The cell theory states that cells are the basic units of structure and function in all organisms, and they are the smallest units that can carry out all the functions of life. This theory was proposed by three scientists who contributed to the cell theory: Robert Hooke, Anton van Leeuwenhoek, and Matthias Schleiden. They observed cells through microscopes and formulated the three parts of the cell theory, which are:
1) All living things are composed of one or more cells
2) Cells are the basic units of structure and function in living things
3) New cells are produced from existing cells
Prokaryotes vs Eukaryotes
There are two types of cells - prokaryotic and eukaryotic. Eukaryotic cells contain a nucleus, while prokaryotic cells do not. Eukaryotes are larger in size (2-1000 um) and have many membrane-bound organelles such as mitochondria, while prokaryotes are smaller (1-10 um) and have no membrane-bound organelles. Eukaryotic cells evolved 1.5 billion years ago and make up all other cells (animal, plant, fungi, protist), while prokaryotic cells evolved 3.5 billion years ago and are only unicellular bacteria and archaebacteria.
In terms of similarities, both prokaryotic and eukaryotic cells have a cell membrane, DNA, and ribosomes. They also have a nucleoid (prokaryotic) or a nucleus (eukaryotic) that contains genetic material.
Endosymbiotic Theory and Cell Structure
The endosymbiotic theory explains the origin of certain organelles, such as mitochondria and chloroplasts. This theory was formulated to explain how these organelles were formed within a cell and is supported by evidence of similarities between these organelles and prokaryotic cells. The endosymbiotic theory is now widely accepted in the scientific community.
In conclusion, the cell theory is a fundamental concept in biology, and understanding the differences between prokaryotic and eukaryotic cells, as well as the endosymbiotic theory, is essential to comprehend the structures and functions of cells. For further details and in-depth information, you can refer to the "Cell Theory and Creation" PDF, which provides comprehensive notes and diagrams on cell theory, prokaryotes vs eukaryotes, and the endosymbiotic theory.
