8. Describe mitochondria and chloroplasts. What are their functions? How do the ribosomes in these organelles differ from the ribosomes in the cytoplasm and on the endoplasmic reticulum of the eukaryotic cell?
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.
A mitochondrion (or mitochondria) is a double-membrane-bound organelle found in most eukaryotic organisms. Mitochondria generate most of the cell's supply of adenosine triphosphate (ATP), subsequently utilized as a source of chemical energy, using the energy of oxygen released in aerobic respiration at the inner mitochondrial membrane. They were first discovered by Albert von Kölliker in 1880 in the voluntary muscles of insects. The mitochondrion is popularly nicknamed the "powerhouse of the cell", a phrase coined by Philip Siekevitz in a 1957 article of the same name.
Some cells in some multicellular organisms lack mitochondria (for example, mature mammalian red blood cells). A large number of unicellular organisms, such as microsporidia, parabasalids and diplomonads, have reduced or transformed their mitochondria into other structures. One eukaryote, Monocercomonoides, is known to have completely lost its mitochondria, and one multicellular organism, Henneguya salminicola, is known to have retained mitochondrion-related organelles in association with a complete loss of their mitochondrial genome.
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