Plant Cells: Definition, Diagram, Structure & Function

Diagram of 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.

Definition

Plant cells are the basic unit of life in organisms of the kingdom Plantae. They are eukaryotic cells, which have a true nucleus along with specialized structures called organelles that carry out different functions. Plant cells have special organelles called chloroplasts, which create sugars via photosynthesis. They also have a cell wall that provides structural support.

Overview of Plant Cells

Animals, fungi, and protists are made of at least one eukaryotic cell. In contrast, bacteria and archaea are made up of a single prokaryotic cell. Plant cells are differentiated from the cells of other organisms by their cell walls, chloroplasts, and central vacuole.

Chloroplasts are organelles that are crucial for function. These are the structures that carry out photosynthesis, using the energy from the sun to produce glucose. In doing so, the cells use carbon dioxide, and they release oxygen.

Other organisms, such as animals, rely on this oxygen and glucose to survive. Plants are considered autotrophic because they produce their own food and do not have to consume any other organisms. Specifically, plant cells are photoautotrophic because they use light energy from the sun to produce glucose. Organisms that eat plants and other animals are considered heterotrophic.

Plant Cells vs. Animal Cells

Plant and animal cells are both eukaryotic cells, meaning they possess a defined nucleus and membrane-bound organelles. They share many common features, such as a cell membrane, nucleus, mitochondria, Golgi apparatus, endoplasmic reticulum, ribosomes, and more.

However, they have some apparent differences. Firstly, plant cells have a cell wall that surrounds the cell membrane, whereas animal cells do not. Plant cells also possess two organelles that animal cells lack: chloroplasts and a large central vacuole.

These additional organelles allow plants to form an upright structure without the need for a skeleton (cell wall and central vacuole), and also allow them to produce their own food through photosynthesis (chloroplasts).

Plant Cell Diagram

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, plant cells 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.

Parts of a Plant Cell

The plant cell has many different features that allow it to carry out its functions. Each of these structures, called organelles, carry out a specialized role.

Animal and plant cells share many common organelles, which you can find out more about by visiting the “Animal Cell” article. However, there are some specialized structures in plant cells, including chloroplasts, a large vacuole, and the cell wall.

Chloroplasts

Chloroplasts are specialized organelles found only in plants and some types of algae. These organelles carry out the process of photosynthesis, which turns water, carbon dioxide, and light energy into nutrients from which the plant can obtain energy. There can be over one hundred chloroplasts in certain plant cells.

Chloroplasts are disk-shaped organelles that are surrounded by a double membrane. The outer membrane forms the external surface of the chloroplast and is relatively permeable to small molecules,

Between the outer and inner membrane is a thin intermembrane space that is about 10-20 nanometers wide.

Vacuoles

Plant cells are unique in that they have a large central vacuole. A vacuole is a small sphere of plasma membrane within the cell that can contain fluid, ions, and other molecules. Vacuoles are essentially just large vesicles. They can be found in the cells of many different organisms.

However, plant cells characteristically have a large vacuole that can take up anywhere from 30% to as much as 90% of the total cell volume.

The central vacuole of a plant cell helps maintain its turgor pressure, which is the pressure of the contents of the cell pushing against the cell wall. A plant thrives best when its cells have high turgidity, and this occurs when the central vacuole is full of water.

Cell Wall

The cell wall is a tough layer found on the outside of the plant cell that gives it strength and also maintains high turgidity. In plants, the cell wall contains mainly cellulose, along with other molecules like hemicellulose, pectin, and lignins. The composition of the plant cell wall differentiates it from the cell walls of other organisms.

For example, fungi cell walls contain chitin, and bacterial cell walls contain peptidoglycan. These substances are not found in plants. Importantly, the main difference between plant and animal cells is that plant cells have a cell wall, while animal cells do not.

Plant Cell Types

There are five types of tissue formed by plant cells, each with different functions. Parenchyma, collenchyma, and sclerenchyma are all simple plant tissues, meaning they contain a single cell type. In contrast, xylem and phloem contain a mixture of cell types and are referred to as complex tissues.

• Parenchyma tissue represents the majority of cells in a plant. They are found in leaves and carry out photosynthesis and cellular respiration, along with other metabolic processes. They also store substances like starches and proteins and have a role in plant wound repair.
• Collenchyma tissue provides support to growing parts of a plant. They are elongated, have thick cell walls, and can grow and change shape as a plant grows.
• Sclerenchyma tissue contains hard cells that are the main supporting cells in the areas of a plant that have ceased growing. Sclerenchyma cells are dead and have very thick cell walls.
• Xylem cells transport mostly water and a few nutrients throughout a plant, from the roots to the stem and leaves.
• Phloem cells transport nutrients made during photosynthesis to all parts of a plant. They transport sap, which is a watery solution high in sugars.

FAQs:

Plant cells are eukaryotic cells present in green plants, photosynthetic eukaryotes of the kingdom Plantae. Their distinctive features include primary cell walls containing cellulose, hemicelluloses and pectin, the presence of plastids with the capability to perform photosynthesis and store starch.

Phloem cells transport nutrients made during photosynthesis to all parts of a plant. They transport sap, which is a watery solution high in sugars.