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		Because the secondary cell wall is added later, it has to be located betweenthe primary cell wall and the plasma membrane. The secondary cell wall is also often strengthened with lignin. When you examine different plant cell types in lab, notice the thickness of the cell wall. A thick cell wall is an indication that the cell is involved in support of the plant. 3. Communication between cells7.30 Both plant and animal cells in tissues are connected by channels. This allows molecules to pass between them. Why is this is important? - because it also allows informationto pass between the cells This information flow is necessary to coordinate complex organisms. C. Function of the vacuole7.15 The combination of the cell wall and large, water-filled vacuole is unique to plants. It is found in all mature plants cells except seeds which suggests that it is important. Q. Why do plant cells have a large bag of water inside them? The central vacuole may be used for storage of some types of molecules. Plants require nutrients that are fairly dilute(CO2, sunlight, mineral ions, water). Plants can't go hunting; they need alternative strategies to obtain these rare nutrients. These strategies include increasing surface areaand assuming a branched or dendritic form. Both of these allow the plant to contact a larger volume of the environment. But, behind all that surface area has to be internal volume. In animals, the internal volume is full of "stuff" - cytoplasm filled with proteins and organelles. In plants, much of.the internal volume is filled with water. Q. What are some possible reasons? - Requires less energy/food to construct and maintain - Requires less fixed nitrogen in the form of protein - Puts all of the cytoplasm and organelles in a thin layer adjacent to the membrane, which makes exchange of O2and CO2easier.