DISCOVERY OF CELL
● Robert Hooke - dead cell discovery
● Anton Van Leeuwenhoek - living cell
● Purkinje - protoplasm
● Robert Brown - nucleus
FORMATION OF CELL THEORY
● Mathias Schleiden and Theodore Schwann
○ All organisms consist of one or more cells
○ Cells are the basic unit of structure of all organisms.
○ All cells arise only from pre-existing cells.
MODERN VERSION OF CELL THEORY
● Cells are the morphological and physiological unit of all living organisms.
● The properties of a given organism depends on those of its individual cells.
● Cells originate from other cells and continuity is maintained through genetic material.
● The smallest unit of life is the cell.
PROKARYOTES
● Those organisms whose cells are not subdivided by membrane into separate nucleus and
cytoplasm.
● Cells surrounded by plasma membranes containing respiratory enzymes.
● Cell wall is non-cellulosic.
● Ribosome (70S) is the only organelle found in prokaryotic cells.
● Nuclear membrane and nucleolus are absent.
● The nuclear material includes a single circular, double stranded DNA molecule which is often
called bacterial chromosome.
● Prokaryotic cells do not contain nucleoli.
EUKARYOTES
● Nucleated cells are structurally larger and complex than prokaryotic cells.
● It has different shapes, sizes and physiology.
● Cell is surrounded by plasma membranes.
● It consists of nucleus, mitochondria, ER, golgi complex, ribosomes (80S), lysosomes etc.
● Nuclear contents such as DNA , RNA , nucleoprotein and nucleolus remain separated from
the cytoplasm by perforated nuclear membrane.
MYCOPLASMAS
● It is the smallest self replicating organisms that are capable of cell free existence.
● Sizes range from 0.1-0.25 micrometres.
● Mycoplasmas were discovered by E. Nocard and E.R. Roux.
● It is also known as pleuropneumonia like organisms(PPLOs)
● They don't contain cell walls.
● They are filterable.
, ● They are resistant to antibiotics.
● Free living, saprophytes or parasites.
VIRUS
● It is a submicroscopic biological organism which lacks a cell wall.
● They are obligate parasites.
● They are infectious packages of genetic information.
● A virus is neither an organism nor a cell but it consists of a core of genetic material DNA or
RNA enclosed in a protein coat.
● They cannot grow or divide alone.
● In order to replicate a virus must first enter a host cell .
● They rely on the host cell's ribosomes and the protein synthetic machinery for translating
mRNA into protein.
● They lack enzymes for ATP generation and protein synthesis.
● The nucleic acid of the virus is protected by a protein coat called capsid.
● Each capsid is composed of protein subunits called capsomeres.
● Viruses whose capsids are not covered by an envelope are called non-enveloped viruses.
VIROIDS
● They are naked molecules of infectious RNA.
● They are pathogens of plants.
● They are smaller than viruses and lack a protein coat.
● Its genomes are single stranded circles of RNA.
● They are extremely stable, highly base paired rod like structures.
● The viroid RNA itself acts as a ribozyme.
VIRIONS
● It is an infectious form of virus.
● It exist outside the hot cell
● It consists of a nucleic acid core, protein coat and in some species an external envelope.
PRIONS
● They are proteinaceous infectious particles without nucleic acids.
● The name was coined by Stanley B Prusiner.
● Prions are responsible for 9 neurobiological diseases generally called transmissible
spongiform encephalopathies (TSE).
○ Mad cow disease in cattle.
○ Creutzfeldt Jakob disease and kuru in humans.
● The prion protein is a glycoprotein attached to the cell membrane by a covalently attached
phospholipid molecule.
● The property of prion protein is that it can fold into 2 alternative conformations.
● Prion disease occurs by 3 mechanisms.
○ Infectious prion disease- the pathological form that passes from one individual to
the other.
● Robert Hooke - dead cell discovery
● Anton Van Leeuwenhoek - living cell
● Purkinje - protoplasm
● Robert Brown - nucleus
FORMATION OF CELL THEORY
● Mathias Schleiden and Theodore Schwann
○ All organisms consist of one or more cells
○ Cells are the basic unit of structure of all organisms.
○ All cells arise only from pre-existing cells.
MODERN VERSION OF CELL THEORY
● Cells are the morphological and physiological unit of all living organisms.
● The properties of a given organism depends on those of its individual cells.
● Cells originate from other cells and continuity is maintained through genetic material.
● The smallest unit of life is the cell.
PROKARYOTES
● Those organisms whose cells are not subdivided by membrane into separate nucleus and
cytoplasm.
● Cells surrounded by plasma membranes containing respiratory enzymes.
● Cell wall is non-cellulosic.
● Ribosome (70S) is the only organelle found in prokaryotic cells.
● Nuclear membrane and nucleolus are absent.
● The nuclear material includes a single circular, double stranded DNA molecule which is often
called bacterial chromosome.
● Prokaryotic cells do not contain nucleoli.
EUKARYOTES
● Nucleated cells are structurally larger and complex than prokaryotic cells.
● It has different shapes, sizes and physiology.
● Cell is surrounded by plasma membranes.
● It consists of nucleus, mitochondria, ER, golgi complex, ribosomes (80S), lysosomes etc.
● Nuclear contents such as DNA , RNA , nucleoprotein and nucleolus remain separated from
the cytoplasm by perforated nuclear membrane.
MYCOPLASMAS
● It is the smallest self replicating organisms that are capable of cell free existence.
● Sizes range from 0.1-0.25 micrometres.
● Mycoplasmas were discovered by E. Nocard and E.R. Roux.
● It is also known as pleuropneumonia like organisms(PPLOs)
● They don't contain cell walls.
● They are filterable.
, ● They are resistant to antibiotics.
● Free living, saprophytes or parasites.
VIRUS
● It is a submicroscopic biological organism which lacks a cell wall.
● They are obligate parasites.
● They are infectious packages of genetic information.
● A virus is neither an organism nor a cell but it consists of a core of genetic material DNA or
RNA enclosed in a protein coat.
● They cannot grow or divide alone.
● In order to replicate a virus must first enter a host cell .
● They rely on the host cell's ribosomes and the protein synthetic machinery for translating
mRNA into protein.
● They lack enzymes for ATP generation and protein synthesis.
● The nucleic acid of the virus is protected by a protein coat called capsid.
● Each capsid is composed of protein subunits called capsomeres.
● Viruses whose capsids are not covered by an envelope are called non-enveloped viruses.
VIROIDS
● They are naked molecules of infectious RNA.
● They are pathogens of plants.
● They are smaller than viruses and lack a protein coat.
● Its genomes are single stranded circles of RNA.
● They are extremely stable, highly base paired rod like structures.
● The viroid RNA itself acts as a ribozyme.
VIRIONS
● It is an infectious form of virus.
● It exist outside the hot cell
● It consists of a nucleic acid core, protein coat and in some species an external envelope.
PRIONS
● They are proteinaceous infectious particles without nucleic acids.
● The name was coined by Stanley B Prusiner.
● Prions are responsible for 9 neurobiological diseases generally called transmissible
spongiform encephalopathies (TSE).
○ Mad cow disease in cattle.
○ Creutzfeldt Jakob disease and kuru in humans.
● The prion protein is a glycoprotein attached to the cell membrane by a covalently attached
phospholipid molecule.
● The property of prion protein is that it can fold into 2 alternative conformations.
● Prion disease occurs by 3 mechanisms.
○ Infectious prion disease- the pathological form that passes from one individual to
the other.
