Cell Theory

Cell is the structural and functional unit of all the living organisms, which is capable of carrying out all life processes.

Robert Hooke observed honeycomb like compartmentsunder a microscope and named them ‘cells’. They were dead cells.
The first microscope was built by Antony Van Leeuwenhoek in 1632- 1723.

The cell theory was presented by two biologists – Schleiden (1838) and Schwann (1839). It was further expanded by Virchow (1855).

Depending on the number of cells, organisms may be unicellular(e.g., yeast), or multicellular(e.g., plants and animals).

Unicellular organisms: They are single celled. For example: Mycoplasma, Amoeba
Mycoplasma are the smallest organisms which are capable of self-replication.They are also called PPLO or Pleuro pneumonia like organisms as they are similar to the agents that cause contagious bovine pleuropneumonia.

Multicellular organisms possess two or more cells for example plant and animal cells.

Animal cells have a number of specialised cell components such as the cell membrane, Golgicomplex, endoplasmic reticulum, nucleus, mitochondria, ribosomes, centrioles, microtubules and lysosomes.

Cell wall is present in plant cell and absent in animal cell.
In animals, reserve food is stored in the form of glycogen. In plants, reserve food is stored in the form of starch.

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  • Q1

    In the plant cell, largest organelle present is

    Marks:1
    Answer:

    vacuole.

    Explanation:
    The centrally placed vacuole in a plant cell generally occupies 30% to 80% volume of the cell.
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  • Q2

    An example of unicellular organism is

    Marks:1
    Answer:

    yeast.

    Explanation:
    Yeast is a single celled organism belonging to kingdom fungi.
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  • Q3

    A microscope has all parts except

    Marks:1
    Answer:

    leg.

    Explanation:
    Arm, body tube and base are all parts of a microscope.
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  • Q4

    The cell is the:

    Marks:1
    Answer:

    Structural and Functional unit of life

    Explanation:
    Cell is the basic building units of an organism. Hence, they form structural unit of life. In the same way the living cell has the capacity to perform certain basic functions that are characteristic of all living forms. Hence the cell is both a structural and functional unit of life.
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  • Q5

    Cell was first discovered by

    Marks:1
    Answer:

    Robert Hooke

    Explanation:
    Robert Hooke observed a thin slice of cork under the microscope. It was a chance observation. Robert Hooke observed small box like structures which he named as cells. Cell is a Latin word for ‘a little room’.
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