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 food, debris, and damaged organelles. In contrast, peroxisomes, present in all eukaryotic cells, focus on detoxifying harmful substances 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, essential 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. And so recall in 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, and 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, and lysosomes are going to originate at the Golgi apparatus. On the other hand, peroxisomes are also vesicles just like lysosomes and contain enzymes as well. Although lysosomes and peroxisomes have some similarities, they're different from each other. Peroxisomes are mainly used for breaking down toxic compounds, such as, for example, hydrogen peroxide or H2O2 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 as well. So that's another important function of peroxisomes. Unlike lysosomes, which are only found in animal cells, peroxisomes are found in all eukaryotic cells, which includes both animal cells and plant cells. And unlike lysosomes, which originate at the Golgi apparatus, peroxisomes are going to originate at the rough endoplasmic reticulum or the rough ER.

So let's take a look at our image down below to better distinguish between these lysosomes and peroxisomes. Notice that the lysosome is a vesicle, a very acidic vesicle or very acidic membrane bubble, tiny little membrane bubble. On the inside of this vesicle, this lysosome, there are digestive enzymes. 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 going to be capable of fusing and merging with other vesicles. So 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 enables the digestive enzymes to break down the cellular debris into its tiny components, helping to break down and recycle the components within the cell. Now peroxisomes, on the other hand, which we're focusing on 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. Peroxisomes can fuse with the toxic compound and then break down the toxic compound into a component that is no longer toxic. Peroxisomes are also crucial for breaking down fatty acids as well as toxic compounds.

This concludes our introduction to lysosomes and peroxisomes, 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.

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. 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. Other functions of the central vacuole include filling up with water to exert what's known as turgor pressure against the cell membrane. 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 of a 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. Over here on the right-hand side, we're showing you some other representations of plants and plant cells. Notice in this image over here, water is actually leaving the cell, with the arrows going in a direction where the water is leaving the cell.

Notice that the plant cell's plasma membrane, which is right here, is not really exerting any pressure onto the cell wall, and the cell wall is the surrounding wall that you see right here. When water is leaving the cell, the plasma membrane does not exert pressure on the cell wall, and that means that there will be very low turgor pressure in this area. When a plant has low turgor pressure, it's not going to be in a healthy state, and that can cause a plant to wilt, like this wilted plant that we see here. Ultimately, this could lead to a cell dying.

Over here on the right-hand side, notice that we are showing you the arrows going into the cell, indicating that water is entering the cell and filling it up with water. One of the roles of the central vacuole is to fill up and store water. Notice that with all this water going into the plant cell, the cell's plasma membrane is expanded, which you can see being traced here in red. The plasma membrane is right up against the cell wall, and so the plasma membrane is exerting pressure on the cell wall, meaning that when water is entering the plant cell, there will be high turgor pressure. Turgor pressure can allow plants to be upright and maintain their normal healthy structure.

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. 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 breaking down these materials, lysosomes play a crucial role in cellular metabolism and homeostasis.

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. Peroxisomes are involved in detoxifying harmful substances like hydrogen peroxide (H₂O₂) and breaking down fatty acids. They are found in all eukaryotic cells, including both animal and plant cells, and originate from the rough endoplasmic reticulum (ER). In contrast, lysosomes are primarily found in animal cells and are responsible for breaking down food, cellular debris, and damaged organelles. Lysosomes originate from the Golgi apparatus and contain digestive enzymes that function in an acidic environment.

What role does the central vacuole play in plant cells?

The central vacuole in plant cells serves multiple functions, including the degradation and recycling of molecules, similar to lysosomes in animal cells. Additionally, it plays a crucial role in maintaining turgor pressure by storing water. Turgor pressure is the force exerted by the central vacuole 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 plasma membrane presses against the cell wall, providing the necessary pressure for the plant to remain healthy and robust.

Why are lysosomes not found in plant cells?

Lysosomes are not found in plant cells 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 the role of lysosomes. Additionally, plant cells have a rigid cell wall that provides structural support and protection, reducing the need for lysosomes to manage cellular debris and damaged organelles. 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 homeostasis?

Lysosomes and peroxisomes are vital for maintaining cellular homeostasis by managing waste and detoxifying harmful substances. Lysosomes contain digestive enzymes that break down food particles, cellular debris, and damaged organelles, recycling their components for reuse. This process helps keep the cell clean and efficient. Peroxisomes, on the other hand, detoxify harmful substances like hydrogen peroxide (H₂O₂) and break down fatty acids, preventing the accumulation of toxic compounds. Together, these organelles ensure that the cell's internal environment remains stable and conducive to proper functioning.