EUKARYOTIC ORGANISMS

Origin of Eukaryotic Organisms

Origin of Eukaryotic Organisms

Introduction

Cells were divided into two main classes, originally defined by whether they contain a nucleus. Prokaryotic cells (bacteria) lack a nuclear membrane; eukaryotic cells have a nucleus in which genetic material is separated from the cytoplasm. Prokaryotic cells are usually smaller and simpler than eukaryotic cells, in addition to the absence of the nucleus, their genomes are less complex, and they do not contain cytoplasmic organelles or the cytoskeleton (Table 1.1). Despite these differences, the same basic molecular mechanisms that regulate life and prokaryotes and eukaryotes, pointing out that all modern cells derived from the same primordial ancestor. As this is the first cell to evolve? And as the complexity and diversity of modern cells have to evolve?

Discussion

All eukaryotic cells are surrounded by plasma membrane and contain ribosomes. However, eukaryotic cells are much more complex and contain a nucleus, a variety of cytoplasmic organelles and cytoskeleton. Largest and most prominent organelles in eukaryotic cell nucleus with a diameter of about 5 microns. Nucleus contains the genetic information to cells, which in eukaryotes is organized as linear rather than circular DNA molecules. Core site of DNA replication and RNA synthesis, translation of RNA into protein occurs on ribosomes in the cytoplasm.

In addition to the nucleus of eukaryotic cells contain a variety of body membranes of organelles in the cytoplasm. These organelles provide the compartments in which different metabolic activity localized. Eukaryotic cells are generally much larger than prokaryotic cells, often with a cell volume of at least a thousand times more. Isolation provided by the cytoplasmic organelles that allow eukaryotic cells to function effectively. Two of these organelles, mitochondria and chloroplasts, play an important role in energy metabolism. Mitochondria, which are almost all eukaryotic cells, are the sites of oxidative metabolism and, thus, responsible for generating most of the ATP derived from the decay of organic molecules (Rodney, 1998). Chloroplasts are sites of photosynthesis and are found only in cells of plants and green algae. Lysosomes and peroxisomes also provide specialized metabolic compartment for digestion of macromolecules and for various oxidation reactions, respectively. In addition, most plant cells contain large vacuoles that perform various functions, including digestion of macromolecules and storage of waste and nutrients.

Because of the size and complexity of eukaryotic cells, transport of proteins to their correct direction within the cell is a formidable task. Two cytoplasmic organelles, the endoplasmic reticulum and Golgi apparatus, specially devoted to sorting and transport of proteins destined for secretion, incorporation into the membrane, and incorporation into lysosomes. Endoplasmic reticulum is an extensive network of intracellular membranes, extending from the nuclear membrane throughout the cytoplasm. It acts not only in the handling and transportation of proteins, but also in the synthesis of lipids. From the endoplasmic reticulum, proteins are transported in small vesicles membranes of the Golgi apparatus, where they are further processed and sorted for transport to final destination. In addition to the role of protein transport, Golgi apparatus serves as a site of lipid ...