Notes on The Cell (Biology)

The most fundamental building block of life are cells. Therefore, the smallest independent component that we would discover if we dissected an organism down to its cellular level is the cell.

Discover the definition, structure, types, and functions of cells by reading the notes on cells. All the cell-related concepts are thoroughly explained in these notes.

definition of cell

“A cell is defined as the smallest, basic unit of life that is responsible for all of life’s processes.”

Who discovered cells?

Robert Hooke – The first person to see cells, he was looking at cork and noted that he saw “a great many boxes. (1665)

Anton van Leeuwenhock – Observed living cells in pond water, which he called “animalcules” (1673)

Theodore Schwann – zoologist who observed that the tissues of animals had cells (1839)

Mattias Schleiden – botonist, observed that the tissues of plants contained cells (1845)

Rudolf Virchow – also reported that every living thing is made of up vital units, known as cells. He also predicted that cells come from other cells. (1850 )

Robert Hooke discovered the cell in 1665. Robert Hooke observed a piece of bottle cork under a compound microscope and noticed minuscule structures that reminded him of small rooms. Consequently, he named these “rooms” as cells. However, his compound microscope had limited magnification, and hence, he could not see any details in the structure. Owing to this limitation, Hooke concluded that these were non-living entities.

Later Anton Van Leeuwenhoek observed cells under another compound microscope with higher magnification. This time, he had noted that the cells exhibited some form of movement (motility). As a result, Leeuwenhoek concluded that these microscopic entities were “alive.” Eventually, after a host of other observations, these entities were named as animalcules.

In 1883, Robert Brown, a Scottish botanist, provided the very first insights into the cell structure. He was able to describe the nucleus present in the cells of orchids.

Describe a cell

The basic and structural component of life is the cell. Cell biology is the study of cells, including their fundamental makeup and each organelle’s functions. Cells were first discovered by a biologist, Robert Hooke.

Cells comprise all living things. They could consist of many cells or just one (unicellular) (multicellular). The tiniest known cells are mycoplasmas. The foundation of all living things are cells. They give the body structure and transform the food’s nutrients into energy.

Cells are complex and their components perform various functions in an organism. They are of different shapes and sizes, pretty much like bricks of the buildings. Our body is made up of cells of different shapes and sizes.

Cells are the lowest level of organisation in every life form. From organism to organism, the count of cells may vary. Humans have more number of cells compared to that of bacteria.

Cells comprise several cell organelles that perform specialised functions to carry out life processes. Every organelle has a specific structure. The hereditary material of the organisms is also present in the cells.

The Cell Theory

1. Every living organism is made of one or more cells.
2. The cell is the basic unit of structure and function.
3. All cells arise from pre-existing cells.

Characteristics of Cells

The following are some of the important features of cells:

  • Cells provide structure and support to the body of an organism.
  • The cell interior is organized into different individual organelles surrounded by a separate membrane.
  • The nucleus (major organelle) holds genetic information necessary for reproduction and cell growth.
  • Endoplasmic reticulum plays a significant role in the internal organization of the cell by synthesizing selective molecules and processing, directing and sorting them to their appropriate locations.
  • Mitochondria, a double membrane-bound organelle is mainly responsible for the energy transactions vital for the survival of the cell.
  • Every cell has one nucleus and membrane-bound organelles in the cytoplasm.
  • Lysosomes digest unwanted materials in the cell.

Types of Cells

Similar to factories, cells have various departments and employees who all work toward a single goal. Different cell types have various functions. There are two different types of cells based on cellular structure:




Functions of Cell

A cell performs major functions essential for the growth and development of an organism. Important functions of cell are as follows:

1.Provides Support and Structure

All the organisms are made up of cells. They form the structural basis of all the organisms. The cell wall and the cell membrane are the main components that function to provide support and structure to the organism. For eg., the skin is made up of a large number of cells. Xylem present in the vascular plants is made of cells that provide structural support to the plants.

2. Facilitate Growth Mitosis

In the process of mitosis, the parent cell divides into the daughter cells. Thus, the cells multiply and facilitate the growth in an organism.

3. Allows Transport of Substances

Various nutrients are imported by the cells to carry out various chemical processes going on inside the cells. The waste produced by the chemical processes is eliminated from the cells by active and passive transport. Small molecules such as oxygen, carbon dioxide, and ethanol diffuse across the cell membrane along the concentration gradient. This is known as passive transport. The larger molecules diffuse across the cell membrane through active transport where the cells require a lot of energy to transport the substances.

4. Energy Production

Cells require energy to carry out various chemical processes. This energy is produced by the cells through a process called photosynthesis in plants and respiration in animals.

5. Aids in Reproduction

A cell aids in reproduction through the processes called mitosis and meiosis. Mitosis is termed as the asexual reproduction where the parent cell divides to form daughter cells. Meiosis causes the daughter cells to be genetically different from the parent cells.

Thus, we can understand why cells are known as the structural and functional unit of life. This is because they are responsible for providing structure to the organisms and perform several functions necessary for carrying out life’s processes.


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