Final answer:
Collenchyma cells are living, flexible cells with thick and uneven cell walls that provide structural support to plants.
Step-by-step explanation:
Living, flexible, cells with cell walls thicker and more uneven than those of parenchyma cells are called collenchyma cells.
Collenchyma cells are elongated cells that provide structural support to the stem and leaves of plants. They are alive at maturity and are usually found below the epidermis. The 'strings' of a celery stalk are an example of collenchyma cells.