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.

Amitosis is formed from the Greek words a meaning not, mito meaning thread and osis meaning state. The process in which a cell directly produces two daughter cells without any complex medium is called amitosis. Walter Flemming first used the term amitosis in 1882. In 1955 scientist Remak first observed amitosis cell division in red blood cells of chick embryos. Amitosis occurs in cells such as bacteria, yeast, amoeba, nostoc, cartilage of vertebrates, embryo membrane, endosperm of seeds etc.

Process of Amitosis cell division
At the beginning of amitosis, cells take in food and grow in size. Its nucleus is also enlarged. The nucleus enlarges and takes the shape of a dumbbell. The cytoplasm of the cell folds inwards. The nucleus then divides into two fragments. The cytoplasm folds further inward. Later the cytoplasm changes into two cells with nucleus
Significance of Amitosis
1. Amitosis is simple cell division process.
2. This process gave rise to complex and advanced cell division.
3. It increases the number of cells rapidly.
4. Lower organisms multiply in this manner.
5. It is very effective in the rapid growth of unicellular organisms.

The name Nucleus is derived from the Latin word Nux-nut. The dense, opaque and spherical organelle located in the protoplasm of the cell which carries the genetic material and controls the vital functions of the cell is called the nucleus. It is also called the nucleus, nucleus and brain of the cell. It is the largest cell organelle.

Dutch scientist Anthony von Leeuwenhoek was the first to observe the lumen or nucleus in the red blood cells of salmon. In 1831, Robert Brown discovered the nucleus from Rasna leaves. In 1882, scientist Strasburger gave the idea of ​​nucleoplasm. In 1953, scientist J. Hammerling sheds light on the function of hereditary characteristics of the nucleus.

Normally each cell has a nucleus. However, cells of Vaucheria, Botrydium, Sphaeroplea, Penicillium, Opalina, Osteoclasts and Paramecium are more numerous. Multinucleated plant cells are called sinocytes. Animal cells with multiple nuclei are called syncytium. Stem cells, stem cells and mammalian red blood cells (except camels) do not have a nucleus. Nucleus may occupy 10-15% of cell space. About 90% of sperm are nuclei.

The nucleus is usually round. But can be ellipsoidal, flattened, fusiform (rounded), toothed etc. Spherical nucleus is one micron in diameter. Cells with more cytoplasm have larger nuclei and cells with less cytoplasm have smaller nuclei.

 

Structure of Nucleus

The parts of the nucleus are:

1. Nuclear membrane or envelope: The membrane that covers the nucleus is called nuclear membrane or nuclear membrane. It is called the envelope, nucleolemma or karyotheca. The nuclear membrane is bilayered. Outer cover and inner cover. It is composed of phospholipids. The space between the two envelopes is called the perinuclear space. The distance between perinuclear spaces is 10-15 nm. Blisters originating from within the nuclear envelope are called nuclear blisters. The nuclear membrane contains nucleoplasmin. Nucleoplasmin mediates the exchange of various substances.

Function: The main function of the envelope is to separate the nucleoplasm, nucleolus and chromatin from the cytoplasm. Endoplasmic reticulum keeps the nucleus connected. Necessary materials transport from inside to outside and from outside to inside.

2. Nuclear Pore: The nuclear envelope consists of octagonal pores. These pores are called nuclear pores. Nuclear membrane has 300 pores. The number of nuclear pores per square micrometer is 40-145. The hole-to-hole distance is 1500 Å. The diameter of each pore is 9 nm. The pores are constricted and expanded by a protein network.

The nuclear pore contains the annulus. The annulus contains 8 granular edge proteins. Peripheral proteins are linked by spokes. At the center of the nuclear pore is a large protein called a transporter. The transporter is attached to the envelope by anchor proteins. Proteins can consist of subunits and fibers. Inside the nucleus is a fibrous cage. Proteins are attached to the fiber cage. Peripheral proteins associate with the transporter to form a wheel-like structure.

Function: It maintains contact with the cytoplasm and transports materials. The product passes through the nuclear pores into the cytoplasm.

3. Nucleoplasm: The clear, granular and jelly-like semi-fluid substance inside the nuclear membrane is called nucleoplasm or karyolymph. It is called protoplasmic juice or nucleo juice of nucleus. It is mainly composed of proteins. It contains DNA polymerase, RNA polymerase, phosphoprotein, histone protein, nucleotide triphosphatase, nucleoside phosphorylase, kinase, dehydrogenase, endonuclease, lipid and mineral salts.

Function: It contains nucleolus and chromosomes. Helps in various biological functions. The nucleoplasm serves as the main site of enzyme activity.

4. Nucleolus: The dense, bright and spherical material seen inside the nucleus is called nucleolus. Each nucleolus consists of three parts. Pars Amorpha, Nucleonima and Matrika. The surrounding part of the nucleolus is called pars amorpha, the central part is called nucleonema and the liquid part inside is called matrix. It is attached to a chromosome called the organizer. The location of the chromosome where the nucleolus is attached is called the SAT or satellite. Nucleolus contains DNA, RNA, proteins, lipids, enzymes, phosphorus, sulphur, potassium etc. In 1781, the scientist Felice Fontana first observed the nucleolus. Nucleolus was named by Bowman in 1840. The SAT gene located on the satellite of the chromosome plays a direct role in the production of nucleolus. Cells that do not synthesize proteins do not have a nucleolus. Spermatozoa, red blood cells and white blood cells do not contain nucleolus.

Function: Nucleolus synthesizes different types of RNA. It synthesizes and stores proteins. It acts as a storehouse of nucleotides. It creates ribosomes.

5. Chromatin: The fine thread-like structure found inside the nucleus is called nuclear reticulum or chromatin fibers. The unit of chromatin is the nucleosome. A necklace-like structure formed by enclosing histone proteins is called a nucleosome. Each human cell contains about 3×107 nucleosomes. It is called chromatin because it contains some basic color (fluorescent color) when the cell is stained. Chromatin is characterized by two regions due to its ability to absorb color. Euchromatin and Heterochromatin. The darker colored denser region of chromatin is called heterochromatin and the lighter colored less dense region is called euchromatin. Chromatin is divided into thick and short sections called chromosomes. Each chromatin contains DNA, histone proteins and non-histone proteins.

Function: Chromatin contains DNA. It acts as a carrier and carrier of hereditary characteristics. It plays a key role in the variation and mutation of organisms.

Function of Nucleus

1. Biological function: The nucleus is called the brain of the cell. It controls all biological functions of cells.
2. Heredity: DNA molecules present in chromosomes control the heredity of organisms.
3. Protein synthesis: Nucleolus forms ribosomes and ribosomes make proteins.
4. Metabolism: Nucleus is the organelle that regulates cell metabolism.
5. Regulation of enzyme activity: Nucleoplasm serves as the main site of enzyme activity.
6. Variation and mutation: It causes variation and mutation in organisms. As a result, evolution takes place in the living world.
7. Metabolism: The nuclear membrane acts as a medium of exchange. It exchanges essential substances between cytoplasm and nucleoplasm.
8. Cell division: It plays an important role in cell division.
9. Differentiation: Nucleus controls cell differentiation during embryonic development.
10. Shape the cell: The nuclear membrane forms the various structural components of the cytoplasm. These elements help in cell shape.

 

Role of nucleus in the growth of organisms

1. The nucleus is called the brain of the cell. It controls all biological functions of cells. It also regulates the growth of organisms.
2. Nucleolus forms ribosomes and ribosomes make proteins. These proteins make up the organism’s body.
3. The nucleus is the cell’s metabolic control organelle. It boosts the metabolism of organisms and helps in growth.
4. The nucleoplasm serves as the main site of enzyme activity. Nucleus promotes growth of organisms by regulating enzyme activity.
5. The nucleus carries out the exchange of essential substances. These substances help in cell growth.
6. Nucleus controls cell mitosis cell division. The number of body cells increases in the process of mitosis. Physical growth of the organism occurs when the number of body cells increases.

 

Role of nucleus in reproduction of organisms

1. Nucleus controls cell mitosis cell division. Genitalia of multicellular organisms are formed in the process of mitosis. Participates in reproductive work.
2. Nucleus controls cell meiosis cell division. In the process of meiosis, sperm and ovum are formed from the generative mother cells. Participates in sperm and egg production.
3. Nucleus Cell Mitosis causes cell division. Mitosis plays an important role in cell division. Roots are produced by vegetative propagation by cuttings, layering, grafting etc. of plants.

Role of nucleus in the heredity of organisms

1. Nucleus helps cell meiosis in cell division. In the process of meiosis, sperm and ovum are formed from the generative mother cells. Sperm and egg play a major role in heredity through sexual intercourse.
2. Nucleus contains chromosomes. Chromosomes contain DNA. DNA acts as the container and carrier of heredity. It carries hereditary characteristics. It transfers the characteristics of the parent to the offspring.

 

 

1. Amitosis is simple cell division process.
2. This process gave rise to complex and advanced cell division.
3. It increases the number of cells rapidly.
4. Lower organisms multiply in this manner.
5. It is very effective in the rapid growth of unicellular organisms.