Mitochondria & Chloroplasts - Video Tutorials & Practice Problems

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 function 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, 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 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 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 option 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 bean-type shape that you see down below in our image. However, 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. Additionally, 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 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, they have several different structures and regions that we should be aware of. The first thing that you should know about their structure is that mitochondria have two membranes, not just one. They have an outer membrane and a folded inner membrane. The folds in the inner membrane are called cristae. The region between the two membranes, the outer and inner mitochondrial membranes, is called the intermembrane space. The matrix specifically refers to the region within the mitochondria that is enclosed by 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 have two membranes: an outer membrane and a folded inner membrane. I’ll put the outer membrane here in red, which is simpler with no folds. However, the inner membrane, highlighted here in green, shows this structure with all of these folds. The folds seen in the inner membrane are called cristae, and the space between the outer and inner membranes is referred to as the intermembrane space. The matrix, colored here in blue throughout this image, is the region within the inner membrane. If we zoom into the matrix, you will notice it contains enzymes, represented in the image, ribosomes as these green circles, and mitochondrial DNA, which is circular in its shape.

This overview concludes our discussion on 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. 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. And so 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, and 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. And so, 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. And so all of these green circles that you see 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 here for the process of photosynthesis, which occurs in many plant cells. So, what we're showing you is a plant that is conducting the process of photosynthesis, and photosynthesis, what it does is it converts carbon dioxide from the atmosphere or 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. And it converts the carbon dioxide, the water, and the sunlight, and it converts them to create sugars like what we see right here, which would actually represent glucose, which is 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. And so, plants, because they perform photosynthesis, produce a lot of the oxygen gas that we breathe in. And so, 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.

And so, 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. And so very similarly to mitochondria, chloroplasts actually have 2 membranes. They have an outer membrane and they have an inner membrane as well. But unlike mitochondria, neither of the chloroplast membranes have folds or cristae. And 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. And so the first thing to note about the chloroplast that we're showing you here is that it has 2 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. And these green pancake-looking structures are called Thylakoids. And so Thylakoids are interconnected pancake-shaped sacs that are within the chloroplast, and they're very important for a part of the photosynthesis reaction. Now, 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 green pancakes, or green pancake stacks, if you will. Now remember, these green-looking pancakes, they're not actually pancakes, of course, they're called thylakoids. And the space, the innermost region of the chloroplast, is specifically referred to as the stroma. And so the stroma is pretty much equivalent to the matrix of the mitochondria. And so it's the innermost region of the Chloroplast that contains enzymes, ribosomes, and Chloroplast DNA as well. And so down below in our image, notice that we're saying that the stroma, well, it's just the innermost region here. It's basically the space that fills the chloroplast here in the innermost region here. And so 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.