Levels of Organization of Living Things Class 9 Notes

Levels Of Organization Of Life

Biomolecules And Heir Behaviour

Inorganic Compounds

Water: Water is the principal fluid medium of a cell. Nearly 70 to 85 per cent of the cell is water. Many cellular chemicals are dissolved in water others are suspended in water as solid particles.

• Chemical reactions take place among dissolved or suspended particles.
• Water concentration of the body is directly related to the age and metabolic activity of an organism Of the total body weight, the approximate percentage of water is as follows
• In newborns 78% by one year of age 65% in adult males 60% in adult females 55%.

Sources:

1. Exogenous water From food and drink.
2. Endogenous water (metabolic water) From the end product of metabolic reactions.
3. Endogenous water may be intracellular and extracellular.

Do you identify some examples of extracellular water in your body?

Physiological homeostasis of water: It is the process of maintaining a balance between fluid intake and fluid loss.

• Fluid intake is primarily by drinking water together with the intake of other liquid materials (for example milk etc). On the contrary, water loss may take place as follows:
• 15 ml/minute by respiration; 500 ml or day by sweat (of course, it depends upon temperature and humidity); 1000 -1500 ml/day by urine; little amount or day by stool.

Read and Learn More Class 9 Life Science

Can you explain why a patient in a hospital is given saline?

What does water do for you?

Importance of Functions of water:

Life can not exist without water. It has versatile functions in the body and life processes:

1. It is a universal solvent for all chemical and physiological reactions.
2. Water maintains electrolyte balance and acid-base balance of body fluids.
3. It allows the body’s cells to grow, reproduce and survive.
4. It is the major component of different body parts.
5. It acts as an important medium for osmosis, diffusion, filtration, transport and other physical processes.
6. It helps to deliver O₂ all over the body and transport CO₂
7. In digestion, it keeps the mucosal membrane moist; makes food bolus; dilutes food for enzyme action; synthesis digestive juice; medium for digestion; absorption of digested food.
8. It provides a medium for all metabolic reactions.
9. It lubricates joints.
10. It regulates body temperature by sweating and respiration.
11. It helps in detoxification and elimination of excretory products.
12. It acts as a shock absorber for the brain and spinal cord.
13. It is needed by the brain to manufacture hormones and neurotransmitters.

Acids: A hydrogen ion is a single free proton released from a hydrogen atom

Acid Definition: Molecules containing hydrogen atoms that can release hydrogen ions involutions are referred to as acids.

Example: HCl (Hydrochloric acid) ionizes in water to form hydrogen ions (H⁺) and chloride ions (Cl). Similarly, H₂CO₃ (Carbonic acid) ionizes in water to form H⁺ and HCO₃.

• Some common organic acids in the human body are HCI in the stomach, H₂CO₃ in the blood etc.
• ‘One apple a day keeps the doctor away’ justifies the statement.
• Prepare a list of organic acids and their functions in plants, animals and microbes.
• (Malic Acid in apple, in tamarind,oiUyteSfljrd in lemon, etc.)

Bases

Bases Definition: A base is an ion or a molecule that can accept an H₄ example. HCO₃” is a base because it can combine with H⁺ to form H₂CO₃. Similarly, HP04“ is a base because it can accept an H⁺ to form H₂P0₄“.

• ‘Do you know? “The protein in the body also function as bases because they readily accept H⁺. example. the protein Haemoglobin in RBC and proteins in other cells of the body are the most important bases of the body.”
• Can you identify some organic bases in plants and animals with their respective functions?
• In the human body, acid-base balance (buffer) is normally regulated by buffering agents in the respiratory system and the renal system.

Salts

Only six nonmetallic essential elements carbon, hydrogen, nitrogen, oxygen, phosphorus and sulphur, make up most of the body weight (98%) of an organism.

• Various metals and nonmetals combine to form different salts that are present in all living cells.
• Inorganic and organic salts of Ca, Mg, Na, K, and Fe, are very common in living cells.
• Prepare a list of Inorganic and organic salts known to you, that are present In plant and animal cells.

Gases

Three important gases needed by all living organisms are oxygen (20-4%), carbon dioxide (0 03%) and nitrogen (78%).

1. Oxygen is needed for aerobic respiration in different plants and animals. In terrestrial animals, O₂ – CO₂ exchange takes place through the trachea in insects, and the lung alveoli in man. Aquatic animals can absorb dissolved 02 for respiration through gills. Terrestrial plants absorb Op from the air for respiration both day and night and aquatic plants absorb dissolved O₂. O₂ is a gas that can be directly absorbed both by plants and animals.
2. Carbon dioxide is released by animals and plants during aerobic respiration. CO₂ is absorbed by green plants during photosynthesis. Terrestrial plants absorb CO₂ from the air whereas aquatic plants absorb dissolved O_2-CO₂ is a gas that can be directly absorbed only by plants but not by animals.
3. Nitrogen can be directly absorbed neither by plants nor by animals Nitrogen is fixed by blue-green algae (for example Nostoc, Anabaena), and N₂-fixing bacteria (for example Azotobacter, Rhizobium etc) because they contain some essential N₂-fixing enzymes. However, these enzymes are absent in higher plants and animals— so they can not fix nitrogen. N₂ is the essential component of various biomolecules like proteins, nucleic acid etc.

Organic Compounds

All living organisms are made of different organic compounds that are again formed of various inorganic elements like carbon, hydrogen, oxygen, nitrogen etc. All the carbon compounds that are obtained from living tissues are called ‘biomolecules’.So living bodies are a mixture of inorganic and organic substances or molecules.

Smaller Molecules Micromolecules

A small molecule is a low molecular weight (less than 900 Dalton) organic compound, soluble in acid. (Dalton is the unit of molecular weight of biomolecules, which signifies the weight of 1 atom of hydrogen). They have tremendous importance in biological functions. Some common examples of smaller molecules are monosaccharides, amino acids, fatty acids, nucleotides etc.

Simple Sugars

• Simple Sugars Definition: Simple sugars (as the name suggests) are the simplest form of carbohydrates that act as primary sources of energy in the human body e.g. monosaccharides.
• Monosaccharides: They contain only one unit of simple sugar example Glucose, fructose, galactose etc. Fructose is the sweetest natural sugar.
• Basic Structural Features: Colourless crystalline compounds, sweet. They undergo fermentation by yeast and other microorganisms.
• Source: Glucose (Dextrose) in grapes; Fructose (Laevulose)- fruit sugar which is present in almost all sweet fruits, honey; Galactose- it does not occur free in nature. In the body, galactose is present as a component of milk sugar (Lactose) which is formed of glucose and galactose.

Try to answer why is glucose called aldose and fructose as ketose. Galactose is absorbed fastest in the body through the small intestine.

Prepare a list of fruits that taste sweet.

Can you explain: Why a green mango is sour but becomes sweet as it is ripened?

Major Role In Life Processes

• Glycolysis:  Glucose undergoes glycolysis to produce pyruvic acid in cell cytoplasm.
• Storage: Excess. glucose may be converted into starch in plants, and glycogen in animals.
• Maintenance of blood sugar: Normally 100 ml of human blood contains 80-120 mg of glucose. An increase of this glucose level results in hyperglycemia (Diabetes mellitus) whereas a decrease in glucose level is called hypoglycemia.
• Synthesis of fats, and proteins:  By various metabolic reactions in the liver excess glucose may be converted to fatty acid, glycerol, amino acids etc.
• What will happen if someone eats a huge amount of rice daily without doing much work?

Amino Acids

They can be variously classified (Classification details will be discussed in higher classes). However, the basic classification is as follows:

• Acidic amino acid: ExampleAspartic acid, Glutamic acid
• Basic amino acid: Example Arginine, Lysine etc.
• Neutral amino acid: Example Glycine, Alanine etc..
• Essential amino acid: Example eight amino acids that are not synthesized in the human body and are taken along with diet example Valine, Histidine, methionine, Phenylalanine, Leucine, Isoleucine, Tryptophan, and Lysine.
• Non-essential amino acid: The remaining 12 amino acids are synthesized in the liver of the human body example Glycine, Alanine, Serine, Cystine etc. Glycine is the simplest amino acid
• Source: All amino acids are present in the protein. Essential amino acids are generally obtained from animal protein (for example egg, meat, fish, milk) and a few plant proteins.

Role In Life Processes

1. Structure and Function of protein: Since protein is made of different amino acids, the structure and function of a protein depend on its component amino acids.
2. First class protein: The protein that contains all essential amino acids and is capable of growth and maintenance example Albumin, globulin proteins of egg, meat, fish, milk etc. (Almost all animal proteins are first class proteins).
3. Second class protein: The protein that contains few essential amino acids but not all and is not suitable for growth and maintenance example Zein of Maize (Most plant proteins are second class proteins),

Fatty Acids

Basic Structural Features

• The fatty acid has a carboxyl group (COOH)attached.
• It is insoluble in water but soluble in fast solvents like chloroforms ether alcohol etc.

Types:

1. Saturated fatty Example: Stearic acid palmitic acid etc
2. Unsaturated fatty acid Example: Oleic acid Crotonic acid.
3. Essential fatty acids are needed for normal growth but are not synthesised in the body so they are taken along with diet Linoleic acid Linoleic acid and Arachidonic acid.

Source: Stearic acid in animal lard palmitic acid in palm oil, milk, meat, butyric acid in milk butter etc, oleic acid in olive oil, animal fat etc.

Do you know that Oleic acid is the most abundant fatty acid in human adipose tissue?

Role In Life Processes :

1. They help in the normal growth of the body
2. They are structural components of cells.
3. They are responsible for normal reproductive functions.
4. They are necessary for healthy skin.

Difference Between Amino Acid and Fatty Acid.

Nucleotide

Nucleotide Definition: Nucleotide is the structural unit of nucleic acid (DMA and RNA). Deoxyribonucleotide is the structural unit of DNA and ribonucleotide is the structural unit of RNA.

Basic Structural Features

One nucleotide consists of a pentose sugar (5-c-sugar), Nitrogenous base (N-Base) and phosphoric acid (H3P04).

1. N-Base can be of – Purine [Adenine (A) and Guanine (G)) and Pyrimidine [Thymine (T), Cytosine (C) and Uracil (U)].
2. A, T, G and C are present in DNA whereas A, U, G and C are present in RNA.
3. Nucleoside consists of pentose sugar and nitrogenous base without H₃P0₄.

Source: Nucleotides are present in Nucleic acid.

Role In Life Processes: DNA and RNA function as genetic material and they consist of nucleotides only.

(How can you explain the term ‘genetic material’ ?)

ATP (Adenosine Tri Phosphate): It is a nucleoside triphosphate used in cells. It is often called the “molecular unit of currency” or “energy currency” of intracellular energy transfer.

• ATP provides chemical energy within cells for various metabolic reactions.
• It is one of the end products of photophosphorylation, cellular respiration, and fermentation.
• ATP is highly soluble in water and one molecule of ATP contains two high energy bonds. A- P – P – P

High energy bond

ATP→ ADP + Pi + energy

ATP → AMP + PPi (Pyrophosphate) + energy.

Synthesis: ATP is synthesised partly in glycolysis, partly in the Krebs cycle but mainly in the electron transport chain (ETC).

Macromolecules

Macromolecules Definition: Those organic compounds that are acid insoluble, having molecular weight- of more than 300 Dayton (except lipid) are called macromolecules.

• They are complex carbohydrates (oligo-and polysaccharides), proteins, lipids and nucleic acids
• . (However, though lipid is considered a biomacromolecule, it has a molecular weight of less than 900 Dalton).

Complex Carbohydrates

Complex Carbohydrates Definition: Complex carbohydrates are oligosaccharides (disaccharides, trisaccharides etc) and polysaccharides. They are formed of two or more monosaccharide units interlinked glycosidic bends.

Disaccharides: They are formed by the combination of two monosaccharide units with the elimination of one molecule of water.

• Lactose (in milk) is formed of glucose and galactose :
• Sucrose (cane sugar) is formed of glucose and fructose;
• Maltose (malt sugar) is formed of glucose and glucose (i.e. two molecules of glucose)

Do You know the name of the bond between two glucose molecules?

• Trisaccharides: They are formed by the union of three monosaccharide units. (Can you explain how many water molecules will be released in this structure ?) Raffinose (found in beans, cabbage, broccoli etc) is formed of glucose + fructose + galactose.
• Tetrasaccharides: This is formed of four monosaccharide units, e;g. Stachyose (found in green beans, soybeans etc.) is formed of two molecules galactose + glucose + fructose.

More Complex Carbohydrates Or Polysaccharides

Polysaccharides are polymers of a large number of monosaccharide units (monomers). Polymer is the ‘garland’ whereas monomer is the ‘individual flower’ of the garland, example Glycogen is the polymer and each glucose unit is the monomer.

Basic Structural Features

1. They are commonly not sweet.
2. Generally, they are soluble in water (except cellulose)

Some Common Polysaccharides

Starch: Polymer of glucose, produced by plants; insoluble in cold water gives a blue colour with iodine tasteless.

Glycogen: Found in animals and fungi, Known as ‘animal starch’ soluble in water, gives a reddish colour with iodine.

Cellulose: Found in plants; insoluble in water; taken in the body along with vegetables; can not be digested in the human body and forms ‘roughage’ (Roughage is the undigested food materials, mainly formed of fibres, that go out along with stool and prevents constipation). Cellulose is the most abundant carbohydrate in nature and starch is the second most abundant carbohydrate.

Role In Life Processes

1. Starch is the main constituent of food grains.
2. Glycogen (animal starch) is generally stored in the liver and muscle as a food reserve.
3. Cellulose forms ‘roughage’, stimulates peristalsis and helps in defecation.
4. Carbohydrate (Simple or complex) is the main source of energy when completely oxidised. One gram of carbohydrate yields 4-0 Kcal energy.

Protein

Protein Definition: Protein is the polymer of amino acids that are interlinked by peptide bonds

For reference only: The protein which is present maximum in the world is a plant enzyme protein called RuBisCO (Ribulose Bis phosphate carboxylase oxygenase)

• which plays a key role in the dark reaction of photosynthesis in the stroma of chloroplast.
• But the animal protein present maximum in the world is collagen.

Basic Structural Or Compositional Features

An essential component of protein is nitrogen.

1. “I ne structural unit of protein is an amino acid.
2. Most of the proteins have a fishy smell.
3. When heated, protein coagulates (You have seen if milk is heated, it gradually condenses).
4. In an acidic medium, protein is precipitated.

Source: In plant products like soybeans, pulses, different seeds etc. Animal products like milk, eggs, fish, and meat are rich sources of animal protein.

Role in life process :

• Body-building food: Protein is the chief organic constituent of the protoplasm of a living cell. So it is called as body building food.
• Maintenance of body: Protein helps to maintain body structure, body growth, repair of damaged tissues due to wear and tear, storage of proteins etc.
• Synthetic function: It helps in the synthesis of plasma proteins (albumin, globulin, prothrombin, fibrinogen etc.) haemoglobin, enzymes, most animal hormones, milk protein (lactalbumin, lactoglobulin) antibodies (Immunoglobulin), melanin pigments etc.
• Calorific value: One gram protein when completely oxidised yields about 4.1 Kcal energy.
• Enzyme Definition: Enzymes are biological catalysts, or proteins in nature, produced by living cells, that accelerate various biochemical reactions, but themselves remain undestroyed after the reaction.

Basic Compositional Features

1. Nature:  Almost all enzymes are proteins.
2. Structure:  Like all other proteins, the enzyme is also formed of several amino acids.
3. Active site: We ingest food through our mouth, so the mouth is the ‘active site’ for ingestion. Similarly, the enzyme also performs its function by the ‘active site’ at a higher rate.
4. Specificity: Each enzyme acts on a specific substrate eg. Protease acts only on protein; lipase acts only on lipids etc.
5. Catalytic property enzymes act as biocatalysts, they are not destroyed at the end of the reaction.
6. Medium (pH): Each enzyme acts in a definite medium eg. ptyalin of the buccal cavity in a neutral medium, pepsin in the stomach in an acidic medium, trypsin in the small intestine in an alkaline medium and so on.
7. Temperature: Enzyme shows maximum activity in optimum temperature (35°C-40°C). At BSP temperature (above 40°C) enzyme may get damaged (denaturation).
8. Action:  Enzyme action is reversible and may be inhibited by a suitable inhibitor.
9. Components: The enzyme consists of two parts: apoenzyme (Protein part of enzyme) and coenzyme (non-protein part) or cofactor. Apoenzyme and coenzyme (cofactor) together form the functional enzyme called Holoenzyme.

Holoenzyme = Apoenzyme + cofactor or coenzyme.

Types of enzymes:

Digestive enzyme: Enzymes taking part in digestion are called digestive enzymes.

They Are Three Types

1. Proteolytic enzymes or Protein-hydrolysing enzymes: These enzymes hydrolyse proteins into polypeptides and amino acids, for example, Pepsin, Trypsin, Chymotrypsin, Erepsin, and Renin.
2. Lipolytic enzymes or Lipid hydrolysing enzymes: These enzymes hydrolyse lipids (fats) into fatty acid and glycerol example Lipase (Gastric Lipase, Pancreatic Lipase, Intestinal lipase).
3. Amylolytic enzymes or Carbohydrate hydrolysing enzymes: These enzymes hydrolyse the carbohydrate into monosaccharides (glucose), for example, Amylase, Sucrase, Lactase, Maltase, etc.

Bile does not contain any digestive enzyme but it breaks down bigger molecules of fat into smaller droplets to increase the surface area for action of lipase. This is called the emulsification of fat.

For reference only Functional classification: According to the type of reaction, enzymes are also classified into 6 types

1. Oxidoreductase,
2. Transferase,
3. Hydrolase,
4. Lyase,
5. Isomerase, and
6. Ligase.

Role In Life Processes:

1. Enzymes accelerate different biochemical reactions.
2. They are essential for any metabolic reaction in living organisms.
3. They play a very significant role in digestion.

Do you know, there is a very special type of enzyme called allosteric enzyme?

Lipid and Fat

Lipid and Fat Definition: Fat is the fatty acid of glycerol. The salt of alcohol (glycerol) with organic acid (fatty acid) is known as ester. Lipid is a broader term which includes fat, wax, cholesterol, and hydrocarbon since all of them are insoluble in water but soluble in organic solvents. Hence all fats are lipids but all lipids are not fats.

Basic Structural Or Compositional Features

They are insoluble in water but soluble in ether, chloroform etc.

1. At ordinary temperatures, some fats remain solid (for example lard) whereas others are in liquid form.
2. Unsaturated fats are generally liquid. Those fats which remain liquid at ordinary temperature are called oils.
3. Some common plant oils are mustard oil, groundnut oil, coconut oil, soyabean oil, sunflower oil etc.
4. Some oils from animals like cod liver oil, shark liver oil, etc. are rich sources of vitamins A and D.
5. They are lighter than water so float on the water’s surface.

Source:

• Plant source: Mustard oil, coconut oil, groundnut oil etc.
• Animal source: Meat, milk and milk products like ghee, butter, cheese etc,

Role In Life Processes :

1. Calorific value: Lipid provides a food with high calorific value. One gram of lipid produces about 9’3 KCal energy.
2. Storage: Lipid acts as reserve food material because it can be easily stored in the body for future use.
   • (Do you know, which tissue of man’s maximum fat is stored )
3. Reaction: The storage (depot) fat protects the vital organs, skin etc. and also acts as cushion and packing tissues.
4. Heat insulations: Lipid acts as an insulator. Thus subcutaneous fat helps to regulate body temperature (thermoregulation).
   (Find out the blubber in Whale and its major function)
5. Solvents: Lipids a good solvents for fat-soluble vitamins like vitamins A, D, E, and K.
6. Hormone synthesis: From cholesterol, all steroid hormones are synthesized in animals.

Nucleic Acids

Nucleic acid Definition: Nucleic acid is the polymer of nucleotides (polynucleotides). They are distributed in the nucleus and cytoplasm of a cell.

Basic Structural Features

DNA (Deoxyribonucleic Acid) (Do you know the structure of DNA was discovered by Watson and Crick for which they were awarded the Nobel Prize.)

1. It is usually double-stranded or double-helical. (Can you mention an exception where single? stranded DNA is present)
2. Two complementary chains are named a (alpha) and β (Beta).
3. Two chains are antiparallei and interlinked by H-bonds.
4. The structural unit of DNA is called deoxyribonucleotide which consists of pentose (deoxyribose) sugar, H₂PO₄ and N-Base. .
5. N-Base can be of two types purine and pyrimidine.
6. Purine of DNA is again of two types Adenine (A) and Guanine (G) whereas pyrimidine is again of two types Thymine (T) and Cytosine (C).

RNA (Ribo Nucleic Acid)

1. It is generally single-stranded or single-helical.
2. If you can identify an exceptional organism which contains double-stranded RNA!
3. The structural unit of RNA is ribonucleotide which consists of a pentose sugar (ribose), H3P04 and N-Base.
4. N-Base can be of two types Purine and Pyrimidine.
5. Purine in RNA is of two types Adenine (A) and Guanine (G) whereas
6. pyrimidine is again of two types Uracil (U) and Cytosine (C)

Source: Nucleic acid is present in all living plant cells, animal cells, microbes, viruses etc (though there are very rare exceptions)

Role In Life Processes

DNA: It contains genes and is responsible for the inheritance of characteristics from parents to offspring.

• It is responsible for all characteristics of an organism.
• It controls cell division where a mother cell divides itself to produce two daughter cells.

RNA: In plant viruses TMV (Tobacco Mosaic Virus) and in some animal viruses like Influenza virus, HIV (Human Immunodeficiency Virus) etc.  RNA contains genes so RNA is the genetic material in them.

• mRNA (Messenger RNA) carries information from DNA and helps in protein synthesis.
• tRNA (Transfer RNA) collects amino acids from cell cytoplasm for protein synthesis.
• rRNA (Ribosomal RNA) is the structural component of ribosomes and helps in protein synthesis.

Difference between DMA and RNA

Role Of ATP As Energy Currency Of A Cell

ATP (Adenosine Tri Phosphate) is the primary molecule for storing and transferring energy in cells. It is often referred to as the “energy currency of the cell” and may be compared to storing money- (ATP) in a bank (cell).

• In any energy-related biochemical reaction of the cell, ATP is either produced or consumed.
• For example, during photosynthesis, ATP is synthesized (photophosphorylation) by using solar energy whereas during respiration, ATP is synthesized through glycolysis, Krebs cycle, ETC.
• The production of ATP in ETC is known as oxidative phosphorylation.
• ATP is a nucleotide consisting of an N-Base [Adenine (A)], attached to a ribose pentose sugar (5-sugar), which is attached to three phosphate groups, that are linked to one another by two high-energy bonds.

ATP: Adenosine – P – P – P

(N- Base)

The symbol – designates a high-energy bond. So, in 1 ATP, there are 2 high-energy bonds.

When these high-energy bonds are broken, energy is released, which is utilized for any biochemical reaction of the cell or body.

ATP ADP + Pi + energy

ATP AMP + PPi + energy

Vitamins And Their Roles In The Human Body

Vitamins And Their Roles In The Human Body: The word vitamin was suggested in 1912 by Casimir Funk.

• He isolated a concentrate from rice polishings which was found to contain nitrogenous bases (amines).
• As these substances were vital for sustaining life, they were called vitamines ( vita, life).
• Later, when it was discovered that all these essential substances were not exclusively amines, the letter ‘e’ was dropped and then the name vitamin was given by J. C. Drummond.

Health And Life Definition: Vitamins are organic compounds present in variable minute quantities in natural foodstuff which are required for normal growth as well as maintenance of health and life.

Importance (Functions) of Vitamins: Vitamins are needed to resist diseases, as they act as protective principles of food.

General Characteristics Of Vitamins

Vitamins are obtained from plant products and animal products.

• The daily requirement of vitamins is very low.
• A small amount of fat-soluble vitamins may be stored in the liver and vitamin C in the adrenal cortex. However, most of the vitamins can not be stored in the human body.
• Vitamins are destroyed after reaction hence they must be supplied to the body regularly.
• Some of the vitamins are heat stable (for example vitamins A, D, E, K, B₂ etc) but some of the vitamins are heat-louble (for example vitamins B₂, B₃, vitamin C etc).
• Vitamins are not synthesized in the human body. It must be supplied to the body along with diet.
• However, a small amount of vitamin A is synthesized in the human liver from carotene pigments.

Source Of Different Vitamins 

Minerals And Their General Role In The Human Body

Minerals And Their General Role In The Human Body: Various minerals are needed to maintain vital functions of our body like enzyme activity, hormonal functions etc. They are essential components for cellular biomolecules, the structure and function of cells and so on.

Macromineral Definition: The minerals that are present: in higher levels in the human body and are required in relatively larger amounts in the diet are called macromineral.

Micromineral Definition: The minerals that are present at low levels in the body or required in smaller amounts in the diet are known as micromineral. They are sometimes also called essential trace minerals.

Role Of Micromineral In The Human Body

Cell

Have you seen the brickworks in the construction of a building? You will observe the arrangement of bricks that are placed one above the other and side by side. So, the bricks are structural units of a building.

• Similarly, the living body of plants and animals is made up of certain tiny (usually microscopic) structural units called cells. Generally, most of the organisms that are commonly visible to us are multicellular they are composed of many cells.
• A vast number of organisms are there that are formed of only a single cell, called unicellular organisms.
• The single cell exhibits all the characteristics of life and maintains its independent existence.

Discovery of cell

The term “cell” was first used by Robert Hooke, an English engineer, in 1665. While he was examining a section of bottle cork under a microscope, he saw many honeycomb-like empty chambers (hollow spaces) in it.

• He named each of these hollow spaces as cells. Hooke used a very simple type of self-made compound microscope.
• After he discovered cells, considerable progress was made in the development of powerful and more sophisticated microscopes that reveal details of cytology.
• Do you know what is meant by ‘cytology’? Have you heard the name of an electron microscope (EM) where maximum magnification is possible?

What is a Cell

Cell Definition: A ceiling may be defined as the structural as well as functional unit of a living organism.

Size of cells: Cells are usually small in size and are not visible to the naked eye. Different parts of the cell can be viewed under a microscope.

• But a few cells are quite large and are thus visible even to the naked eye.
• RBC is the smallest cell of the human body. What: ‘s the largest cell? in the human body?
• Do you know the ostrich egg is the largest single cell on the earth?
• Elementary idea about structures and functions of different cell components :

Cell Wall

Cell Wall Definition: The thick rigid, porous, permeable non-living, outer envelope of plant cells made up of cellulose is called the cell wall.

Most plant cells (but not animal cells) have a cell wall. It is lying just outside the cell membrane.

• Structure: The main constituent of the cell wall is cellulose, a type of carbohydrate. The cell wall of a mature plant cell consists of two parts
• Primary cell wall: It is the outer permeable and thinner wall in comparison to the secondary cell wall.
• Secondary cell wall: It is the thicker inner part of the cell wall formed after the primary cell wall.
• It has three layers thin outer layers thick middle layers and thin. The common host-formed wall lying between the two adjacent cells is called the There are sonic minute pores present in the cell wall through which protoplasmic connections between the adjacent cells arc established. These intercellular connections are known as plant cells.

Cell Wall  Functions:

1. The cell wall gives shape and rigidity to the cell.
2. It protects the protoplasm from external injury.
3. Unless deposition of special chemical substances occurs (as in the cells of bark), the cell wall is freely permeable to the molecules i.e. allows them to pass through in and out freely.
4. The plasmodesmata are meant for cell-to-cell conduction of water and different chemical substances.

Cell Membrane or Plasma Membrane Plasmalemma

Cell Membrane Or Plasma Membrane Definition: The thin flexible semi-permeable living membrane that surrounds the protoplasm of a cell is called the cell membrane or plasma membrane.

• The cell membrane lies as the external covering layer of animal cells.
• However, in plant cells, the membrane lies between the protoplasm and the cell wall.

Structure: Thccellmcmbrane is a thin limiting membrane. Under an electron microscope (EM), the cell membrane is found to be made up of three layers a layer of lipid is present between two protein layers. Such a membrane is called the unit membrane (P-L-P) by J. D. Robertson.

Different models related to the structure of cell membranes have been proposed by various scientists of which the most accepted one is the Fluid Mosaic model as proposed by Singer and Nicolson(1972)

Do you know the Fluid Mosaic Model represents floating icebergs of protein in the seawater of Lipid?

Cell Membrane Or Plasma Membrane Functions :

1. The cell membrane protects the protoplasm and the cell organelles from external injury.
2. It maintains the normal structure of the cell.
3. It retains the cell contents and controls the transfer of food materials and waste products inside and outside the cell respectively.
4. It allows the entry and exit of selected molecules.
5. Cell membrane gives mechanical support.

Protoplasm (Protos = First Plasma = Shape)

Protoplasm is a translucent jelly-like viscid material constituting the essential substance of living cells. Protoplasm = Cytoplasm + nucleus.

• Max Schultze and Thomas Huxley proposed protoplasm as the physical basis of life.
• Because all the vital functions like nutrition, secretion, growth, reproduction, irritability, mortality etc. of the living cells are controlled by the protoplasm.
• It is made up of cytoplasm and nucleus. The term protoplasm was coined by Purkinje. The protoplasm exhibits streaming movement called cyclosis or Brownian movement.

1. Cytoplasm Definition: A thick, semi-transparent, elastic fluid containing suspended particles and a series of minute tubules and filaments is known as cytoplasm. Cytoplasm is the matrix or ground substance which is present between the cell membrane and the nuclear membrane of the cell. Cytoplasm = Protoplasm – nucleus
2. Structure: Under the ordinary compound microscope the cytoplasm appears to be.a semi-fluid, apparently transparent and homogenous substance. The outer denser portion of the cytoplasm is known as the ectoplasm. It is a relatively non-granular and transparent part. The inner less denser portion is lying towards the nucleus and is called the endoplasm. It is granular and viscous. The fluid part of the cytoplasm is known as the hyaloplasm or cytoplasmic matrix. This fluid part contains various cell organelles (mitochondria, Golgi bodies, endoplasmic reticulum, chloroplasts etc!), non-living inclusions and vacuoles. Hyaloplasm = Cytoplasm – cellular organelles.

Protoplasm Functions :

1. Various cytoplasmic organelles, the nucleus and non-living cytoplasmic inclusions remain embedded in the cytoplasm
2. The cytoplasm is the site of several chemical reactions which are essential for life (e.g. part of respiration).

Cytoplasmic Organelles

Cytoplasmic Organelles Definition: The tiny specialized subunit of a cell which remains embedded in the cytoplasm having a specific physiological function of the cell is called cytoplasmic organelles. Thus the relation between organ and body is similar to organelle and cell.

Examples—Nucleus, mitochondria, plastids, Golgi bodies, centrosomes, ribosomes, endoplasmic reticulum, lysosome, vacuole etc. are such structures.

Nucleus Definition: The double membrane-bound dense spherical protoplasmic body (largest cellular organelle) containing chromosomes is called the nucleus.

The nucleus is usually present at the centre of the cell, but in mature plant cells, it is pushed towards the periphery by the vacuole. Generally, a single nucleus is present in most cells (uninucleate). In some cases, however, more than. one nucleus may be present in each cell (multinucleate).

Examples: skeletal muscle, certain algae and fungi. In bacteria organised nucleus is absent.

Human mature erythrocytes and plant’s sieve tube (cell) do not contain a nucleus. So they are non-nucleated living animal cells and plant cells respectively.

Structure: The nucleus is a specialized protoplasmic denser body lying embedded in the cytoplasm. Under a powerful microscope, the nucleus shows the following parts

Nuclear membrane: The porous delicate double membrane-bound structure which surrounds the nucleus is called the nuclear membrane. The space between two membranes is called perinuclear space. Functions The nuclear membrane separates the nucleus from the surrounding cytoplasm.

Nucleoplasm or Nuclear sap: it is a dense but clear fluid present in the nucleus, forming the matrix. Functions. It stores reserve materials that are used up at the time of the cell division.

Nuclear reticulum: Suspended in the nuclear sap there lies. an irregular network of delicate threads called the nuclear reticulum or chromatin reticulum. Functions During cell division, thread-like bodies, called chromosomes are developed from this reticulum. They contain the hereditary material (DNA and genes) and control the characteristics of the organism.

Nucleolus: The highly retractile, dense and non-membranous spherical body present within the nucleus is called the nucleolus. Functions Nucleolus helps in the formation of ribosomes. It also helps in the synthesis of ribosomal RNA and protein.

Functions Of Nucleus:

1. The nucleus is thought to be the centre of all chemical activities of the cell- the so-called brain of the cell
2. It acts as the controlling centre of the major physiological processes taking place within the cell,
3. It contains chromosomes the bearers of hereditary characters called genes and helps in the transmission of these hereditary characteristics from parents to offspring,
4. It also initiates and regulates the cell division.

Mitochondria (sing Mitochondrion)

Mitochondria Definition: The spherical or elongated double membrane-bound filamentous cytoplasmic bodies associated with cellular respiration are called mitochondria. Mitochondria appears throughout the cytoplasm of all living cells except the prokaryotic cells like blue-green algae and bacteria, as well as the matured erythrocytes of mammals.

Structure: The oval or rod-like mitochondria possess two unit membranes. The outer membrane of the mitochondria is smooth but the inner membrane remains folded inwards to form finger-like projections at several points to form several partitions or shelves called cristae (sing, crista).

On the wall of cristae of mitochondria, there are numerous particles called elementary particles, or Fa particles. The two membranes lie apart from each other and the space between them is filled up with a fluid. The central cavity of the mitochondrion is enclosed by the inner membrane and cristae is filled up with a ground substance called Matrix.

Function: The mitochondria are associated with cellular respiration. During respiration food is oxidized and a considerable amount of energy is liberated in the form of ATP. As mitochondrion acts as a source of energy generator, it is regarded as the ‘power-house of the cell’.

Plastids Definition: The pigmented or non-pigmented double membrane cytoplasmic bodies in ant cells associated with the preparation or the storage of food materials are called plastids.

Plastids are present in the cytoplasm of most plant cells. The plastids do not occur in the cells of bacteria, blue-green algae, fungi and animals (except for Euglena).

Plastids Are Of Three types

1. chloroplasts,
2. chromoplasts and
3. leucoplasts.

Different Types Of Plastids

EES Chloroplasts: (Gr. Chloro = green; plastos = formed): Green-coloured plastids are called chloroplasts. They are found in most green parts of plants, such as foliage leaf, young stem, calyx of flower etc.

Structure: The chloroplasts are double membrane-hound structures containing granular bodies known as the grana and a ground substance of fluid nature called the stroma. Each granum is made up of a stack of minute bag-like structures, each of which is called a  Green photo or synthetic pigment, called chlorophyll, which is present in high concentration in the thylakoids. They also contain other photosynthetic pigments, such as orange carotene, yellow xanthophyll etc.

Plastids Function —The chloroplasts are meant for photosynthesis. Chlorophyll is present in the thylakoid of grana of the chloroplast.

Chromoplasts :(Gr. Chrome = colour; lists = formed); The plastids having colour other than green are called chromoplasts. Chrornoplastids are found in the cells of five petals, fruit skin, coloured roots (for example carrot) etc.

• Structure: It is almost similar to that of the chloroplasts but they contain membranous tubes instead of thylakoids. It contains pigments like carotene, /xanthophyll etc. but never chlorophyll.
• Functions: It attracts insects for pollination and imparts various colours to the various plant organs like petals, fruits etc.

Do you know which pigment in the petals of a rose makes the flower so beautiful? The flower of jasmine has a fantastic smell—try to discover which chemical is it.

Leucoplasts : (Gr.Leuco white; plastics – formed); The colourless plastids are called the leucoplasts. leucoplast is found in roots, underground sterns (for example potato) etc.

• structure: I leucoplasts are double membrane-bound rod-like or sphere-shaped colourless plastids.
• Functions: leucoplast can be converted to chloroplasts on exposure to sunlight and reconverted to leucoplast when kept in the dark for a long time, fhe leucoplasts are concerned with the storage of food materials like carbohydrates (starch), protein, and lipids within the cell.

You have observed that a young leaf Is green, but as It becomes old, it turns yellow why  Similarly skin of an unripe mango Is green In colour but as It Is ripened, It turns orange and yellow try to find the answer yourself.

If a piece of beet is placed In water, the water turns red but if a piece of carrot Is placed In water, water does not turn yellow how can you explain It?

Endoplasmic Reticulum

Endoplasmic Reticulum Definition: fhe membrane-bound channels of various shapes form Irregular nH work In the cytoplasm Is called endoplasmic  (ER). The endoplasmic reticulum is present In all eukaryotic animal arid plant cells.

Structure: Based on its association with ribosomes ER is divided into two types. Granular (rough) RER or GER is studded with ribosome. Ribosomes are attached to the membrane of RER by a protein called ribophorin.

Agranular (smooth) SER is free of ribosomes. Agranular ER is synthesised from granular ER. Eachtypeofendoplasmicreticulum consists of inter-communicating narrow tubes, the tubules, a small spherical or oval sac-like structure, the vesicles and large flat sacs the cisternae. All these structures are filled up with fluid called endoplasmic matrix and are surrounded by a single lipoprotein membrane.

Endoplasmic Reticulum Functions :

1. Proteins are synthesized by ribosomes attached to the membranes of granular ER (RER)
2. The agranular ER (SER) synthesizes sterol, fats and phospholipids,
3. The ER is also involved in the intracellular exchange of materials between the nucleus and cytoplasm.

Golgi body :

Glogi Body Definition: The parallelly arranged membrane-bound cytoplasmic bodies occurring near the nucleus and participating in the secretory process of cells are known as the Golgi bodies.

• The Golgi bodies are abundant in animal cells and are less frequently found in plant cells.
• In plants, these organelles are called dictyosomes.

Structure: The Golgi bodies consist of four to eight thin membrane-bound flattened sacs, stacked upon each other like a pile of dishes with expanded areas at their end.

The stacked elements are called cisternae. In the peripheral part of cisternae small droplet-like sacs, known as the vesicles bulge out. They also possess vacuoles.

Glogi Body Functions :

1. Golgi bodies are associated with the secretory activity of the cell.
2. They help in the formation of plant cell walls, plasma membranes and secretory vesicles.
3. Do you know what are the major secretory substances of a cell?

Lysosome

Lysosome Definition: The single membrane-enclosed tiny spheroid or irregular vesicles containing hydrolytic enzymes which help in both intracellular and extracellular digestion are known as lysosomes. Lysosomes remain scattered in the cytoplasm of animal cells. The number increases in the secretory cells.

Structure: A mature spherical lysosome is surrounded by a lipoprotein membrane. Inside the membrane, finely granular regions of different densities are observed. Within it different hydrolytic enzymes are present. Lysosomal enzymes are called acid hydrolases.

Lysosome Functions :

1. Lysosome helps in cellular digestion
2. It helps in autolysis (digesting the various organelles of the cells) hence lysosome is called the “suicidal bag of the cell”.

Vacuole Definition: The single membrane-bound cavities containing a kind of watery fluid (cell sap) present within the cytoplasm are called vacuoles.

The vacuoles are considered one of the non-living bodies of the cell and contain stored food materials and certain secretory and excretory products. Vacuoles can occasionally be seen in animal cells but they are quite common and larger in plant cells.

Structure: In a young plant cell, several vacuoles are found. But as the cell matures the vacuoles fuse forming a large central vacuole which pushes the cytoplasm along with the nucleus against the cell wall. This peripheral layer of cytoplasm thus formed surrounding the vacuole is known as the primordial utricle. Each vacuole cell sap. A vacuole is surrounded by a single membrane similar to a plasma membrane called a tonoplast. The cell sap (Tonoplasm) may contain mineral salts, sugar etc. dissolved in water.

You should know that the fluid in the vacuole is called a tonoplast.

Vacuole Functions :

1. The vacuoles are of different types which perform different functions, such as
2. Food vacuole acts as the store-houses of water, mineral salts, sugar, etc.
3. Gas vacuoles store gases which helps the aquatic plant remain floating on the water,
4. Water vacuole formed by pinocytosis contains water
5. Contractile vacuole contains water which is expelled to the outside by its contraction and relaxation (for example Amoeba)
6. The excretory vacuole contains excretory products, gases, etc. and maintains cell turgidity.

Ribosome Definition: Ribosomes are non-membranous small, dense, round and granular particles of ribonucleoprotein. Ribosomes are present freely in the cytoplasm. The free ribosomes occur singly or in clusters (polyribosomes). The ribosomes also remain attached to the membranes of the endoplasmic reticulum, (bound ribosome), mitochondria, chloroplast etc.

Structure: A ribosome consists of two sub-units, one about half the size of the other. The larger sub-unit is dome shaped and the smaller sub-unit forms a cap-like structure. These two sub-units are situated to the flat surface of the other. In eukaryotic cells, the sub-units of the ribosome consist of 60S and 40S (jointly 80S). In prokaryotic cells, the sub-units of ribosomes consist of 50S and 30S (jointly 70S). The large unit is ‘cup-shaped’ and the smaller unit is ‘cap-shaped’. During protein synthesis, two units get interconnected by Mg++ ions. Ribosome of eukaryotic cell

Do you know that ‘S’ in ribosome stands for ‘sedimentation coefficient’ or Svedberg’s unit?

Ribosome Function: Ribosome helps in protein synthesis.

Centrosome Definition: In animal cells, two tiny hollow cylindrical Dodies, the centrioles, remain surrounded by a recognizable clear zone of cytoplasm and form a complex which is known as the centrosome. Centrosomes are generally present in animal cells and occasionally in the cells of some lower plants.

Structure: The centrosome consists of two parts the centriole and the centrosphere. The centrioles are usually two in number which are tiny cylindrical bodies arranged at right angles to each other. The centrosphere is the dense cytoplasm surrounding the centrioles.

Centrosome Functions:

1. Centrosome plays an important role in animal cell division
2. It also plays an important part in the formation of cilia and flagella.

Microtubule

Microtubule Definition: In the cytoplasm of eukaryotic cells, there are numerous non-membranous hollow cylinders known as microtubules.

Structure: Microtubules have variable length. They are formed of a special type of protein called tubulin. Each tubulin consists of two sub-units (dimer)

Microtubule Functions:

1. They form a supporting framework or cytoskeleton and give shape to the cell
2. Microtubules form spindle during mitotic or meiotic cell division
3. They form cilia and flagella which help in movement.

Prokaryotic and Eukaryotic cells

Prokaryotic cells Definition: A cell which lacks a nuclear envelope, nucleolus and well-defined cytoplasmic organelles, such as endoplasmic reticulum, Golgi body, mitochondria, centriole, etc. is known as a prokaryotic cell.

Examples: All Bacteria (Azotobocter, Clostridium), all Blue-green algae (Nostoc, Anabaena), Mycoplasma, etc.

Eukaryotic cell Definition: The cell which contains a true nucleus (nucleus covered by a nuclear membrane) together with well-defined cytoplasmic organelles like endoplasmic reticulum (ER), Golgi bodies, mitochondria, lysosome, etc. is known as a eukaryotic cell.

Examples: Cells of higher plants and animals.

Plant Cells and animal cells: Both plant cells and animal cells are eukaryotic cells They contain so many common organelles like the nucleus mitochondria, and Golgi bodies in plant cells Golgi bodies are also called dictyosome Er(Ser and RER), ribosomes etc. But they have some differences as follows:

Organelles present in plant cells but not in animal cells Plastid, cell wall Organelles present in animal cells but not in plant cells Centrosome, Lysosome.

Do you know what is the cause of so beautiful colour of butterflies, aquarium fishes, colourful birds etc. It is not due to plastid. Then what is this colour? This is due to chromatophores.

Plant C And Its Distribution

Concept Of Tissue As An Organization Level within A Multicellular Living Body

The Cell Is The Structural And Functional Unit Of Life: Living organisms are either unicellular or multicellular. In unicellular organisms, the body consists of a single cell, which is capable of performing all the activities of life. In multicellular organisms, the body consists of more than one cell. Here the cells form different groups based on their common origin and specific functions.

Tissue Definition: A group of cells, similar or dissimilar in shape and of the same origin and performing particular functions in a multicellular living body is called tissue. The term tissue was given by Bichat.

Different Types of Plant Tissue

Plant Tissue: There Are two broad kinds of plant tissues, namely – Meristematic Tissue and Permanent Tissue

Meristematic Tissue

Meristematic Tissue Definition: A tissue comprising immature cells which are always in a state of division forming new cells is called meristematic tissue.

Characteristic features:

1. Cells are arranged compactly without intercellular spaces,
2. Cells filled up with dense cytoplasm,
3. Vacuoles if present are small and few,
4. The cell wall is thin, made up of cellulose and pectin
5. The nucleus is prominent and larger
6. Cells are always in a constant state of division.

Distribution: According to location i.e. distribution meristematic tissues are

Apical meristem: Present at the growing apex of root, stem and leaf. If apical meristem divides and grows, the plant increases in length known as primary growth.

Intercalary meristem-Present in between the permanent tissues.

Lateral meristem- Present at the lateral sides of roots and stems. If lateral meristem divides and grows, the plant increases in width and thickness, called secondary growth.

Can you state the reason?

What will happen by cutting a stem tip of a plant? You will observe no further growth in the length of the stem occurs, why?

Function:

1. Meristematic tissues help in the overall growth of plant organs from which other tissues develop.
2. What type of tissue is responsible for the growth in length of the stem and root?
3. What type of tissue is responsible for the increase in width of the stem and root?

Activity: Take two glass jars of the same size. Next, pour water into each jar. Now take two bulbs of onion more or less the same size and put one in each jar. The fibrous roots of the bulb in one jar i.e. jar No. lisas such, but the roots of the bulb on the second jar are trimmed with the help of a scissor. The roots of both bulbs are submerged in water. Observe the growth of roots of two onion bulbs note down your observation and mention the reasons behind it.

Permanent Tissue

Permanent Tissue Definition: The tissue in the plant body which have lost the power of division is called permanent tissue.

Characteristic Features :

1. Intercellular space may be present in between the cells
2. Cells may or may not contain protoplasm and, hence may be living or dead.
3. The cell wall is made up of cellulose and may be thin or thick
4. Cells are matured and have no power of division
5. Vacuoles are present.

Types Of Permanent Tissue: Permanent tissue is classified into two broad types, namely:

Simple tissue: Example Parenchyma, Collenchyma and Sclerenchyma and

Complex tissue: Example Xylem and Phloem.

Simple permanent Tissue :

Simple permanent Tissue Definition: Tissue consisting of only one type of cells (homogenous) forming uniform and mass performing the same function is called simple permanent tissue.

Types of simple tissue: According to the shape of the cell, there are three types such as parenchyma, collenchyma and sclerenchyma.

Parenchyma

Parenchyma Definition: Simple permanent tissue with thin-walled living cells are parenchyma.

Characteristic features: The living cells are oval to round in shape, thin-walled and with intercellular spaces.

• The cells contain central vacuole and starch granules in their cytoplasm.
• Cells contain abundant cytoplasm with a prominent nucleus. Parenchyma cells with chloroplasts are called chlorenchyma,
• which helps in photosynthesis and cells with abundant air cavities in between are called aerenchyma. Air cavities filled up with gases help the aquatic plants float.

Distribution: Parenchyma tissue forms the ground tissue of plants and occupies large portions of plant bodies. They are present in the cortex, pith, medullary rays, epidermis of roots and stems, mesophyll tissue of leaves, the pulp of fruits, embryos, the endosperm of seeds and Parenchyma. in the conducting tissues like the xylem and phloem.

Parenchyma  Functions :

1. Helps in manufacturing food by photosynthesis. Parenchyma contains chlorophyll is called chlorenchyma (as in leaf) whereas parenchyma containing air is called aerenchyma (as in lotus).
2. They function as storage tissue by storing starch (reserve food).
3. When associated with conducting tissues like the xylem and phloem, they help in the transportation of water and food matters. In turgid conditions, they provide support to delicate parts.

Collenchyma Definition: Simple permanent tissue walls whose cells are unevenly thickened by additional cellulose deposition, are called collenchyma. ,

Characteristic Features: The living cells are closely packed, and elongated in shape, with thickenings at their corners due to uneven deposition of cellulose. Cells have no intercellular spaces in between. The cells contain chloroplast and appear to be polygonal in cross-section.

Distribution: Collenchyma is present below the epidermis of dicot stems and also in the stalk of flowers pedicel and stalk of leaf, petiole, leaf blades.

Collenchyma Functions :

1. Provides mechanical support to plant organs.
2. Collenchyma cells containing chloroplastids can prepare food by photosynthesis.
3. The cells are responsible for providing flexibility and plasticity and also give strength to the plant parts.

Sclerenchyma Definition: Simplepermanenttissuewhose cells contain thick uniformly hard lignified walls, and are dead are called sclerenchyma.

Characteristic Features: The tissue comprises two types of cells—Sclerenchyma fibres and Sclereids or Stone cells.

Sclerenchyma fibres: Long, narrow cells with pointed ends, uniformly thickened lignified walls, and small openings (pits) are called sclerenchyma fibres. At maturity, the cells die due to loss of protoplast. Cross section of fibres shows angular cells e.g., fibres of hemp, flax, and jute are sclerenchyma fibres, fibres are present in the vascular tissues of root, stem and leaf. Cotton fibre is not sclerenchyma fibre but they are outgrowth a cross-section, of the epidermis of the seed coat.

Difference between Parenchyma and Collenchyma :

Difference between Collenchyma and Sclerenchyma :

Difference of Parenchyma, Collenchyma and Sclerenchyma :

Sclereids or Stone cells: Spherical, or oval cells with unevenly very thickened walls are called sclereids or stone cells. They are shorter in size with many pits on their walls. Walls of sclereids are hard and lignified, also called stone cells or grit cells.

Distribution: Sclerenchyma fibres are present in the hypodermis and the vascular tissues and sclereids are present in the fruit wall of guava, pears, etc. seed coats, and the bark of trees and leaves.

Sclereids or Stone cells Functions:

• Provides rigidity and strength to plant parts.
• The tissue also helps in withstanding stress and strains.

Things To Remember

1. The structural and functional unit of life is called ceil.
2. A complex of cells of common origin (Fahn, 1967) is called tissue.
3. One type of immature cells which possess the power of division is called meristematic tissue.
4. The type of meristem present at the apices of stems and roots of vascular plants is called apical meristem. ‘
5. Sclerenchyma is a dead simple tissue.
6. Parenchyma cells containing chlorophyll are called chlorenchyma.
7. The parenchyma containing the air cavity is called aerenchyma.

Complex Permanent tissue :

Complex Permanent Tissue Definition: Tissue made up of two or more cell (heterogeneous) types is called complex tissue.

Types of Complex Tissue: The Xylem and Phloem are the two types of complex tissues, also called conducting tissues or vascular tissues and together they form vascular bundles.

Xylem

Xylem Definition: The complex permanent tissue associated with the conduction of water and mineral salts in vascular plants is called the xylem.

Types: The Xylem is a complex tissue as it consists of different types of cells, both living and non-living, namely Tracheid, Trachea or Xylem vessels, Xylem parenchyma or Wood parenchyma and Xylem fibre or Wood fibre.

1. Tracheid: Elongated dead cells, tubular and with tapering end walls.
2. Trachea or Xylem vessels: Elongated dead cells, tubular but with no end walls and joined end to end forming a continuous pipe, are trachea or vessels. The cells are thick and lignified.
3. Xylem parenchyma or Wood parenchyma: The living parenchyma cells of xylem tissue are called xylem parenchyma or wood parenchyma. The cells may be thin or thick-walled. This is the only living tissue of xylem.
4. Xylem fibre or Wood, fibre: Thick-walled fibre like sclerenchyma fibres forming components of xylem tissue are xylem fibres or wood fibres.

Distribution: Xylem is present in the vascular bundles of higher plants.

Functions :

1. The xylem helps in the transportation of water and solutes unidirectionally called the ascent of sap.
2. Acts as supportive tissue, imparting mechanical strength to the plant body, (iii) Helps in the storage of water and mineral salts.
3. All xylem elements take part in the Conduction of water and mineral salts except one, can you ^ name that element?

Phloem

Phloem Definition: A phloem is complex permanent vascular tissue responsible for transporting food in a plant body.

Types: The components of the phloem are the Sieve tube, Companion cells, Phloem fibres or Bast fibres and Phloem parenchyma.

1. Sieve tube: Elongated tube-like living cells arranged in a row, with their perforated end walls forming a sieve. The cells are non-nucleated and their protoplasts are interconnected through sieve plates. They possess vacuolated cytoplasm. . .
2. Companion cell:  Elongated, lens-shaped cells containing dense cytoplasm and prominent. nuclei are companion cells. Cells maintain a connection with sieve cells through pits.
3. Phloem fibre or Bast fibre:  Elongated fibres like sclerenchymatous dead cells with thick walls containing pits and interlocked ends, are phloem fibres or bast fibres. Jute fibres are bast fibres.
4. Phloem parenchyma: Living thin-walled parenchyma cells associated with phloem are called phloem parenchyma.

Distribution: Phloem occurs in the vascular bundles of higher plants, forming conducting or vascular tissue.

Things to Remember:

• The xylem is a dead complex tissue.
• The only living component of the Xylem is the Xylem parenchyma.
• Pholem is a complex food-conducting system of vascular plants.
• Sieve tubes of phloem are living cells without nuclei.
• Jute fibre is the bast fibre of Phloem.

Functions :

1. Conduction of food by sieve tubes of phloem both in upward and downward directions
2. Storage of organic food matters,
3. Lateral translocation of food by the companion cells.

Know The Fact: Out of the four elements of phloem, only the sieve tubes have the power of bidirectional movement of food matters.

Activity:

The figure shows a transverse section of a sunflower stem. Observe the section and note down the different tissues composing every layer in a notebook. Then observe each type of tissue element present within the section

Difference between Xylem and Phloem :

Animal Tissue

The multicellular animal body is made up of many cells. In most cases, one type of cell is closely packed together and serves the same general function. All these cells form tissues.

Classification Of Animal Tissue:

Epithelial Tissue

Epithelial Tissue Definition: The tissue which acts as covering material over the internal (hollow organs) and external surfaces of the body is known as epithelial tissue.

Classification (Types) of Epithelial Tissue: Epithelial tissues are classified into two main divisions depending on the number of cell layers. These are (a) simple epithelial tissue and (b) stratified epithelial tissue.

• Simple epithelial tissues or Simple epithelium: The hardest epithelial tissue is the enamel of the tooth. Enamel is the hardest substance in the body. It is harder than bone.
• Simple epithelial tissue: Simple epithelial tissue is composed of a single layer of cells, present on a thin basement membrane (composed of loose connective tissue). Based on the shape of cells

Compound epithelial tissues or Stratified epithelium :

Stratified epithelium stratified epithelial tissue or compound epithelium is composed of many layers of cells. Depending on the shape of the constituting cells and structural arrangements this variety of tissue is sub-divided into the following types

1. Stratified squamous cornified: Found in the skin and helps to protect from injury (Cornified means layers of epithelial tissue to form a horny structure).
2. Stratified squamous nom cornified: Found in the cornea, mouth, pharynx, etc. and helps to afford mechanical protection.
3. Stratified cubical: Found in the pharynx, epiglottis etc.
4. Stratified columnar ciliated: Found in the soft palate, some stratified cubical epithelium parts of the larynx, etc.

Do you know that the horn of the Rhinoceros is a bunch of modified highly keratinised hair? The spine on the body of a Porcupine is modified hair.

Connective Tissue

Connective Tissue Definition: The tissue which serves the important function of connecting the various tissues and organs of the body or supporting the functionally active structures is known as connective tissue.

Classification ( Types) of Connective Tissue :

Muscular Tissue

Types of Muscular Tissue:

• So, Striated muscle or skeletal muscle is voluntary
• Unstriated muscle or smooth muscle is involuntary.

Do you know ‘titin’ protein in muscle is the largest known protein in animals

Nervous Tissue

Do you know, that neurons can not divide after birth? Then, how does the brain grow with increasing age?

Do you know what is the chemical nature of Nissl’s granules in neurons?

In the cyton of neuron RER (Rough Endoplasmic Reticulum), a cluster of ribosomes forms granular substances called Nissl’s granules.

Major Organs Of The Human Body And Their Function

Major Organs Definition: A distinct and differentiated part of the body of an organism, formed of one or more types of tissues, that performs one or more specialized functions is called an organ. Some common examples of organs in the human body are the eye, ear, lungs, heart etc. The human body is formed of all four types of animal tissue epithelial, connective, muscular and neural.

Thus the sequence of aggregation in the body of a multicellular animal (Example: human) may be as follows:

The Positions of Different Organs in Man and Two Major Functions of Each Organ :