PROKARYOTIC CELL AND EUKARYOTIC CELL
PROKARYOTIC CELL
Prokaryotes are one of the most
ancient categories of living organisms on our blue planet Earth, with fossil
records dating back to almost
3.5 billion years ago.
The term “prokaryote” is obtained from the Greek
word “pro”, (meaning: before) and “karyon” (meaning: kernel). It
translates to “before nuclei.”
These prokaryotes flourished in
the earth’s very old environment, some using up chemical energy and others
using the sun’s energy. These extremephiles flourished for millions of
years, evolving and adapting. Scientists consider that these living beings gave
rise to the eukaryotes.
DEFINING
CHARACTERISTIC OF PROKARYOTIC CELLS
·
Prokaryotic cells are comparatively tinier
and much uncomplicated than eukaryotic cells.
·
Prokaryotic cells do not possess
membrane-bound cell organelles such as a nucleus.
·
Reproduction happens through the
process of binary fission.
STRUCTURE
OF PROKARYOTES
Structurally, Prokaryotes have:
·
A casing or capsule like structure
enveloping its whole body, and it functions as a protective layer or coat. This
is crucial for preventing the process of phagocytosis.
Ø PHAGOCYTOSIS: The process by which certain living cells called
phagocytes ingests or engulfs other cells or particles. The phagocyte may
be a free-living one-celled organism, such as an amoeba, or one of the body
cells, such as a white blood cell. The process of phagocytosis often happens
when the cell is trying to destroy something, like a virus or an infected cell,
and is often used by immune system cells.
· PILUS: The Pilus is a hair-like (Latin for 'hair'; plural: pili) appendage found on the external surface of most prokaryotes. Pilus helps the organism to attach itself to various environments. They range from a few fractions of a micrometer to > 20 μ.m. in length and vary from < 2 to 11 nm in diameter. Their functions include mediation of cell-to-cell interactions, motility, and DNA (Deoxyribonucleic acid) uptake. It is commonly observed in bacteria.
·
CELL WALL:
located right below the protective layer, which gives potency and rigidity to
the cell.
·
CYTOPLASM: it
helps in cellular growth and this is contained within the plasma membrane,
which separates the interior contents of the cell from the outside
environment. Within the cytoplasm, ribosome exists and it plays an important
role in protein synthesis. It is also one of the smallest components
within the cell.
·
SPECIAL STRUCTURES
Some
prokaryotic cells contain special structures called Mesosomes, which helps in cellular respiration.
·
PLASMIDS
Most prokaryotes also contain
plasmids, which contains small, circular pieces of DNA. To assist with
locomotion, flagella are present, though; Pilus can also serve as an aid
for locomotion.
EXAMPLES
OF PROKARYOTES:
v Bacteria: Are types
of biological cell. They constitute a
large domain of prokaryotic microorganisms. Typically a
few micrometers in length, bacteria have a number of shapes,
ranging from spheres to rods and spirals. Bacteria
were among the first life forms to appear on Earth, and are present in
most of its habitats.
v Archaea: A
domain of single-celled organisms, these microorganisms lack cell nuclei
and are therefore prokaryotes.
v Kingdom
Monera: These are the oldest known microorganisms on earth. The
organisms belonging to this kingdom do not contain a true nucleus meaning they
are prokaryotes. Their DNA is not enclosed within the nucleus. They do not
possess any membrane-bound organelles. They are found mostly in a moist environment, in hot springs, snow,
deep oceans, or as parasites in other organisms. Bacteria and Archaea are also Monerans.
Ø
MONERAN: Monerans are unicellular, prokaryotic organisms found in a
moist environment and lack a true nucleus.
EUKARYOTIC CELL
Eukaryotes are more complicated and
much larger than the prokaryotes. They include almost all the major
kingdoms except kingdom Monera.
The term “Eukaryotes” is
derived from the Greek word “eu“, (meaning: good) and “karyon”
(meaning: kernel), therefore, translating to “good or true nuclei.”
STRUCTURE
OF EUKARYOTES
Structurally, eukaryotes have:
·
CELL WALL:
it provides both additional support and
protects the plasma membrane. It can be tough, flexible, and
sometimes rigid. Cell is surrounded by the plasma
membrane and it controls the entry and exit of certain substances.
·
NUCLEUS: The nucleus was the first of the cell
organelles to be discovered by scientists.
Nucleus is a large, spherical organelle present in all the cells. It contains DNA, which is accountable for storing all
genetic information called chromosomes. The nucleus is surrounded by the
nuclear membrane.
·
NUCLEOULES:
Within the nucleus exists the nucleolus, and it plays an important role in
synthesizing proteins.
· \
MITOCHONDRIA:
They are responsible for the creation of energy, which is then utilized by the cell.
·
CHLOROPLASTS:
Present in only plant cells, chloroplasts are the sub cellular sites of
photosynthesis.
·
ENDOPLASMIC RETICULUM or ER: it helps in the
transportation of materials. Besides these, there are also other cell organelles that perform various other
functions and these include Ribosome, Lysosome, Golgi bodies, cytoplasm,
chromosomes, vacuoles and Centrosomes.
EXAMPLES OF EUKARYOTES:
It includes almost all the unicellular
organism with a nucleus and all multi-cellular organisms.
DIFFERENCE BETWEEN PROKARYOTIC AND
EUKARYOTIC CELL
The nucleus is defining
characteristic feature that differentiates the prokaryotic and eukaryotic
cell. In prokaryotic cells, does not have a true nucleus and membrane-bound
organelles on the other hand eukaryotic cells have membrane-bound organelles and
true nucleus is present.
One
more differentiating characteristic is prokaryotic entirely unicellular while
the same does not apply to eukaryotic cells.
Comments
Post a Comment