Cell- The smallest unit that can live on its own and that makes up all living organisms and the tissues of the body:
Robert Hooke (1635-1703) in 1665 made thin section of wood cork and observed them under a microscope. He found there numerous little boxes like bee hives. Then he remembered seeing such small rooms for the priests to stay in the monastery. From this, he named the cork’s little box as “cell”. The word cell is derived from the Latin word cellula, means little box.
Pic: Cell, Photo Credit: freepik.
Deffinition
Different scientist defined cell with different definitions. Some of them noted below
- According to Jean Bracket (1961), ‘Cell is the basic structural unit of an organism.’
- According to Loewy and Siekevitz (1963), a cell is a unit of biological activity surrounded by a semi permeable membrane and capable of self reproduction without any help of other living medium.
- According to C. P Hickman (1970), Cell is the unit of biological structure and function and is the smallest biological unit capable of self-regulation and reproduction.
- According to De Roberties (1979), a cell is the basic structural and functional unit of an organism.
Characteristics
- Cells carry all the structural and molecular components necessary for life.
- Necessary raw materials can be taken inside.
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It can collect the necessary energy by using raw materials and synthesize its own necessary molecules.
- Can grow in a controlled manner.
- Can respond to any surrounding stimuli.
- Can maintain a homeostatic state (i.e. an internal steady state despite changes in environmental conditions).
- Can be evaluated during course of time.
Types
Based on physiological activity:
- Somatic Cell:
Cells that build the organs and organ systems of living organisms are called somatic cells. Somatic cells of higher organisms usually have diploid number (2n) of chromosomes. For example: Cells in roots, stems, leaves, nerves and blood vessels.
- Reproductive Cell or Gamete:
The haploid cells produced by the process of meiosis in the genitalia of diploid organisms for sexsual reproduction are called gamete cells. Sperm and egg are the example of gametes. Gametes are always haploid (n) in number.
Name two types of cells in the basis of nature of nucleus:
- Prokaryotic:
that do not have a true and organized nucleus, cell membranes and chromosomes, are called prokaryotic cells .Example included Bacteria, blue green algae etc.
- Eukaryotic:
that have a well-organized or organized nucleus and membrane-enclosed organelles are called eukaryotic cells. That is, the cells in which the nucleus is organized (nuclear membrane, nucleoplasm, nucleolus and nuclear reticulum are present) and nuclear membrane is surrounded, chromosomes contain alkaline protein, cell membranes are surrounded by multiple cell organelle, called eukaryotic cells. For example: plant and animal cells.
Structure
A plant cell is a eukaryotic cell that forms the basic structural unit of a plant. It has a complex structure with various membrane-bound organelles that carry out specific functions. The main components of a typical plant cell are:
Pic: Plant Cell, Photo Credit: freepik.
Cell Wall:
A rigid, protective outer layer made of cellulose that provides support and maintains the shape of the cell.
Cell Membrane:
A selectively permeable membrane that surrounds the cell and controls the movement of substances in and out of the cell.
Nucleus:
The control center of the cell that contains the genetic material (DNA) and regulates cellular activities.
Cytoplasm:
A jelly-like substance that fills the cell and houses various organelles.
Endoplasmic Reticulum (ER):
A network of membrane-bound tubes and sacs involved in protein synthesis and lipid metabolism.
Golgi Apparatus:
A stack of flattened sacs that processes, packages, and transports proteins and lipids.
Mitochondria:
The powerhouses of the cell that produce energy through cellular respiration.
Chloroplasts:
Organelles that contain chlorophyll and are responsible for photosynthesis, the process by which plants convert sunlight into energy.
Vacuole:
A large, membrane-bound sac that stores water, nutrients, and waste products.
Ribosomes:
Small organelles that synthesize proteins.
Lysosomes:
Membrane-bound vesicles containing enzymes that break down waste materials and cellular debris.
Peroxisomes:
Small organelles involved in lipid metabolism and detoxification.
Microtubules and Microfilaments:
Structural components of the cytoskeleton that provide support and maintain cell shape.
Plasmodesmata:
Small channels that connect adjacent plant cells and allow for communication and transport between cells.
Function
Structural Support
Cells provide structural support to living organisms.
Metabolism
Cells carry out metabolic processes that are essential for energy production, growth, and maintenance.
Reproduction
Cells are responsible for reproduction, either through mitosis (cell division) for growth and tissue repair or meiosis (cell division with genetic recombination) for sexual reproduction in multicellular organisms.
Communication and Signaling
Cells communicate with each other through various signaling mechanisms, including chemical signals such as hormones, neurotransmitters, and cytokines, as well as direct cell-to-cell communication through gap junctions (in animal cells) or plasmodesmata (in plant cells).
Transport and Exchange
Cells regulate the movement of substances in and out of the cell, maintaining a stable internal environment
Sensing and Response
Cells have specialized structures, such as receptors and sensory organelles, that allow them to sense and respond to changes in their environment.
Genetic Information Management
Cells store, replicate, and utilize genetic information encoded in DNA. This includes DNA replication, transcription (RNA synthesis), translation (protein synthesis), and DNA repair processes.
Defense and Protection
Cells play a role in defending the organism against pathogens and other harmful agents. Cells of the immune system, such as white blood cells, are responsible for identifying and eliminating foreign substances, while cells such as mucous-producing cells and skin cells provide physical barriers against pathogens.
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