Endomembrane System: Digestive Organelles - Online Tutor, Practice Problems & Exam Prep

Lysosomes and peroxisomes are vital organelles in the endomembrane system. Lysosomes, found only in animal cells, contain digestive enzymes that break down cellular debris and recycle materials. In contrast, peroxisomes, present in all eukaryotic cells, focus on detoxifying harmful compounds like hydrogen peroxide and breaking down fatty acids. Additionally, the central vacuole, unique to plant cells, serves multiple functions, including recycling molecules and maintaining turgor pressure, which is crucial for plant structure and health.

Lysosomes & Peroxisomes

In this video, we're going to introduce some digestive organelles that are part of the endomembrane system. Recall from our previous lesson videos, we mentioned that some of the organelles of the endomembrane system are more specialized for cellular digestion or essentially breaking things down inside the cell. There are 2 specific organelles that we're going to focus on here in this video, and those are the lysosomes and the peroxisomes. Now lysosomes are vesicles, acidic vesicles that carry digestive enzymes. These digestive enzymes are responsible for breaking down and recycling food, cellular debris, bacteria, and damaged organelles, and all kinds of different things that are inside of the cell. So lysosomes are important for breaking down and recycling things. Lysosomes are primarily only found in animal cells, so they're not really found in plant cells. Lysosomes are going to originate at the Golgi apparatus.

On the other hand, peroxisomes are also vesicles, just like lysosomes. Peroxisomes also contain enzymes, just like lysosomes. Lysosomes and peroxisomes have some similarities, but they are also different from each other. Peroxisomes are mainly used for breaking down toxic compounds. They are used for breaking down toxic compounds, such as hydrogen peroxide or H 2O2 is a toxic compound inside of the cell, and peroxisomes are really important for helping to break down hydrogen peroxide because it can be toxic. Peroxisomes are also really important for breaking down fatty acids. Unlike lysosomes, which are only found in animal cells, peroxisomes are found in all eukaryotic cells, which includes both animal cells and plant cells. Unlike lysosomes, which originate at the Golgi apparatus, peroxisomes are going to originate at the rough endoplasmic reticulum or the rough ER.

Let's take a look at our image down below to better distinguish between these lysosomes and peroxisomes. In the top image, it specifically focuses on lysosomes. Notice that the lysosome is a vesicle, a very acidic vesicle, or a very acidic membrane bubble, a tiny little membrane bubble. On the inside of this, the lysosome is capable of fusing with other vesicles or other membrane structures. Notice here we're showing you a vesicle here that's carrying cellular debris, and the cellular debris is basically the contents that you see on the inside of this vesicle. The lysosome is capable of fusing and merging with other vesicles. Here you can see the fusion, so that the internal compartments are combined. This means that the digestive enzymes are going to be exposed to the cellular debris. This means that the digestive enzymes can break down the cellular debris into its tiny little components, thus helping to break down and recycle the components within the cell.

Peroxisomes, on the other hand, which we're focusing on down below, notice that there are also these vesicles, and they also contain enzymes as well, which are represented by these little green structures that you see. However, the enzymes in peroxisomes are specific for breaking down toxic compounds, like this, representation right here is supposed to be a toxic compound. It can fuse peroxisomes can fuse with the toxic compound and then break down the toxic into a component that is no longer toxic. Peroxisomes are really important for breaking down fatty acids as well as toxic compounds. This concludes our introduction to lysosomes and peroxisomes, and we're ready to get some practice applying these concepts as we move forward in our course. I'll see you all in our next video.

Which of the following organelles are involved in cellular digestion?

• A. Golgi Apparatus & Vesicles.
• B. Nucleus & Nucleolus.
• C. Lysosomes & Peroxisomes.
• D. Smooth & Rough Endoplasmic Reticulum.
• E. Nucleus & Chloroplasts.

Central Vacuole

In this video, we're going to introduce yet another digestive organelle of the endomembrane system and that is the central vacuole. And so the central vacuole is really just a large membrane-enclosed vesicle in plant cells. And so the central vacuole is not going to be found in animal cells. Again, the central vacuole is a feature found in plant cells. Now the central vacuole can actually have several diverse functions. However, some of those functions include degrading and recycling molecules which is why the central vacuole can be considered a digestive organelle. Now, other functions of the central vacuole include filling up with water in order to exert what's known as turgor pressure against the cell membrane. And so, if we take a look at our image down below, we can get a better understanding of this central vacuole.

And so notice on the left-hand side over here we're showing you our representation of a plant cell, and we know that plant cells have a cell wall and they also have several organelles which are going to include a central vacuole. Now notice over here we're showing you a plant, whose cell wall is right here around the perimeter, but notice that this plant cell membrane is not right up against the cell wall. And so in this scenario right here what's happening is water is going to be leaving the plant cell, and so you could draw an arrow coming out of this plant cell and say that water or H₂O, would be leaving this plant cell. And so when water leaves the plant, the plant is going to somewhat become dehydrated and the plasma membrane is going to shrivel up and so the plasma membrane will not be exerting pressure on the cell wall. And so what we can say is that under these conditions, there will be low turgor pressure. And when the turgor pressure is low, this can cause plants to wilt as you see here and a wilted plant is not going to be thriving as it should and so this plant here is likely to die very soon under these conditions of low turgor pressure.

Now, notice over here on the right-hand side of the image, we're showing you another plant cell, again its cell wall is around the perimeter, but notice that this time the cell membrane is going to be exerting pressure up against the cell wall. And notice that the central vacuole is actually much larger over here whereas on the left-hand side it's much smaller. And the central vacuole, again one of its roles is to fill up with water to exert turgor pressure. And so, over here in this scenario what we're saying is that there is high turgor pressure. And the high turgor pressure allows the plant to take on an upright healthy position so that that plant can thrive and survive very well. And so, this here concludes our brief introduction to the central vacuole, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

Which are recycling centers for the cell?

• A. Ribosome and Golgi apparatus.
• B. Endoplasmic reticulum and chloroplast.
• C. Mitochondria and nucleus.
• D. Central vacuole and lysosome.
• E. All are correct.

Which type of plant organelle often occupies the majority of the cell's volume?

• A. Food vacuole.
• B. Plant vacuole.
• C. Central vacuole.
• D. Contractile vacuoles.
• E. Chloroplasts.

Here’s what students ask on this topic:

What are the main functions of lysosomes in animal cells?

Lysosomes are essential organelles in animal cells, functioning primarily in the breakdown and recycling of various cellular materials. They contain acidic vesicles filled with digestive enzymes that degrade food particles, cellular debris, bacteria, and damaged organelles. This process not only helps in clearing out waste but also recycles useful components back into the cell. Lysosomes originate from the Golgi apparatus and are crucial for maintaining cellular health by preventing the accumulation of unwanted materials.

How do peroxisomes differ from lysosomes in terms of their functions and origins?

Peroxisomes and lysosomes, while both are vesicles containing enzymes, serve different functions and originate from different cellular structures. Lysosomes, found only in animal cells, originate from the Golgi apparatus and are involved in breaking down cellular debris and recycling materials. Peroxisomes, present in all eukaryotic cells, originate from the rough endoplasmic reticulum and focus on detoxifying harmful compounds like hydrogen peroxide and breaking down fatty acids. These differences highlight their specialized roles in cellular maintenance and health.

What role does the central vacuole play in plant cells?

The central vacuole in plant cells is a large membrane-enclosed vesicle that serves multiple functions, including the degradation and recycling of molecules, making it a digestive organelle. Additionally, it plays a crucial role in maintaining turgor pressure by filling with water. High turgor pressure helps the plant maintain its structure and stay upright, while low turgor pressure can cause the plant to wilt. This pressure is essential for the plant's overall health and ability to thrive.

Why are lysosomes not found in plant cells?

Lysosomes are not found in plant cells primarily because plant cells have other organelles, such as the central vacuole, that perform similar functions. The central vacuole can degrade and recycle molecules, thus taking over some of the roles that lysosomes play in animal cells. Additionally, plant cells have a rigid cell wall and other mechanisms to manage cellular waste and recycling, reducing the need for lysosomes.

How do lysosomes and peroxisomes contribute to cellular health?

Lysosomes and peroxisomes are crucial for maintaining cellular health through their specialized functions. Lysosomes, found in animal cells, break down and recycle cellular debris, damaged organelles, and other waste materials, preventing their accumulation. Peroxisomes, present in all eukaryotic cells, detoxify harmful compounds like hydrogen peroxide and break down fatty acids, preventing cellular damage. Together, these organelles ensure that cells remain free of toxic substances and efficiently recycle useful components.