Think about this: the body is made up of trillions of cells, but it doesn't end there. From head to toe, within each cell exists even tinier structures that are continually performing very specific "jobs" to keep them alive and thriving.
Let's start at the beginning. The cell, the smallest unit of life, is enclosed by a protective membrane with the pieces of the puzzle inside. Many cells form tissues that make up your vital organs such as the heart, liver and brain. Others have more specific functions throughout the body, such as muscle cells that contract when called upon or vital immune cells that fight infection. Despite having a multitude of varied functions, each cell contains similar structures — called organelles — that are required to maintain its health and function. Think of each cell like a factory that requires clear instructions, tight protocols and hard workers in order to run efficiently.
Let's break down the cell's main organelles and their functions.
Nucleus: Each cell has a complete set of DNA that is stored in the nucleus (that's a lot of DNA!) that contains the instructions to make everything it needs to function. Cells have different needs at different times, such as when they are stressed or replicating. The nucleus is similar to the executive board or CEO - it has access to all the plans the factory needs to function and delegates work to the other organelles appropriately.
Ribosomes: Instructions are sent from the nucleus to the ribosomes, the part of the cell that produces much-needed proteins. Proteins are vital to every process within every cell at any given point. Once produced by ribosomes, proteins can be moved to other organelles, or even shipped out of the cell entirely to their next destination. Think of ribosomes like the assembly lines and machines of a factory — producing a product ready for its departure.
Endoplasmic Reticulum: With anything in life, mistakes happen. That's where the endoplasmic reticulum steps in. Ribosomes may be loose in the cell or attached to the endoplasmic reticulum, also called the rough endoplasmic reticulum. This structure makes any necessary modifications to the protein it receives from the ribosomes and performs a check. This vital task prevents any proteins that were not made properly from impairing cell function.
On the contrary, the smooth endoplasmic reticulum doesn't contain any ribosomes. Instead, it makes lipids that are needed by the cell to produce hormones and form membranes, creating the boundary of a cell and enclosing organelles inside. Vesicles (small bubbles made from lipid membranes) are also present, and work to package and transport material within its own cell, as well as to other nearby cells. This is one way that cells can communicate with each other. This is your factory's quality control.
Golgi Apparatus: Despite its complicated name, this structure is quite straightforward. The golgi apparatus is essentially the distribution center responsible for organizing and shipping proteins. Vesicles are used to send protein from the endoplasmic reticulum to the golgi, where it's further modified, packaged and distributed to its final destination.
Mitochondria: The function and maintenance of a healthy cell (and anything else, really) requires energy at all levels to do the work. Mitochondria use oxygen and nutrients from diet to form ATP molecules that the cell is then able to use as energy. ATP is constantly used by cells to maintain their environment, produce protein, and for overall cellular function.
Lysosomes: Production of material and energy-consuming processes, whether in a factory or a cell, will always create waste that has to be dealt with accordingly. Like your local waste management plant, lysosomes digest unwanted material and recycle components that can be reused. Additionally, lysosomes can merge with damaged or aged organelles in a process called autophagy. The fusion of a lysosome with an organelle allows the enzymes in the lysosome to remove organelles that are no longer functioning properly. Lysosomes are also very important for the immune system. Foreign material, such as bacteria and viruses, are taken up into immune cells where lysosomes degrade the foreign material and prevent infection. We sure do thank them for that.
Microtubules and Actin Filaments: Compared to the other organelles discussed so far, microtubules and actin filaments are not membrane enclosed. They're thin, string-like structures located throughout the cell that act as support structures, similar to the support beams or maintenance crews in a factory. These organelles are also needed for cellular movement and growth in multiple forms. Since microtubules stretch throughout the cell, they also act as roads for the movement of material from one place in the cell to the other. Actin is a dynamic structure that can grow and shrink to physically move a cell in the body.
After covering the various organelles and their functions, it's easy to see why cells are such complex structures. While all cell types contain each type of organelle, the amount and strength of each can vary by function. The muscle cells mentioned earlier, for example, generally have more mitochondria, microtubules, and actin filaments to support movement while immune cells tend to have more lysosomes to digest bacteria and other foreign materials.
Regardless of a cell’s function, the organelles they contain work together in a similar and consistent way to maintain the cell’s health. Just like a factory, each component plays an integral role; if one organelle is not functioning properly, the entire cell suffers.
Organelles are the true "tiny but mighty" powerhouses of life itself.