The cell is life’s basic structural and functional unit; it is also called the “building blocks of life.” In 1839, Schleiden and Schwann proposed the cell theory. According to cell theory, all living things are composed of a single cell or a collection of cells. The cell’s cytoplasm includes proteins and nucleic acids and is surrounded by a membrane. Animal and plant cell structures are visible under a microscope and range in size from 1-100 μm. Cell count varies between species. Cell structure and function have helped our understanding of life.
In general, cells are classified into two types:
- The Prokaryotic Cell
- The Eukaryotic Cell
Structure of cells and their functions
A cell comprises three components: the cell membrane (cell wall), the nucleus, and the cytoplasm, which lies between the two. The cytoplasm has complicated fibre patterns and hundreds or thousands of microscopic but distinct organelles. Cell organelles enable a cell to live and accomplish all of its activities.
Whether bone, nerve, or other, any cell has the same organelles, regardless of function or organism.
The following are the major organelles of the cell:
1. Cell membrane
The cell membrane encloses the cell and controls the passage of substances in and out. Additionally, it is referred to as the plasma membrane, which serves as the outermost layer of an animal cell. It is an elastic, living, two-layer membrane that is permeable. It is composed of proteins and lipids.
Function: It controls cellular molecule mobility.
2. Cell wall
The cell wall is the plant cell’s external (outermost) layer. The cell wall is located outside the plasma membrane. The primary components of the plant cell wall are cellulose and chitin. Cellulose gives plants strength.
Function: If a growing plant cell loses water, the contents shrink away from the cell wall.
3. The nucleus and the nucleolus
The cell’s centralised control centre is the nucleus, which comprises a fluid nucleoplasm and a nuclear membrane. The cell’s genetic material is contained in chromatin threads in the nucleus. Ribonucleic acid (RNA) is concentrated in the nucleolus that forms ribosomes.
Functions: The nucleus determines the basic cell structure and function.
4. The cytoplasm
The cytoplasm is the material that lies between the plasma and nuclear membranes. It is composed of a matrix and organelles. Hyaloplasm or cytoplasmic matrix is an amorphous, transparent, homologous colloidal liquid known as the matrix.
Functions: Glycolytic enzyme and structural components, including sugar, amino acids, water, nutrients, and nucleotides, are found in the cytoplasmic matrix. The nucleus sends them instructions, and they follow those instructions. Cellular activity can also take place at these locations.
Cytoplasmic Organelles: Organelles are membrane-bound living entities found in the cytoplasm. Biosynthetic and metabolic processes such as transport, support, storage, reproduction, respiration, and so on are often carried out by these organisms.
5. Golgi bodies
The Golgi bodies are composed of a collection of tubes, vesicles, and vacuoles. Additionally, these are referred to as Golgi apparatuses. Camilo Golgi discovered the Golgi apparatus.
Function: It can store, process, modify, and package items in vesicles. Additionally, it is involved in forming the cell wall, plasma membrane, and lysosomes.
6. Endoplasmic reticulum (ER)
They are vesicles and tubules connected by a single membrane that encircles them. Due to the presence or lack of ribosomes, the membranes might be rough or smooth.
Functions: They regulate intracellular circulation. They function as organs of synthesis and storage. They support the cytoplasmic framework of the cell.
It is present exclusively in animal cells and is composed of microscopic spheroid particles containing hydrolytic enzymes. They are encapsulated within the lipoprotein membrane’s single layer.
Functions: They are involved in intracellular digestion via pinocytosis and phagocytosis.
A cell structure resembling the small granules connected to the endoplasmic reticulum (ER) or the free state. Ribonucleic acid (RNA) is the primary component.
Function: The ribosome is involved in protein synthesis.
It is a hollow filamentous or granular structure surrounded by a bilayer lipoprotein membrane. There are two chambers in mitochondria: an outer chamber and an inner chamber filled with matrices.
Functions: They are referred to as the body’s powerhouses because they generate energy in the form of ATP in the Krebs cycle and fatty acid oxidation.
It is a disc-shaped organelle that contains chlorophyll and is surrounded by a double membrane. It is found exclusively in plant cells. The inner membrane contains a stroma or matrix. Stroma is composed of microscopic cylindrical cell structures known as grana. Granum is a vesicle that has been flattened and includes microscopic entities called quantasomes.
Functions: Serve as a reservoir for starch and pigments used in photosynthesis. They contribute to food biosynthesis through the process of photosynthesis.
It is found only in animal cells. It has thick cytoplasm towards the nucleus.
Functions: It helps construct the spindle during cell division and moves chromosomes.
Vacuoles contain solid or liquid substances. Animal cells contain small vacuoles, but plant cells have enormous ones. Vacuoles store several essential chemicals for plant cell survival. Amino acids and a few proteins fall under this category.
Function: It contributes to osmoregulation. It is used to store hazardous metabolic waste.
Cell discovery is one of the most significant achievements in science. It reminds us that all organisms contain cells that help carry out numerous life processes. With time, ideas concerning cell structure have evolved significantly. Then, they were simple membranous sacs with fluid and several floating components. Nowadays, biologists know that cells are much more complicated than that.