Question 1

Who formulated the cell theory initially?

Accepted Answer

The cell theory was initially formulated by Matthias Schleiden and Theodor Schwann in 1838 and 1839 respectively. Schleiden examined plants and Schwann examined animals to conclude that bodies of plants and animals are composed of cells and products of cells.

Question 2

Who modified the cell theory by giving the statement 'Omnis cellula e cellula'?

Accepted Answer

Rudolf Virchow in 1855 first explained that cells divided and new cells are formed from pre-existing cells ('Omnis cellula e cellula'). He modified the hypothesis of Schleiden and Schwann to give the cell theory a final shape.

Question 3

Which of the following lacks a true nucleus and membrane-bound organelles?

Accepted Answer

Prokaryotic cells lack a true membrane-bound nucleus and other membrane-bound cell organelles. Examples include bacteria, blue-green algae, mycoplasma, and PPLO.

Question 4

What is the fluid mosaic model of plasma membrane proposed by?

Accepted Answer

The fluid mosaic model of the plasma membrane was proposed by Singer and Nicolson in 1972. According to this model, the quasi-fluid nature of lipid enables lateral movement of proteins within the overall bilayer.

Question 5

Which organelle is known as the powerhouse of the cell?

Accepted Answer

Mitochondria are known as the powerhouse of the cell because they produce cellular energy in the form of ATP (adenosine triphosphate) through aerobic respiration.

Cell: The Unit of Life — MP Board Class 11 Biology Important Questions & Revision Notes