Oracle IAS, the best coaching institute for UPSC/IAS/PCS preparation in Dehradun brings to you UKPCS Science Life Sciences (paper 6)
Characteristics of plants
Plants are multicellular organisms in the kingdom . Plants are multicellular organisms with eukaryotic cells. A eukaryotic cell is a relatively large cell with a true nucleus and other organelles that perform specific functions.
Plants that use photosynthesis to make their own food are autotrophs. They produce their own food. They do so via photosynthesis, which is the process of making nutrients such as sugars from light energy and carbon dioxide.
Plants have an important role in the world’s ecosystems. They produce most of the world’s oxygen, and are important in the food chain, as many organisms eat plants or eat organisms which eat plants. The study of plants is called botany.
Many plants have vascular tissue, such as xylem and phloem, that carries water and nutrients throughout the plant. This is particularly important for plants that grow upwards; water needs to travel from the roots up the stem to the leaves. Vascular tissue is found in more “complex” plants.
Plants reproduce both sexually and asexually and have what is known as alternation of generations. A haploid stage alternates with a diploid stage. Haploid is when cells contain one set of chromosomes, while diploid is when cells contain two sets.
Plant Cell Structures and Organelles
Plant cells are eukaryotic cells, or cells with a membrane-bound nucleus. In addition to having a nucleus, plant cells also contain other membrane-bound organelles (tiny cellular structures) that carry out specific functions necessary for normal cellular operation. Organelles have a wide range of responsibilities that include everything from producing hormones and enzymes to providing energy for a plant cell. Plant cells are generally larger than animal cells. A plant cell also contains structures not found in an animal cell. Some of these include a cell wall, a large vacuole, and plastids. Plastids, such as chloroplasts, assist in storing and harvesting needed substances for the plant.
Structures and Organelles
The following are examples of structures and organelles that can be found in typical plant cells:
- Cell (Plasma) Membrane – a thin, semi-permeable membrane that surrounds the cytoplasm of a cell, enclosing its contents.
- Cell Wall – outer covering of the cell that protects the plant cell and gives it shape.
- Chloroplast – the sites of photosynthesis in a plant cell. They contain chlorophyll, a green pigment that absorbs energy from sunlight.
- Cytoplasm – gel-like substance within the cell membrane containing water, enzymes, salts, organelles, and various organic molecules.
- Cytoskeleton – a network of fibers throughout the cytoplasm that helps the cell maintain its shape and gives support to the cell.
- Endoplasmic Reticulum (ER) – extensive network of membranes composed of both regions with ribosomes (rough ER) and regions without ribosomes (smooth ER). The ER synthesizes proteins and lipids.
- Golgi Complex – responsible for manufacturing, storing and shipping certain cellular products including proteins.
- Microtubules – hollow rods that function primarily to help support and shape the cell. They are important for chromosome movement in mitosis and meiosis, as well as cytosol movement within a cell.
- Mitochondria – these organelles generates energy for the cell by converting glucose (produced by photosynthesis) and oxygen to ATP. This process is known as respiration.
- Nucleus – membrane bound structure that contains the cell’s hereditary information (DNA).
- Nucleolus – structure within the nucleus that helps in the synthesis of ribosomes.
- Nucleopore – tiny hole within the nuclear membrane that allows nucleic acids and proteins to move into and out of the nucleus.
- Peroxisomes – tiny structures bound by a single membrane that contain enzymes that produce hydrogen peroxide as a by-product. These structures are involved in plant processes such as photorespiration.
- Plasmodesmata – pores or channels between plant cell walls that allow molecules and communication signals to pass between individual plant cells.
- Ribosomes – consisting of RNA and proteins, ribosomes are responsible for protein assembly. They can be found either attached to the rough ER or free in the cytoplasm.
- Vacuole – structure in a plant cell that provides support and participates in a variety of cellular functions including storage, detoxification, protection, and growth. When a plant cell matures, it typically contains one large liquid-filled vacuole.
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