Chapter 2 : Plant Cells



Plant Cells arrow_upward


  • A cell structural and functional unit of life and the fundamental building block of any organism.
  • All cells share similar characteristics and can be defined by the cell theory:
    • All living things are composed of cells
    • All cells arise from pre-existing cells through cell division
    • Cells contain hereditary material, which they pass to daughter cells during cell division
    • The chemical composition of all cells is quite similar
    • The metabolic processes associated with life occur within cells

    Types of Plant Cells arrow_upward


  • Eukaryotic cells that are similar to animal cells
  • As a plant matures, its cells become specialized.
  • There are a number of important specialized types of plant cells. Some examples of specialized plant cells include:
    • Parenchyma cells
    • Collenchyma cells
    • Sclerenchyma cells
    • Water-conducting cells
    • Sieve tube members

    Parenchyma Cells arrow_upward


  • Usually depicted as the typical plant cell because they are not very specialized
  • These cells synthesize and store organic products in the plant.
  • Most of the plant's metabolism takes place in these cells.

  • Collenchyma Cells arrow_upward


  • Have a support function in plants, particularly in young plants
  • Help to support plants while not restraining growth due to their lack of secondary walls and the absence of a hardening agent in their primary walls

  • Sclerenchyma Cells arrow_upward


  • Also have a support function in plants but unlike collenchyma cells, they have a hardening agent and are much more rigid

  • Water Conducting Cells arrow_upward


  • Also have a support function in plants but unlike collenchyma cells, they have a hardening agent and are much more rigid

  • Sieve Tube Members arrow_upward


  • Conduct organic nutrients such as sugar throughout the plant

  • Structure of Plant Cells arrow_upward


  • When you compare a plant cell with an animal cell, you find them to be closely similar except that the animal cell lacks chloroplast and cell wall.
  • A plant cell generally ranges from 10 to 100 micrometers in size.
  • Each cell contains the following organelles:
    • Nucleus
    • Nuclear membrane
    • Cytoplasm
    • Cell membrane
    • Cell wall
    • Plastids
    • Mitochondria
    • Ribosomes
    • Endoplasmic reticulum
    • Golgi apparatus
    • Vacuoles

    Nucleus arrow_upward


  • Supposed to be the most important organelle
  • Carries the genetic information present in this organelle which inherits the physical traits from one generation to another
  • Has a dark stained nucleolus mainly responsible for protein formation
  • Apart from this, the nucleus coordinates all the cell functions and regulates the metabolism of plants.
  • The passage of food and water and the influx of nutrients in and out of the cells are some of the characteristic functions of a plant cell.

  • Nuclear Membrane arrow_upward


  • As the name indicates, this membranous sheath surrounding the nucleus protects it from physical damage.

  • Cytoplasm arrow_upward


  • The ground substance or the matrix which is jelly-like material in which all the cell organelles are embedded and suspended
  • The main cytoplasm function in a cell is to keep all the cell constituents intact.

  • Cell Membrane arrow_upward


  • Similar to a nuclear membrane, the main cell membrane function is to give the cell an appropriate shape and size.
  • This thin membrane is made up of cellulosic fibers and proteins and its main function is transport of materials through cells.

  • Cell Wall arrow_upward


  • Distinguishing part which is not present in animals and mainly responsible for imparting rigidity to the cells
  • Made up of cellulose and provides support and protection to the plant
  • The cell wall material differs with plant species and gives a definite shape (elongated, oval, round, rectangular, squarish).

  • Plastids arrow_upward


  • Another peculiar organelle present in plant cells
  • As mentioned before, plants prepare their own food with a unique process called photosynthesis with the aid of these plastids.
  • The plastids consist of pigments which absorb light and make food.
  • The most common plastid is chloroplast containing the green pigment chlorophyll.

  • Mitochondria arrow_upward


  • Among the largest cell organelles also known as the engine house or the energy house of the cells
  • Provide the energy required for all the cellular activities by breaking down complex carbohydrates prepared during photosynthesis (glucose to energy)

  • Ribosomes arrow_upward


  • The main site for protein synthesis since these are rich in ribonucleic acids
  • Could be bound to the endoplasmic reticulum or free-floating in the cytoplasm

  • Endoplasmic Reticulum (ER) arrow_upward


  • Structure that modifies proteins produced in the ribosomes
  • Not all of the proteins made by ribosomes need changing, but those that do, get altered here.
  • On the basis of presence or absence of ribosome on the surface, two classes of ER can be recognized:
    • Rough endoplasmic reticulum: covered with ribosome, helps to transport materials through the cell and produce proteins
    • Smooth endoplasmic reticulum:  responsible for the production of hormones and secretory products

    Golgi Apparatus arrow_upward


  • The proteins formed and bound by the ER need to be processed so as to perform normal functions.
  • Golgi membranous sacs or dictyosomes chiefly associated with ER release protein chains after processing them.

  • Vacuoles arrow_upward


  • Plant cells are characterized by larger and lesser number of vacuoles and mainly responsible for maintaining the fullness of a cell.
  • An alternative function of these is to store ions, sugars and secondary metabolites.


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