Mitochondria & Chloroplasts - Online Tutor, Practice Problems & Exam Prep

Mitochondria, known as the powerhouse of the cell, generate energy through cellular respiration, producing adenosine triphosphate (ATP) from food sources. They possess a unique structure with two membranes: an outer membrane and a highly folded inner membrane containing cristae. The space between these membranes is the intermembrane space, while the matrix houses enzymes, ribosomes, and mitochondrial DNA. In contrast, chloroplasts, found in plant cells, facilitate photosynthesis, converting sunlight, carbon dioxide, and water into glucose and oxygen, featuring thylakoids and stroma without membrane folds.

Mitochondria

In this video, we're going to begin our lesson on mitochondria and chloroplasts. But we're going to start focusing only on the mitochondria. And then later in our course in a different video, we'll talk about the chloroplasts. And so if you've ever taken a biology course before in the past, then you probably know that mitochondria are the powerhouse of the cell, and this is because mitochondria are organelles that synthesize lots and lots of energy for the cell. And so that's why they call it the powerhouse of the cell because it provides the energy that the cell needs. Now the energy that the mitochondria provide for the cell is in the form of a molecule called Adenosine Triphosphate or for short, ATP. And so Adenosine Triphosphate or ATP is a high-energy molecule that is used to power cellular reactions. And so if the cell has a lot of ATP, then the cell has a lot of energy to power its cellular reactions. But on the other hand, if the cell has a little bit of ATP then the cell only has a little bit of energy to power its cellular reactions. And so ATP is really the energy for the cell. Now, mitochondria perform a process that's called cellular respiration. And so cellular respiration is just the name of the mitochondrial process that breaks down food sources like sugars and lipids in order to make lots and lots of ATP or in order to make lots and lots of energy for the cell. And so later in our course in a different video, we'll talk a lot more details about cellular respiration, but here in this video, you should just know that mitochondria perform cellular respiration in order to break down food sources and make lots and lots of ATP or energy for the cell. And so if we take a look at our image over here on the left-hand side, notice that we're zooming in here to a eukaryotic cell, and here we're focusing on a specific organelle, the mitochondria. And the mitochondria function specifically as the powerhouse of the cell, and that's because it provides lots and lots of ATP or energy for the cell. And so, the energy that's being provided is ATP, which can be abbreviated, and shown like this. But really, adenosine triphosphate or ATP is a molecule that can also be shown, in this form right here, where, again, the t, here in adenosine triphosphate stands for tri, and tri means 3, which means that it has 3 phosphate groups. And so, the rest of this here is going to be a sugar, and this part up here is going to be a nitrogenous base of adenine. And so that means that ATP is a nucleotide, which we covered nucleotides when we talked about nucleic acids in some of our previous lesson videos. But once again, the main takeaway here is that mitochondria, they are the powerhouse of the cell, providing lots and lots of energy for the cell in the form of ATP, and cellular respiration is the name of the process that makes ATP for the cell. And so this here concludes our introduction to the mitochondria, and in our next video, we'll be able to talk about the components and the structure of the mitochondria itself. So I'll see you all there.

Mitochondria & Chloroplasts Example 1

Alright. So here we have an example problem that's asking which of the following processes is highly associated with mitochondria? And we've got these 4 potential answer options below. Now, option a says photosynthesis, but this is not a process that's highly associated with mitochondria. And so, for that reason, we can go ahead and cross off option a. Instead, what we'll learn a little bit later in our course is that photosynthesis is a process highly associated with chloroplasts.

Now, option b here says plasmolysis, which is a process that we have not yet introduced in our course. We'll talk a little bit more about plasmolysis later in our course when we're talking about osmosis. But for now, we haven't introduced this yet, so we should have been able to eliminate answer option b. And then also with answer option d, it says crenation, which is another process that we have not yet talked about. We'll get to talk more about crenation a little bit later in our course when we're talking about osmosis as well.

But, of course, we know from our last lesson video that cellular respiration is the name of the mitochondrial process that breaks down foods to create ATP or energy for the cell. And so cellular respiration is the process that is highly associated with mitochondria. And so c here is the correct answer to this example problem, and that concludes this example. So I'll see you all in our next video.

Mitochondria Structure

In this video, we're going to talk about mitochondria structure. Mitochondria in textbooks are always shown with the same typical shape, which is this bean type of shape that you see down below in our image. But in reality, it turns out that mitochondria can actually vary in their shape, and they're not always bean-shaped; they can be all kinds of different shapes. Moreover, mitochondria have their own set of ribosomes, as well as their own set of DNA. The ribosomes are independent from the ribosomes found throughout the rest of the cell. The DNA that's found in the mitochondria is also independent of the DNA found in the rest of the cell, such as the nuclear DNA.

When it comes to mitochondrial structure, there are several different structures and regions that we should be aware of. The first thing that you should know about their structures is that mitochondria have two membranes, not just one. They have an outer membrane, and then they also have a folded inner membrane. The folds in the inner membrane are called cristae. We'll be able to see that down below when we get to our image. The region that's in between the two membranes, the outer mitochondrial membrane and the inner mitochondrial membrane, is called the intermembrane space. We'll be able to see that down below in our image as well. The matrix specifically refers to another region within the mitochondria, located within the inner membrane. This region contains enzymes, ribosomes, and mitochondrial DNA.

Let's take a look at our image down below to get a better understanding of mitochondrial structure. The mitochondria are going to have two membranes, an outer membrane and a folded inner membrane. The outer membrane, which I'll put here in red, is more simple; there are no folds in the outer membrane. But when you take a look at the inner membrane, which I'll highlight here in green, you'll see that it creates all of these folds in here, and the inner membrane is not just rounded and smooth; it's highly folded. Those folds that you see in the inner membrane are called cristae. The space that's in between the outer membrane and the inner membrane is called the intermembrane space. It's the region between the two membranes. The matrix refers to the region that's within the inner membrane. And the matrix here is colored with a blue color throughout this image. It contains enzymes, ribosomes, and mitochondrial DNA. If we zoom into the matrix here, what you'll notice is that it contains enzymes, which we're showing you, are represented here in the image. They also contain ribosomes, which are represented as these green circles in the image, and they also contain mitochondrial DNA, which is circular in its shape.

This here really concludes mitochondrial structure, and we'll be able to get some practice applying the concepts that we've learned here as we move forward in our course. So, I'll see you all in our next video.

Which part of a mitochondria contains the mitochondrial DNA, ribosomes, and enzymes?

• A. Cristae.
• B. Matrix.
• C. Inter-membrane space.
• D. Cytoplasm.

Chloroplasts

In this video, we're going to introduce chloroplasts. Chloroplasts are organelles that are actually green in color. Chloroplasts are green organelles and they function specifically as the site of a process called photosynthesis. This process of photosynthesis occurs in many plant cells that contain these green chloroplast organelles. But what is this process of photosynthesis exactly? Well, photosynthesis is once again a cellular process that uses energy from the sun or sunlight in order to synthesize sugars such as glucose, for instance.

If we take a look at our image down below, over here on the left-hand side, notice that we're showing you an image using a light microscope, looking at plant cells that contain chloroplasts. All of these green circles that you see here throughout this image represent chloroplasts. Chloroplasts are these green organelles that function as the site of photosynthesis, the process that uses energy from the sunlight to synthesize sugars such as glucose.

Over here on the right-hand side, we're showing you a little reaction here for the process of photosynthesis, which occurs in many plant cells. Here what we're showing you is a plant that is conducting the process of photosynthesis. Photosynthesis converts carbon dioxide from the atmosphere (CO₂), water from the environment, and sunlight into sugars like glucose, which is a very specific sugar. In addition to creating the sugar, it also creates oxygen gas (O₂), which is a really important gas for us because we breathe in oxygen gas. Plants, because they perform photosynthesis, produce a lot of the oxygen gas that we breathe in.

This here concludes our introduction to chloroplasts and how chloroplasts are these green organelles that serve as the site of photosynthesis inside many plant cells. Photosynthesis is the process that uses sunlight to synthesize sugars. Now that we've covered the general basics of the chloroplast, in our next video we'll be able to talk about the structures of the chloroplast. So, I'll see you guys in that video.

The products of photosynthesis are:

• A. Water & Carbon Dioxide.
• B. Oxygen & Water
• C. Sugar & Water.
• D. Oxygen & Sugar.

Chloroplast Structure

In this video, we're going to talk about chloroplast structure. Similarly to mitochondria, chloroplasts have two membranes. They have an outer membrane and an inner membrane as well. Unlike mitochondria, however, neither of the chloroplast membranes have folds or cristae. Recall from our previous lesson videos that mitochondria have folds or cristae in the inner mitochondrial membrane. But once again, the chloroplast membranes, neither of them have folds or cristae.

And so if we take a look at our image down below, notice the left-hand side of our image is showing the same light microscope image from our last lesson video zooming into plant cells. And all of these green circles that we see here represent chloroplasts. And so if we zoom into one of these green circles, it'll look something like this, what we're showing you here. The first thing to note about the chloroplast that we're showing you here is that it has two membranes. It has an outer membrane that we're labeling, right here on the outside, and then it has an inner membrane as well that's on the inside. But notice that neither the outer membrane nor the inner membrane has folds or cristae. They don't have folds or cristae.

Now, you'll also notice that inside of the chloroplast, there are these other structures, and one of the things that you'll notice right away are these green pancake-looking structures that are all over the place on the inside. These green pancake-looking structures are called Thylakoids. Thylakoids are interconnected pancake-shaped sacs that are within the chloroplast, and they're very important for a part of the photosynthesis reaction. You'll also notice that the thylakoids, each of these individual green pancake-looking structures are forming stacks, and these stacks of the thylakoids are referred to as grana, and that is the plural form here. So, grana are referring to stacks of thylakoids, or in other words, stacks of the green pancakes, or green pancake stacks, if you will.

Remember, these green looking pancakes, they're not actually pancakes. They're called thylakoids. And the space, the innermost region of the chloroplast, is specifically referred to as the stroma. The stroma is pretty much equivalent to the matrix of the mitochondria. It's the innermost region of the chloroplast that contains enzymes, ribosomes, and chloroplast DNA as well. Down below in our image, notice that we're saying that the stroma is just the innermost region here. It's basically the space that fills the chloroplast here in the innermost region here.

This here concludes our introduction to chloroplast structure, 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.

Thylakoids, DNA, and ribosomes are all components found in ________.

• A. Chloroplasts.
• B. Mitochondria.
• C. Lysosomes.
• D. Vacuoles.
• E. Nuclear Envelopes.

Here’s what students ask on this topic:

What is the primary function of mitochondria in a cell?

The primary function of mitochondria in a cell is to generate energy through a process called cellular respiration. This process involves breaking down food sources like sugars and lipids to produce adenosine triphosphate (ATP), which is the main energy currency of the cell. Mitochondria are often referred to as the powerhouse of the cell because they produce large amounts of ATP, which is used to power various cellular reactions and processes. Without sufficient ATP, cells would not have the energy required to perform essential functions.

How do chloroplasts contribute to photosynthesis in plant cells?

Chloroplasts are essential organelles in plant cells that facilitate the process of photosynthesis. They capture energy from sunlight and use it to convert carbon dioxide (CO₂) and water (H₂O) into glucose (C₆H₁₂O₆) and oxygen (O₂). This process occurs in the thylakoids, which are stacked into structures called grana within the chloroplast. The stroma, the innermost region of the chloroplast, contains enzymes, ribosomes, and chloroplast DNA, all of which are crucial for the photosynthetic process. Photosynthesis not only provides energy in the form of glucose for the plant but also produces oxygen, which is vital for many living organisms.

What are the structural differences between mitochondria and chloroplasts?

Mitochondria and chloroplasts have distinct structural differences. Mitochondria have two membranes: an outer membrane and a highly folded inner membrane containing cristae. The space between these membranes is called the intermembrane space, and the matrix within the inner membrane houses enzymes, ribosomes, and mitochondrial DNA. In contrast, chloroplasts also have two membranes but lack the folds or cristae found in mitochondria. Instead, chloroplasts contain thylakoids, which are interconnected pancake-shaped sacs that form stacks called grana. The innermost region of the chloroplast is the stroma, which contains enzymes, ribosomes, and chloroplast DNA.

Why are mitochondria referred to as the powerhouse of the cell?

Mitochondria are referred to as the powerhouse of the cell because they produce the majority of the cell's supply of adenosine triphosphate (ATP), the main energy currency. Through the process of cellular respiration, mitochondria break down food molecules like sugars and lipids to generate ATP. This ATP is then used to power various cellular reactions and processes, providing the energy necessary for the cell to function. Without mitochondria, cells would not be able to produce sufficient energy to sustain life.

What role do thylakoids play in chloroplasts?

Thylakoids play a crucial role in chloroplasts by serving as the site where the light-dependent reactions of photosynthesis occur. These reactions capture energy from sunlight and convert it into chemical energy in the form of ATP and NADPH. Thylakoids are organized into stacks called grana, which increase the surface area for light absorption. The thylakoid membrane contains chlorophyll and other pigments that capture light energy, as well as proteins and enzymes essential for the photosynthetic process. The energy produced in the thylakoids is then used in the stroma for the light-independent reactions, which synthesize glucose from carbon dioxide and water.