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Information about Cell: Life’s Basic Building Block
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- Discovery: Cells were first discovered by Robert Hooke in 1665.
- Cell is a Latin word for ‘a little room’.
- He observed the cells in a cork slice with the help of a primitive microscope.
- In 1674, Leeuwenhoek used an advanced microscope to unveil free-living cells in pond water.
- Then, in 1831, Robert Brown identified the cell’s nucleus, while in 1839, Purkinje introduced the term ‘protoplasm’ for the cell’s fluid component.
- The Cell Theory ( Schleiden (1838) and Schwann (1839)):
- All the plants and animals are composed of cells and the cell is the basic unit of life.
- All cells arise from pre-existing cells , given by Virchow (1855).
- Unicellular Organisms: The discovery of magnifying lenses revealed the microscopic world, where a single cell can form an entire organism (e.g. Amoeba, Chlamydomonas, bacteria), known as unicellular organisms.
- Multicellular Organisms: Organisms such as fungi, plants, and animals, consist of cells working together in various body parts.
- All life begins as a single cell that divides to produce more cells, demonstrating that every cell comes from pre-existing cells.
- Shape and Size: Cell shape and size relate to their function of the cell wall, some, like Amoeba, exhibit changing shapes, while others have fixed, distinct shapes (e.g., nerve cells).
- Functions: All living cells share fundamental functions.
- function of the cell wall efficiently due to division of labor, akin to multicellular organisms.
- Organelles: They contain specialized components called cell organelles, each performing specific tasks such as material synthesis and waste removal.
- These organelles collectively form the cell’s basic unit, and intriguingly, all cells, regardless of their function or organism, possess the same organelles.
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Cell Wall: The Structural and Functional Unit of Life
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- Function of cell wall: Each living cell has the capacity to perform certain basic functions of the cell wall that are characteristic of all living forms.
- Cell Organelles: The Cellular component is called Cell Organelles.
- Examples: plasma membrane, nucleus and cytoplasm.
- A cell is able to live and perform all its function of the cell wall because of these organelles.
- These organelles together constitute the basic unit called the cell.
- Under Microscope: If we study a cell under a microscope, we would find three features in almost every cell, plasma membrane, nucleus and cytoplasm.
- Crucial Role: All activities inside the cell and interactions of the cell with its environment are possible due to these features.
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Plasma Membrane Or Cell Membrane: The Dynamic Border of Life’s Essential Space
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- Outermost Layer: This is the outermost covering of the cell that separates the contents of the cell from its external environment.
- The cell membrane is an active part of the cell.
- Selectively Permeable Membrane: The plasma membrane allows or permits the entry and exit of some materials in and out of the cell.
- It also prevents movement of some other materials.
- The cell membrane, therefore, is called a selectively permeable membrane.
- Flexibility: The plasma membrane is flexible and is made up of organic molecules called lipids and proteins.
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Plant Cell Armor: The Strength of Cellulose Protection
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- Special Feature: Plant cells have another rigid outer covering called the cell wall.
- The cell wall lies outside the plasma membrane.
- Composition: The plant cell wall is mainly composed of cellulose.
- Cellulose is a complex substance and provides structural strength to plants.
- Protective Layer: Cell walls permit the cells of plants, fungi and bacteria to withstand very dilute (hypotonic) external media without bursting.
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Nucleus
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- Discovery: It was Robert Brown in 1831 who discovered the nucleus in the cell.
- Membrane: The nucleus has a double layered covering called a nuclear membrane.
- Chromosomes: The nucleus contains chromosomes, chromosomes contain information for inheritance of characters from parents to the next generation in the form of DNA (DeoxyriboNucleic Acid) molecules.
- Chromosomes are composed of DNA and protein.
- DNA molecules contain the information necessary for constructing and organizing cells.
- Functional segments of DNA are called genes.
- Central Role: The nucleus plays a central role in cellular reproduction.
- Advancement: Eventual advancements in science and technology shed more light into the cell, with new findings and discoveries about its structure and cellular components.
- During the 1950s, scientists postulated the concept of prokaryotic cells and eukaryotic cells, with earlier groundwork being laid by Edouard Chatton, a French Biologist in 1925.
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