The Plant Cell is the most basic and basic unit of all plants. Plant cells are eukaryotic, which means they have a membrane-bound nucleus and organelles, just like animal cells. That’s all there is to the similarity. In comparison to animal cells, plant cells have cell walls that surround the cell membrane. Except for mechanical and technical requirements, the plant cell wall serves a variety of different activities that are dependent on the plant’s life. Plant cell walls are made up of cellulose, which distinguishes them from other cell walls found in bacteria (peptidoglycan) and fungi (chitin). Plant cells are rectangular in shape and larger than animal cells.
Despite the fact that plant and animal cells are both eukaryotic and share a few cell organelles, plant cells perform different roles than animal cells. When the cells are inspected under an electron microscope, some of these changes become obvious. In this article read more about Plant Cell, Diagram, Functions, and Types.
What is Plant Cell?
The Plant Cell is a eukaryotic cell consisting of a definite nucleus and various membrane and non-membrane bound cell organelles. Plants are multicellular organisms in which the plant cells act as the basic structural and functional units. These cells carry out specific functions in a coordinated manner to bring about various physiological functions like growth, photosynthesis, exchange of gases, transpiration, etc.
Definition of a Plant Cell
“Plant cells are eukaryotic cells with a true nucleus along with specialized structures called organelles that carry out certain specific functions.”
It is rectangular and comparatively more significant than the animal cell. Even though plant and animal cells are eukaryotic and share a few cell organelles, plant cells are quite distinct compared to animal cells as they perform different functions. These differences can be clearly understood when the cells are examined under an electron microscope. Observe the labelled diagram of plant cell structure as given below:
Are Plant Cells Prokaryotic or Eukaryotic?
The cell is the basic structural and functional unit of life in all living organisms. The cells can be divided into two major groups – Prokaryotic and Eukaryotic. The difference between both the cells are explained below:
Prokaryotic cell: Cell without a well-defined nucleus, i.e. cell of bacteria.
Eukaryotic cell: Cell with a well-defined nucleus, i.e. Cells of plants, fungi, animals and protists.
Let us have a detailed look at the plant cell, its structure and the functions of different organelles.
Components of a Plant Cell
The small membrane or non-membrane bound structures that are found in the cytoplasm or cellular matrix of a cell that works in a coordinated manner to maintain the homeostasis of a cell are termed as cell organelles. The structures t are as follows:
Plant Cell Wall
It is a rigid layer that is composed of cellulose, glycoproteins, lignin, pectin and hemicellulose. It is located outside the cell membrane and is completely permeable.
The primary function of a plant cell wall is to protect the cell against mechanical stress and to provide a definite form and structure to the cell. The cell wall consists of four layers namely:
Middle lamella: Outermost cementing layer between the cells, made up of Ca and Mg pectates, absent in outer free spaces and ruptures to create intercellular spaces.
Primary cell wall: Thin, elastic, capable of growing cells and diminishes as the cells mature possess more hemicellulose and less cellulose in their cell wall, only cell wall in meristematic and parenchymatous cells.
Secondary cell wall: Formed by accretion (growth or increase by the gradual accumulation of additional layers or matter). They have more cellulose, found in collenchyma, sclerenchyma and xylem vessels; it is rigid and non-elastic and contains pits at intervals.
Tertiary cell wall: It is present occasionally, purely cellulosic and sometimes contains xylem found in the tracheids of gymnosperms.
Plant Cell Membrane
It is the semipermeable membrane also called the plasma membrane that is present within the cell wall. It is composed of a bilayer of fat having intermediate proteins incorporated as protein channels. The transport of molecules across it is one of the most important functions of plasma membranes.
It is the gelatinous liquid that fills the space inside a cell. It is mainly composed of water, various organic molecules, and salts. Some intracellular organelles, such as the nucleus and mitochondria, are enclosed by membranes that separate them from the cytoplasm.
It is the largest cell organelle and occupies around 90% of the cell’s volume. The outermost membrane of the vacuole is called the tonoplast, which facilitates the transport of a number of ions and other materials against the concentration gradient into the vacuole. The central vacuole consists of cell sap. It is a mixture of salts, enzymes and other substances. Vacuole functions in the storage of substances, maintenance of osmolarity and sustaining turgor pressure.
Plastids in Plant Cell
They are membrane-bound organelles that have their own DNA.
They are necessary to store starch, to carry out the process of photosynthesis.
It is also used in the synthesis of many molecules, which form the building blocks of the cell.
Based on the type of pigment, they are of Plastidsare of three types:
a. Chromoplasts: They are yellow or red in colour due to the presence of carotenoids. They are found in fruits, flowers and leaves.
b. Leucoplasts: They are colourless plastids, which generally occur near the nucleus in non-green cells. They are further of three types depending upon the type of food stored like Amyloplasts that store starch, Aleuroplasts the store proteins and Elaioplasts that store lipids
c. Chloroplasts: These are green coloured plastids containing chlorophylls and carotenoids. These double membranous structures contain thylakoids in their stroma. The stroma also contains enzymes required for the synthesis of carbohydrates and proteins. They are also called the Kitchen of the cell.
Endoplasmic Reticulum (ER)
These are membrane-bound channels, which are seen in the form of a network of delicate strands and vesicles in the cytoplasm. Two basic morphological types of ER are Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER).
SER – Smooth Endoplasmic Reticulum
Ribosomes are absent on the surface of smooth ER. Smooth ER is the major site of lipid synthesis.
RER – Rough Endoplasmic Reticulum
Ribosomes are present on the surface of rough ER. Rough ER is quite common in those cells which are actively involved in protein synthesis. They are extensive and continuous with the outer membrane of the nucleus.
These are the flattened stacks of membranes found within the endomembrane system. They are also called packaging factories of the cell. They help in the formation of the acrosome of sperms and are important sites for the formation of glycoproteins and glycolipids.
It is a spherical or rod-shaped, two-layered granular structure and forms part of the endomembrane system. They are also called the powerhouse of the cell as they are involved in the formation of ATP.
They contain enzymes for peroxide biosynthesis and neutralize the peroxide radicals due to the presence of catalase enzymes. In a plant cell, along with chloroplast and mitochondria, they are involved in photorespiration.
The nucleus is enclosed by a double-membrane nuclear envelope. The space between the two membranes is called the perinuclear space. It is also called the brain or managing centre of the cell.
The nuclear membrane is interrupted by minute pores at various places. These pores provide passage to RNA and protein molecules. The fluid inside the nucleus is called nucleoplasm or nuclear matrix. The nucleoplasm contains nucleolus and chromatin.
The nucleoli are spherical structures. The nucleolus is not a membrane-bound structure. Synthesis of ribosomal RNA takes place in the nucleolus. The nucleus also contains chromatin fibres; which are distinct during some stages of cell division. The chromatin contains DNA and some basic proteins; called histones and some non-histones.
What Makes Plant Cell Unique?
Features or cell organelles that make it different from other eukaryotic cells:
Cell wall made up of cellulose
Different types of plastids
Large central vacuole
Types of Plant Cells and Tissues
There are many types of cells that form six various types of tissues in plants, some of them are:
The cell wall is thin and made up of a homogeneous substance called cellulose. The meristematic tissue formed of meristematic cells occurs in the growing regions of the plant body and contributes to plant growth.
The cell wall is thin and made up of a homogeneous substance called cellulose. It forms the ground tissue, which is the most widely distributed tissue of the plants.
They are hard or rigid cells, as the corner walls are thickened with pectin. They form a living mechanical tissue that helps in providing support.
These cells are more rigid compared to collenchyma cells and this is because of the presence of a hardening agent. These cells form the part of dead mechanical tissue and fibres.
Xylem is a tissue that is formed of four different types of cells, i.e. tracheids, xylem vessels, xylem fibres and xylem parenchyma. They are the transport cells in vascular plants. They help in the transport of water and minerals from the roots to the leaves and other parts of the plants. The movement of water is unidirectional.
Phloem is a tissue that is formed of four different types of cells, i.e. companion cells, sieve tubes, phloem parenchyma and phloem fibres. They transport organic food prepared by the leaves to different parts of the plants. The movement of organic food is bidirectional.
Plant Cell Functions
The building block of plants is known as Plant Cells and Photosynthesis is one of the significant functions performed by them. Photosynthesishappens in the chloroplasts of the plant cell. Photosynthesis is the process of preparing food by plants on their own with the help of sunlight, carbon dioxide and water.
Difference Between Plant Cell and Animal Cell
The plant cell is rectangular and comparatively larger than the animal cell. Even though plant and animal cells are eukaryotic and share a few cell organelles, they are quite distinct when compared to animal cells as they perform different functions. Some of these differences can be clearly understood when the cells are examined under an electron microscope.
Students can read about the major difference between plant cells vs animal cells as explained in the table below.
The cell wall is present
The cell wall is absent
Chloroplast is present
Chloroplast is absent
Vacuoles are large and can occupy 90% of cell space
Vacuoles are small or absent
The endoplasmic reticulum and nucleus is compact
The endoplasmic reticulum and nucleus is enlarged and occupy the majority of cell space
Cells connected by plasmodesmata
Cells connected by desmosomes
Centrioles are absent
Centrioles are present
Plastids are present
Plastids are absent
Cilia and microvilli are absent on the cell surface
Cilia and microvilli are present on the cell surface
Plant Cell and Animal Cell Diagram
Students can check below the diagram of plant and animal cells, which can help them in understanding how to draw a cell diagram concept.
Q.1. When will a plant cell protoplasm shrink? Ans: When a plant cell is placed in a hypertonic solution, water will move outside the plant cell, i.e. exosmosis takes place. This exosmosis causes shrinkage of protoplasm, i.e. plasmolysis of a cell takes place.
Q.2. How to make a model of a plant cell diagram step by step procedure? Ans: The plant cell diagram can be checked above and on a similar pattern the diagram can be created.
Q.3. Why do plant cells possess large-sizedvacuoles? Ans: Vacuole functions in the storage of substances, maintenance of osmolarity and sustaining turgor pressure.
Q.4. Who discovered the plant cell? Ans: In 1665, Robert Hooke discovered the plant cell in the cork of a plant. He observed the cell walls of these cells and called them small, uniform compartments.
Q.5. Which is the largest cell organelle present in a plant cell? Ans: Vacuoles are the largest cell organelles as it occupies 90% of the cell volume.
Q.6. What is a plant cell? Ans: The Plant Cell is a eukaryotic cell made up of a definite nucleus and various membrane and non-membrane bound cell organelles. Plants are multicellular organisms, in which these cells act as the basic structural and functional units. These cells carry out specific functions in a coordinated manner to bring about various physiological functions like growth, photosynthesis, exchange of gases, transpiration, etc.
Q.7. When will a plant cell burst? Ans: When this cell is placed in a hypotonic solution, water will enter inside the plant cell, i.e. endosmosis takes place. This endosmosis causes an increase in turgor pressure of the cells, which generate pressure on the cell wall. The excessive increase in this turgor pressure causes cells to burst.
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