Differentiate between the structural characteristics and functions of parenchyma and sclerenchyma tissues in plants.

Parenchyma cells are living, thin-walled, loosely packed, and often have large intercellular spaces. Their primary functions include storage of food, photosynthesis (in chlorenchyma), and secretion. Sclerenchyma cells, on the other hand, are dead, thick-walled due to lignin deposition, and closely packed with little to no intercellular space. Their main function is to provide mechanical strength and support to the plant.