Download Basic structure and organization of Eukaryotic cell in Comparison to

Structure and Organization of
Eukaryotic cell
Plasma membrane
• Eukaryotes resemble Prokaryotes in membrane
structure and functions except for sterols
• Source: http://bioweb.wku.edu.
Cell wall
• Cell wall is quite simple.
• In algae and plant cells, the cell
wall is usually composed of
cellulose.
• In molds it is composed of chitin
and/or cellulose.
• Animal cells and protozoans lack
cell walls.
Flagella and Motility in eukaryotes
• Many eukaryotic microorganisms move by flagella
and cilia
• Cilia are shorter than flagella - structurally similar
• Flagella are long, flexible structures move in a
whiplash fashion
• Both consist of 9 fused pairs of protein microtubules
(tubulin) with side arms of the motor molecule dynein
that originate from a centriole. These form a ring around
an inner central pair of microtubules that arise from a
plate near the cell surface. The arrangement of
microtubules is known as a 2X9+2 arrangement. This
complex of microtubules is surrounded by a sheath
continuous with the cytoplasmic membrane.
Source: http://. micro.magnet.fsu.edu
• cilia are more in numbers, beat in a coordinated
fashion called metachronal rhythm
• Amoeba and slime moulds show a movement
produced by their cytoplasm, called cytoplasmic
streaming
• produces projections, called pseudopodia
Mitochondria
• Approximately the same size as bacteria
• Number - varies in cells
• The process of respiration and oxidative
phosphorylation localized in mitochondria
• The mitochondrial membranes lack sterols.
ATP synthesized within the mitochondrion can
move into the cytoplasm
• Cristae - project into the mitochondrial lumen
• enzymes involved in ATP production are located
within the inner membrane
• Enzymes of TCA cycle and β – oxidation are
located in the matrix
• Mitochondria use its DNA, ribosomes to produce
some of its own proteins
• Mitochondria reproduce by binary fission
Chloroplasts
• All photosynthetic eukaryotic organisms, possess
chloroplasts
• structures of chloroplast reveals thylakoids
• thylakoid membrane is impermeable to ions well
suited for its role in protein translocation
• thylakoids are stacked grana
• stroma of chloroplasts contain enzymes for
reduction of CO2 to organic material
• outer chloroplast membrane is highly permeable
• Although some bacteria are photosynthetic, do not
possess chloroplasts
Structure of a chloroplast
Eukaryotic ribosomes
Endoplasmic Reticulum and Golgi bodies
• The endoplasmic reticulum or ER is a maze of parallel
membranous tubules and flattened sacs surrounding the
nucleus that connects with the nuclear membrane and
runs throughout the cytoplasm
• provide a surface area for protein and lipid synthesis;
• form a pathway for transporting molecules within the cell;
and
• provide a storage area for molecules the cell has
synthesized.
• Golgi
• sort proteins and lipids received from the ER;
• modify certain proteins and glycoproteins; and
• sort and package these molecules into vesicles for
transport to other parts of the cell or secretion from the
cell.
Nuclei
• Eukaryotic organisms possess a nuclear envelope
contains the genetic material
• envelope consists of two membranes
• outer membrane carries ribosomes and forms
continuous structure with the endoplasmic reticulum
and cytoplasmic membrane
• nuclear envelope encloses chromosomes in
chromosomal proteins
• called histones
• DNA exists as a single linear molecule to which
histones and other proteins are attached
• number of chromosomes vary from a few to many
hundreds
Structure of a nucleus
Source: http://micro.magnet.fsu.edu.
•Eukaryotic cells contain much
more DNA than do bacteria,
•DNA is organized as multiple
chromosomes located within a
nucleus.
•The nucleus in eukaryotic cells
is separated from the
cytoplasm by a nuclear
envelope
• The nucleus divides my
mitosis , a process that ensures
each daughter cell receives the
same number of chromosomes
as the original parent cell.
•Haploid sex cells are produced
from diploid cells by meiosis
The cytoskeleton
• cytoplasm of eukaryotic cells contain network of
microfilaments and microtubules
• filaments contain a number of proteins including
actin and myosin
• Cytoskeleton maintenance of cell shape,
positioning
cell
organelles
cell
motility
(Spirochactes
is
an
exception
among
Prokaryotes in having cytoskeleton)
Cytoskeleton
http://academic.brooklyn.cuny.edu.
Comparison of Prokaryotic and
Eukaryotic cell
Characters
Prokaryotes
Eukaryotes
Groups where
found
Bacteria, Cyanobacteria,
Archaea
Algae, Fungi, Protoza, Plants
and Animals
Size
1-2 by 1-4 µm or less
Greater than 5 µm
Cell wall
Made up of peptidoglycan
Made of cellulose in algae and
plants, of fungal cellulose or
chitin in fungi, absent in
protozoan and animals
Osmotic control
Wall possesses mechanical
strength necessary to counter
balance turgor pressure of
cytoplasm
Plasma membrane Does not contain sterols except
in Mycoplasma
Maintained by contractile
vacuole
Sterol present
Plasma membrane is the Several cell organelles also covered
only membrane
by membrane (Unit membrane)
Plasma membrane folded
to form mesosomes.
Mesosomes are absent, but in
animal cells, it is folded to form
finger like microvilli.
Cytoplasm
Ribosomes
Granular due to presence
Fibrillar made up of fibrous
of ribosomes, fibrous
proteins which form fibrous
cytoskeleton absent
cytoskeleton
70S, freely distributed in 80S free as well bounded to ER.
cytoplasm
70S in mitochondria and
chloroplast.
Mitochondria
Chloroplast
Absent
Present
Absent, in cyanobacteria Present in plant cells and absent
thylakoid vesicles present. in fungi, protozoa and animal cell.
Golgi apparatus
Absent
Present
Lysosomes
Absent
Present
Endoplasmic Reticulum
Absent
Present
Peroxisomes
Absent
Present
Centrioles
Absent
Present
Nucleolus
Absent
Present
True vacuoles
Absent
Present
Gas vesicles
Present
Absent
Made up of flagellin fibrils.
Made up of tubulin
Flagellin sub-units arranged
microtubules arranged in
in a ring helically around a
9+2 formation
and
carboxysomes
Flagella
central core.
Pili
Present
Absent
Cilia
Absent
Present in protozoans
Chromosome
Usually 1
Variable, 2 to many
Circular, single chromosome,
Single, linear, double
single or double stranded,
stranded, helically
number
DNA
helically coiled, usually haploid coiled, chromosome
Extranuclear DNA
chromosome.
diploid.
Present in bacteria (plasmid
Absent except in
0.1-5% of bacterial
yeasts
chromosome)
Histone proteins
Absent
Present
DNA position,
Usually central, not surrounded
Surrounded by
nuclear membrane
by nuclear membrane
nuclear membrane
Locomotion
Present in some
Absent in plants, algae, fungi, except in
bacteria, by flagella.
zoospores and few unicellular algae
and fungi, present in animals and
protozoans. (flagellated, ciliary,
amieboid, gliding)
Reproduction Simple fragmentation
Complex, meosis present, also by
or binary fission, no
fragmentation, binary fission and
meosis, asexual
asexual spores in some plants. Algae
spores produced in
and fungi and few protozoans.
some.
Genetic
Present in some but
recombination chromosomal cross
over absent.
By chromosomal cross over during
meiosis.