When cells were visualized with microscopes, two basic cellular architectures were recognized: eukaryotic and prokaryotic. Refer to the presence (eukaryotic) or absence (prokaryotic) of a membrane-bounded nucleus. Prokaryotes do not have an internal membrane system or numerous membrane-bounded organelles. Consist of cytoplasm surrounded by a plasma membrane and are encased within a rigid cell wall. Many prokaryotes harvest light by photosynthesis, others breakdown dead organisms and recycle their components. Some cause disease or have uses in many important industrial processes. Two main domains of prokaryotes are: archaea and bacteria. Strength and shape of cell is determined by the cells wall not by a cytoskeleton, but it is influenced by the cytoskeleton. Photosynthetic functions are found folded into the plasma membrane. Dna, enzymes, and other cytoplasmic constituents have access to all parts of the cell. Composed of peptidoglycan which consists of a carbohydrate matrix that is cross-linked by short polypeptide units. Protect cell, maintain shape, prevent excessive water loss or intake.