Plant cell


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Plant cells are a eukaryotic cell that varies in several fundamental factors from other eukaryotic organisms. Both plant and animal cells contain nucleus along with similar organelles. One of the distinctive aspects of a plant cell is the presence of a cell wall outside the cell membrane. They are comparatively larger than animal cells which are in rectangular shaped.

Cell Structure and Function

Plant cell

Plants have a distinct lifestyle when compared to animals. These differences can be seen only when the cells are examined under the electron microscope. Thus the unique feature of a plant cell can be observed in the above diagram.

Plant cell anatomy

The Cell Wall: It is a rigid layer which is composed of cellulose, glycoproteins, lignin, pectin, and hemicellulose. It is located outside the cell membrane. It comprises of protein, polysaccharides, and cellulose. The primary function of the cell wall is to protect and provide structural support to the cell. Plant cell wall is also involved in protecting the cell against mechanical stress and other infections.

The formation of the cell wall is guided by microtubules.  It consists of three layers the primary, secondary and the middle lamella. The primary cell wall is formed by cellulose laid down by enzymes.

Cell membrane:  It is the semi-permeable membrane present within the cell wall, composed of a thin layer of protein and fat.   The cell membrane plays an important role in regulating the entry and exit of specific substances within the cell.

Nucleus: It is a membrane-bound structure. The vital function of a nucleus is to store DNA or hereditary material which include cell division, metabolism, and growth.

  • Nucleolus: It manufactures cell’s protein-producing structures and ribosomes.
  • Nucleopore: Nuclear membrane is perforated with holes called as nucleopore that allows proteins and nucleic acids.

Plastids: They are membrane-bound organelles that comprise of own DNA. They are necessary to store starch, to carry out the process of photosynthesis and in the synthesis of many molecules that are required for cellular building blocks. Some of the vital types of plastids and their functions are  stated below:

Leucoplasts: They are found in non-photosynthetic tissues of plants. They are used for the storage of protein, lipid, and starch.

Chloroplasts

  • Chloroplasts: It is an elongated organelle enclosed by phospholipid membrane. The shape of the chloroplast is disk-shaped and the stroma is the fluid within the chloroplast that comprises a circular DNA. Each chloroplast contains a green colored pigment called chlorophyll which is involved in the process of photosynthesis. The chlorophyll absorbs light energy from the sun and uses it to synthesize carbon dioxide and water to produce glucose.
  • Chromoplasts: They are heterogeneous,  colored plastids organelle which is responsible for pigment synthesis and for the storage in photosynthetic eukaryotic species.Chromoplasts have red, orange and yellow colored pigments which provide color to all ripen fruits and flowers.The Central Vacuole: It occupies around thirty percent of the cell’s volume in a mature plant cell. Tonoplast is a membrane that surrounds central vacuole. The vital function of central vacuole apart from storage is to sustain maintain turgid pressure against the cell wall. The central vacuole consists of cell sap. It is a mixture of salts, enzymes, and other substances.

    Golgi Apparatus:  They are found in all eukaryotic cells which are involved in the distributing synthesized macromolecules to various parts of the cell.

    Ribosomes: They are the smallest membrane-bound organelle which comprises of RNA and protein. They are the sites for protein synthesis, hence they are also referred as the protein factories of the cell.

    Mitochondria: They are the double-membraned organelles found in the cytoplasm of all eukaryotic cells.  They provide energy by breaking down carbohydrate and sugar molecules, hence they are also referred as the powerhouse of the cell.

    Lysosome: Lysosomes are called as a suicidal bags as they hold digestive enzymes, worn out organelles, food particles and any foreign bodies in the cell.

    Three different types of Plant Cell

    Cells of a matured plant become specialized to perform certain vital functions that are essential for survival. Some plants cells are used for transferring nutrients and for storing food. Beneath are some of the specialized plant cells.

    • Collenchyma Cells: It acts as a supporting system when there is a restraining growth in a plant due to lack of hardening agent in primary walls.
    • Sclerenchyma Cells: These cells are more rigid compared to collenchyma cells. Sclerenchyma cells consist of a hardening agent and their main function is to provide support to the plants.
    • Parenchyma Cells: These cells are used to store organic products in plants.

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Practise This Question

Which of the following organelle have these features?
A.  Large, spherical structure.
B.  Present in almost all eukaryotic cell.
C.  In animal cell it present at the centre of the cell.
D.  In plant cells, it is present at the periphery.