3-2 Protein degradation Brain cells of people with Parkinson's disease and Alzheimer's disease fail to degrade abnormal proteins resulting in their accumulation in the cytosol. Which of the following cellular organelles is responsible for degrading the faulty protein? Rough endoplasmic reticulum Peroxisome Proteasome Smooth endoplasmic reticulum Golgi complex

The correct answer is **Proteasome**.<br /><br />Here's why:<br /><br />* **Proteasomes** are the primary structures responsible for degrading misfolded, damaged, or unnecessary proteins in the cytosol. They recognize proteins tagged with ubiquitin and break them down into smaller peptides. This process is crucial for maintaining cellular health.<br /><br />Let's look at why the other options are incorrect:<br /><br />* **Rough Endoplasmic Reticulum (RER):** The RER is involved in protein synthesis and folding, not degradation. While it plays a role in quality control by identifying misfolded proteins, it doesn't degrade them directly. Misfolded proteins identified in the RER are typically targeted for degradation by the proteasome.<br /><br />* **Peroxisome:** Peroxisomes are involved in various metabolic processes, including the breakdown of fatty acids and detoxification of harmful substances. While they do degrade some molecules, they are not the primary organelle responsible for protein degradation.<br /><br />* **Smooth Endoplasmic Reticulum (SER):** The SER is involved in lipid synthesis, carbohydrate metabolism, and calcium storage. It does not play a role in protein degradation.<br /><br />* **Golgi Complex:** The Golgi complex processes, sorts, and packages proteins for transport to their final destinations. It is not directly involved in protein degradation.<br />