Understanding Biology: Exploring the Outside of the Eukaryotic Cell

In the field of biology, eukaryotic cells are very complex concept to understand. Inside, they have a large number of different organelles that compose them and serve unique purposes for the cell. However, the outside is also very complex and just as important. Though both plants and animals have eukaryotic cells, there are some key differences between them. Additionally, cells are joined together through different junctions that are dependent on the purpose that the cells serve.

Plant life has two different types of cell walls, known as the primary and the secondary cell walls. The primary cell wall is composed of cellulose fibrils and other non-cellulose substances. As the cell growth, this is the wall that is able to expand and stretch to accommodate this growth. The secondary cell wall is formed just inside of this primary cell wall. It is found most often in woody plants and its main function is to add strength to the cell wall. Additionally, plants have plasmodesmata, which are cells that are connected by channels that pass through the cell walls. The main purpose of this is the plant is able to move water and other materials between cells.

The outside of the eukaryotic cell for animals is different in formation than that of plants. Animal eukaryotic cells do not have a cell wall, which is a major difference from plants. Instead, they have an extracellular matrix, or ECM for short. The ECM is a mesh of proteins and polysaccharides. Additionally, this matrix can vary in function; it is hard when it is a part of the bone, and it can be flexible when it makes up some of the cartilage.

Their three types of junctions that these animal cells use in order to connect one another. They are adhesion junctions, tight junctions, and gap junctions. In adhesion junctions is formed when cytoplasmic plaques are joined together by cellular filaments. This type of junctions forms a very sturdy connection, but it will remain flexible. A tight junction is when the plasma membrane proteins attach to one another. He creates a normal zipper like pattern of cells that serve as barriers for the tissues. Finally, gap junctions are type of junction that allow cells to communicate with one another through the plasma membrane channels. They are very strong junctions, but they also allow small molecules and ions to pass through in order to transfer from one cell to another.

Source:

Benitz, Bill. Lecture: Biology. September 7, 2009