Download Animal Cell Structure

Cell Structure
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Animal Cell Structure
Animal cells are typical of the eukaryotic cell, enclosed by a plasma membrane and containing a membranebound nucleus and organelles. Unlike the cells of the two other eukaryotic kingdoms, plants and fungi, animal
cells don't have a cell wall. This feature was lost in the distant past by the single-celled organisms that gave rise
to the kingdom Animalia.
The lack of a rigid cell wall allowed animals to
develop a greater diversity of cell types, tissues, and
organs. Specialized cells that formed nerves and
muscles -- tissues impossible for plants to evolve -gave these organisms mobility. The ability to move
about by the use of specialized muscle tissues is the
hallmark of the animal world. (Protozoans locomote,
but by non-muscular means, i.e. cilia, flagella,
pseudopodia.)
The animal kingdom is unique amongst eukaryotic
organisms because animal tissues are bound together
by a triple helix of protein, called collagen. Plant and
fungal cells are bound together in tissues or
aggregations by other molecules, such as pectin. The
fact that no other organisms utilize collagen in this
manner is one of the indications that all animals arose
from a common unicellular ancestor.
Animals are a large and incredibly diverse group of organisms. Making up about three-quarters of the species on
Earth, they run the gamut from sponges and jellyfish to ants, whales, elephants, and -- of course -- human
beings. Being mobile has given animals the flexibility to adopt many different modes of feeding, defense, and
reproduction.
The earliest fossil evidence of animals dates from the Vendian Period (650 to 544 million years ago), with
coelenterate-type creatures that left traces of their soft bodies in shallow-water sediments. The first mass
extinction ended that period, but during the Cambrian Period which followed, an explosion of new forms began
the evolutionary radiation that produced most of the major groups, or phyla, known today. Vertebrates (animals
with backbones) are not known to have occurred until the Ordovician Period (505 to 438 million years ago).
Components of a cell
Centrioles - Centrioles are self-replicating organelles made up of nine bundles of microtubules and are found
only in animal cells. They appear to help in organizing cell division, but aren't essential to the process.
Cilia and Flagella - For single-celled eukaryotes, cilia and flagella are essential for the locomotion of individual
organisms. In multicellular organisms, cilia function to move fluid or materials past an immobile cell as well as
moving a cell or group of cells.
Endoplasmic Reticulum - The endoplasmic reticulum is a network of sacs that manufactures, processes, and
transports chemical compounds for use inside and outside of
the cell. It is connected to the double-layered nuclear envelope,
ET YMOLOGY OF CELL
providing a connection between the nucleus and the
Derived from Latin cella "small room,
cytoplasm.
hut, store room, clam, secret;"related to
Golgi Apparatus - The Golgi apparatus is the distribution and
L. celare "to hide, conceal"; Also from
Gk. kalia "hut, nest". Earliest sense was
shipping department for the cell's chemical products. It
for monastic rooms, then prison rooms
modifies proteins and fats built in the endoplasmic reticulum
(1722). Used in biology in 17c., but not in
and prepares them for export to the outside of the cell.
modern sense until 1845. Also means
Lysosomes - The main function of these microbodies is
"small group of people working within a
digestion. Lysosomes break down cellular waste products and
larger organization", usage of which
debris from outside the cell into simple compounds, which are
was from 1925. Cellphone was from
1984.
(Called
so
because
the
transferred to the cytoplasm as new cell-building materials.
geographic region served by a cellular
Microfilaments - Microfilaments are solid rods made of
system is subdivided into areas called
globular proteins called actin. These filaments are primarily
cells!!)
structural in function and are an important component of the
cytoskeleton.
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Microtubules - These straight, hollow cylinders, composed of tubulin protein, are found throughout the
cytoplasm of all eukaryotic cells and perform a number of functions.
Mitochondria - Mitochondria are oblong shaped organelles that are found in the cytoplasm of every eukaryotic
cell. In the animal cell, they are the main power generators, converting oxygen and nutrients into energy.
Nucleus - The nucleus is a highly specialized organelle that serves as the information and administrative center
of the cell.
Peroxisomes - Microbodies are a diverse group of organelles that are found in the cytoplasm, roughly spherical
and bound by a single membrane. There are several types of microbodies but peroxisomes are the most
common.
Plasma Membrane - All living cells have a plasma membrane that encloses their contents. In prokaryotes, the
membrane is the inner layer of protection surrounded by a rigid cell wall. Eukaryotic animal cells have only the
membrane to contain and protect their contents. These membranes also regulate the passage of molecules in and
out of the cells.
Ribosomes - All living cells contain ribosomes, tiny organelles composed of approximately 60 percent RNA
and 40 percent protein. In eukaryotes, ribosomes are made of four strands of RNA. In prokaryotes, they consist
of three strands of RNA.
Nucleus
The nucleus is a highly specialized organelle that serves as the
information and administrative center of the cell. This
organelle has two major functions. It stores the cell's
hereditary material, or DNA, and it coordinates the cell's
activities, which include intermediary metabolism, growth,
protein synthesis, and reproduction (cell division).
ET YMOLOGY OF NUCLEUS
Means "kernel of a nut," or, "head of a
comet," from L. nucleus "kernel," from
nucula "little nut". General sense of
"central part or thing, about which
others cluster" is from 1762. Use in
reference to cells was first recorded in
1831. Modern atomic meaning was in
1912, first by Ernest Rutherford, though
theoretical use for "central point of an
atom" was from 1844, by Faraday.
Only the cells of advanced organisms, known as eukaryotes,
have a nucleus. Generally there is only one nucleus per cell,
but there are exceptions such as slime molds and the
Siphonales group of algae. Simpler one-celled organisms
(prokaryotes), like the bacteria and cyanobacteria, don't have
a nucleus. In these organisms, all the cell's information and administrative functions are dispersed throughout
the cytoplasm.
The spherical nucleus occupies about 10 percent of a cell's volume, making it the cell's most prominent feature.
Most of the nuclear material consists of chromatin, the unstructured
form of the cell's DNA that will organize to form chromosomes during
mitosis or cell division. Also inside the nucleus is the nucleolus, an
organelle that synthesizes protein-producing macromolecular
assemblies called ribosomes.
A double-layered membrane, the nuclear envelope, separates contents
of the nucleus from the cellular cytoplasm. The envelope is riddled
with holes called nuclear pores that allow specific types and sizes of
molecules to pass back and forth between the nucleus and the
cytoplasm. It is also attached to a network of tubules, called the
endoplasmic reticulum, where protein synthesis occurs. These tubules
extend throughout the cell and manufacture the biochemical products
that a particular cell type is genetically coded to produce.
Chromatin/Chromosomes - Packed inside the nucleus of every human cell is nearly 6 feet of DNA, which is
divided into 46 individual molecules, one for each chromosome and each about 1.5 inches long. Packing all this
material into a microscopic cell nucleus is an extraordinary feat of packaging. For DNA to function, it can't be
crammed into the nucleus like a ball of string. Instead, it is
combined with proteins and organized into a precise, compact
structure, a dense string-like fiber called chromatin.
ETYMOLOGY OF CHROMOSOME
From Greek. khroma "colour" + soma
Each DNA strand wraps around groups of small protein
"body." So called because the structures
molecules called histones, forming a series of bead-like
contain a substance that stains readily
structures, called nucleosomes, connected by the DNA strand.
with basic dyes. The prefixes of
Under the microscope, uncondensed chromatin has a "beads
Euchromatin and Heterochromatin are
on a string" appearance.
derived from Greek. eu- "well" and
The string of nucleosomes, already compacted by a factor of
heteros "the other (of two), another,
different".
six, is then coiled into an even denser structure, compacting
the DNA by a factor of 40. This compression and structuring
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Cell Structure
of DNA serves several functions. The overall negative charge of the DNA is neutralized by the positive charge
of the histone molecules, the DNA takes up much less space, and inactive DNA can be folded into inaccessible
locations until it is needed.
There are two types of chromatin. Euchromatin is the genetically active portion and is involved in transcribing
RNA to produce proteins used in cell function and growth. Heterochromatin contains inactive DNA and is the
portion of chromatin that is most condensed, since it not being used.
Throughout the life of a cell, chromatin fibers take on different forms inside the nucleus. During interphase,
when the cell is carrying out its normal functions, the chromatin is dispersed throughout the nucleus in what
appears to be a tangle of fibers. This exposes the euchromatin and makes it available for the transcription
process.
When the cell enters metaphase and prepares to divide, the chromatin changes dramatically. First, all the
chromatin strands make copies of themselves through the process of DNA replication. Then they are
compressed to an even greater degree than at interphase, a 10,000-fold compaction, into specialized structures
for reproduction, termed chromosomes. As the cell divides to become two cells, the chromosomes separate,
giving each cell a complete copy of the genetic information contained in the chromatin.
Nucleolus - The nucleolus is a membrane-less organelle within the nucleus that manufactures ribosomes, the
cell's protein-producing structures. Through the microscope, the nucleolus looks like a large dark spot within the
nucleus. A nucleus may contain up to four nucleoli, but within each species the number of nucleoli is fixed.
After a cell divides, a nucleolus is formed when chromosomes are brought together into nucleolar organizing
regions. During cell division, the nucleolus disappears. Some studies suggest that the nucleolus may be involved
with cellular aging and, therefore, may affect the aging of an organism.
Nuclear Envelope - The nuclear envelope is a double-layered membrane that encloses the contents of the
nucleus during most of the cell’s lifecycle. The space between the layers is called the perinuclear space and
appears to connect with the rough endoplasmic reticulum. The envelope is perforated with tiny holes called
nuclear pores. These pores regulate the passage of molecules between the nucleus and cytoplasm, permitting
some to pass through the membrane, but not others. The inner surface has a protein lining called the nuclear
lamina, which binds to chromatin and other nuclear components. During mitosis, or cell division, the nuclear
envelope disintegrates, but reforms as the two cells complete their formation and the chromatin begins to
unravel and disperse.
Nuclear Pores - The nuclear envelope is perforated with holes called nuclear pores. These pores regulate the
passage of molecules between the nucleus and cytoplasm, permitting some to pass through the membrane, but
not others. Building blocks for building DNA and RNA are allowed into the nucleus as well as molecules that
provide the energy for constructing genetic material.
The pores are fully permeable to small molecules up to the size of the smallest proteins, but form a barrier
keeping most large molecules out of the nucleus. Some larger proteins, such as histones, are given admittance
into the nucleus. Each pore is surrounded by an elaborate protein structure called the nuclear pore complex,
which probably selects large molecules for entrance into the nucleus.
Centrioles
Found only in animal cells, these paired organelles are found together
near the nucleus, located at right angles to each other. Each centriole
is made of nine bundles of microtubules (three per bundle) arranged in
a ring. They have a role in building cilia and flagella, during which
time they are referred to as basal bodies.
Centrioles also play a role in cell division, although not as significant
a role as once thought. Plant cells reproduce without centrioles and in
experiments that have removed centrioles from animal cells, the cells
were able to reproduce successfully without the organelles.
Apparently they organize the microtubules in the mitotic spindles
during mitosis and meiosis. The mitotic spindles in plant cells are less
tightly organized.
These structures are self-replicating and make copies of
ETYMOLOGY OF CENTRIOLE
themselves just before cell division begins. As the cell
Origin German Zentriol from Zentrum “or
prepares to divide, the centrioles separate and move toward
Greek Kentron for “centre”.
opposite poles of the cell. As they're moving apart, they
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radiate microtubules in a spindle-shaped formation that spans the cell from pole to pole. The spindle fibers act as
guides for the alignment of the chromosomes as they separate.
Cilia and Flagella
Cilia and flagella are made up of microtubules, which are
composed of linear polymers of globular proteins called
tubulin. The core (axoneme) contains two central fibers that
are surrounded by an outer ring of nine double fibers and
covered by the cellular membrane.
These motile appendages are constructed by basal bodies
(kinetostomes), which also function as centrioles. The basal
body is located at the base of each filament, anchoring it to the
cell and controlling its movement. Cilia and flagella have the
same structure. The only difference is that the flagella are
longer.
For single-celled eukaryotes, cilia and flagella are essential for
the locomotion of individual organisms. Protozoans belonging to the phylum Ciliophora are covered with cilia.
Flagella are a characteristic of the protozoan group Mastigophora.
In multicellular organisms, cilia function to move fluid or
materials past an immobile cell as well as moving a cell or
group of cells. The respiratory tract in humans is lined with
cilia that keep inhaled dust, smog, and potentially harmful
microorganisms from entering the lungs. Cilia generate water
currents to carry food and oxygen past the gills of clams and
transport food through the digestive systems of snails. Flagella
are found primarily on gametes, but also create the water
currents necessary for respiration and circulation in sponges
and coelenterates.
ETYMOLOGY OF CILIUM &
FLAGELLUM
Cilium (pl Cilia) is derived from from
Latin for “eyelid”; akin to Latin celare to
conceal. Flagellum (pl flagella) is
derived from Latin for "whip", “shoot of a
plant”.
Endoplasmic Reticulum
The endoplasmic reticulum (ER) is a network of sacs that
manufactures, processes, and transports chemical compounds for use
inside and outside of the cell. The ER is a continuous membrane with
branching tubules and flattened sacs that extend throughout the
cytoplasm. It is connected to the double-layered nuclear envelope,
providing a connection between the nucleus and the cytoplasm.
There are two kinds of ER, rough and smooth. Rough ER is covered
with ribosomes, giving it a bumpy appearance when viewed through
the microscope. This type of ER is involved mainly with the
production of proteins that will be exported, or secreted, from the cell.
The ribosomes assemble amino acids into units of proteins, which are transported into the rough ER for further
processing. Once inside, the proteins are folded into the correct three-dimensional conformation, as a flattened
cardboard box might be opened up and folded into its proper shape in order to become a useful box. Chemicals,
such as carbohydrates or sugars, are added, then the ER either transports the completed proteins to areas of the
cell where they are needed, or they are sent to the Golgi apparatus for export.
Smooth ER has a smoother appearance than rough ER when viewed through the microscope because it does not
have ribosomes attached to it. This portion of the ER is
involved with the production of lipids (fats), carbohydrate
metabolism, and detoxification of drugs and poisons. Smooth
ETYMOLOGY OF ENDOPLASMIC
ER is also involved with metabolizing calcium to mediate
RETICULUM
From Greek. endon "within, + plassein,
some cell activities. In muscle cells, smooth ER releases
to mold + Latin reticulum "little net," dim.
calcium to trigger muscle contractions. Cells specializing in
of rete "net".
lipid and carbohydrate metabolism (brain, muscle) or
detoxification (liver) usually have more of this type of ER.
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Cell Structure
Golgi Apparatus
The Golgi apparatus (GA), also called Golgi body or Golgi
complex, is a series of five to eight cup-shaped, membranecovered sacs that look something like a stack of deflated balloons.
The GA is the distribution and shipping department for the cell's
chemical products. It modifies proteins and lipids (fats) that have
been built in the endoplasmic reticulum and prepares them for
export as outside of the cell. The number of GAs in each cell
varies according to its function, but animal cells generally contain
between ten and twenty per cell.
Proteins and lipids built in the smooth and rough endoplasmic reticulum bud off in tiny bubble-like vesicles that
move through the cytoplasm until they reach the GA. The
vesicles fuse with the GA membrane and release the molecules
into the organelle. Once inside, the compounds are further
ETYMOLOGY OF GOLGI APPARATUS
processed by the GA, which adds molecules or chops tiny
Eponymous. Italian histologist Camillo
Golgi (1844-1926) who first observed it in
pieces off the ends. Once completed, the
1909. He shared 1906 Nobel Prize for
product is extruded from the GA in a vesicle
research on the structure of the nervous
and directed to its final destination inside or
system, with Ramón y Cajal. He
outside the cell. The exported products are
recognized that the three types of
secretions of proteins or glycoproteins that are
malaria are caused by different
part of the cell's function in the organism.
protozoan organisms. Golgi taught at
the Univ. of Pavia from 1875.
Other products are returned to the
endoplasmic reticulum or become lysosomes.
Lysosomes
The main function of these microbodies is digestion. Lysosomes break down
cellular waste products and debris from outside the cell into simple
compounds, which are transferred out into the cytoplasm as new cell-building
materials.
Like other microbodies, lysosomes are spherical organelles contained by a
single layer membrane. This membrane protects the rest of the cell from the
lysosomes’ harsh digestive enzymes that would otherwise damage it.
Lysosomes originate in the Golgi apparatus, but the digestive enzymes are
manufactured in the rough endoplasmic reticulum. Lysosomes are found in all
eukaryotic cells, but are most numerous in disease-fighting cells, such as
white blood cells.
Some human diseases are caused by lysosome enzyme disorders. Tay-sachs disease is caused by a genetic defect
that prevents the formation of an essential enzyme that breaks
down a complex lipid called ganglioside. An accumulation of
ETYMOLOGY OF LYSOSOME
this lipid damages the nervous system, causes mental
From Greek, lysein or lysis "a loosening,
retardation and death in early childhood. Arthritis
setting free, releasing, dissolution"+
soma, “body”.
inflammation and pain are related to the escape of lysosome
enzymes.
Microfilaments
Microfilaments are solid rods made of globular proteins called
actin and are common to all eukaryotic cells. Long chains of the
molecules are intertwined in a helix to form individual
microfilaments. These filaments are primarily structural in
function and are an important component of the cytoskeleton,
along with microtubules. In association with myosin,
microfilaments help to generate the forces used in cellular
contraction and basic cell movements. They enable a dividing
cell to pinch off into two cells and are involved in amoeboid movements of certain types of cells. They also
enable the contractions of muscle cells.
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Microtubules
These straight, hollow cylinders are found throughout the cytoplasm of all
eukaryotic cells (prokaryotes don't have them) and perform a number of
functions.
Microtubules form part of the cytoskeleton that gives structure and shape to a
cell, serve as conveyor belts moving other organelles through the cytoplasm, are
the major components of cilia and flagella, and participate in the formation of
spindle fibers during cell division (mitosis). Microtubules can function
individually or join with other proteins to create larger structures (e.g. cilia).
These filaments are composed of linear polymers of tubulin, which are globular
proteins, and can increase or decease in length by adding or removing tubulin
proteins
Mitochondria
Mitochondria (singular, mitochondrion) are oblong shaped organelles that
are found in the cytoplasm of every eukaryotic cell. They occur in varying
numbers, depending on the cell and its function.
These organelles are the power generators of the cell, converting oxygen
and nutrients into ATP (adenosine triphosphate). ATP is the chemical
energy "currency" of the cell that powers the cell's metabolic activities.
This process is called aerobic respiration and is the reason animals breathe
oxygen.
The mitochondrion is different from other organelles because it has its own
DNA and reproduces independently of the cell in which it is found; an
apparent case of endosymbiosis. Scientists hypothesize that millions of
years ago small, free-living prokaryotes were engulfed, but not consumed, by larger prokaryotes; perhaps
because they were able to resist the digestive enzymes of the engulfing organism.
The two organisms developed a symbiotic relationship over time, the larger organism providing the smaller with
ample nutrients and the smaller organism providing ATP molecules to the larger one. Eventually, the larger
organism developed into the eukaryotic cell, the smaller organism into the mitochondrion. Nonetheless, there
are a number of prokaryotic traits that mitochondria continue to exhibit. Their DNA is circular, as it is in the
prokaryotes, and their ribosomes and reproductive methods (binary fission) are more like those of the
prokaryotes.
Mitochondrial DNA can be used study different aspects of inheritance. In most animal species, mitochondria are
inherited through the maternal lineage. A sperm carries mitochondria in its tail as an energy source for its long
journey to the egg. When it attaches to the egg during fertilization, the tail falls off. Consequently, the only
mitochondria the new organism gets is from the egg its mother provided.
Unlike nuclear DNA, mitochondrial DNA doesn't get shuffled every generation, so it is presumed to change at a
slower rate. That fact is being used to study human evolution
and suggests that modern humans descended from a small
group of hominids in Africa around 200,000 years ago.
ETYMOLOGY OF MITOCHONDRION
Mitochondrial DNA is also being used in forensic science, as a
tool for identifying corpses or body parts, and has been
implicated in a number of genetic diseases such as Alzheimer's
disease and diabetes.
Derived from Greek, mitos, “thread” +
chondrion, diminutive of chondros
grain” (pl. mitochondria)
Peroxisomes
Microbodies are a diverse group of organelles that are found in the cytoplasm, roughly spherical and bound by a
single membrane. There are several types of microbodies but peroxisomes are the most common.
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Cell Structure
Peroxisomes function to rid the cell of toxic substances, in particular,
hydrogen peroxide -- a common byproduct of cellular metabolism.
These organelles contain enzymes that convert the hydrogen peroxide to
water, rendering the potentially toxic substance safe for release back into
the cell. Some types of peroxisomes, such as those in liver cells,
detoxify alcohol and other harmful compounds by transferring hydrogen
from the poisons to molecules of oxygen.
Peroxisomes are similar in appearance to lysosomes, another type of
microbody, but the two have very different origins. Lysosomes are
formed in the Golgi complex while peroxisomes are self-replicating.
Unlike mitochondria, however, peroxisomes and lysosomes do not have
their own internal DNA molecules.
Except for mature red blood cells, all human cells have peroxisomes. Since the early 1980s, a number of
metabolic disorders have been found to be caused by molecular defects in the peroxisomes. Two major
categories have been described so far. The first category is Disorders of Peroxisome Biogenesis (PBD) in which
the organelle fails to develop normally, causing defects in
numerous peroxisomal proteins. The second category includes
ETYMOLOGY OF PEROXISOME
involves defects of single peroxisomal enzymes. At present,
From peroxide + Greek, soma, “body”.
there are no treatments for these genetic disorders, save for
genetic counseling.
Plasma Membrane
All living cells, prokaryotic and eukaryotic, have a plasma
membrane that encloses their contents. The membrane has two
functions. First, it is a boundary holding the cell constituents
together and keeping other substances out.
Second, it is permeable, allowing nutrients and other essential
elements to enter the cell and waste materials to leave the cell.
Small molecules, such as oxygen, carbon dioxide, and water,
are able to pass freely across the membrane, but the passage of
larger molecules, such as amino acids and sugars, is carefully
regulated.
The membrane is made of a two molecule thick layer (bilayer)
of phospholipids, an oily substance found in all cells. This layer
is embedded with many diverse proteins and has carbohydrates attached to its outer surface. The lipids in the
membrane can exist either in a gel-like, nearly solid, state or in a liquid-like state, which gives the lipid
molecules more mobility. In living cells, the membrane seems to be in a transition between the two states,
depending on physical conditions and what lipids and proteins are present in the membrane layer.
In prokaryotes and plants, the plasma membrane is the inner layer of protection. A rigid cell wall forms the
outside boundary for the cell. While it has pores that allow materials to enter and leave the cell, they are not as
selective about what passes through. The membrane, which lines the cell wall, provides the final filter between
the cell interior and the environment.
Eukaryotic animal cells probably descended from prokaryotes that lost their cell walls. With only the flexible
membrane left to enclose them, they were able to expand in size and complexity. Eukaryotic cells are generally
ten times larger than prokaryotic cells and have membranes
enclosing interior components, the organelles. Like the exterior
ETYMOLOGY OF PLASMA MEMBRANE
plasma membrane, these membranes also regulate the flow of
Derived from Latin plasma, from Greek
materials, allowing the cell to segregate its chemical functions
plasma "something molded or created,"
from plassein "to mold. Usage as “liquid
into discrete internal compartments.
part of blood" was from 1845; that of
"ionized gas" was from 1928. Plasma in
plasma TV refers to to gases like neon
and xenon which glow when exposed
to an electrical field.
Although plants have evolved another version of the cell wall,
in animal cells the plasma membrane is the only barrier
between the cell and its environment.
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Ribosomes
All living cells contain ribosomes, tiny organelles composed of approximately 60 percent RNA and 40 percent
protein. In eukaryotes, ribosomes are made of four strands of RNA. In prokaryotes, they consist of three strands
of RNA.
Ribosomes are scattered throughout the cytoplasm and are the protein production
sites for the cell. Some of the proteins are synthesized for the cell's own use,
particularly in single-celled organisms. In multicellular organisms, many of the
proteins produced by a specialized cell, e.g. antibodies, will be transported and
used elsewhere in the organism.
Eukaryote ribosomes are produced and assembled in the nucleolus. Three of the
four strands are produced there, but one is produced outside the nucleolus and
transported inside to complete the ribosome assembly. Ribosomal proteins enter
the nucleolus and combine with the four strands to create the two subunits that
will make up the completed ribosome. The ribosome units leave the nucleus
through the nuclear pores and unite once in the cytoplasm. Some ribosomes will
remain free-floating in the cytoplasm, creating proteins for the cell's use. Others will attach to the endoplasmic
reticulum and produce the proteins that will be "exported" from the cell.
Protein synthesis requires the assistance of two other RNA molecules. Messenger RNA (mRNA) provides
instructions from the cellular DNA for building a specific
protein. Transfer RNA (tRNA) brings the protein building
ETYMOLOGY OF RIBOSOME
blocks, amino acids, to the ribosome. Once the protein
Coined
by
R.B.
Roberts
from
backbone amino acids are polymerized, the ribosome releases
ribo(nucleic acid) + -soma "body" in
1958.
the protein and it is transported to the Golgi apparatus. There,
the proteins are completed and released inside or outside the
cell.
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