Cell The Unit of Life Class 11 Notes - Chapter 8

What is a Cell?

A cell is defined as the most basic, structural and functional unit of all living organisms. Essentially, a cell is a structure that contains organelles which provide necessary functions to sustain itself. However, not all cells are the same.

Plants have cells that are vastly different from animals. One of the primary differences between the two is the absence of cell walls in animal cells. Cells also vary in size, with the largest one in the human body being the egg or the female ovum. It measures roughly around 1 millimetre across. The smallest cell is the granule cell which is found in the human cerebellum, measuring roughly around 4.5 micrometres in size.

Cell Theory

This scientific theory, initially formulated by Matthias Schleiden and Theodor Schwann, proposed that all living organisms are composed of cells, and new cells are formed from pre-existing cells. Even though the theory was put forth by Schleiden and Schwann, other notable scientists have contributed to this theory, turning its status from a theory to a universally accepted fact.

Cell: The Unit of Life – Class 11 MCQs

  1. Choose the incorrect option:
    1. The cell was discovered by Robert Brown
    2. The Cell Theory was introduced by Schleiden and Schwann
    3. The concept of cells forming from preexisting cells was given by Virchow
  1. New cells are formed from ________
    1. Existing cells
    2. Fermentation
    3. Spontaneously
  1. Which of the following is correct?
    1. All cells have a nucleus
    2. Animal cells have a cell wall
    3. Plastids are found only in plant cells

 

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