Cells are the structure and basic unit of life, the study of the cell structure and function is called cell biology. Robert Hook was the first biologist to discover cells. All living things are made up of cells. They can be composed of single cells (single cells) or multi-cells (multi-cells). Mycoplasma is the smallest known cell.
Cells are the cornerstone of all living things. They provide structure to the body and convert nutrients from food into energy. Cells are complex, and their components perform various functions in an organism. They are different in shape and size, very much like the bricks of the building.
Our body is made up of cells of different shapes and sizes. Cells are the lowest level of tissue in every life form. From organism to organism, the count of cells may vary. Compared with bacteria, the number of cells in humans. Cells are composed of several organelles, which perform specialized functions to carry out life processes. Each organelle has a specific structure. The genetic material of the organism is also present in the cell.
Types of Cells
Cells are similar to factories, with different workers and departments, committed to a common goal. Various types of cells perform different functions. Based on the cell structure, there are two types of cells:
- Prokaryotic cells have no nucleus. Instead, some prokaryotes such as bacteria have a region within the cell where the genetic material is freely suspended. This region is called the nucleoid.
- They all are single-celled microorganisms. Examples include archaea, bacteria, and cyanobacteria.
- The cell size ranges from 0.1 to 0.5 µm in diameter.
- The hereditary material can either be DNA or RNA.
- Prokaryotes generally reproduce by binary fission, a form of asexual reproduction. They are also known to use conjugation – which is often seen as the prokaryotic equivalent to sexual reproduction (however, it is NOT sexual reproduction).
- Eukaryotic cells are characterised by a true nucleus.
- The size of the cells ranges between 10–100 µm in diameter.
- This broad category involves plants, fungi, protozoans, and animals.
- The plasma membrane is responsible for monitoring the transport of nutrients and electrolytes in and out of the cells. It is also responsible for cell to cell communication.
- They reproduce sexually as well as asexually.
- There are some contrasting features between plant and animal cells. For eg., the plant cell contains chloroplast, central vacuoles, and other plastids, whereas the animal cells do not.
The function of cells
Cells perform these main functions necessary for the growth and development of an organism. The important functions of the cell are as follows:
* Provide support and structure All living things are made up of cells. They form the structural basis of all living things. Cell walls and cell membranes are the main components that provide support and structure for organisms. For example, The skin consists of a large number of cells. The xylem present in vascular plants consists of cells that provide structural support for plants.
* Promote growth mitosis In the process of mitosis, parent cells divide into daughter cells. Therefore, the cells multiply and promote the growth of the organism.
* Allow the transport of substances Cells introduce various nutrients and carry out various chemical processes inside the cell. Waste generated by chemical processes is eliminated from cells through active and passive transport. Small molecules such as oxygen, carbon dioxide and ethanol diffuse to the cell membrane along the concentration gradient. This is called passive transmission. Larger molecules diffuse on the cell membrane through active transport, in which cells need a lot of energy to transport substances.
*Energy production Cells need energy to carry out various chemical processes. This energy is produced by cells through photosynthesis of plants and respiration of animals.
* Assisted reproduction Cells assist in reproduction through a process called mitosis and meiosis. Mitosis is called asexual reproduction, in which parent cells divide to form daughter cells. Meiosis causes daughter cells to be genetically different from their parents. Therefore, we can understand why cells are called the structural and functional units of life. This is because they are responsible for providing structures for organisms and performing a variety of functions required to perform life processes.
The cell structure comprises individual components with specific functions essential to carry out life’s processes. These components include- cell wall, cell membrane, cytoplasm, nucleus, and cell organelles. Read on to explore more insights on cell structure and function.
- The cell membrane supports and protects the cell. It controls the movement of substances in and out of the cells. It separates the cell from the external environment. The cell membrane is present in all the cells.
- The cell membrane is the outer covering of a cell within which all other organelles, such as the cytoplasm and nucleus, are enclosed. It is also referred to as the plasma membrane.
- By structure, it is a porous membrane (with pores) which permits the movement of selective substances in and out of the cell. Besides this, the cell membrane also protects the cellular component from damage and leakage.
- It forms the wall-like structure between two cells as well as between the cell and its surroundings.
- Plants are immobile, so their cell structures are well-adapted to protect them from external factors. The cell wall helps to reinforce this function.
- The cell wall is the most prominent part of the plant’s cell structure. It is made up of cellulose, hemicellulose and pectin.
- The cell wall is present exclusively in plant cells. It protects the plasma membrane and other cellular components. The cell wall is also the outermost layer of plant cells.
- It is a rigid and stiff structure surrounding the cell membrane.
- It provides shape and support to the cells and protects them from mechanical shocks and injuries.
- The cytoplasm is a thick, clear, jelly-like substance present inside the cell membrane.
- Most of the chemical reactions within a cell take place in this cytoplasm.
- The cell organelles such as endoplasmic reticulum, vacuoles, mitochondria, ribosomes, are suspended in this cytoplasm.
- The nucleus contains the hereditary material of the cell, the DNA.
- It sends signals to the cells to grow, mature, divide and die.
- The nucleus is surrounded by the nuclear envelope that separates the DNA from the rest of the cell.
- The nucleus protects the DNA and is an integral component of a plant’s cell structure.
Cells are composed of various cell organelles that perform certain specific functions to carry out life’s processes. The different cell organelles, along with its principal functions, are as follows:
Nucleolus: Is the site of ribosome synthesis. Also, it is involved in controlling cellular activities and cellular reproduction.
Nuclear membrane: Protects the nucleus by forming a boundary between the nucleus and other cell organelles.
Chromosomes: Play a crucial role in determining the sex of an individual. Each human cells contain 23 pairs of chromosomes.
Endoplasmic reticulum: Is involved in the transportation of substances throughout the cell. It plays a primary role in the metabolism of carbohydrates, synthesis of lipids, steroids and proteins.
Golgi Bodies: Are called the cell’s post office as it is involved in the transportation of materials within the cell.
Ribosome: Are the protein synthesisers of the cell
Mitochondria: Is called “the powerhouse of the cell.” It is called so because it produces ATP – the cell’s energy currency
Lysosomes: Protect the cell by engulfing the foreign bodies entering the cell and helps in cell renewal. Therefore, it is known as the cell’s suicide bags.
Chloroplast: Are the primary organelles for photosynthesis. It contains the pigment chlorophyll.
Vacuoles: Store food, water, and other waste materials in the cell.