Ray was a member of Science Olympiad, participates in science and health writing competitions, and studied at a sci-tech school.
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 be able to perform all functions mentioned, a cell has even smaller, often membrane-bound parts.
What is the chemical composition of a cell? The table below gives the average form of living matter. The table shows that living matter consists of both organic and inorganic substances.
|Compound||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 essential compounds in cells called nucleotides and nucleic acids.
Two nucleic acids are deoxyribose nucleic acid (sometimes called as DNA) and nucleic ribose acid (sometimes called as RNA). DNA is 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 mainly 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 components 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 type of plastid called chromoplastid contains two kinds of dyes: carotene, which gives cream, white, yellow, orange, and red colors and xanthophylls, which provide bright yellow and brown colors. Not all plant pigments are inside plastids. For instance, anthocyanin, a purple dye, 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 comprises cellulose. Cellulose 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 contains 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 cell activities 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 noticeable in the structure of plant cells. They are abundant in mature plant cells. They are fewer and smaller in young plant cells. The liquid inside a vacuole is known as a cell sap. Cell sap 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 fold easily. 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 quickly 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.
Naturally, 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 usually 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. The pocket grows deeper and deeper, bringing with it the protein molecule. Then, a vacuole forms within the cell with the protein molecule and a little fluid enclosed in a layer. 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 control sugar.
- The cell membrane allows a plant cell to monitor 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 an essential part of a plant cell. It directs and coordinates all the activities of the cell, especially in a cell division. A cell with no nucleus can no longer divide and produce new cells. They die in one to four days after the removal of the nucleus.
A nuclear membrane covers the nucleus. 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 in this fluid. One of these is the nucleolus. Some cells have two or more nucleoli. They contain molecules of protein and RNA. Besides the nucleoli, the nucleus also contains long threadlike structures called chromosomes responsible for hereditary functions.
Functions of Nucleus
- The nucleus stores the DNA of a plant cell. The nucleus contains the majority of the plant cell's genetic 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, various inner membranes, and a liquid that fills the rest of the space. The layers 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 unique protein molecules, 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 is a component of the cytoplasm. The figure above shows that a mitochondrion consists of an outer membrane, an inner layer that that folds inward, and a liquid that fills the cavity. The fluid 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 primary 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 do not characterize 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 for 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 essential 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 significant 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 collection consists of small bands of very fine parallel cavities or flat sacs. Golgi bodies are rich in fatty materials. They are in high numbers that secrete certain substances, or those that makeup 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 small 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 fats 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 Raycaptiosus