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

Mitochondria, known as the powerhouse of the cell, generate energy in the form of Adenosine Triphosphate (ATP) through cellular respiration, which breaks down food sources like sugars and lipids. Structurally, mitochondria have two membranes: an outer membrane and a highly folded inner membrane with cristae. They contain their own DNA and ribosomes, allowing for independent protein synthesis. In contrast, chloroplasts, found in plant cells, are green organelles responsible for photosynthesis, converting sunlight, carbon dioxide, and water into glucose and oxygen, and also possess a double membrane structure without 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, they are the powerhouse of the cell, and this is because mitochondria are organelles that synthesize lots and 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 and lots of ATP or in order to make lots and 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 functions specifically as the powerhouse of the cell, and that's because it provides lots and 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 you can see the 3 phosphate groups down below here in our image. 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. 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 down 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. And 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 introduce mitochondria structure, and so mitochondria are usually shown with this bean-shaped structure, as you see right here. You'll find that, looking across your textbook, the mitochondria are almost always shown with this bean-shaped structure. However, it's important to note that mitochondria can actually vary in their shape and they don't always have this same exact bean-shaped structure. The mitochondria can take on a variety of different structures that are elongated and flattened, among other forms. Now, it's also important to note that mitochondria actually have their own ribosomes. They have their own mitochondrial ribosomes, and the mitochondrial ribosomes are different than the ribosomes from the rest of the eukaryotic cell. Also, mitochondria have their own DNA. They have their own mitochondrial DNA that is independent of the nuclear DNA or the DNA that is found in the nucleus. And so, the DNA in the mitochondria will be different than the DNA that is found in the nucleus.

Now, mitochondria actually have two membranes, and those two membranes are an outer membrane and a folded inner membrane. And so, the inner membrane is going to have lots and lots of folds, and those folds in the inner mitochondrial membrane are referred to as cristae, and so you should be familiar with this term 'cristae'. Now, in between the two mitochondrial membranes, in between the outer mitochondrial membrane and the folded inner mitochondrial membrane, is a region that is called the intermembrane space. And so the intermembrane space is defined as the region in between the two mitochondrial membranes. Now, there's also a space in the mitochondria called the matrix or the mitochondrial matrix. And again, this is a space or a region within the mitochondria, specifically it's a region within the inner membrane of the mitochondria. And so, it is going to contain enzymes, ribosomes, and mitochondrial DNA.

If we take a look at our image down below, we can get a better understanding of the structure of the mitochondria. Once again, the most important thing to note is that the mitochondria are going to have two membranes. It has an outer membrane, which we can highlight here in red, going all the way around the perimeter. But then it also has a folded inner membrane, and the folded inner membrane, you can see, is going to be extremely highly folded here, and it goes all the way around, as you see right here. Now, the inner membrane, again, is going to be very folded, and those folds in the inner membrane are specifically referred to as cristae, and so you should be familiar with that. Now again, there is a region in between the inner and outer membrane called the intermembrane space. So, the intermembrane space, if we were to highlight it, would go all the way around and is going to be, again, in between the inner and outer membranes, as you see here highlighted in that dark pink. And then there's another region called the mitochondrial matrix; this is going to be the region inside of the inner mitochondrial membrane and so the matrix would be this region highlighted here in green. And so, this is really important to keep in mind, to differentiate the intermembrane space from the mitochondrial matrix.

Now, in the mitochondrial matrix, if we were to zoom into this particular region, right here, of the mitochondrial matrix, that's what this box is, this is where you're going to find the mitochondrial enzymes, mitochondrial ribosomes, and mitochondrial DNA. And so, notice in this image, the mitochondrial ribosomes are being shown in green here. Notice that the mitochondrial enzymes are being shown in this grayish circle, right here. And then notice that the mitochondrial DNA is circular in its shape and it is also going to be found in the mitochondrial matrix.

This here concludes our brief lesson on mitochondria structure and this will be very important to keep in mind as we move forward in our course. And 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. They 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 or to produce sugars such as glucose, for instance.

If we take a look at our image down below 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, and once again, 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 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 from the atmosphere), also water from the environment or atmosphere, and it takes carbon dioxide, water, along with the sunlight from the environment or the atmosphere, which we're showing you here. It then converts the carbon dioxide, the water, and the sunlight to create sugars like what we see right here, which would actually represent glucose, a very specific sugar. In addition to creating the sugar, it also creates oxygen gas or O₂, like what we see here, which is a really important gas for us because we breathe in oxygen gas.

So plants, because they perform photosynthesis, they 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 of many plant cells and 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 introduce chloroplast structure. Chloroplasts actually have two membranes, just like the mitochondria, and so the chloroplast is going to have an outer chloroplast membrane and an inner chloroplast membrane. Now, unlike the mitochondria, which does have folds and cristae in its inner mitochondrial membrane, the chloroplast membranes do not have folds or cristae, and so neither of the chloroplast membranes have folds or cristae. If we take a look at our image down below, we can get a better understanding of the chloroplast structure. Notice on the left-hand side, we're showing you a micrograph of these plant cells and notice that each of these green structures represents a chloroplast. If we zoom in, notice on the right we're showing you a typical representation of a chloroplast. The chloroplast has two membranes; they have an outer membrane that goes around the entire perimeter and then an inner membrane as well. Notice that the inner membrane, unlike the inner membrane of the mitochondria, does not have any folds or cristae.

Within the chloroplast, specifically in this region right here, you'll notice that there are these green pancake-looking structures throughout, and each of these green pancake-looking structures are actually referred to as thylakoids. The thylakoids can be defined as interconnected pancake-shaped sacs made of membranes found within the chloroplast. It's also important to keep in mind that these thylakoids are hollow on the inside and consist of a membrane, but inside the thylakoid is a hollow space called the thylakoid space.

A stack of these thylakoids is referred to as a granum, and the plural form of granum is grana. The grana are really just referring to stacks of thylakoids. The granum can be thought of as green pancake stacks within the chloroplast. There's also a region known as the stroma that is important; it is the innermost region of the chloroplast, and so the stroma is going to be analogous to the mitochondrial matrix. The stroma is going to contain chloroplast enzymes, chloroplast ribosomes, and chloroplast DNA as well. The chloroplast is going to have its own independent DNA that's separate from the DNA of the nucleus and is also going to have its own ribosomes and enzymes, separate from the enzymes and ribosomes of the rest of the eukaryotic cell.

This concludes our brief lesson on chloroplast structure which is going to be important to keep in mind as we move forward in our course, especially when we get to talk about photosynthesis, since the chloroplast is the site of photosynthesis for plant cells. 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 main function of mitochondria in a cell?

The main function of mitochondria in a cell is to generate energy in the form of Adenosine Triphosphate (ATP) through a process called cellular respiration. Mitochondria break down food sources like sugars and lipids to produce ATP, which is used to power various cellular reactions. This is why mitochondria are often referred to as the powerhouse of the cell. The energy produced is crucial for the cell's survival and function.

How do chloroplasts contribute to photosynthesis?

Chloroplasts are essential for photosynthesis, a process that converts sunlight, carbon dioxide, and water into glucose and oxygen. Chloroplasts contain thylakoids, which are membrane-bound structures where the light-dependent reactions of photosynthesis occur. The stroma, the fluid-filled space surrounding the thylakoids, is where the light-independent reactions (Calvin cycle) take place. These reactions collectively enable the plant to produce glucose, which serves as an energy source, and oxygen, which is released into the atmosphere.

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 with cristae, creating an intermembrane space and a mitochondrial matrix. The matrix contains enzymes, ribosomes, and mitochondrial DNA. Chloroplasts also have two membranes but lack cristae. Instead, they contain thylakoids, which are stacked into grana, and a fluid-filled stroma. The stroma contains chloroplast enzymes, ribosomes, and chloroplast DNA. These structural differences are related to their functions in cellular respiration and photosynthesis, respectively.

Why do mitochondria have their own DNA?

Mitochondria have their own DNA because they are believed to have originated from free-living prokaryotic organisms that entered into a symbiotic relationship with early eukaryotic cells. This endosymbiotic theory suggests that these prokaryotes provided the host cell with additional energy, and over time, they became an integral part of the cell. Mitochondrial DNA is distinct from nuclear DNA and encodes some of the proteins and enzymes required for mitochondrial function, supporting the organelle's role in energy production.

What is the role of ATP in cellular processes?

ATP, or Adenosine Triphosphate, is the primary energy carrier in cells. It provides the energy needed for various cellular processes, including muscle contraction, nerve impulse propagation, and chemical synthesis. ATP releases energy when its high-energy phosphate bonds are broken, converting it to ADP (Adenosine Diphosphate) and an inorganic phosphate. This energy is then used to power cellular reactions, making ATP essential for maintaining cellular function and homeostasis.