooming into one of these little blue circles here, you can see this represents the eukaryotic ribosome, which we know is going to be quite large, and it's going to be a large 80 S ribosome. And so once again, the number here is going to imply, with the size, and the S is just an abbreviation for a fancy unit that we're not really going to talk about in this course. And so, once again, zooming into the ribosome of the eukaryotic cell, it is going to be larger. It is a larger 80 S ribosome.

And so this here concludes our introduction to some of the features of eukaryotic cells. And as we move forward in our course, we'll be able to talk more and more about these cells. So I'll see you all in our next video.

Which organelle packages the genetic/hereditary material in eukaryotes but not in prokaryotic cells?

• A. Nucleus.
• B. Mitochondria.
• C. Chloroplasts.
• D. Nucleolus.

Recap: Prokaryotic vs. Eukaryotic Cells

In this video, we're going to do a recap of prokaryotic versus eukaryotic cells. And so notice down below we have this chart, and the chart is broken up into 3 different sections. We've got the left section over here, which is all about prokaryotic cells, then we have the right section over here in green, which is all about eukaryotic cells, and then in the middle here, we have features of both prokaryotic and eukaryotic cells. And so what you'll notice is through the numbering that we have over here and over here is that prokaryotic and eukaryotic cells really have 8 key differences. And so we're going to go through the differences first and then we'll wrap up talking about the similarities.

So the first and major key difference between prokaryotic and eukaryotic cells is that prokaryotic, once again, have no nucleus, whereas eukaryotic cells, they do have a nucleus. Now, also their size is really different, so prokaryotic cells tend to be much much smaller, only somewhere between 1 to 10 micrometers, whereas eukaryotic cells on the other hand, they are much, much larger and they can be between 10 to 100 micrometers on average, and so that's significantly larger. This means that prokaryotic cells, because they're smaller, they're going to be less complex, whereas eukaryotic cells that are larger, they're going to be more complex. Now, prokaryotic cells, they are only going to be unicellular, made up of only one single cell. Whereas, eukaryotic cells on the other hand, they can either be unicellular or they can be multicellular as well.

All multicelled organisms are going to be eukaryotic. Now in terms of the DNA, prokaryotic cells have circular DNA in shape, whereas eukaryotic cells, on the other hand, they have DNA that is linear in its shape. Prokaryotic cells, they have absolutely no membrane-bound organelles, whereas eukaryotic cells, they do have membrane-bound organelles. Now in terms of the type of cell division, prokaryotic cells, they divide by a process called binary fission, which is much more simple than the process that eukaryotic cells divide by, which is going to be mitosis and cytokinesis. And so, we'll talk more about mitosis and cytokinesis later in our course in a different video.

And then last but not least, prokaryotic cells have very very small ribosomes that we call 70S ribosomes, where the 70 here is implying the size here, that they're smaller. Whereas eukaryotic cells, they have larger 80S ribosomes. So the 80 here is larger than 70 and that's why eukaryotic cells have larger ribosomes. Now those are the 8 key differences between prokaryotic and eukaryotic cells, but once again they do have some similarities that we have here in the middle. And so both prokaryotic and eukaryotic cells are going to have a cell membrane.

All cells have a cell membrane, and we'll get to talk more about the cell membrane in a different part of our course. Now, also, both prokaryotic and eukaryotic cells contain the major biomolecules that we talked about in some of our previous lesson videos, including carbohydrates, proteins, nucleic acids, and lipids. So both prokaryotic and eukaryotic cells take advantage of these major biomolecules here. And so this here really concludes our recap of prokaryotic and eukaryotic cells, and we'll be able to apply the concepts that we've learned here as we move forward through our course. So I'll see you all in our next video.

Which of the following is/are a primary difference(s) between all prokaryotes and eukaryotic cells?

• A. Prokaryotes have DNA that floats freely in the cytoplasm.
• B. Prokaryotes are significantly smaller than eukaryotic cells.
• C. Prokaryotes do not have ribosomes like eukaryotic cells.
• D. a and b.
• E. a, b, and c

Which of the following is not a common feature shared by all types of cells?

• A. Contains DNA as the genetic material.
• B. Contains a protective cell wall or cell membrane.
• C. Contains a fluid-like portion called the cytoplasm.
• D. Contains a nucleus that stores the genetic material.

You isolate a cell with the following characteristics: (1) no nucleus, (2) a cell wall, and the cell is (3) 2 μm in size. This cell could be a/an:

• A. Bacterium.
• B. Plant cell.
• C. Animal cell.
• D. Bacterial cell or a plant cell.
• E. Plant cell or an animal cell.

Here’s what students ask on this topic:

What are the main differences between prokaryotic and eukaryotic cells?

The main differences between prokaryotic and eukaryotic cells include the presence of a nucleus, cell size, complexity, and organelles. Prokaryotic cells, such as bacteria and archaea, lack a nucleus and membrane-bound organelles, featuring circular DNA located in a nucleoid. They are unicellular and smaller, with 70S ribosomes, and divide through binary fission. In contrast, eukaryotic cells possess a nucleus, linear DNA, and various organelles. They can be unicellular or multicellular, utilize larger 80S ribosomes, and divide via mitosis and cytokinesis. These differences highlight the complexity and diversity of eukaryotic cells compared to the simpler structure of prokaryotic cells.

How do prokaryotic cells divide?

Prokaryotic cells divide through a process called binary fission. During binary fission, the circular DNA of the prokaryotic cell replicates, and the cell grows in size. The cell then divides into two identical daughter cells, each containing a copy of the original DNA. This process is simpler and faster than the division process in eukaryotic cells, which involves mitosis and cytokinesis. Binary fission allows prokaryotic cells to reproduce quickly, contributing to their abundance and diversity.

What are the similarities between prokaryotic and eukaryotic cells?

Despite their differences, prokaryotic and eukaryotic cells share several similarities. Both cell types have a cell membrane that regulates the movement of substances in and out of the cell. They also contain essential biomolecules such as carbohydrates, proteins, nucleic acids, and lipids. Additionally, both prokaryotic and eukaryotic cells have ribosomes, which are responsible for protein synthesis. These shared features highlight the fundamental biological roles that both cell types play in living organisms.

What is the function of ribosomes in prokaryotic and eukaryotic cells?

Ribosomes are essential organelles found in both prokaryotic and eukaryotic cells, responsible for protein synthesis. In prokaryotic cells, ribosomes are smaller (70S) and float freely in the cytoplasm. In eukaryotic cells, ribosomes are larger (80S) and can be found either free in the cytoplasm or attached to the endoplasmic reticulum, forming rough ER. Ribosomes translate mRNA into polypeptide chains, which then fold into functional proteins. Despite the size difference, the fundamental role of ribosomes in protein synthesis is conserved across both cell types.

What are the characteristics of bacterial cells?

Bacterial cells, which are prokaryotic, have several distinct characteristics. They lack a nucleus, with their circular DNA located in a region called the nucleoid. Bacteria have small ribosomes (70S) for protein synthesis. They are unicellular and can reproduce quickly through binary fission. Bacterial cells also have a cell membrane and often a cell wall for structural support. Some bacteria have additional structures like flagella for movement and pili for attachment to surfaces. These features contribute to their adaptability and diversity in various environments.