# INTRODUCTION:
-> 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 up the spaces that are not occupied by the organelles.
-> In a prokaryotic organism, all the cellular components are contained within the cell's cytoplasm.
-> Whereas, In eukaryotic organism nucleus of cell is seperated from cytoplasm.
-> It was discovered by ROBERT BROWN and other scientists in 1835.
# GENERAL CHARACTERISTICS:
-> Cytoplasm is made up of 70 - 80% of water .
-> It is usually colourless fluid .
-> Metabolic pathways like glycolysis and cellular processes like cell
division take 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 plants cells, a process known as cytoplasmic streaming takes place where there is movements of the cytoplasm around the vacuoles. ( Cytoskeleton present helps in cytoplasmic streaming's movement).
-> It is heterogenous mixture of opaque granules and organic compounds
which gives it its colloidal nature.
-> The peripheral zone of cytoplasm is thick and jelly-like substance,
known as the plasmogel , which is capable of absorbing and removing water according to 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 and water. It also contains protein filaments that make up the cytoskeleton, and also 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 perform functions which are necessary for 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 minerals , ions and fir organic compounds such as proteins, etc .
-> The water is used by cell as the transporting media 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 ionized to form a sodium cation (Na+)and a chlorine anion (CI–).
->The inorganic compounds which by dissolving in water become ionized are known as electrolytes ( Na+) but those which do not dissociate in the solvent but remain as such in the molecular stated 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 more other elements as hydrogen (H), nitrogen (N), sulphur (S), etc., are
called organic compounds.
-> The organic compounds usually contain large molecules which are formed by the similar or dissimilar unit structures known as the monomers.
-> The main organic compounds of the protoplasm are the carbohydrates, lipids, proteins and nucleotides.
(i) Carbohydrates:-
-> These are the compounds containing the carbon, hydrogen and oxygen.
-> The carbohydrates are the main source of the
energy for all living beings.
-> Only green plants and certain microbes
have the power of synthesizing 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 contain carbon, hydrogen, and oxygen .
(iii) Proteins :-
-> The proteins are the most important constituents of the protoplasm.
-> All proteins are composed of carbon, hydrogen, oxygen, 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) is known as amino acid).
-> 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 influence 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 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 nucleoside and phosphoric acid .
-> They control the important biosynthetic activities of the cell and carry hereditary information’s 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 pyrimidine’s). The
purines are adenine and guanine and pyrimidine’s are cytosine,
thymine and uracil ).
# FUNCTIONS :
-> The cytoplasm is the main site of many important biochemical reactions that are essential for maintaining life inside the cell. Most of the cell’s activities take place here.
-> It is the region where the cell grows and expands, helping in overall cell
development.
->The cytoplasm acts as a supporting medium, keeping all the cell organelles suspended in it so they can function properly.
-> The enzymes present in the cytoplasm break down large macromolecules into smaller molecules, making them easily available for organelles like mitochondria to produce energy.
-> It also plays a role in the transport of genetic material within the cell when -needed.
-> The cytoplasm helps in transporting products of cellular respiration to different parts of the cell.
-> Finally, it acts as a protective buffer, safeguarding the genetic material and organelles from damage due to internal movement or external mechanical stress.
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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