In the past 6 parts on the Simple Cell, we have looked at the cell membrane and just a few of the membrane bound proteins, the cytoskeleton and molecules that walk, the protein synthesizing, processing, packaging and shipping systems of the endoplasmic reticulum and the Golgi apparatus. We have compared them to the infrastructure and transportation systems of a large city, FedEx and a steel processing plant. In Part 7, we are going to take a look at vesicles.
Vesicles are tiny membrane bound sacs used for the storage and transportation of various items throughout the cell. Their membrane is similar to that of the plasma or cell membrane and often fuses with it in the exchange of materials. They can also fuse with other cell organelles whose layers are different than the plasma membrane. It all depends upon the specific function of the vesicle in question.
There are four basic types of vesicles: transport, secretory, vacuole and lysosome. Each of these has a different function.
The most basic type of vesicle is the transport vesicle. If you recall in earlier discussions, proteins are manufactured by ribosomes in the rough endoplasmic reticulum. These proteins are packaged in a small membrane sac known as the transport vesicle. The transport vesicle carries the proteins to the Golgi apparatus where it is modified according to its specific purpose. The modified proteins are again encased in a transport vesicle and carried via the cytoskeleton to its destination in the cell.
Secretory vesicles are used to carry various materials to the cell membrane to be excreted from the cell. Often, the material being excreted is cell waste products, which can be toxic to the cell if released into the cytoplasm. Other secretory vesicles store chemicals until they are needed to carry out various other functions. One such secretory vesicle is a synaptic vesicle. Synaptic vesicles carry neurotransmitters to the ends of neurons where they are released in conjunction with the transmission of nerve impulses. Other secretory vesicles contain various hormones such as adrenaline which are then released as the body needs it. The Islets of Langerhans in the pancreas contain a large number of secretory vesicles that package the hormones produced there, then transports them to various locations in the cell where they are either released for immediate use or store for later use. Still other secretory vesicles contain various enzymes that are used for the construction of cell walls in plant cells and the extracellular matrix in animal cells.
As we will be discussing vacuoles in Part 8 next week, it will suffice to say that vacuole vesicles generally contain enzymes in a liquid solution which are used in the vacuoles to help them carry out their functions.
As we will be discussing lysosomes in Part 9 in two weeks it will suffice to say that lysosome vesicles contain the enzymes used in the lysosome (which are only found in animal cells).
Nothing just randomly happens or floats around inside the cell. The various vesicles either serve as shipping boxes to package or transport materials within the cell and to the cell membrane or to as storage for hormones, enzymes and neurotransmitters like Tupperware, everything neatly packaged and stored until time to use it.
Detail, detail, detail. Our Creator God is definitely a God of detail, not a god of randomness and chaos. No matter how small you look into the cell, even down to the molecular level, you will see the infinite detail of our Master Designer.