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Ergastic substances are non-protoplasmic materials found incells.[1] The living protoplasm of a cell is sometimes called the bioplasm and distinct from the ergastic substances of the cell. The latter are usually organic or inorganic substances that are products of metabolism, and include crystals, oil drops, gums,tannins, resins and other compounds that can aid the organism in defense, maintenance of cellular structure, or just substance storage. Ergastic substances may appear in theprotoplasm, invacuoles, or in thecell wall.
Reserve carbohydrate of plants are the derivatives of the end products of photosynthesis.Cellulose andstarch are the main ergastic substances of plant cells. Cellulose is the chief component of the cell wall, and starch occurs as a reserve material in the protoplasm.
Starch, as starch grains, arise almost exclusively inplastids, especiallyleucoplasts andamyloplasts.
Althoughproteins are the main component of living protoplasm, proteins can occur as inactive, ergastic bodies—in an amorphous or crystalline (or crystalloid) form. A well-known amorphous ergastic protein isgluten.
Fats (lipids) and oils are widely distributed in plant tissues. Substances related to fats—waxes,suberin, andcutin—occur as protective layers in or on the cell wall.
Animals eliminate excess inorganic materials; plants mostly deposit such material in their tissues. Suchmineral matter is mostly salts ofcalcium and anhydrides ofsilica.