Module 1 : Introduction to Bioorganic Chemistry

Lecture 6 : Chemistry of the Living Cells

1.10 Chemistry of the Living Cells 

1.10.1. Cell-The Basic Unit of Life
A cell is a microscopic, structural and functional unit of all living organisms capable of independent existence. Some functioning cells come together to form a tissue and tissues collectively form organs. In more complex living organisms, organs work together for the purpose of survival as system. However, in all living organisms, the cell is a functional unit and all of biology revolves around the activity of the cell.
The word ‘cell’ was first coined by Robert Hooke in 1665 to designate the empty honey-comb like structures viewed in a thin section of bottle cork, which he examined. In 1838, the German botanist Matthias Schleiden proposed that all the plants are made up of plant cells. Then in 1839, his colleague, the anatomist Theodore Schwann studied and concluded that all animals are also composed of animal cells. But still the real nature of a cell was in doubt. Cell theory was again rewritten by Rudolf Virchow in 1858.
In his theory he said that all living things are made up of cells and that all cells arise from pre-existing cells. It was German biologist Schulze who found in 1861 that the cells are not empty as were seen by Hooke but contain a ‘stuff’ of life called protoplasm.
During the 1950s scientists developed the concept that all organisms may be classified as prokaryotes or eukaryotes. For example, in prokaryotic cells, there is no nucleus; eukaryotic cells have a nucleus. Another important difference between prokaryotes and eukaryotes is that the prokaryotic cell does not have any intracellular components. Bacteria and blue- green algae come under the prokaryotic group, and protozoa, fungi, animals, and plants come under the eukaryotic group.

Figure 1.33: The structure of Prokaryotic and Eukaryotic Cells.

1.10.2. Modern Cell Theory
Modern biologists have made certain additions to the original cell theory, which now states that: