Lysosomes

Learning Goals

By the end of this lesson, you will be able to:

• Explain the basic structure of lysosomes
• Explain the basic functions of lysosomes

Key Vocabulary

Lysosome– a type of cellular organelle found in eukaryotic cells. It is a spherical, membrane-bound structure that contains a variety of hydrolases, which are enzymes that break down and digest cellular waste and damaged materials.

Cellular homeostasis– refers to the maintenance of a stable and balanced internal environment within a cell. This internal environment includes factors such as the concentration of ions and nutrients, pH, and the presence of waste products.

Phagosome – a double-membrane structure formed during the process of autophagy, which is a cellular degradation and recycling process.

Apoptosis – also known as programmed cell death, is a process by which cells naturally self-destruct in a controlled and regulated manner.

Lysosomes

Lysosomes are like the recycling centers of our cells. They play a very important role in keeping our cells healthy and functioning properly.

Think of our cells as tiny cities. Just like how cities need to get rid of their waste, our cells need to get rid of old and damaged materials too. That’s where lysosomes come in! They contain special enzymes, called hydrolases, that break down and recycle old or damaged materials in our cells, just like how recycling centers break down and reuse waste.

As the “digestive system” of the cell, lysosomes contain a variety of hydrolases. Hydrolases are enzymes that break down complex molecules into smaller components, and they require a certain pH in order to function effectively. Lysosomes have an acidic environment with a pH of around 5.0. The low pH of the lysosome provides the optimal environment for these enzymes to work and digest the contents within the lysosome, including cellular waste, damaged organelles, and bacteria.

When vesicles, called phagosomes, containing cellular waste or damaged materials are delivered to the lysosome, the acidic environment within the lysosome activates the hydrolases and the contents of the vesicles are digested and recycled.

NurseHub Note: The pH of the lysosome is maintained by a proton pump, which actively pumps hydrogen ions into the lysosome to keep the pH low. This proton pump is regulated by a variety of factors, including the availability of energy within the cell and the needs of the cell for the degradation of specific materials.

By breaking down and digesting cellular waste, lysosomes help to prevent the buildup of harmful materials within the cell. This allows the cell to maintain a stable internal environment, supporting its normal functions and overall health.

The Golgi apparatus and lysosomes work together to ensure that cellular waste is processed and eliminated efficiently, maintaining cellular homeostasis. Cellular homeostasis (when the inside environment of the cell is stable and balanced) is essential to the proper functioning and health of the cell.

There are two types of processes that cells can use to prepare materials that are targeted for digestion – endocytosis and autophagy. Endocytosis is the process by which the cell takes in materials and substances from outside the cell, and then processes and digests them within the lysosome. Autophagy is the process by which cells degrade and recycle their own cellular components, also facilitated by the lysosome.

Autophagosomes

An autophagosome is a double-membraned vesicle that is formed during the process of autophagy.

Autophagy is a cellular process in which the cell identifies and engulfs its own damaged or unnecessary parts, such as proteins or organelles into a double-membraned vesicle known as an autophagosome. The autophagosome then fuses with a lysosome, which digests and recycles the contents of that vesicle.

Autophagy plays an important role in cellular homeostasis by making sure that damaged and unnecessary cell parts are removed and recycled. This prevents any build-up of cellular waste and allows the cell to continue functioning properly. It is also involved in a variety of physiological processes, such as an organism’s growth and development, immunity, and cellular stress responses.

Lysosomal damage can lead to apoptosis, which is programmed cell death. When lysosomes are damaged they can become dysfunctional and fail to effectively digest and recycle cellular components. This can lead to the accumulation of cellular waste and damaged materials, causing cellular stress and potentially triggering apoptosis. In some cases, lysosomal damage can also trigger the release of lysosomal contents into the cytoplasm, where they can activate apoptotic pathways and lead to cell death.

NurseHub Note: Gaucher disease is a lysosomal storage disease caused by a deficiency of the enzyme glucocerebrosidase, which is involved in the breakdown of a specific type of fat molecule. As a result, this fat accumulates within the lysosome, causing cellular damage and leading to symptoms such as enlarged liver and spleen, anemia, and low platelet count.

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