Molecular Biology of the Cell - Volume 3 - Alberts B., Bray D., Lewis J., Raff M., Roberts K., Watson J. 1994

From Cells to Multicellular Organisms
Plant Cell Characteristics

Each of us can easily distinguish a plant from an animal or a bird. Furthermore, it is usually not difficult to determine whether an individual Cell belongs to a plant or an animal Organism, although this task can sometimes be puzzling. Upon closer examination of The Cell—its Cytoplasm, Organelles, and ultimately its individual chemical components—similarities between the two kingdoms of living nature begin to take precedence over differences. Only through highly sophisticated Methods is it possible to distinguish the Mitochondria, nuclei, Ribosomes, or cytoskeletal components of plant Cells from the corresponding organelles of animal cells. The specific nature of PLANT AND ANIMAL life is manifested not in such fundamental Features of the Molecular Organization of living systems as METABOLISM/36.html">DNA Replication, Protein Biosynthesis, Oxidative Phosphorylation in mitochondria, or cell membrane construction, but rather in the more Specialized Functions of Cells and Tissues.

Based on a comparison of ribosomal RNA nucleotide sequences, it can be suggested that during eukaryote evolution, the divergence of plants, Yeasts, invertebrates, and vertebrates occurred relatively late (see Fig. 1-16). Apparently, the differences between plants and animals accumulated over approximately 600 million years, and most of these differences can be attributed to two major traits acquired by plant ancestors: The ability to fix carbon dioxide during Photosynthesis (see Ch. 7) and the presence of a rigid Cell wall. The first property enabled plants to independently synthesize the Organic compounds necessary for their growth and metabolism; the second property imposed strict constraints on all aspects of plant behavior. This chapter will examine the FEATURES OF PLANT Cells that are determined by these two properties.