Molecules of Cell of Class 11

Minerals are substances present in the earth’s crust. Those useful to organisms are called essential elements or essential minerals. An essential minerals or element is that which is required for nutrition, growth, development or functioning of organisms.

Minerals occur in the living beings in two states (i) complex state as component of organic molecules (e.g., Phosphorus, Sulphur). (ii) Inorganic molecules or ions (e.g., Na+, K+, Ca2+,

Mg2+, Cl–). Living beings maintain a balance between the amounts of minerals present in the complexed and free states.

Depending upon their concentration required, essential minerals are differentiated into two categories - major and minor (in case of animals) or macronutrients and micronutrients (in case of plants).

Major Minerals : Calcium, Phosphorus, Sodium, Chlorine, Magnesium and Sulphur.

Minor Minerals : Iron, Copper, Cobalt, Manganese, Molybdenum, Zinc, Fluorine, Iodine and Selenium.

Minerals required in extemely low concentration are known as ultra-trace minerals e.g., Silicon, Vanadium, Aluminium, Boron, Chromium, Tin.

Macronutrients : Phosphorus, Potassium, Calcium, Magnesium, Sulphur and Iron.

Micronutrients : Manganese, Cobalt, Zinc, Boron, Copper, Molybdenum, Chlorine and Nickel. Minerals are found as part of the cellular structure, biologically active substances, enzyme activators and have

several other functions.

Minerals as part of Cellular Structure

Calcium carbonate forms strengthening material of exoskeleton of arthropods.

Calcium is an important component of molluscan shells. On burning, the shells yield lime or CaO.

Some Algae have calcareous covering around them.

Corals secrete a calcareous skeleton or corallite.

Siliceous and calcareous shells are common in protists.

Middle lamella contains calcium and magnesium pectates.

Bones contain calcium phosphate and calcium carbonate. Bone dust is used as fertilizer.

Teeth are made of hydroxyapetite or 3 (Ca3PO4)2. Ca(OH)2.

Calcium fluoride occurs in bones and teeth. Fluorine prevents dental caries.

Magnesium gives rigidity to the bones and teeth.

Calcareous and siliceous spicules occur in sponges.

Magnetite helps in navigation in many birds, bees and even some bacteria.

Cell Components

Silica occurs in cell wall of grasses. Silicon provides stiffness as well as roughness.

Sulphurous amino acids form proteins and several other chemicals.

Phosphorus is a constitutent of phospholipids that form lipid bilayer of cell membrane.

Phosphorus is a constituent  of nucleotides.

Minerals as Part of Biologically Active Substances

Plant pigment chlorophyll has  magnesium in its porphyrin ring.

Iron combines with porphyrin to form heme which is a constituent of haemoglobin, myoglobin and cytochromes.

Copper is present in haemocyanin, a blood plasma respiratory pigment of some invertebrates.

Iodine occurs in mammals as minerals salt, constituent of organic compounds and thyroid hormone thyroxine. Deficiency of iodine reduces thyroid secretion but enlarges the gland. The disorder is called goitre.

Higher nucleotides function as energy carriers due to occurrence of high energy phosphate bonds. ATP also known as energy currency of the cell.

Magnesium takes part in association and dissociation of the two subunits of ribosomes.

Calcium is essential for blood clotting.

Minerals as Enzyme Activators

Some minerals are constituents of enzymes. They include molybdenium (nitrate reductase and nitrogenase), iron (nitrogenase, catalase, peroxidase or ferredoxin), copper (cytochrome oxidase, ribulose biphosphate carboxylase).

A number of trace elements are active in the  functioning of the enzyme -

Magnesium is essential for the functioning of enzymes connected with utilization of ATP in fat metabolism.

Manganese is activator of enzymes connected with synthesis of glycoproteins and oligosaccharides. Its concentration is maximum in mitochondria where it is activator of several enzymes.

Zinc is activator of enzymes connected with synthesis of RNA, carbonic anhydrase and carbohydrate metabolism

Iron and copper are required for the functioning of enzymes connected with chlorophyll synthesis.

Cobalt present in B12 is essential for erythrocyte formation.

Other Roles

Salts present in cell sap of plant cells maintain a particular osmotic concentration required for absorbing and retaining water in the cells.

Sodium and Potassium maintain fluid balance of the body. They control the volumes of extracellular and intracellular fluids through osmotic effects.

Salts of organic acids, monovalent phosphates (H2PO4–) and bivalent phosphate (HPO4–) function as the acid base buffers by neutralizing both strong bases as well as strong acids.

Calcium is essential for membrane permeability.

Calcium and Magnesium are required for muscle activity.

Na+ and K+ maintain membrane potentials, and take part in transmission of electric impulses in the nerve cells.

K+ fluxes govern movements of stomata and movement of variations in several plants including Mimosa pudica (seismonasty) and Oxalis (nyctinasty).

Specific Minerals

1. Calcium

Most abundant mineral of animal body available in all types of vegetables, grain, milk, cheese, eggs, fish and butter.

Its absorption, however, depends upon the presence of adequate amounts of vitamin D and phosphorus in the diet.

The various functions of calcium are

(a) Formation of bones and teeth alongwith magnesium and phosphorus.

(b) Transmission between nerves and muscles.

(c) Working of muscles

(d) Blood clotting

(e) Membrane permeability

(f) As constitutent of calcium pectate in middle lamella

(g) As constituent of exoskeleton of many invertebrates and molluscan shells.

(h) It acts as activator of some enzymes like ATP-ase, phospholipase, etc.

2. Phosphorus

Pesent in vegetables, grains (oat meal, wheat meal), milk, eggs, cheese, meat, fish etc.

Its absorption is controlled by adequate amounts of vitamin D in diet.

Various functions are :

(a) Constituent of bones and teeth.

(b) Component of phospholipids and nucleotides.

(c) Energy rich phosphate bonds are required in energy transfer through the formation and hydrolysis of ATP.

(d) Most carbohydrates become active only in their phosphorylated state.

(e) Phosphate is a constituent of co-enzymes NAD+, NADP+, FMN, FAD.

(f) Phosphates function as pH buffers.

3. Iron

Present in bread, potatoes, green vegetables, especially spinach, lettuce, cocoa, raisins, red meat, liver, kidney, egg yolk, etc.

Iron is also available in the body internally through the breakdown of old red blood corpuscles stored as ferretin in liver, spleen and intestinal mucosa.

Vitamin C (ascorbic acid) is essential for iron absorption.

The important functions of iron are

(a) Constituent of haemoglobin, myoglobin and cytochromes. Haemoglobin transports oxygen. Myoglobin occurs in muscles and stores oxygen. Cytochromes take part in electron transport and function as oxidising enzymes.

(b) Component of ferredoxin, nitrogenase, catalase, peroxidase.

(c) Activator of enzymes nitrate reductase and aconitase.

(d) Required for the formation of chlorophyll in plants.

4. Copper

A trace element which is available in most of the fruits.

Copper is

(a) Required for synthesis of haemoglobin.

(b) Component of cytochrome oxidase and ribulose biphosphate carboxylase, plastocyanin, ascorbic acid oxidase, etc.

(c) Connected with the formation of chlorophyll and maintenance of carbohydrate nitrogen balance.

5. Sulphur  

The major sources of sulphur are crucifers and animal proteins.

The various functions of sulphur are :

(a) Sulphur containing amino acids take part in synthesis of proteins

(b) Some sulphur containing amino acids form coenzymes, e.g. glutathione.

(c) Sulphur is a component of vitamins like biotin and thiamine.

6. Magnesium

Available in most of the plants, specially vegetables.

Its imporant functions are :

(a) Along with calcium salts a component of bones and teeth.

(b) Present in plant pigment chlorophyll that takes part in photosynthesis.

(c) Occurs in the middle lamella or cementing layer of plant cells.

(d) Essential for working of muscle cells along with calcium

(e) An activator of enzymes connected with metabolism and transfer of phosphate.

7. Sodium

Available in table salt.

A proper balance of sodium and potassium is essential.

The various functions of sodium are :

(a) Maintains along with chlorine a proper osmotic concentration in the blood for dissolution of blood proteins and turgidity of red blood corpuscles.

(b) Maintains the osmotic concentration of tissue fluid.

(c) Alongwith potassium, it maintains membrane permeability and membrane potential.

(d) Alongwith potassium it is essential for conduction of impulses in the nerve cells.

8. Iodine

Available in drinking water, vegetables and fish.

Table salt is iodized to provide iodine in the diet required only in traces for the proper functioning of thyroid gland, especially the secretion of thyroxine.

In the deficiency of iodine, thyroid gland enlarges and a disorder called goitre is produced.

9. Fluoride

Mostly available in drinking water essential for the formation of enamel of the teeth.

Deficiency causes dental caries, excess of  fluoride is equally harmful and causes a disorder known as fluorosis indicated by mottling of teeth, weakening of bones and swelling of joints.

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