Of the following, which is incorrect evidence of the endosymbiotic theory? O Mitochondria have their own particular DNA OMitochondrial ribosomes, and enzymes are similar to the bacteria Mitochondria and bacteria differ in size
Structure and Composition of Cell Membrane
Despite differences in structure and function, all living cells in multicellular organisms are surrounded by a cell membrane. Just like the outer layer of the skin separates the body from its environment similarly, the cell membrane, also known as 'plasma membrane,' separates the inner content from its exterior environment.
Cell Membrane
The cell membrane is known by different names like plasma membrane or cytoplasmic membrane, or biological membrane. The term "cell membrane" was first introduced by C. Nageli and C. Cramer in the year 1855. Later on, in 1931, the term "plasmalemma" for cell membrane was given by J. Plowe. The cell membrane separates the cell's internal environment from the extracellular space. This separation allows the protection of cells from their environment.
Prokaryotes vs Eukaryotes
The cell is defined as the basic structural and functional unit of life. The cell membrane bounds it. It is capable of independent existence.
Prokaryotes are those organisms which lack a membrane bound nucleus. They consist of eubacteria and archaebacteria. Eukaryotes have complex internal organisation and differ from the prokaryotes. They have membrane bound nucleus and other internal membranous organelles.
The cellular structures connecting prokaryotes and eukaryotes are mitochondria and chloroplasts. The origin of these organelles in the eukaryotes is explained by the serial endosymbiosis theory. It was promoted by Lynn Margulis. It states that eukaryotic cells evolved when free living prokaryotes became incorporated into larger prokaryotic cells which eventually gave rise to the mitochondria and the chloroplast. It is believed that the phagocytosis of a bacteria by another prokaryotic cell resulted in the development of the eukaryotic cell. The phagocytosed bacteria obtain nutrients from the host cell. They continued to reproduce independently with subsequent generations retaining the endosymbiont. They lost the ability to function without each other. These bacteria are what formed the mitochondria of the present day eukaryotic cell.
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