Cells are divided into 3 types,based on presence of nuclear membrane and cellular organelles.
1.Prokaryotes are single-celled organisms
that are the earliest and most primitive forms of life on earth.
Pro = before; karyon = nucleus
Relatively small - 5 to 10 um
Lack membrane-bound organelle
Prokaryotes are single
celled organisms that do not have a nucleus, mitochondria or any other membrane
bound organelles. In other words neither their DNA, nor any of their other
sites of metabolic activity, are collected together in a discrete membrane
enclosed area. Instead everything is openly accessible within the cell,
Prokaryotes come in two
sorts, Archaea and Bacteria.
2.Archaea :
Originally thought to be prokaryotes
Relatively small - 5 to 10 um.Lack membrane-bound organelles.
Usually live in extreme environments (thermophiles, halophiles, etc)
Usually live in extreme environments (thermophiles, halophiles, etc)
But these are connecting link between Prokaryotes and Eukaryotes
Archaea
at first appear to be a mixture between the two. A nice way to sum it up "eukaryote in a bacterium's clothing".
Their cells look a lot like prokaryotes because they are similar size, have no
nucleus, endomembranes or cytoskeleton. However, some archaeas' DNA is
bound by histones and they use similar machinery as eukaryotes for DNA
replication, transcription and translation.
3.Eukaryotes:
Eu = true; karyon = nucleus
contain membrane-bound organelles
Evolved from prokaryotes by endosymbiotic
association of two or more prokaryotes
Include Protists, Fungi, Animals, and Plants
Eukaryotic
cells are ten times greater in size than prokaryotic cells.
Eukaryotic
cells possess a plasma membrane (a phospholipid bilayer that encloses the
cell).
Both cystol and ribosomes make up the cytoplasm in eukaryotic cells.
The Endomembrane system in a
eukaryotic cell is a system of membranes that exchange materials.
The golgi apparatus, endoplasmic reticulum, and lysosomes are all members of the endomembrane system.
The golgi apparatus, endoplasmic reticulum, and lysosomes are all members of the endomembrane system.
Transport and signalling functions are carried out
on a eukaryotic cell's plasma membrane.
A eukaryote's extra-cellular matrix is composed of proteins and glycoproteins that have been secreted by cells .The extra-cellular matrix surrounds many animal cells.
A eukaryote's extra-cellular matrix is composed of proteins and glycoproteins that have been secreted by cells .The extra-cellular matrix surrounds many animal cells.
Cell organelles
are Nucleus , Endoplasmic
Reticulum Rhibosomes , Lysosomes , Mitochondria , Chloroplast, Golgi apparturs, Vacuole , all are membranous and non-membranous organelles that have specific functions within the
cell .Different eukaryotic cells contain different types and quantities of other
organelles depending on the type and function of the particular cell e.g. many
plant cells contain chloroplasts which are the sites of photosynthesis within
those cells .Locomotion of a eukaryotic cell is aided by flagella
or cilia.Cell division is usually by mitosis
although meiosis applies to some specific types of cells concerned with sexual
reproduction.Examples of eukarotic cells are muscle fibres,leucocytes and neuroglia are types of animal cells,and parenchyma cells, collenchyma
cells and sclerenchyma cells, which are types of plant cells
