Exceptions Of The Cell Theory

Cell theory was proposed past Theodor Schwann, Matthias Schleiden and Rudolf Virchow
The iii tenets are

1. All living organisms are composed of one or more than cells (Schwann and Schleiden, 1838-39)
2. The cell is the basic structural and functional unit of life (Schwann and Schleiden, 1838-39)
3. All cells ascend from pre existing cells by cell partition (Rudolf Virchow, 1858)
Even though cell theory is universal to a greater extend notwithstanding there are exceptions.

Notable exceptions are
1. Viruses are obligate intracellular parasites capable of replicating only within the host cell using the machinery of the host.

It consists of genetic material either DNA or RNA surrounded by a protein coat
Viruses are devoid of cell, protoplasm or cellular compartments like mitochondrion, chloroplast etc
Viruses don't accept a machinery to replicate independently. It depends on the host cell replication machinery to replicate inside the host prison cell

2. Viroids are pocket-sized, unencapsidated or naked ssRNA molecules

the smallest known pathogen of plants
smaller than the smallest virus
it consist of linear strand of RNA without a protein coat

Viroids

constitute in the cytoplasm of higher plants

eg: spud spindle tuber viroid (PSTVd)

3. Virusoids: are infectious sub viral particles consisting of single round RNA
These are viroids located within protein coat of true virus.

4. Prions: infectious protein particles causing diseases in man and domestic animals
Prions cause other neurological diseases such as Kuru and Gerstmann-Strausler-Sheinker syndrome, CJD (Creutzfeld-Jakob affliction)

5. Coenocytic algae like Vaucheria, and many fungus: The trunk is a continuous mass of protoplasm without cell wall and with many nucleus.
All the above mentioned particles exhibit characters of life just not cellular in its organisation.