Peroxisomes: Study with Video Lessons, Practice Problems & Examples

Peroxisomes are essential organelles that facilitate toxic chemical reactions in cells, primarily producing hydrogen peroxide, which is then utilized by the enzyme catalase to oxidize harmful substances like ethanol. They also play a role in lipid synthesis, including the production of plasmalogens. In plants, peroxisomes convert fatty acids to carbohydrates and participate in β-oxidation. Proteins enter peroxisomes via the SKKL sorting signal, and defects can lead to severe conditions such as Zellweger syndrome. Understanding peroxisome functions is crucial for grasping cellular metabolism and detoxification processes.

Peroxisomes

Hi. In this video, we're going to be talking about peroxisomes. So peroxisomes are actually organelles, and you may not have even heard of them before because they're typically not an organelle that's talked about a lot because they don't have this huge function. But, they do have an important function in the cell, and so we're going to mention them briefly here. So, peroxisomes are the organelle that contain toxic chemical reactions. One of the main reactions that peroxisomes do is they use oxygen to produce hydrogen peroxide. And we know hydrogen peroxide is this kind of toxic chemical; it's especially toxic in cells and so, cells don't want it, but they need to produce it for other things; they need to contain it. They do that in peroxisomes. There's an enzyme in peroxisomes called catalase, and this is an enzyme that uses the hydrogen peroxide that's made by the cell and it oxidizes other toxic molecules. Things like ethanol, or any other kind of toxic chemical that the peroxisome, that the cell doesn't want, so the peroxisome needs to handle. There are about 50 enzymes responsible for various chemical pathways in peroxisomes, one of these is involved in lipid synthesis. And so, one of the lipids that they do that you might see in your book is called plasminogen, and these are just phospholipids with glycerol attached via the special ether bond. So the peroxisome function isn't only toxic reactions, it's other things as well, including lipid synthesis. Now, in plants, peroxisomes have a special function in this special cycle that you don't necessarily need to know about other than there's this cycle, it's called this if you read about it. That converts fatty acids to carbohydrates and peroxisomes do that location. And then also, beta oxidation which is otherwise known as the breakdown of fatty acids, also occurs in peroxisomes. Here's an example of a reaction. Now, you don't need to know this reaction whatsoever in any way, but this is kind of how peroxisomes can use this hydrogen peroxide that's created by the cell or within the peroxisomes to oxidize other toxic molecules, so this is just some kind of toxic molecule. And you end up with a less toxic molecule and water. So, hydrogen peroxide is important for that, but you don't want it running rampant through the cell, so the peroxisome contains it there. Now, peroxisomes are created in the ER, and so when they're created they actually bud off and fuse with other buds to form new peroxisomes. So they start off with these little buds, these little vesicles that will join together to form these larger peroxisomes, which handle these toxic reactions. And, how proteins actually get to peroxisomes is they use this sorting signal called an SKKL sorting signal. And this exists on proteins called peroxins proteins. These are proteins found in the peroxisome. If so, this is how proteins get into the peroxisomes, but if there's some kind of mess up here, so the proteins that are supposed to get there don't or there's defects in peroxisomal proteins, it can cause some serious diseases. One of these is Zellweger syndrome, which is really a devastating disease, found in very young children and, that's not good. So, I don't think there's an example here just because, there's not really a good image or a good example for this. So sorry about that, but just know, peroxisomes handle toxic reactions, and you'll be good to go. So with that, let's now move on.

What is the function of a peroxisome?

• A. Maintain acidity of the cell
• B. Contain toxic reactions
• C. Protein synthesis
• D. Protein glycosylation

Here’s what students ask on this topic:

What are peroxisomes and what is their function in the cell?

Peroxisomes are essential organelles in cells that facilitate toxic chemical reactions. They primarily produce hydrogen peroxide (H₂O₂), which is then utilized by the enzyme catalase to oxidize harmful substances like ethanol. Besides detoxification, peroxisomes play a role in lipid synthesis, including the production of plasmalogens. In plants, they convert fatty acids to carbohydrates and participate in β-oxidation. Understanding peroxisome functions is crucial for grasping cellular metabolism and detoxification processes.

How do peroxisomes detoxify harmful substances in the cell?

Peroxisomes detoxify harmful substances by producing hydrogen peroxide (H₂O₂) through the use of oxygen. The enzyme catalase within peroxisomes then uses this H₂O₂ to oxidize and neutralize toxic molecules such as ethanol. This process converts harmful substances into less toxic molecules and water, ensuring that these toxic reactions are contained within the peroxisome and do not harm the rest of the cell.

What role do peroxisomes play in lipid synthesis?

Peroxisomes play a significant role in lipid synthesis, particularly in the production of plasmalogens. Plasmalogens are a type of phospholipid with glycerol attached via a special ether bond. These lipids are crucial for the proper functioning of cell membranes, especially in the brain and heart. By synthesizing these lipids, peroxisomes contribute to maintaining cellular structure and function.

What is Zellweger syndrome and how is it related to peroxisomes?

Zellweger syndrome is a severe genetic disorder caused by defects in peroxisomal proteins. These defects prevent the proper formation and function of peroxisomes, leading to the accumulation of toxic substances in cells. Symptoms of Zellweger syndrome include developmental delays, liver dysfunction, and neurological abnormalities. The condition is typically diagnosed in infancy and is often fatal. Understanding peroxisome function is crucial for grasping the impact of this syndrome on cellular health.

How are peroxisomes formed in the cell?

Peroxisomes are formed in the endoplasmic reticulum (ER). They start as small vesicles that bud off from the ER and then fuse with other vesicles to form larger peroxisomes. This process ensures that peroxisomes are equipped with the necessary enzymes and proteins to carry out their functions. Proteins are targeted to peroxisomes using a specific sorting signal called the SKKL sorting signal, which ensures they are correctly delivered to the organelle.