What are the general physical characteristics, location in a plant and the special functions of these cells?

Parenchyma Cells. These cells are the most general of plant cells. They consist of thin flexible cell walls. They contain a large central vacuole and can carry out most of the metabolic functions of the plant. Mesophyll cells of the leaf are parenchyma cells. The fleshy tissue of most fruits also contain much parenchyma.
Collenchyma Cells. These cells have a much thicker primary wall than the parenchyma cell. Grouped in strands or cylinders they support young plants.
Sclerenchyma Cells. Function in support of the plant. They contain a thick secondary wall containing lignin. For all intent and purpose these cells function best when dead.
Guard cells. The stomata allow gases and water vapor into and out of the leaf. Each stoma is controlled by two bean shaped guard cells. They contain chloroplasts and are found on the under side of the leaf.