1.6 : Estrutura Celular Animal e Vegetal

Animal and plant cells not only differ in their structure, function, and mode of nutrition but also in how they reproduce, specialize, and organize into complex structures.

Cell Division

Though both plant and animal cells divide by mitosis (for non-gametic cells) and meiosis (for gametic cells), they differ in the specifics of this process. Unlike animal cells, plant cells lack centrosomes — an organelle responsible for organizing the spindle fibers and segregating the chromosomes during cell division. Instead, they have a microtubule-organizing center (MTOC) that helps the self-assembly of the tubules forming the spindle. Cytokinesis in plant cells is achieved by forming a cell plate, which develops from the center of the cell to the periphery. However, in the flexible animal cells, the contractile ring causes the cell membrane to contract and pinch off two daughter cells.

Cellular Organization

Plant cells typically have a fixed shape, mostly rectangular, due to the rigid cell wall primarily made of cellulose. Therefore, tissue organization in plants is simple, and intercellular communication and exchange of molecules occur via junctions called plasmodesmata. Animal cells are usually smaller and not as rigid due to the absence of a cell wall. This flexibility allows these cells to take up many different shapes and forms. Their tissue organization can be highly complex, with various junctions and channels facilitating intercellular communication.

Cell Specialization

While both animal and plant cells can specialize into different cell types, the specialization spectrum is relatively limited in plant cells. The primary cell types in plants include the parenchyma, sclerenchyma, and collenchyma, with a few special cells such as xylem, phloem, and root hair cells. On the other hand, animal cells have a diverse spectrum of structure and function ranging from the round, biconcave red blood cells that transport oxygen to the highly branched, star-shaped nerve cells that relay electrical signals.