Cell Theory: Important Characters & it’s 4 exceptions

Cell Theory : theory of Biogenesis
Cell Theory
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The cell is smallest unit of life. Since the origin of cell it has evolved into a unicellular to multicellular and acellular (partially unicellular or multicellular) structure. Cell is consider as smallest entity in living system. There are several theories have been given to explain the formation and evolution of cell. Cell theory by the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann has explained the characters of the cell.

Cell Theory:

There are four distinct characters defined for cell . First three are given by the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann and the fourth one is given by German pathologist Virchow .

Cell Theory : theory of Biogenesis
Characters of Cell Theory

Characters of cell:

1) Structural unit:

Cell is structural unit of an organism. Every cell has its own specific structure which include cell organelles, cytoplasm and plasma membrane as outer protective structure.

2) Functional unit:

Cell is the functional unit of an organism. Each cell is functionally independent, as each of them has their own metabolism their own genetic structure etc.

3) Hereditary unit:

Cell is hereditary unit of an organism. Each cell has their own genetic material. In case of eukaryote it is specifically enclosed in double membrane spherical structure called as nucleus. While in case of prokaryotes it is suspended freely into cytosol.

4) Biogenesis:

Theory of biogenesis explains every cell arises from its pre existing cell. A single living cell behave as maternal cell and can divide and form two daughter cells. Then these two daughters cells have ability to under goes division. Formation of new cell from pre-existing cell is called as biogenesis. Where ‘Bio’ means life and ‘Genesis’ means synthesis. The theory which give an idea about formation of new cell from pre existing cell is known as theory of biogenesis.

But as we know that life science is incomplete without exceptions. Hence cell theory also has 4 exceptions with respect to their four characters.

Exceptions of cell Theory:

1) Viroids:

Cell is a structural unit , which has their specific solid structure with the help of which it can multiply itselves. But viroid are any molecules, consisting about 150 to 200 nucleotide in their structure. Which act as a infectious RNA and infects plant. They don’t have any proper structure still they can multiply their number. Hence the presence of viroid is an exception for cell as structural unit.

2) Virus :

Viruses are the best exception for cell as functional unit. Viruses are obligate parasite which lacks its own metabolism. As it lacks its own metabolism it requires host’s metabolism for their survival. So we can’t culture virus as they lacks their own metabolism, hence viruse are not functionally independent.

3) RBC’s:

Cell is considered as heridatory unit, but there are few cells which lacks genetic material in them. RBC’s are one of them. RBC lacks nucleus hands it won’t have any kind of genetic material so they can’t inherit their genetic material. Even the WBC’s B cells specifically undergoes genetic rearrangement, hence also lacks genetic equivalence in genome. So this can’t be considered as hereditary units.

4) Abiogenesis :

Theory of biogenesis can explain the formation of existing cells from its pre-existing cell. But when we look at it from the origin point of you. Origin of first cell remained unanswered. The origin of first cell can be explained with the help chemogenesis process in chemosynthetic theory. Hence the origin of first cell becomes exception for Theory of biogenesis.

After understanding the Cell theory if you want to attempt some more Life Science test series ??? Then try this :

Life-Science-quiz
Life-Science-test series

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Sachin Chavan

Sachin Chavan is working as Ph. D. Scholar with CSIR NET JRF AIR 21, GATE, MH-SET Online content writer and founder of Sachin's Biology and biologywala.com.

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