Plant Cells – Definition, Diagram, Structure & Function
The cell is the basic unit of life in all organisms. Plants are also comprised of several cells just like humans and animals. There is a cell wall present around the plant cell that helps in providing shape to the plant cell. Other than the cell wall, some other organelles are there which are in association with different cellular activities.
What is a Plant Cell?
“Eukaryotic cells with a true nucleus that carry out certain specific functions along with specialized structures called organelles.”
Plant cells vary in several fundamental factors from other eukaryotic organisms. Along with similar organelles, both plant and animal cells contain a nucleus. Outside the cell membrane, the presence of a cell wall is one of the distinctive aspects of a plant cell.
Plant Cell Diagram
The plant cell is comparatively larger than the animal cell and is rectangular in shape. 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 studied under an electron microscope, some of these distinctions become apparent.
Plant Cell Structure
Just like different organs within the body, plant cell structure includes various components known as cell organelles that perform different functions to sustain themselves. The components of cell organelles are as follows:
It is a rigid layer which is composed of ignin, cellulose, glycoproteins, pectin, and hemicellulose. It is located outside the cell membrane. It comprises of proteins, polysaccharides, and cellulose.
The cell wall’s primary function is to secure the cell and provide structural support. The plant cell wall also functions to shield the cell against mechanical stress and to provide its shape and structure. It also filters the molecules entering and exiting the cell.
Microtubules direct the forming of the cell wall. It is made up of three layers: primary, secondary, and middle lamellas. Enzymes lay down cellulose to form the primary cell wall.
It’s the semi-permeable membrane that’s found within the cell wall. It is made up of a thin layer of protein and fat.
The cell membrane is responsible for controlling the entry and exit of various substances into and out of the cell.
The cell membrane, for example, prevents toxins from entering the cell while allowing nutrients and essential minerals to pass through.
Only eukaryotic cells have a nucleus, which is a membrane-bound structure. A nucleus’s main job is to store DNA, or hereditary knowledge, which is required for cell division, metabolism, and development.
- Nucleolus: The nucleolus is where the cell’s protein-producing structures and ribosomes are produced.
- Nucleopore: The nucleopore is an opening in the nuclear membrane that allows proteins and nucleic acids to pass through.
They are membrane-bound organelles with their own genetic material. They are required to store starch and to carry out the photosynthesis process. It is also used in the synthesis of several molecules that make up the cell’s building blocks. Some of the vital types of plastids and their functions are stated as follows:
They are found in the non-photosynthetic tissues of plants. They are used for the storage of protein, lipid, and starch.
It is an elongated organelle enclosed by phospholipid membrane. The chloroplast is shaped like a disc and the stroma is the fluid within the chloroplast that comprises a circular DNA. Each chloroplast contains a green coloured pigment known as chlorophyll required for the photosynthesis process. The chlorophyll absorbs light energy from the sun and further use it for transforming carbon dioxide and water into glucose.
They are heterogeneous, coloured plastid which is responsible for pigment synthesis and for storage in photosynthetic eukaryotic organisms. Chromoplasts have red, orange, and yellow coloured pigments which provide color to all ripe fruits and flowers.
It occupies around 30% of the cell’s volume in a mature plant cell. Tonoplast is a membrane that surrounds the central vacuole. The vital function of the central vacuole apart from storage is to sustain turgid pressure against the cell wall. The central vacuole consists of cell sap. It is a mixture of salts, enzymes, and other substances.
They are found in all eukaryotic cells which are involved in distributing synthesized macromolecules to various parts of the cell.
They are the smallest membrane-bound organelles which comprise RNA and protein. They are the sites for protein synthesis, hence, also referred to as the protein factories of the cell.
They are the double-membrane organelles found in the cytoplasm of all eukaryotic cells. They provide energy by breaking down carbohydrate and sugar molecules; hence they are also referred to as the “Powerhouse of the cell.”
Lysosomes are called suicidal bags as they hold digestive enzymes in an enclosed membrane. They perform the function of cellular waste disposal by digesting worn-out organelles, food particles, and foreign bodies in the cell.
Plant Cell Types
Cells of a matured and higher plant become specialized to perform certain vital functions that are essential for their survival. Few plant cells are involved in the transportation of nutrients and water, while others for storing food.
The specialized plant cells include parenchyma cells, sclerenchyma cells, collenchyma cells, xylem cells, and phloem cells.
Following are some of the different types of plant cells:
They are hard or rigid cells, which play a primary role in providing support to the plants when there is restraining growth in a plant due to lack of hardening agent in primary walls.
These cells are more rigid compared to collenchyma cells and this is because of the presence of a hardening agent. These cells are usually found in all plant roots and mainly involved in providing support to the plants.
Parenchyma cells play a significant role in all plants. They are the living cells of plants, which are involved in the production of leaves. They are also involved in the exchange of gases, production of food, storage of organic products, and cell metabolism. These cells are typically more flexible than others because they are thinner.
Xylem cells 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.
Phloem cells are other transport cells in vascular plants. They transport food prepared by the leaves to different parts of the plants.
Plant Cell Functions
Plant cells are the building blocks of plants. Photosynthesis is the major function performed by plant cells.
Photosynthesis occurs in the chloroplasts of the plant cell. It is the process of preparing food by the plants, by utilizing sunlight, carbon dioxide, and water. Energy is produced in the form of ATP in the process.
A few plant cells help in the transport of water and nutrients from the roots and leaves to different parts of the plants.
Important points to remember
i. A plant cell is a eukaryotic cell that contains a true nucleus and certain organelles to perform specific functions. However, some of the organelles present in plant cells are different from other eukaryotic cells.
ii. The different types of plant cells include- collenchyma, sclerenchyma, parenchyma, xylem, and phloem.
iii. The organelles found only in plant cells include- chloroplast, cell wall, plastids, and a large central vacuole. The chloroplasts contain green pigment chlorophyll that is responsible for the process of photosynthesis.
iv. The cell wall of a plant is made up of cellulose. Cellulose is a long, linear polymer of several glucose molecules.
v. Photosynthesis occurs inside the chloroplast of the plant cells. Chloroplast consists of a green pigment called chlorophyll. The light reactions occur within the thylakoids of the chloroplast where the chlorophyll pigment is found.
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