Plant Cell: Its 6 Main Parts and Their Functions
Chemical Composition of a Plant Cell
The cell is the fundamental unit of the structure of life. It is responsible for fore initiating, directing, regulating, and coordinating all life-sustaining chemical reactions. To do all these, a cell is made up of even smaller, often membrane-bound parts.
What is the chemical composition of a cell? The table below gives the average composition of living matter. The table shows that living matter consists of both organic and inorganic substances.
Percent By Weight
Carbohydrates and others
The inorganic compounds in cells are water and mineral solids. The organic compound in cells are proteins, fats, and carbohydrates. The others mentioned in the table refer to very important compounds in cells called nucleotides and nucleic acids.
Two nucleic acids are deoxyribose nucleic acid or deoxyribonucleic acid (DNA) and ribose nucleic acid or ribonucleic acid (RNA). DNA was found to be the genetic material. It is responsible for the passing on of hereditary traits from parents to offspring. The principal role of RNA is the synthesis of proteins.
The table also shows that living matter is mostly water. This water is found mostly in the cytoplasm. The table shows that the most abundant organic matter of the cell is protein. Proteins are the building materials of cells.
Main Parts of a Plant Cell Structure
The figure above shows the different parts of a plant cell. The main parts of a plant cell are:
- Cell membrane
- Cell Wall
- Large, or many vacuoles
In addition to these three, animal cells, on the other hand, also have the following parts:
1. Plastids (Chloroplasts)
Chloroplasts are easy to find and observe. They are "chlorophyll-bearing plastids." Plastids are cellular structures of a plant cell that generally hold pigments. Plants have other kinds of plastids besides chloroplasts. For instance, one kind of plastid called chromoplastid contains two types of pigments: carotene, which gives cream, white, yellow, orange, and red colors and xanthophylls, which give bright yellow and brown colors. Not all plant pigments are located inside plastids. For instance, anthocyanin, a purple pigment, is dissolved in the cytoplasm.
Functions of Plastids
- Plastids provide color to flowers and fruits.
- Plastids help in the storage of food such as starch, oil, and proteins.
- Plastids have many essential metabolic pathways that are important for plant growth and development.
- Plastids trap solar energy that is essential for the food manufacturing process of photosynthesis.
- Plastids maintain the balance between oxygen and carbon dioxide.
2. Cell Wall
The cell wall of plant cells is made up of cellulose. This is a carbohydrate with a long chain of sugars linked together. Most animals cannot digest cellulose. When we eat vegetables and fruits, the cellulose part passes out the food tube without undergoing digestion.
The cell wall differs from the cell membrane in at least three ways. First, it is made of a combination of fat, protein, and carbohydrate molecules. Second, it is relatively rigid, while the cell membrane is elastic. Its rigidity permits the plant cells to maintain their shape. Third, it does not participate in the activities of the cell while the cell membrane does.
Functions of Cell Walls
- Cell walls provide structure to a plant cell.
- Cell walls protect the plant cell.
- Cell walls act as filters on molecules passing in and out of the cell.
- An example of a cell wall is cellulose. Cellulose, a complex sugar, is a structural carbohydrate that protects the structure of the plant cell.
Vacuoles are parts of a plant cell that are commonly observed in the structure of plant cells. They are large in mature plant cells. They are fewer and smaller in young plant cells. The liquid inside a vacuole is known as a cell sap. This is water with dissolved substances such as salts, sugars, and organic acids.
Functions of Vacuoles
- Vacuoles act as a storage area for materials and wastes in a plant cell.
- Vacuoles maintain the pressure within the plant cell.
- Vacuoles, just like cell walls, provide structure and protection on the growing plant.
- Vacuoles act as decomposers of complex molecules.
- Vacuoles store water.
4. Cell Membrane
The cell membrane consists of a double layer of fats and proteins. It is elastic. The elasticity of the cell membrane is due to the structure of protein molecules. They are relatively long molecules that can easily be folded. The cell membrane is also differentially permeable. By this, we mean that it permits some substances to pass through readily, others slowly, and others not at all. For instance, gases and alcohol pass through the cell membrane rapidly. Water passes through it fast but not as fast as gases and alcohol. The large molecules of proteins, fats, and carbohydrates do not pass through it at all. They have to be broken down or digested first before they can pass through the cell membrane.
Simply sugars, fatty acids, glycerol, and amino acids pass through the cell membrane slowly. Inorganic salts, acids, and bases pass through the cell membrane very slowly. Although the large molecules of proteins, carbohydrates, and fats normally do not pass through the cell membrane, they can enter some cells through the process involving an active movement of the cell membrane. The cell membrane, being elastic, forms a pocket at the site where the protein molecule is found. The pocket grows deeper and deeper, bringing with it the protein molecule. The membrane is cut off, and a vacuole is formed within the cell with the protein molecule and a little fluid enclosed in a membrane. This process is known as pinocytosis. It is similar to how an amoeba takes in food. A food vacuole, containing the food particle and a little water, is formed in the cell.
Functions of Cell Membrane
- The cell membrane allows a plant cell to regulate oxygen.
- The cell membrane allows a plant cell to regulate sugar.
- The cell membrane allows a plant cell to regulate enzymes inside.
- The cell membrane allows a plant cell to regulate proteins and hormones.
- The cell membrane keeps harmful substances out of the plant cell.
- The cell membrane also acts as a protection for the plant cell.
- The cell membrane acts as a receptor.
The nucleus is the most important part of a plant cell. It has been found that the nucleus directs and coordinates all the activities of the cell, especially in a cell division. A cell in which the nucleus has been removed can no longer divide and produce new cells. They die in one to four days after the removal of the nucleus.
The nucleus is covered by a membrane, the nuclear membrane. Like the cell membrane, it consists of a double layer of fats and proteins and associated short chains of sugars. However, it differs from the cell membrane in that it has many holes or pores.
Inside the nuclear membrane is a fluid called the nuclear sap, also called nucleoplasm or karyoplasm. Several structures are suspended in this fluid. One of these is the nucleolus. Some cells have two or more nucleoli. They are made up of molecules of protein and RNA. Besides the nucleoli, the nucleus also contains chromosomes. These are long threadlike structures that are made up of molecules of protein and DNA. The chromosomes are responsible for the transmission of traits from one generation to the next. Their DNA molecules are the key materials in heredity.
Functions of Nucleus
- The nucleus stores the DNA of a plant cell. The nucleus contains the majority of the plant cell's hereditary materials.
- The nucleus is the center of coordination for all activities of the plant cell.
- The nucleus regulates activities such as metabolism and reproduction or cell division.
Early cytologists referred to the cytoplasm as complex fluids. Suspended in this fluid are different kinds of structures. The most common plastid is the chloroplast. As shows that a chloroplast consists of an outer membrane, numerous inner membranes, and a liquid that fills the rest of the space. The membranes lie almost parallel to one another. In certain areas, several membranes lie in close contact with each other. These areas are called grana. A granum consists of protein layers with fat and pigment molecules between them. The liquid and the membrane inside a chloroplast contain special protein molecules, photosynthetic enzymes because they promote chemical reactions of photosynthesis.
Functions of Cytoplasm
- Cytoplasm gives a plant cell shape. Without Cytoplasm, the cell would be flat and deflated.
- Cytoplasm acts as a protection to prevent external damage in a plant cell.
- Cytoplasm stores molecules that are responsible for cellular processes.
- Cytoplasm stores molecules such as enzymes.
Mitochondria are found in the cytoplasm. The figure above shows that a mitochondrion consists of an outer membrane, an inner membrane that is folded inward, and a liquid that fills the cavity. The liquid and membranes of a mitochondrion contain respiratory enzymes that promote the chemical reactions that lead to the release of energy stored food, making it available for use by the cell.
Functions of Mitochondria
- Mitochondria is the main source of energy of a plant cell.
- Mitochondria produces the energy currency of a plant cell through respiration.
- Mitochondria is responsible for regulating the metabolic processes in a plant cell.
- Mitochondria acts like a digestive system allowing nutrients to get through and be digested by a plant cell through breaking down process.
Also found in the cytoplasm of many animal cells are the lysosomes. These are bodies that are structurally similar to mitochondria except that their inner walls are not thrown into folds. They contain the enzymes which promote the breakdown or digestion of carbohydrates, fats, and proteins.
Functions of Lysosomes
- Lysosomes help in the digestion of food molecules entering a plant cell. This part of a plant cell contains digestive enzymes that are perfect for cell metabolism.
- Lysosomes store proteins and fat lipids to be used in the metabolic processes of a plant cell.
- Lysosomes are responsible for the removal of wastes in a plant cell.
Also found in the cytoplasm of most animals and some blue-green algae are the centrosome. It plays an important role in cell division.
Functions of Centrosomes
- Centrosomes organize microtubules in a plant cell. They are also responsible for the nucleation of microtubules.
- Centrosomes, just like any other part of a plant cell, is responsible for the structure of a plant cell.
- Centrosomes play a big role in cell division. A centrosome of a plant cell is responsible for pulling chromatids apart.
- Centrosomes regulate cell cycle during cell division.
6d. Golgi Bodies
Also found in the cytoplasm of some cells are the Golgi bodies. A Golgi body consists of short bands of very fine parallel cavities or flat sacs. Golgi bodies are rich in fatty materials. They are found in great numbers that secrete certain substances, or those that make up cell glands.
Functions of Golgi Bodies
- Golgi bodies are responsible for the transport of proteins and lipids in a plant cell.
- Golgi bodies are responsible for the modification of proteins and lipids,
- Golgi bodies package proteins and lipids for secretion.
- Golgi bodies are responsible for the creation of lysosomes in a plant cell.
6e. Endoplasmic Reticulum
The endoplasmic reticulum is the intricate system of very fine tubes or cavities, the endoplasmic reticulum, which connects the cell membrane and the nuclear membrane at several points. Like these two membranes, the endoplasmic reticulum consists of a double layer of fats and proteins.
The endoplasmic reticulum may be smooth or rough. The rough endoplasmic reticulum (RER) is associated with tiny spherical structures called ribosomes. Other ribosomes float in the cytoplasm. Ribosomes are rich in RNA molecules. They are the sites where protein molecules are built.
Functions of Endoplasmic Reticulum
- The endoplasmic reticulum is responsible for the production of proteins and lipids in a plant cell. It produces proteins and lipids for its membrane and other cell components such as lysosomes, Golgi bodies, cell membranes, and vacuoles.
- The endoplasmic reticulum is responsible for the transport of proteins and lipids in a plant cell.
- The endoplasmic reticulum is responsible for the processing of proteins and lipids.
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This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2020 Ray