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, plays a crucial role in recycling molecules and maintaining turgor pressure, which is essential for plant structure and health.

Lysosome & Peroxisome

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, 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, and they originate at the Golgi apparatus.

On the other hand, peroxisomes are also vesicles, just like lysosomes. Peroxisomes contain enzymes as well, and they also have some similarities with lysosomes, but they are also different from each other. Peroxisomes are mainly used for breaking down toxic compounds, such as hydrogen peroxide (H2O2) which is a toxic compound inside of the cell. 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, including both animal and plant cells. Unlike lysosomes, which originate at the Golgi apparatus, peroxisomes originate from the rough endoplasmic reticulum (rough ER).

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

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

Hydrolytic enzymes must be segregated and packaged to prevent general destruction of cellular components. In animal cells, which of the following organelles contains these hydrolytic enzymes?

• A. Rough ER.
• B. Central vacuole.
• C. Smooth ER.
• D. Lysosomes.
• E. Golgi apparatus.

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 talk about yet another digestive organelle of the endomembrane system, and that is the central vacuole. Now, the central vacuole is a large membrane-enclosed vesicle found inside of plant cells. Central vacuoles are not found in animal cells. They're really only found in plant cells. Now central vacuoles actually have a lot of different types of functions, but those functions include degrading and recycling molecules. So they're part of the digestive organelles for that reason. Now, other functions of the central vacuole include filling up with water to exert what's known as turgor pressure against the cell membrane.

So let's take a look at our image down below to get a better understanding here of this central vacuole. Over here on the left-hand side, notice that we're showing you our representation plant cell, and recall central vacuoles are really only found in plant cells, not in animal cells. And so you can see the central vacuole is this blue structure that we see right here. Okay? And we have it labeled as the central vacuole.

And so over here on the right-hand side, we're showing you some other representations of plant, and plant cells. Notice that in this image over here, notice that water is actually leaving the cell. We have the arrows going in a direction where the water is leaving the cell. And so notice that the plant cell's plasma membrane, which is right here, it's not really exerting any pressure onto the cell wall, and the cell wall is the surrounding wall that you see right here. And so the plasma membrane or the cell membrane, which we have in red, when water is leaving the cell, it doesn't exert pressure on the cell wall, and so that means that it's going to have very very low turgor pressure over here.

And so when a plant has low turgor pressure, it's not going to be in a healthy state, and so that can cause a plant to wilt, like this wilted plant that we see here. And so, ultimately, this could lead to a cell dying.

Now over here on the right-hand side, notice that we're showing you the arrows going into the cell, showing that water is going into the cell and filling the cell up with water. And so one of the roles of the central vacuole is to fill up and store water, and what you'll notice is that with all of this water going into the plant cell, the cell's plasma membrane is expanded, and you can see the cell's plasma membrane is being traced right here in red. And, I'll do it here with a thicker color so that you can see it easier. It's being, right here in red is where the plasma membrane here.

And so the plasma membrane is right up against the cell wall, and so the plasma membrane is exerting pressure on the cell wall, which means that when water is going into the plant cell, there is going to be high turgor pressure. And so turgor pressure can allow plants to be upright and to have their normal healthy structure.

And so this here concludes our brief introduction to central vacuoles, and we'll be able to get some practice applying these concepts as we move forward throughout our course. 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 digestive enzymes that degrade food particles, cellular debris, bacteria, and damaged organelles. This process helps maintain cellular health by removing waste and recycling components for reuse. Lysosomes originate from the Golgi apparatus and are characterized by their acidic environment, which is optimal for the activity of their enzymes. By fusing with other vesicles containing material to be degraded, lysosomes ensure efficient digestion and recycling within the cell.

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

Peroxisomes and lysosomes, while both are vesicles containing enzymes, have distinct functions and origins. Lysosomes, found only in animal cells, originate from the Golgi apparatus and are involved in breaking down and recycling cellular debris, food particles, and damaged organelles. In contrast, peroxisomes are present in all eukaryotic cells and originate from the rough endoplasmic reticulum. Their primary function is to detoxify harmful compounds like hydrogen peroxide (H₂O₂) and to break down fatty acids. This detoxification is crucial for cellular health, as it prevents the accumulation of toxic substances.

What role does the central vacuole play in plant cells?

The central vacuole is a large, membrane-enclosed vesicle found exclusively in plant cells. It serves multiple functions, including the degradation and recycling of molecules, similar to lysosomes in animal cells. Additionally, the central vacuole is crucial for maintaining turgor pressure by storing water. Turgor pressure is the force exerted by the plasma membrane against the cell wall, which helps maintain the plant's structural integrity and keeps it upright. When the central vacuole is filled with water, it ensures that the plant remains healthy and turgid, preventing wilting.

Why are lysosomes not found in plant cells?

Lysosomes are not found in plant cells because plant cells have other organelles that perform similar functions. The central vacuole in plant cells takes on many of the roles of lysosomes, such as degrading and recycling cellular materials. Additionally, plant cells have a rigid cell wall that provides structural support and protection, reducing the need for lysosomes. The presence of peroxisomes in both plant and animal cells also helps in detoxifying harmful substances, further compensating for the absence of lysosomes in plant cells.

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, contain digestive enzymes that break down and recycle cellular debris, damaged organelles, and pathogens, preventing the accumulation of waste. Peroxisomes, present in all eukaryotic cells, detoxify harmful compounds like hydrogen peroxide (H₂O₂) and break down fatty acids. This detoxification process is vital for preventing cellular damage from toxic substances. Together, these organelles ensure that cells remain clean, functional, and free from harmful compounds.