Category: Biology Second Paper

The varied colors of flower petals depend on pigments such as anthocyanins and betacyanins. Anthocyanins are a group of several complex compounds. It is incorporated into the cells as a glycoside. The color of the flower changes when the pH of the soil changes. If the pH of the soil is acidic, the color of the flower is red, if the pH is alkaline, the color of the flower is blue, and if the pH is neutral, the color of the flower is purple or dark blue.

Plastids are formed from important chemical compounds used in cells. Protocells and plastids have evolutionary similarities in origin. They both have double-stranded circular DNA. Plastids are thought to have originated from some endomitotic cyanobacteria. About 1.5 million years ago such mitosis evolved and made true cells photosynthetic.

Plastids are divided into three types based on the pigment content. These are-

1. Leucoplast : Greek word Leuco means colorless. Colorless plastids are called leucoplasts. In presence of light it can transform into chromoplast or chloroplast. It can be semicircular, rectangular or cylindrical in shape. Leucoplasts are found in plant roots, lower stems, seeds, dividing tissues, gametes etc. Polytoma algae contain leucoplasts. There are three types of leucoplasts. These are-

(i) Amyloplast : The leucoplasts that store starchy food are called amyloplasts. Amyloplasts are present in plants like rice, wheat, potato, bhutra, barley, cown etc.

(ii) Elioplast: The leucoplasts that store fatty food are called elaioplasts. Plants like mustard, coconut, Chinese almond, soybean, linseed etc. contain elaioplast.

(iii) Aleuroplast: All leucoplasts that store protein food are called aleuroplast or proteinoplast. Chickpeas, peas, kesari and lentils contain aleuroplasts.

2. Chloroplast: Greek word Chloros means green. Green colored plastids are called chloroplasts.
3. Chromoplast : Greek word Chroma means colored. Plastids of color other than green are called chromoplasts. It is colored due to carotene and xanthophyll. Chromoplasts probably evolved from chloroplasts. Flower petals, colored fruits and seeds, and carrots contain chromoplasts. Insects are attracted to the colors of flowers and leaves and help in pollination. Different types of chromoplasts are-

(i) Carotenoplast: The orange colored chromoplast is called carotenoplast. Monica Sánchez flowers, bignonia flowers and carrots contain carotenoids.

(ii) Rhodoplast : Red colored chromoplast is called rhodoplast. Rhodoplasts are present in spp.

(iii) Pheoplast: Yellow-brown colored chromoplast is called pheoplast. Diatoms and brown algae contain pheoplasts.

(iv) Xanthoplast: Yellow colored chromoplast is called xanthoplast. Dandelion flower, sunflower flower, golden flower, ginger flower, marigold flower, ripe fruit skin contain xanthoplast.

Greek word Chroma means colored. Plastids of color other than green are called chromoplasts. It is colored due to carotene and xanthophyll. Chromoplasts probably evolved from chloroplasts. Flower petals, colored fruits and seeds, and carrots contain chromoplasts. Insects are attracted to the colors of flowers and leaves and help in pollination. Different types of chromoplasts are-

(i) Carotenoplast: The orange colored chromoplast is called carotenoplast. Monica Sánchez flowers, bignonia flowers and carrots contain carotenoids.

(ii) Rhodoplast : Red colored chromoplast is called rhodoplast. Rhodoplasts are present in spp.

(iii) Pheoplast: Yellow-brown colored chromoplast is called pheoplast. Diatoms and brown algae contain pheoplasts.

(iv) Xanthoplast: Yellow colored chromoplast is called xanthoplast. Dandelion flower, sunflower flower, golden flower, ginger flower, marigold flower, ripe fruit skin contain xanthoplast.

Greek word Leuco means colorless. Colorless plastids are called leucoplasts. In presence of light it can transform into chromoplast or chloroplast. It can be semicircular, rectangular or cylindrical in shape. Leucoplasts are found in plant roots, lower stems, seeds, dividing tissues, gametes etc. Polytoma algae contain leucoplasts. There are three types of leucoplasts. These are-

(i) Amyloplast : The leucoplasts that store starchy food are called amyloplasts. Amyloplasts are present in plants like rice, wheat, potato, bhutra, barley, cown etc.

(ii) Elioplast: The leucoplasts that store fatty food are called elaioplasts. Plants like mustard, coconut, Chinese almond, soybean, linseed etc. contain elaioplast.

(iii) Aleuroplast: All leucoplasts that store protein food are called aleuroplast or proteinoplast. Chickpeas, peas, kesari and lentils contain aleuroplasts.

Almost all plant cells contain plastids. Photosynthetic bacteria and blue-green algae have chromatophores. Fungi, myxomycetes and most bacteria do not have plastids.

In 1883, A.F.W Schimper first observed green colored plastids in plant cells and named them chloroplasts. In 1883, scientist Meyer described green plastids as autoplasts and other colored plastids as trophoplasts. In 1886 scientist Haeckel first used the term plastid. In 1923, scientists provided information about the location and function of plastids in female plant cells.

The Greek word plastikas means molded. The ovoid, plate-shaped, ribbon-shaped or star-shaped organisms located in the cytoplasm of plant cells are called plastids. It is the largest organelle in the cytoplasm. Fungi and bacteria do not have plastids, but do have chromatophores. Blue green algae or cyanobacteria (BGA) contain chlorophyll in their thylakoids. Animal cells do not have plastids.

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.

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.