11th Class Biology Cell - The Unit Of Life Metabolically Inactive Cell Inclusions

Metabolically Inactive Cell Inclusions

Category : 11th Class

Within the cytoplasm of a cell there occur many different kinds of non-living structures which are called inclusions or ergastic / Deutoplasmic substances.

(1) Vacuoles : The vacuole in plants was discovered by Spallanzani. It is a non-living reservoir, bounded by a differentially or selectively permeable membrane, the tonoplast. The vacuole is filled with cell sap or tonoplasm. They contain water, minerals and anthocyanin pigments.

Some protozoans have contractile vacuoles which enlarge by accumulation of fluid or collapse by expelling them from the cell. The vacuoles may be sap vacuoles, contractile vacuoles or gas vacuoles (pseudo vacuoles).

Function of vacuoles : Vacuole maintains osmotic relation of cell which is helpful in absorption of water. Turgidity and flaccid stages of a cell are due to the concentrations of sap in the vacuole.

(2) Reserve food material

The reserve food material may be classified as follows :

(i) Carbohydrates : Non-nitrogenous, soluble or non- soluble important reserve food material. Starch cellulose and glycogen are all insoluble.

(a) Starch : Found in plants in the form of minute solid grains. Starch grains are of two types :

Assimilation starch : It is formed as a result of photosynthesis of chloroplasts.

Reserve starch : Thick layers are deposited around an organic centre called hilum.

(b) Glycogen : Glycogen or animal starch occurs only in colourless plants like fungi.

(c) Inulin : It is a complex type of polysaccharide, soluble and found dissolved in cell sap of roots of Dahlia, Jaruslem, Artichoke, Dandelion and members of compositae.

(d) Sugars : A number of sugars are found in solution of cell sap. These include glucose, fructose, sucrose, etc.

(e) Cellulose : Chemical formula is \[{{({{C}_{6}}{{H}_{10}}{{O}_{5}})}_{n}}.\]The cell wall is made up of cellulose. It is insoluble in water.

(ii) Fats and Oils : These are important reserve food material. These are always decomposed into glycerol and fatty acids by enzymatic action. Fat is usually abundant in cotyledons than in the endosperm. e.g., flax seed produce linseed oil, castor produce castor oil, cotton seeds produce cottonseed oil, etc.

(iii) Proteins and Amides (Aleurone grains) : Storage organ usually contain protein in the form of crystalline bodies known as crystalloids (potato). Proteins may be in the form of aleurone grains as in pea, maize, castor, wheat, etc.

(3) Excretory Products : The organic waste products of plants are by-product of metabolism. They are classified as :

(i) Resins : They are believed to be aromatic compounds consisting of carbon, hydrogen and oxygen and are acidic in nature. Sometimes they are found in combination with gums and are called gum resin. e.g., Asafoetida (heeng).

(ii) Tannins : They are complex nitrogenous compounds of acid nature having an astringent taste. Presence of tannin in plants makes its wood hard durable and germ proof.

(iii) Alkaloids : These are organic, basic, nitrogenous substance. They occur in combination with organic acids and most of them are poisonous. From plants, cocaine, hyoscine, morphine, nicotine, quinine, atropine, strychnine and daturine etc. are extracted.

(iv) Glucosides : Some glucosides or glycosides function as storage substance e.g., amygdaline of the bitter almond.

(v) Etherial and Essential oils : These consist mixture of various hydrocarbons known as tarpenes and their oxygen derivatives. They are responsible for flavor of many fruits and scent of many flowers etc. They are volatile and are soluble in water, ether, petroleum etc. e.g., lavender, mint, clove oil, eucalyptus oil, theme oil etc.

(vi) Mineral matter : Many minerals are waste products in plants.

(a) Calcium oxalate : It occurs in the form of crystals of various shapes.

Raphides : Needle shaped crystals are known as raphides. e.g., in plants like jamikand, Colocasia, water hyacinth (Jal kumbhi) etc.

Rosette or Sphaeraphides : Star shaped crystals. They occur in special mucilaginous parenchyma cells of the petiole of arum, water hyacinth, etc. Crystals in the form of cubes are found in tunic of onion bulb. In the leaf of belladona, these crystals are in the form of sand and also called as sand crystals.

Calcium oxalate crystals : In members of family solanaceae. They are found as cubics, rods and prisms.

(b) Calcium carbonate : It is deposited in the form of crystalline masses hanging from a cellulose stalk in enlarged epidermal cells of leaves of Ficus elastica (Indian rubber plant) and is called as cystolith.

(vii) Latex : It is an emulsion in water having many substances either in suspension or in true solution. It may contain sugars, alkaloids and oils. It is watery in banana, milky white in Euphorbia, yellow or orange red in opium (poppy) is dried latex.

(viii) Organic acids : Tartaric acid in tamarind, and grapes, citric acid in lemon, orange etc. malic acid in apple and Bryophyllum. Oxalic acid in the form of crystals.

(ix) Gums : It is formed by decomposition of cellulose cell wall. Gum arabic of commerce is obtained from Acacia senegal.

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