# INTRODUCTION
-> Every living cell contains a remarkable substance that holds everything together — the cytoplasm. This thick, semi-transparent fluid fills the space between the cell membrane and the nucleus, creating the perfect environment for life's most critical processes to occur.
-> From supporting organelles to driving metabolic reactions, cytoplasm is far more than just "cell filler." It is the command centre of biochemical activity within every living organism.
# What is cytoplasm?
-> Cytoplasm is the thick and semi-transparent fluid substance of a cell that is present within the cellular membrane. It also surrounds the nuclear membrane. It fills the spaces not occupied by organelles.
-> In a prokaryotic organism, all the cellular components are contained within the cell's cytoplasm.
->In eukaryotic organisms, the nucleus of the cell is separated from the cytoplasm.
-> It was discovered by ROBERT BROWN and other scientists in 1835.
# GENERAL CHARACTERISTICS OF CYTOPLASM:
-> Cytoplasm is made up of 70 - 80% of water.
-> It is usually a colourless fluid.
-> Metabolic pathways like glycolysis and cellular processes like cell
Division takes place in the cytoplasm.
-> The outer clear and glassy layer of the cytoplasm is called the ectoplasm or the cell cortex.
-> The inner granular mass is called the endoplasm.
-> In plant cells, a process known as cytoplasmic streaming takes place where there is movement of the cytoplasm around the vacuoles. (Cytoskeleton present helps in the movement of cytoplasmic streaming).
-> It is a heterogeneous mixture of opaque granules and organic compounds which gives it its colloidal nature.
-> The peripheral zone of cytoplasm is a thick and jelly-like substance,
known as the plasmogel, which is capable of absorbing and removing water according to the cell's need.
-> The physical nature of cytoplasm is colloidal. It has a high percentage
of water.
-> It also contains carbohydrates, proteins ( soluble proteins 20-25%), inorganic salts and lipids etc.
# STRUCTURE :
-> The cytoplasm is made of proteins, carbohydrates, salts, sugars, amino acids and nucleotides.
-> The constituents of the cytoplasm are cytosol, organelles and cytoplasmic inclusions.
1) CYTOSOL - Cytosol makes up about 70% of the volume of the cell. It is composed of a mixture of cytoskeleton filaments, organic and inorganic molecules that are dissolved in water. It also contains protein filaments that make up the cytoskeleton, as well as soluble proteins and structures like
ribosomes, are also present.
2) ORGANELLES - This means ' little organs ' which are membrane-bound It includes endoplasmic reticulum, mitochondria etc It is present inside the cell and performs functions which are necessary for the survival of the cell
3) CYTOPLASMIC INCLUSIONS - They are tiny particles suspended in the cytosol. A vast range of inclusion are present in different cell types. The inclusions range from calcium oxalate crystals or silicon dioxide crystals in plants to storage granules of materials like starch, glycogen, etc. Lipid droplets are a widespread example of inclusions (these are spherical droplets, they are made of lipids and proteins and are present in both prokaryotes and eukaryotes as a medium to store lipids)
# INORGANIC COMPOUNDS OF PROTOPLASM :
(i) Water -
-> Most abundant inorganic constituent. It constitutes about 65 - 80 % of protoplasm. It is the best biological solvent for inorganic substances such as mineral ions and for organic compounds such as proteins, etc
-> The water is used by the cell as the transporting medium for the food nitrogen wastes and other necessary substances.
(ii) Minerals -
-> They are the inorganic chemical substances which occur in the crust of the earth.
-> In the protoplasm the minerals usually occur in the form of salts and in combination with the organic compounds. The mineral salts occur in the form of ions in the protoplasm.
-> The positively charged ions are known as cations and the negatively
charged ions are known as anions. For example, when sodium chloride
(NaCl) is dissolved in water, it is ionised to form a sodium cation (Na+)and a chlorine anion (CCl).
->The inorganic compounds that, by dissolving in water become ionised are known as electrolytes ( Na+) but those which do not dissociate in the solvent but remain as such in the molecular state are known as non-electrolytes. (Na, K, Ca, Mg, Cu, I, Fe, Mn, Fl, Mo, CI, Zn, Co, Ni, etc).
-> The protoplasm contains both electrolytes and non- electrolytes.
# ORGANIC COMPOUNDS OF PROTOPLASM :
-> The chemical substances which contain carbon (C) in combination with one or other elements such as hydrogen (H), nitrogen (N), sulphur (S), etc are
called organic compounds.
-> The organic compounds usually contain large molecules which are formed by similar or dissimilar unit structures known as tonomers.
-> The main organic compounds of the protoplasm are the carbohydrates, lipids, proteins and nucleotides.
(i) Carbohydrates:-
-> These are the compounds containing carbon, hydrogen and oxygen.
-> The carbohydrates are the main source of energy for all living beings.
-> Only green plants and certain microbes have the power of synthesising the carbohydrates from water and CO2 in the presence of sunlight and chlorophyll by the process of photosynthesis.
-> Chemically the carbohydrates are the polyhydroxy aldehydes or ketones.
(ii) Lipids -
-> These are the organic compounds which are insoluble in water but soluble in ether, chloroform, benzene, hot alcohol and petroleum ether.
-> The lipids are nonpolar and hydrophobic.
-> They are important constituents of the cellular membranes, hormones and vitamins of the cells and are the source of energy for the cells.
-> It contains carbon, hydrogen, and oxygen
(iii) Proteins -
-> The proteins are the most important constituents of the protoplasm.
-> All proteins are composed of carbon, hydrogen, oxygen, and nitrogen
-> The protoplasm is dependent almost entirely upon proteins for its supply of nitrogen, sulphur and phosphorus.
-> The proteins are the polymers of the amino acids. { An organic
compound containing one or more amino groups (-NH2) and one or
More carboxyl groups (-COOH) are known as amino acids.
-> The amino acids occur freely in the protoplasm
(iv) Enzymes -
-> The protoplasm and many cellular organelles contain very important
organic compounds known as the enzymes
-> The enzymes are the specialised proteins having the capacity to
act as catalysts in chemical reactions. It influences the rate of a chemical
reaction, while themselves remain quite unchanged at the end of the
reaction
-> The enzymes play a vital role in various metabolic and biosynthetic
activities of the cell such as the synthesis of DNA, RNA and protein
molecules and metabolism of carbohydrates, lipids, fats and other
chemical substances.
(V) Vitamins -
-> They are complex organic compounds of diverse chemical
nature which are required in minute amounts for normal growth,
functioning and reproduction of cells.
-> The cell cannot synthesise the vitamins from the standard food and so
they are taken along with the food. Their deficiency in the cell causes
metabolic disorders and leads to various diseases.
(Vi) Nucleic acids -
-> A nucleotide is composed of a nucleoside and phosphoric acid
-> They control the important biosynthetic activities of the cell and carry hereditary information from generation to generation
-> There occur two types of nucleic acids in living organisms, ribonucleic acid (RNA) and deoxyribonucleic acid (DNA).( nucleoside is composed of the pentose sugar (ribose or deoxyribose) and nitrogen bases (purines and pyrimidines. The purines are adenine and guanine and pyrimidine’s are cytosine, thymine and uracil ).
# FUNCTIONS :
Function Description
Metabolic Hub - Site of glycolysis, protein synthesis, and other key biochemical reactions.
Cell Growth - Region where cells grow, expand, and develop
Structural
Support - Keeps organelles suspended and properly positioned
Macromolecule - Enzymes digest large breakdown molecules for energy production
Genetic - Facilitates the movement of transport genetic material within the cell
Respiration - Transports cellular
Product respiration products
Distribution across the cell
Protective - Shields organelles DNA and buffers mechanical stress and damage
The cytoplasm is a vital component of the cell that supports organelles, maintains cell shape, and serves as the site of essential metabolic and biochemical reactions necessary for cell survival and growth.
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