Plant Cells – Definition, Diagram, Structure and Function
Oct 28, 2022, 16:45 IST
A basic unit of life in all organisms is the cell. Like humans and animals, plants also consist of several cells. A plant cell is surrounded by the cell wall, which is involved in creating the shape of the plant cell. In addition to the cell wall, other organelles are associated with various cellular activities.
Let’s take a look at the plant cell, structure, and the functions of various plant cell organelles.
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What is Plant Cell?
Plant cells are eukaryotic cells that differ in different fundamental factors from the other eukaryotic organisms. Both plant cells and the animal cells contain a nucleus along with the organelles. One of the distinctive aspects of the plant cell is the presence of the cell wall present outside the cell membrane.
Plant Cell Diagram
A plant cell is rectangular and relatively more significant than an animal cell. Although plant and animal cells are eukaryotic and share several cell organelles, plant cells are quite different compared to animal cells because they perform other functions. Some of these differences can be easily understood when cells are examined under an electron microscope.
Plant Cell Structure
Like different organs in the body, the structure of plant cells includes different components known as cell organelles that perform various functions to sustain themselves. These organelles include:
Cell Wall
It is a rigid layer that consists of the polysaccharides cellulose, pectin and hemicellulose. It is located outside the cell membrane. It also contains polymers and glycoproteins such as cutin, suberin or lignin. A primary function of a cell wall is to protect and to provide structural support to the cell.
A plant cell wall is involved in protecting the cell against the mechanical stress and also providing shape and structure to the cell. It also filters molecules passing in and out. Cell wall formation is controlled by microtubules. It consists of three layers i.e., primary, secondary, and middle lamellae. A primary cell wall is made of cellulose deposited by enzymes.
Cell membrane
It is a semi-permeable membrane that is present inside the cell wall. It consists of a thin layer of protein and fat. The cell membrane plays an essential role in regulating the entry and exit of specific substances in the cell. For example, the cell membrane prevents toxins from entering while nutrients and essential minerals are transported.
Nucleus
A nucleus is a membrane-bound structure that is only present in eukaryotic cells. A vital function of the nucleus is to store the DNA or hereditary information needed for cell division, metabolism, and growth.
- Nucleolus: Makes cell structures that produce proteins and ribosomes.
- Nucleopore: The nuclear membrane is perforated with openings called nucleopores that allow the passage of proteins and nucleic acids.
Plastids
They are membrane-bound organelles that have their own DNA. They are necessary for the storage of starch and for carrying out the process of photosynthesis. It is used in the synthesis of many molecules that form the building blocks of the cell. Some of the vital types of plastids and their functions are listed below:
Leukoplasts
They are found in non-photosynthetic plant tissue. They are used to store proteins, lipids, and starch.
Chloroplasts
It is an elongated organelle enclosed by a phospholipid membrane. The chloroplast is disc-shaped, and the stroma is the fluid within the chloroplast that contains the circular DNA. Each of the chloroplast contains a green pigment called chlorophyll necessary for the process of photosynthesis. Chlorophyll absorbs light energy from the sun and uses it to convert carbon dioxide and water into glucose.
Chromoplasts
They are heterogeneous, colored plastids responsible for pigment synthesis and storage in photosynthetic eukaryotic organisms. Chromoplasts have red, orange, and yellow pigments that give color to all ripe fruits and flowers.
Central vacuole
In a mature plant cell, it occupies approximately 30% of the cell volume. A tonoplast is a membrane that surrounds the central vacuole. In addition to storage, the vital function of a central vacuole is to maintain the turgor pressure against a cell wall. The central vacuole consists of cell sap. It is a mixture of salts, enzymes, and other substances.
Golgi apparatus
They are usually found in all the eukaryotic cells, which are also involved in distributing synthesized macromolecules to different parts of the cell.
Ribosomes
They are the smallest membrane-bound organelles that contain RNA and protein. They are the sites for protein synthesis, that is why they are also known as cell protein factories.
Mitochondria
They are double-membrane organelles found in the cytoplasm of all the eukaryotic cells. They provide energy by breaking down carbohydrates and sugar molecules, that is why they are also known as the “powerhouse of the cell.”
Lysosome
Lysosomes are also known as suicide bags because they contain digestive enzymes in a closed membrane. It fulfills the function of disposal of the cellular waste by digesting worn-out organelles, food particles, and foreign bodies in the cell. In plants, vacuoles take over the role of lysosomes.
Types of Plant Cell
The cells of mature and higher plants are specialized to perform certain vital functions necessary for survival. Few plant cells are involved in transporting nutrients and water, while others are interested in food storage. Specialized plant cells include sclerenchyma cells, parenchyma cells, xylem cells, collenchyma cells, and phloem cells.
Below are some of the different types of plant cells:
- Collenchyma Cells
They are hard or rigid cells that provide support to plants when stunted due to a lack of toughener in the primary walls.
- Sclerenchyma cells
These cells are rigid compared to collenchyma cells, and this is due to the presence of a hardener. These cells are generally found in all plant roots and are mainly involved in providing support to plants.
- Parenchymal cells
Parenchyma cells play an important role in all plants. They are living plant cells that participate in the formation of leaves. They are also involved in gas exchange, food production, storage of organic products, and cellular metabolism. These cells are usually more flexible than the others because they are thinner.
- Xylem cells
Xylem cells are transport cells in vascular plants. They help transport water and the minerals from the roots to the leaves and other plant parts.
- Phloem Cells
Phloem cells are the other transport cells in vascular plants. They transport the food prepared by the leaves to the different parts of the plant.
Plant Cell Functions
A plant cells are the building blocks of the plants. Photosynthesis is the primary function of plant cells. Photosynthesis takes places in the chloroplasts of a plant cell. It is the process of making food by plants using sunlight, carbon dioxide, and water. Energy is produced in the form of ATP. Several plant cells help transport water and nutrients from the roots and leave them in different parts of the plant.
Frequently Asked Question (FAQs)
Q1. What is unique about plant cells?
Ans. The Plant cells have three unique structures which set them apart from the other eukaryotes, such as animal cells: the cell wall, vacuoles, and plastids. Plant cells are microscopic (0.01 to 1.0 mm).
Q2. Do all plants have plant cells?
Ans. A basic unit of all plants is the plant cell. Plant cells, like animal cells, are eukaryotic, meaning they have a membrane-bound nucleus and organelles.
Q3. What are the different types of a plant cell?
Ans. The different types of plant cells include- sclerenchyma, collenchyma, parenchyma, xylem, and phloem.
Q4. What is the composition of the plant cell wall?
Ans. A cell wall of a plant is usually made up of cellulose. A cellulose is a long, linear polymer of several glucose molecules.
Q5. Which cell is the longest cell?
Ans. Neurons
Q6. Do plant cells have collagen?
Ans. Though plants don’t make collagen, they have their own type of supportive extracellular structure: the cell wall.
