Category: Biology Second Paper

The process by which the cell nucleus or karyon divides is called karyokinesis. Mitosis cell division refers to karyokinesis. In 1879, Strasburger and Schleicher discovered the division of the nucleus and named it karyokinesis. Karyokinesis is divided into five stages.

Mitosis is derived from the Greek word Mitos meaning twisted thread. The process in which the nucleus and cytoplasm of the original cell divides to form two daughter cells and the chromosome number of the daughter cell is equal to the number of chromosomes of the mother cell is called mitosis. Because the number and quality of chromosomes of the offspring cells created in this process are similar to the mother cells, it is called equational division.

 

Discovery and naming

In 1973, the scientist Strasburger was the first to observe the creation of a nucleus from a nucleus. In 1873 Polish scientist Waclaw Mayzel observed cell division in frog, rabbit and cat corneas and described it in 1875. In 1855, the scientist Rudolf Virchow first explained that new cells are formed by division from previous cells. In 1879, scientist Snyder gave a complete description of the process of mitosis. Mitosis was named by scientist Walter Fleming in 1882. In 1960 Cockraum & Mac-Caulay explained the chemical nature of mitosis cell division. Scientist Walter Whitman called the division of cytoplasm as cytokinesis.

 

Mitosis is a characteristic of cell division

1. Mitosis Cell division occurs in body cells of organisms.
2. It occurs in haploid, diploid and polyploid cells.
3. In this process, two daughter cells are formed from each mother cell.
4. In this process the nucleus and chromosomes of the cell divide once.
5. The chromosome number of the resulting daughter cell is equal to the chromosome number of the mother cell.
6. Wound healing and necessary cell regeneration is done through mitosis cell division.
7. Mitosis cell division occurs in all unicellular and multicellular organisms.
8. In this process the division of the nucleus first and then the cytoplasm takes place.
9. The development and growth of various organs of the organism takes place in the process of mitosis.
10. Mitosis occurs in the formation and growth of the genitalia.
11. Mitosis occurs due to cytokines, steroids, lymphokines, EGF, PDGF etc.
12. The number of cells increases in the process of mitosis.
13. Mitosis causes the cell to increase in size.

Where does mitosis occur?

1. All embryonic cells divide into multicellular organisms by the process of mitosis.
2. The development and growth of various organs of the organism takes place in the process of mitosis.
3. All organelles in multicellular organisms divide by mitosis.
4. Mitosis takes place in the stem tip, root tip, embryonic root, flower bud, primary bud, developing leaf, cambium etc. region of the growing plant.
5. Mitosis occurs in the formation and growth of the genitalia.

 

Mitosis causes cell division

1. Mitosis cell division takes place to fill the wound in any part of the body.
2. Mitosis cell division occurs when the cell has more cytoplasm than nucleus.
3. Mitosis cell division occurs when the amount of DNA in the cell is high.
4. Mitosis accelerates cell division as protein synthesis occurs in the cell.
5. Mitosis Cell division occurs when there is more RNA than DNA in the cell.
6. Cell division is induced by cytokinins, steroids, lymphokines, EGF, PDGF etc.
7. Mitosis Cell division occurs to increase the number of cells.
8. Mitosis Cell division occurs to increase cell size.
9. Different types of metabolism take place in cells. Cell division is necessary for carrying out metabolism.
10. Nucleo-cytoplasmic ratio is maintained through cell division.

 

Why Mitosis is called Equivalent Division

Mitosis occurs in the body cells of organisms. Somatic cells have a diploid number of chromosomes. In this process two cells are formed from one cell. Both the cell nucleus and the chromosomes divide once in the process of mitosis. The resulting daughter cells resemble the mother cells. The chromosome number of the daughter cell is equal to the chromosome number of the mother cell. Hence, mitosis is called symmetrical division.

The word Mitochondria is formed from the Greek word mitos meaning thread and chondrion meaning grain. Mitochondria means filamentous grains. The energy producing organelles located in the cytoplasm are called mitochondria. It is called Power House as it provides the necessary energy for cells.

 

Discovery and naming of mitochondria

In 1850, the Swiss scientist A.V. Kolliker noticed tiny organelles in insect muscle cells and named them sarcosomes. He is called the discoverer of mitochondria. In 1882 W. Fleming observed filamentous mitochondria and named them Fila. In 1890, Altman named it Bioplast. Mitochondria was named by Carl Benda in 1898. In 1904, Frederick Mavis was the first to observe mitochondria in the plant cell Nymphaea alba. In 1957 scientist Philip Siekevitz coined the term Power House of the cell. Modern scientists call mitochondria semi-autonomous cells. They also called it electrosome. Mitochondria are also known as chondriosomes and plasmosomes. Mitochondria of birds’ flight muscles are called sarcosomes.

 

All true cells contain mitochondria. Stem cells, progenitor cells, and red blood cells do not contain mitochondria.

In shape it is round, rod, oval, star or coil shape.

Mitochondria make up 20% of cell volume. Mitochondria are typically 3-40 microns in length and 0.2-2.0 microns in diameter. Rod mitochondria are 9 microns in length and 0.5 microns in width. Circular mitochondria are 40-70 microns in length. Circular mitochondria are 0.2-2.0 microns in diameter.

 

Number of mitochondria

Each cell has an average of 300-400 mitochondria. Advanced plant cells contain 100-3000 mitochondria. Liver and kidney cells contain 1000 or more mitochondria. Human sperm has 20 mitochondria. A sea urchin egg has 140,000 mitochondria, an amphibian egg has 300,000, and an Amoeba has 500,000. Mammalian red blood cells do not contain mitochondria.

Origin of Mitochondria

There are three theories about the origin of mitochondria.

1. De novo origin: According to this theory, amino acids and lipids combine to form mitochondria. This doctrine is not accepted at present.
2. Cell membrane or endoplasmic origin: According to scientist Morison (1966), vesicles are formed from endoplasmic reticulum or cell membrane and mitochondria are formed from vesicles. This doctrine is now defunct.
3. Mitochondrial origin: According to this theory, during cell division, old mitochondria divide to form new mitochondria. The new mitochondria quickly change shape and move to other parts of the cell. It grows rapidly and divides to increase the number of cells to meet more energy.

Structure of Mitochondria

1. Membrane: Each mitochondrion is covered by a bilayered membrane. Outer cover and inner cover. The outer layer is called the outer layer and the inner layer is called the inner layer. The outer coat is smooth and the inner coat is rough. Each coat is 40–60 Å thick. The outer end of the mitochondrial membrane is called the H-face and the inner end is called the C-face. The outer membrane contains porin proteins and acts as a transporter. The space between the two membranes is called the perimitochondrial space. The distance of perimitochondrial space is 6-8 nm. It is composed of lipoproteins. It gives the mitochondria specific shape and protects them from external injury.
2. Chambers: Mitochondria have two types of chambers. Outer chamber and inner chamber. The compartment between the outer and inner envelope is called the outer compartment and the compartment between the inner envelope is called the endocompartment (70 Å wide). It is filled with various chemicals.
3. Matrix: The jelly-like substance inside the cell is called matrix. It is dense, homogenous and full of enzymes and co-enzymes.
4. CRISTIE: The inner membrane of the mitochondria folds inwards to form a number of finger-like extensions. It’s called Christy. The space between each cristae is called the intercristi space.
5. Oxysome or F1 Cells: Mitochondria have numerous fine granules like tennis bats on the inner envelope. These are called oxisomes or F1 cells. It consists of head, stem and base. There are two types of oxisomes. Sabrintak and Abrintak. The oxisomes which have a stalk are called stalked oxisomes and the oxisomes which do not have a stalk are called unstalked oxisomes. It has ATP-ase enzyme in its head.
6. ETS: Electron Transport System is abbreviated as ETS. It is called ETC (Electron Transport Chain). Christy has ETS on him. It transfers electrons from one place to another.
7. ATP-Synthases: All substances that synthesize ATP are called ATP-Synthases. Christy has spherical or oval ATP-synthases. It produces ATP.
8. mDNA: Each mitochondrion contains circular double-stranded DNA. These DNAs have their own characteristics. It is called mitochondrial DNA. It is self-reproducing. Human mDNA contains 37 genes.
9. Ribosomes: Mitochondria contain 70S ribosomes. It is called mitoribosomes. It synthesizes enzymes for cells.

 

Chemical structure of mitochondria

1. Protein: About 65% of the dry weight of mitochondria is protein. It contains both soluble and insoluble proteins.
2. Lipids: Mitochondria contain about 35% lipids. Of this, 90% are phospholipids and 10% are fatty acids and carotenoids. It contains glycerides 29%, lecithin and cephalin 4% and cholesterol 2%. Its inner membrane contains phospholipid called cardiolipin.
3. Pigments: Contains small amounts of carotenoids.
4. Nucleic acid: It contains DNA and RNA as nucleic acids. Each mitochondrion contains about 200 pieces of DNA. It contains 5% RNA.
5. Enzymes: It contains about 100 types of enzymes and co-enzymes.

 

Function of Mitochondria

1. Respiration Process: Krebs cycle and electron transport system of respiration process are completed in mitochondria. It is called mitochondrial respiration as it takes place in the mitochondria.
2. Energy production: ATP is produced in mitochondria. ATP is the source of energy.
3. Protein production: Mitochondria make proteins for the cell.
4. Nucleic acid production: It makes DNA and RNA. It plays a role in heredity.
5. Blood cell and hormone production: It helps in blood cell and hormone production.
6. Contains enzymes: It contains enzymes and co-enzymes required for respiration.
7. Ion balance: They maintain the correct concentration of calcium ions in different parts of the cell.
8. Metabolism: It metabolizes neurotransmitters and cholesterol or fat.
9. Control of apoptosis: Mitochondria control cell apoptosis.
10. Heredity: Mitochondria help in the formation of sperm and egg.
11. Energy regulation: It regulates the storage and release of energy in cells. ADP is converted into ATP and stored in the body by creating high energy bonds.
12. Cation storage: Mitochondria store Ca2+, S2+, Fe2+, Mn2+ etc.
13. Heat production: Mitochondria help in the production of excess heat in hibernating animals.
14. Production of chemical compounds: Mitochondria are capable of creating, breaking down and producing substances necessary for the cell. It produces compounds like cytochrome, ferridoxine, hemoglobin, chlorophyll, steroids, alkaloids etc.
15. Biosynthesis: It causes biosynthesis of iron and steroids in cells.
16. Transport: It is capable of active transport of calcium, potassium etc.
17. Disinfection: It participates in ammonia disinfection.
18. Pathogenesis: Mutations can occur in mitochondrial DNA that cause mitochondrial disorders. 100 such disorders are known. In old age, diseases like Parkinson’s, Alzheimer’s, type-1 diabetes etc. can occur. Proper health is dependent on the structure and function of mitochondria.

 

Mitosis occurs in the body cells of organisms. Somatic cells have a diploid number of chromosomes. In this process two cells are formed from one cell. Both the cell nucleus and the chromosomes divide once in the process of mitosis. The resulting daughter cells resemble the mother cells. The chromosome number of the daughter cell is equal to the chromosome number of the mother cell. Hence, mitosis is called symmetrical division.

1. Mitosis cell division takes place to fill the wound in any part of the body.
2. Mitosis cell division occurs when the cell has more cytoplasm than nucleus.
3. Mitosis cell division occurs when the amount of DNA in the cell is high.
4. Mitosis accelerates cell division as protein synthesis occurs in the cell.
5. Mitosis Cell division occurs when there is more RNA than DNA in the cell.
6. Cell division is induced by cytokinins, steroids, lymphokines, EGF, PDGF etc.
7. Mitosis Cell division occurs to increase the number of cells.
8. Mitosis Cell division occurs to increase cell size.
9. Different types of metabolism take place in cells. Cell division is necessary for carrying out metabolism.
10. Nucleo-cytoplasmic ratio is maintained through cell division.

1. All embryonic cells divide into multicellular organisms by the process of mitosis.
2. The development and growth of various organs of the organism takes place in the process of mitosis.
3. All organelles in multicellular organisms divide by mitosis.
4. Mitosis takes place in the stem tip, root tip, embryonic root, flower bud, primary bud, developing leaf, cambium etc. region of the growing plant.
5. Mitosis occurs in the formation and growth of the genitalia.

1. Mitosis Cell division occurs in body cells of organisms.
2. It occurs in haploid, diploid and polyploid cells.
3. In this process, two daughter cells are formed from each mother cell.
4. In this process the nucleus and chromosomes of the cell divide once.
5. The chromosome number of the resulting daughter cell is equal to the chromosome number of the mother cell.
6. Wound healing and necessary cell regeneration is done through mitosis cell division.
7. Mitosis cell division occurs in all unicellular and multicellular organisms.
8. In this process the division of the nucleus first and then the cytoplasm takes place.
9. The development and growth of various organs of the organism takes place in the process of mitosis.
10. Mitosis occurs in the formation and growth of the genitalia.
11. Mitosis occurs due to cytokines, steroids, lymphokines, EGF, PDGF etc.
12. The number of cells increases in the process of mitosis.
13. Mitosis causes the cell to increase in size.

In 1973, the scientist Strasburger was the first to observe the creation of a nucleus from a nucleus. In 1873 Polish scientist Waclaw Mayzel observed cell division in frog, rabbit and cat corneas and described it in 1875. In 1855, the scientist Rudolf Virchow first explained that new cells are formed by division from previous cells. In 1879, scientist Snyder gave a complete description of the process of mitosis. Mitosis was named by scientist Walter Fleming in 1882. In 1960 Cockraum & Mac-Caulay explained the chemical nature of mitosis cell division. Scientist Walter Whitman called the division of cytoplasm as cytokinesis.

Mitosis is derived from the Greek word Mitos meaning twisted thread. The process in which the nucleus and cytoplasm of the original cell divides to form two daughter cells and the chromosome number of the daughter cell is equal to the number of chromosomes of the mother cell is called mitosis. Because the number and quality of chromosomes of the offspring cells created in this process are similar to the mother cells, it is called equational division.

The word Chloroplast is derived from the Greek word chloros meaning green. Chloroplast means green cell. Chloroplasts are the largest green colored organelles in the cytoplasm that produce sugary food in the process of photosynthesis. It is green in color because it contains more green pigment called chlorophyll. It is called the cell’s kitchen, carbohydrate food factory and energy conversion organ. A.F.W Schimper first observed it in plant cells in 1883 and named it chloroplast. Julius von Sachs (1832-1897), the father of plant physiology, discovered chloroplasts.

Location of chloroplasts

Green leaves, young green stems, unripe fruits, green shoots etc. contain chloroplasts in palisade cells. C3 plants have granulated chloroplasts. C4 plants have granulated and non-granulated chloroplasts.

Number of chloroplasts

Each cell contains one or more chloroplasts. Its number is 10-40 in higher plant cells. Spirogyra has 1-16 chloroplasts and Chara has hundreds of chloroplasts. Each cell of Mnium has 106 and Ricinus communis plant has 400,000 chloroplasts per square millimeter.

 

Size and shape Chloroplast

The lens-shaped chloroplasts of higher plant cells are 3-5 microns in diameter. Spiral chloroplasts of Spirogyra are longer than the length of the cell.

Chloroplasts of algae are more diverse. In higher plant cells, chloroplasts are lens-like. Chloroplasts vary in shape in lower class plant cells. Spiral (Spirogyra), star-shaped (Zygnema), cup-shaped (Chlamydomonas), round (Pithophora), reticulate (Oedogonium), ribbon or ring-like (Ulothrix) etc.

 

Origin of Chloroplast

In lower plants, old chloroplasts divide to form new chloroplasts. They originate from primitive plastids in higher plants. In the presence of sunlight, the original plastid transforms into a mature chloroplast. In the absence of sunlight, chloroplasts transform into leucoplasts.

 

Structure of Chloroplast

1. Membrane: Each chloroplast is covered by a bilayer membrane. Outer cover and inner cover. The outer layer is called the outer layer and the inner layer is called the inner layer. The space between the two coats is called the periplastidal space. Distance of periplastidal space is 6-8 nm. The outer coat contains porin proteins. Chloroplast membranes contain glycosyl glycerides instead of phospholipids. It gives specific shape to chloroplast and protects it from external injury.
2. Stroma: The transparent, granular and semi-fluid material inside the chloroplast is called stroma. It is a colloidal and hydrophilic liquid. The stroma contains about 200 DNA, RNA and circular DNA or plasmids. It contains protein plastogaebuli, osmophilic granules, sugar, oil droplets, vitamins, mineral salts etc. The stroma contains glucose-forming enzymes and a variety of rubisco enzymes. C3 and C4 cycles occur in the stroma.
3. Thylakoid: The sac-shaped three-dimensional structure in the stroma is called thylakoid. It is called the structural and functional unit of chloroplast. Its width is 100-300 Å. Thylakoid membranes contain photosystem-I, photosystem-II, various types of electron carriers, ATP-ase enzymes etc. Inside the thylakoid cells are chlorophyll-a, chlorophyll-b, carotenoids, xanthophylls and enzymes. These elements together look like crystalline grains. Then they are called quantosomes.
4. Granum: 10-100 thylakoids arranged in a row forming a stack is called granum. Some quantosomes are present on the inner surface of the granum cycle membrane. Each chloroplast contains 40-60 grana. Each granule is 0.3-1.70 microns in size.
5. Stroma lamellae: Two adjacent thylakoids are connected by ducts called stroma lamellae or intergranular frets. Stroma lamellae contain chlorophyll.
6. ATP Synthase: The round or oval object in the thylakoid membrane is called ATP synthase. It contains enzymes for making ATP. It makes ATP for cells.
7. Photosynthetic Unit: Photosynthetic units are present on the thylakoids. It is called photosynthetic unit. Each photosynthetic unit contains 300-400 molecules of chlorophyll-a, chlorophyll-b, carotene and xanthophyll. It contains various enzymes, phospholipids, sulfolipids, metal ions, quinones, etc. Photosynthetic units absorb light energy and cause photophosphorylation.
8. DNA: Chloroplasts contain short and circular DNA. DNA has its own characteristics. This is called chloroplastic DNA. Each chloroplast contains 200 cpDNA. Without cpDNA, photosynthesis cannot occur in chloroplasts.

The chloroplast genome consists of 120–160 kb. It consists of inverted duplicate repeats. It contains the coding sequence of 120 types of proteins.

9. Ribosomes: Chloroplasts contain 70S ribosomes. It synthesizes proteins.
10. Unidentified granules: Chloroplasts contain some unidentified granules. Nothing is known about their nature and function yet.

 

Chemical Structure of Chloroplast

1. Protein: About 35-55% of the dry weight of chloroplasts is protein. Of this, insoluble protein is 80% and soluble protein is 20%.
2. Lipids: 10-20% of the dry weight of chloroplasts are lipids. Among them, phospholipids are the most.
3. Dyes: It contains 6-12% dyes. Among them 75% chlorophyll-a, 25% chlorophyll-b, carotene, xanthophyll etc.
4. Nucleic acid: Chloroplast contains 5% nucleic acid. Nucleic acids are DNA and RNA.
5. Mineral Salt: It contains 3% mineral salt. Mineral salts are high in magnesium. Besides, ion and copper are worth mentioning.
6. Carbohydrates: Chloroplasts do not contain specific amounts of carbohydrates. It is always changing. Starch is its simple carbohydrate.

 

Importance of Chloroplast

1. Energy conversion: Chloroplast is the only converter of solar energy in the living world. Chloroplasts convert solar energy into chemical energy.
2. Food production: Chloroplast is the only green organelle present in the plant body. It produces sugary food in the process of photosynthesis. As a result, the food needs of the living world are met.
3. Protein production: 70S ribosomes are present in chloroplasts. It synthesizes proteins. So plants that have more chloroplasts produce more protein.
4. Nucleic acid production: Nucleic acid is the most essential element of the organism. Chloroplasts play an important role in making nucleic acids. Nucleic acid acts as the container and carrier of heredity in organisms.
5. Cytoplasmic heredity: Cytoplasmic heredity is a hot topic in modern research. Chloroplastic DNA of cells plays an important role in cytoplasmic inheritance. Heredity holds its own characteristics.
6. Photophosphorylation: Chloroplast produces ATP by combining ADP and Pi in the presence of sunlight. This process is called photophosphorylation. ATP stores and supplies energy.
7. Photorespiration: Photorespiration or light respiration takes place in the chloroplasts of plants. In this process, oxygen is taken in and carbon dioxide is released. Photolysis is a harmful process.
8. Photolysis: Photolysis occurs in chloroplasts. In this process, H2O is broken down to produce O2.
9. Carbon dioxide fixation: Carbon dioxide fixation occurs in the chloroplast quantum. This phenomenon occurs in the light neutral phase of photosynthesis.
10. Stored material: Enzymes, co-enzymes, DNA, RNA, sugars, proteins, fats etc. are stored in the matrix of chloroplasts.
11. Production of phosphoglyceric acid: It uses absorbed energy to produce 3-carbon phosphoglyceric acid from 6-carbon sugars.

 

Role of chloroplasts in food production

Chloroplast is the only green organelle present in the plant body. It produces sugary food (glucose) in the process of photosynthesis.

1. Ribulose 1, 5 bisphosphate reacts with atmospheric CO2 to form 3-phosphoglyceric acid.
2. 3-phosphoglyceric acid is then converted to 1,3-bisphosphoglyceric acid.
3. 1, 3 Bisphosphoglyceric acid produces 3-phosphoglyceraldehyde and dihydroxyacetone phosphate.
4. Fructose 1, 6 bisphosphate is produced from 3-phosphoglyceraldehyde.
5. Fructose 1,6 bisphosphate is converted to fructose 6-phosphate.
6. Glucose 6-phosphate is produced from fructose 6-phosphate
7. Glucose/food is produced from glucose 6-phosphate.

 

Ecological importance of chloroplasts

1. Chloroplasts of green plants produce O2 during photosynthesis. Plants and animals take in O2 and release CO2 in the process of respiration. As a result, the atmosphere of the environment is purified.
2. Green plants release water vapor in the process of respiration. This water vapor condenses and forms precipitation.
3. Plants provide shade and keep the environment cool. It makes the living environment happy.
4. Green gardens and meadows create a unique environment.
5. Green plants increase soil fertility.
6. High chloroplast content in plants increases fruit and crop production. As a result, the food demand is met. In this orderly condition prevails in the living environment.
7. Green grass is used as animal feed. Cattle consuming green grass have higher milk and meat production capacity.
8. Green algae produce large amounts of oxygen in the water of ponds, reservoirs, rivers, seas and oceans. It keeps the water environment clean.
9. Green chlorella is used to keep the bathing environment clean. Chlorella algae produce oxygen.
10. Green forests meet demand for wood and fuel. Necessary furniture is made from wood.