Plant Cell

Plant cell are photosynthetic eukaryotic cells. There are the members of the kingdom Plantae. Characterized by cellulosic cell walls, plastids, and the ability to perform photosynthesis. These are also the significant features that differentiate them from animal cells. Plant cells also possess a large central vacuole surrounded by a tonoplast membrane. This vacuole helps in osmoregulation and acts as a site of storage.

History

Plant cell was discovered by an English scientist Robert Hooke in 1665 while observing cork under a microscope. He commented that his observation looked similar to cellular or small compartments, thus deriving the name.

Structure of a Plant Cell

A Plant Cell consists of a Cell Wall and a Protoplasm (=Protoplast).

The Protoplasm has subunits,

• Plasma Membrane,
• Cytoplasm, and
• Nucleus.

The cytoplasm is distinguishable into Cytoplasmic Matrix (=Hyaloplasm) and Cell Organelles. 

1. Cell Wall: It is the outer rigid, protective, supportive, and semi-transparent layer covering the Plant Cell. Although non-living, Cell Wall is capable of growth. It comprises Cellulose, Hemicellulose, and Pectin. It is divided into three parts: Middle Lamella, Primary Wall, and Secondary Wall. The cell wall provides shape, rigidity, and protection to a Plant Cell.

2. Protoplasm (=Protoplast): It is the living part of the cell.
   1. Plasma Membrane: Discovered by Shwann in 1838, the term Cell Membrane originally used by Nageli and Cramer in 1855. The plasma membrane is selectively permeable for solutes and semi-permeable for water. It is dynamic, i.e., any injury is repaired in no time. It majorly composes of lipids (20-79%) and proteins (20-70%), and carbohydrates (1-5%). Plasma membranes cause the compartmentalization of cells as they separate the cell from the outer environment and allow it to maintain its Functional individuality. It also regulates the flow of information and materials from one cell to another.
   2. Cytoplasm: The cytoplasm is jelly-like semi-fluid, containing the cytoplasmic matrix, cell organelles, and cell inclusions. The cytoplasmic matrix (the cytosol) is a crystal-colloidal complex comprising 90% water. Various biomolecules, like minerals, sugars, amino acids, vitamins, proteins, enzymes, etc., are suspended in the matrix.
      1. Mitochondria: Mitochondrion (pl. Mitochondria) is a double membranous organelle found in cells of aerobic eukaryotic organisms. Popularly known as the “Powerhouse of the Cell”, it produces ATP by oxidative phosphorylation.
      2. Ribosomes: Ribosomes are giant macromolecules in the cytoplasm, which serve as a site for protein synthesis. They are naked (i.e., not bound by a membrane) with a length of 200-340 A and diameter of 170-240 A and are made up of proteins and RNA. They are popularly called “protein factories.”
      3. Endoplasmic Reticulum: Endoplasmic Reticulum (ER) is a continuous and complex system of interconnected flattened membranous sacs and tubules that runs through the cytoplasm. It divides the cytoplasm into two compartments- luminal (inside the ER) and extraluminal (rest of the cytoplasm). It provides mechanical support by Serving as a skeletal framework and producing various proteins and lipids.
      4. Golgi Apparatus: Golgi apparatus or Golgi complex is a system of stacks of flattened, membrane-bound sacs, vesicles, and tubules that participate in the transformation, secretion, and production of complex biochemicals.
      5. Lysosomes are small vesicles encloses by a single impermeable membrane. It contains hydrolytic (digestive) enzymes in the form of granules which can be crystalline or semicrystalline. Popularly called “suicide bags” of the cell.
      6. Vacuoles: Non-cytoplasmic compartments enclosed by a membrane
   3. Nucleus: It is a specialized double membranous body that carries all the hereditary information in the form of a genome. It is the control center for cell metabolism and cell differentiation. It is the site of synthesis and/or replication of DNA, RNA, and ribosomes. 

Types of Plant Cells

Plant cells differentiate from undifferentiated meristematic cells:

1. Parenchyma: It is a simple permanent living tissue made up of thin-walled and isodiametric cells. They perform most of the metabolic functions of plants and are the primary site for the storage and synthesis of various organic compounds.
2. Collenchyma: It is a superficial permanent living tissue consisting of non-lignified living cells possessing pectocellulose thickening in specific wall areas. Their primary function is to provide mechanical strength to the plant.
3. Sclerenchyma is a simple, supportive tissue of highly thickened walls. The walls consist of cellulose or lignin, or both. Sclerenchyma is the principal mechanical tissue of the mature plant.
4. Xylem (=Wood): A complex tissue transports water or sap inside the plant. It consists of four cells: tracheids, vessels, xylem (=wood) parenchyma, and xylem (=wood) fibers.
5. Phloem (=Bast): It is a complex tissue that transports food inside the plant. It consists of cells: sieve tubes, companion cells, phloem parenchyma, and fibers.

Difference between Plant Cell and Animal Cell

Functions of a Plant Cell

Green plants are responsible for performing photosynthesis. This is one of the most important processes which ultimately sustains all life on earth. It is an enzyme-regulated anabolic process to Manufacture organic compounds inside chlorophyll-containing cells from carbon dioxide and water with the help of sunlight as the energy source.

Related Topics:

• Difference Between the Cell Membrane and Cell Wall

Questions

1. What is a plant cell?

Plant cells are photosynthetic eukaryotic cells, the members of the kingdom Plantae. They are characterized by cellulosic cell walls, plastids, and the ability to perform photosynthesis.

2. Describe the plant cell wall?

The outer rigid, protective, supportive, and semi-transparent cell wall covers the Plant Cell. Although non-living, Cell Wall is capable of growth. It comprises Cellulose, Hemicellulose, and Pectin and can be divided into three parts: Middle Lamella, Primary Wall, and Secondary Wall. The cell wall provides shape, rigidity, and protection to a Plant Cell.

FAQs