by C Song

Created on: June 02, 2009   Last Updated: June 03, 2009

Eukaryotic plant and animal cells have some similarities and marked differences in structure that are key to understanding life; Every organism does occurs fundamentally because of functions at a cellular level.

If you have ever observed plant cells and animal cells under a microscope, you can plainly see that plant cells are shaped like bricks, a feature that is attributed to the cell's rigid structure. On the other hand, animal cells are typically less uniform in shape and more rounded.

At the center of plant cells is the central vacuole, which is much larger and more significant to the plant than that of animal cells. A plant's central vacuole typically occupies most of the space in a cell, while in animal cells, vacuoles are much smaller and merely used to temporarily store or transport substances. The central vacuole of a plant serves many purposes. It stores water, organic compounds, pigments, toxins, and cell wastes. The water in the central vacuole also has the added benefit of providing turgor pressure for the plant, allowing it to stay rigid and maintain structural integrity.

Another feature of plant cells vital to preserving structure is the cell wall. Composed of polysaccharides, cellulose, and proteins wound together into fibers, the cell wall of a plant cell ranges in thickness from 0.1 micrometers to several micrometers. Depending on the species of plant, cell walls can have 3 separate components: the thin flexible primary cell wall, a middle lamella made of pectins that "glue" adjacent cells together, and the secondary cell wall.

In animal cells, the extracellular matrix (ECM), composed of a complex system of proteins and carbohydrate polymers, serves a very similar function as the cell wall in plants. Integrins anchor the ECM to the cell's plasma membrane and the microfilaments inside the cell. Another type of protein called fibronectins attach the ECM to the integrins, Proteoglycans and the polysaccharide glycogen form a mesh outside the cell. Aside from providing structural support, the ECM also plays a role in regulating a cell's behavior. It reacts to signals from other cells or physiological changes in the environment and signals to the interior of the cell through the integrins.

Only plant cells contain chloroplasts, a double membraned organelle that engage in the process of photosynthesis. The structure of chloroplasts are critical to its function. Located in the palisade mesophyll area of cells in a plant's leaves and stem, chloroplasts

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