Eukaryotes
Eukaryotes comprise all members of Plant
Kingdom, Fungi and Animal Kingdoms, including the unicellular fungus Yeast, and
protozoans. Eukaryotic cells, like prorkaryotic cells are surrounded by a
plasma membrane. However, unlike prokaryotic cells, most eukaryotic cells
contain internal membrane bound organelles.
Each type of organelle plays a unique role in
the growth and metabolism of the cell, and each contains a set of enzymes that
catalyze requisite chemical reactions.
The largest organelle in a eukaryotic cell is
generally the nucleus, which houses
most of the cellular DNA. The DNA of eukaryotic cells is distributed among 1 to
about 50 long linear structures called chromosomes.
The number
and size of the chromosomes
are the same in all cells of an organism but vary among different species of
organisms. The total DNA ( the genetic information) in the chromosomes of an
organism is referred to as its genome.
In addition to the nucleus, several other organelles are present in nearly all
eukaryotic cells, the mitochondria in
which the cell's energy metabolism is carried out, the rough and smooth endoplasmic reticula, a network of membranes in which proteins and
lipids are synthesized and peroxysomes,
in which fatty acids and amino acids are degraded. Chloroplasts, the site of photosynthesis are found only in plants
and some single celled organisms. Both plant cells and some single celled
eukaryotes contain one or more vacuoles,
large, fluid - filled organelles in which nutrients and waste compounds are
stored and some degradative reactions occur. The cytosol of eukaryotic cells
contains an array of fibrous proteins collectively called the cytoskeleton. Cytosol is the soluble
part of the cytoplasm. It is located between the cell organelles. The plant cell has a rigid cell wall composed of cellulose and
other polymers. The cell wall contributes to the strength and rigidity of plant
cell.
Some
familiar prokaryotes are: Bacteria,
filamentous bacteria (Actinomycetes)
and Cyanobacteria.
Some familiar eukaryotes are: Fungi, plants and animals.
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