Protoplasm
From Wikipedia, the free encyclopedia
In biology, protoplasm is the viscid, translucent, polyphasic colloid with water as the continuous phase that makes up the essential material of all plant and animal cells. Protoplasm is composed mainly of nucleic acids, proteins, lipids, carbohydrates, and inorganic salts. The protoplasm surrounding the nucleus is known as the cytoplasm and that composing the nucleus is the nucleoplasm (sometimes termed bioplasm).
Protoplasm is the living substance inside the cell, and is distinct from non-living cell components lumped under "ergastic substances", although ergastic substances can occur in the protoplasm. In many plant cells most of the volume of the cell is not occupied by protoplasm, but by "tonoplast," a large water filled vacuole enclosed by a membrane.
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[edit] Older theories
The idea that protoplasm is divisible into a ground substance called "cytoplasm" and a structural body called the Cell nucleus reflects most of the more primitive knowledge of cell structure that preceded the development of powerful micrographs of organic and inorganic substances, when it seemed that cytoplasm was mysteriously directed by the nucleus and controlled by the cell membrane. Today, it is known that the cytoplasm is structurally very complex, and that protoplasm is living because of the complexity of the "cytoplasmic organelles" and their careful separation and orchestration of multiple chemical processes.
[edit] Phase
Protoplasm exists in three forms: in the solid state, the liquid state and sometimes in a combined solid and liquid state. The physiological state of the cell determines which form it is in at any given time.
[edit] History of the term
The concept of protoplasm was perceived as the essence of life ("vital force"), being something nearly sacred, induplicable by man as it can evolve into quite a number of other living creatures. Some also believed that the seabed was covered in an ooze of pure protoplasm, as the ocean was the ultimate origin of life.
Charles Darwin and his 19th century contemporaries viewed "protoplasm" as the holistic content of a cell; in other words, cells were composed of a mysterious "proto-plasm," a substance that had the ability of self replication.
This simplified view of cell biology circumvented the problem of the origin of life and protogenesis that Darwin and others struggled with, and was a part of the reason for the 30 years delay for Darwin's publication.. However, that problem was later introduced in the 1950s when the complex molecular structure of DNA was discovered with following research into the complex biochemistry of living things, that elucidated the mechanisms for self-replicating biological nano-machinery.
