Protoplasm
Encyclopedia
Protoplasm is the living contents of a cell
that is surrounded by a plasma membrane. It is a general term of the Cytoplasm . Protoplasm is composed of a mixture of small molecules such as ion
s, amino acid
s, monosaccharide
s and water
, and macromolecule
s such as nucleic acid
s, protein
s, lipid
s and polysaccharide
s. In eukaryote
s the protoplasm surrounding the cell nucleus
is known as the cytoplasm
and that inside the nucleus as the nucleoplasm
. In prokaryote
s the material inside the plasma membrane is the bacterial cytoplasm, while in gram-negative bacteria the region outside the plasma membrane but inside the outer membrane is the periplasm
.
Protoplasm is distinct from non-living cell components lumped under "ergastic substance
s" or inclusion bodies, although ergastic substances can occur in the protoplasm. In many plant cell
s most of the volume of the cell is not occupied by protoplasm, but by "tonoplast", a large water filled vacuole
enclosed by a membrane
. A protoplast
is a plant or fungal cell that has had its cell wall removed.
to describe the "tough, slimy, granular, semi-fluid" substance within plant cells, to distinguish this from the cell wall
, cell nucleus
and the cell sap within the vacuole
. Thomas Huxley later referred to it as the "physical basis of life" and considered that the property of life resulted from the distribution of molecules within this substance. Its composition, however, was mysterious and there was much controversy over what sort of substance it was. Attempts to investigate the origin of life through the creation of synthetic "protoplasm" in the laboratory were not successful, yet.
The idea that protoplasm is divisible into a ground substance called "cytoplasm" and a structural body called the cell nucleus
reflects the more primitive knowledge of cell structure that preceded the development of electron microscopy, when it seemed that cytoplasm was a homogeneous fluid and the existence of most sub-cellular compartments, or how cells maintain their shape, was unknown. Today, it is known that the cell contents are structurally very complex and contain multiple organelle
s.
Protoplasm can exist in two forms:
1. Sol state
2. Gel state, so called because it s consistency resembles that of jelly.
Whether protoplasm is in the sol or the gel state depends on the physiological state of the cell.
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
that is surrounded by a plasma membrane. It is a general term of the Cytoplasm . Protoplasm is composed of a mixture of small molecules such as ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s, amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s, monosaccharide
Monosaccharide
Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...
s and water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
, and macromolecule
Macromolecule
A macromolecule is a very large molecule commonly created by some form of polymerization. In biochemistry, the term is applied to the four conventional biopolymers , as well as non-polymeric molecules with large molecular mass such as macrocycles...
s such as nucleic acid
Nucleic acid
Nucleic acids are biological molecules essential for life, and include DNA and RNA . Together with proteins, nucleic acids make up the most important macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information...
s, protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s, lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
s and polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...
s. In eukaryote
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
s the protoplasm surrounding the cell nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
is known as the cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
and that inside the nucleus as the nucleoplasm
Nucleoplasm
Similar to the cytoplasm of a cell, the nucleus contains nucleoplasm or karyoplasm. The nucleoplasm is one of the types of protoplasm, and it is enveloped by the nuclear membrane or nuclear envelope. The nucleoplasm is a highly viscous liquid that surrounds the chromosomes and nucleoli...
. In prokaryote
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...
s the material inside the plasma membrane is the bacterial cytoplasm, while in gram-negative bacteria the region outside the plasma membrane but inside the outer membrane is the periplasm
Periplasmic space
The periplasmic space or periplasm is a space between the peptidoglycan cell wall and inner membrane of Gram-negative bacteria or the equivalent space outside the inner membrane of Gram-positive bacteria. It may constitute up to 40% of the total cell volume in Gram-negative species, and is...
.
Protoplasm is distinct from non-living cell components lumped under "ergastic substance
Ergastic substance
Ergastic substances are non-protoplasm materials found in cells. The living protoplasm of a cell is sometimes called the bioplasm and distinct from the ergastic substances of the cell...
s" or inclusion bodies, although ergastic substances can occur in the protoplasm. In many plant cell
Plant cell
Plant cells are eukaryotic cells that differ in several key respects from the cells of other eukaryotic organisms. Their distinctive features include:...
s most of the volume of the cell is not occupied by protoplasm, but by "tonoplast", a large water filled vacuole
Vacuole
A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain...
enclosed by a membrane
Biological membrane
A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...
. A protoplast
Protoplast
Protoplast, from the ancient Greek πρῶτον + verb πλάθω or πλάττω , initially referred to the first organized body of a species.Protoplast has several biological definitions:...
is a plant or fungal cell that has had its cell wall removed.
History of the term
The word 'protoplasm' comes from the Greek protos for first, and plasma for thing formed. It was first used in 1846 by Hugo von MohlHugo von Mohl
Hugo von Mohl was a German botanist from Stuttgart.He was a son of the Württemberg statesman Benjamin Ferdinand von Mohl , the family being connected on both sides with the higher class of state officials of Württemberg...
to describe the "tough, slimy, granular, semi-fluid" substance within plant cells, to distinguish this from the cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
, cell nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
and the cell sap within the vacuole
Vacuole
A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain...
. Thomas Huxley later referred to it as the "physical basis of life" and considered that the property of life resulted from the distribution of molecules within this substance. Its composition, however, was mysterious and there was much controversy over what sort of substance it was. Attempts to investigate the origin of life through the creation of synthetic "protoplasm" in the laboratory were not successful, yet.
The idea that protoplasm is divisible into a ground substance called "cytoplasm" and a structural body called the cell nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
reflects the more primitive knowledge of cell structure that preceded the development of electron microscopy, when it seemed that cytoplasm was a homogeneous fluid and the existence of most sub-cellular compartments, or how cells maintain their shape, was unknown. Today, it is known that the cell contents are structurally very complex and contain multiple organelle
Organelle
In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....
s.
Protoplasm can exist in two forms:
1. Sol state
2. Gel state, so called because it s consistency resembles that of jelly.
Whether protoplasm is in the sol or the gel state depends on the physiological state of the cell.