The cell (from
Latin cella, meaning "small room") is the basic
structural, functional, and biological unit of all known living
organisms. A cell is the smallest unit of life. Cells are often called
the "building blocks of life". The study of cells is called cell
Cells consist of cytoplasm enclosed within a membrane, which contains
many biomolecules such as proteins and nucleic acids. Organisms can
be classified as unicellular (consisting of a single cell; including
bacteria) or multicellular (including plants and animals). While
the number of cells in plants and animals varies from species to
species, humans contain more than 10 trillion (1013) cells. Most
plant and animal cells are visible only under a microscope, with
dimensions between 1 and 100 micrometres.
The cell was discovered by
Robert Hooke in 1665, who named the
biological units for their resemblance to cells inhabited by Christian
monks in a monastery. Cell theory, first developed in 1839 by
Matthias Jakob Schleiden
Matthias Jakob Schleiden and Theodor Schwann, states that all
organisms are composed of one or more cells, that cells are the
fundamental unit of structure and function in all living organisms,
that all cells come from preexisting cells, and that all cells contain
the hereditary information necessary for regulating cell functions and
for transmitting information to the next generation of cells. Cells
emerged on Earth at least 3.5 billion years ago.
2 Subcellular components
2.3 Genetic material
Eukaryotic and prokaryotic
3 Structures outside the cell membrane
3.1 Cell wall
4 Cellular processes
4.1 Growth and metabolism
5.1 Cell specialization
5.2 Origin of multicellularity
6.1 Origin of the first cell
6.2 Origin of eukaryotic cells
7 History of research
8 See also
11 External links
Comparison of features of prokaryotic and eukaryotic cells
protists, fungi, plants, animals
~ 1–5 µm
~ 10–100 µm
Type of nucleus
nucleoid region; no true nucleus
true nucleus with double membrane
linear molecules (chromosomes) with histone proteins
coupled in the cytoplasm
RNA synthesis in the nucleus
protein synthesis in the cytoplasm
50S and 30S
60S and 40S
very few structures
highly structured by endomembranes and a cytoskeleton
flagella made of flagellin
flagella and cilia containing microtubules; lamellipodia and filopodia
one to several thousand
in algae and plants
usually single cells
single cells, colonies, higher multicellular organisms with
binary fission (simple division)
mitosis (fission or budding)
more than one chromosome
Cell membrane and membrane-bound organelles
Cells are of two types, eukaryotic, which contain a nucleus, and
prokaryotic, which do not.
Prokaryotes are single-celled organisms,
while eukaryotes can be either single-celled or multicellular.
Main article: Prokaryote
Structure of a typical prokaryotic cell
Prokaryotic cells were the first form of life on Earth, characterised
by having vital biological processes including cell signaling and
being self-sustaining. They are simpler and smaller than eukaryotic
cells, and lack membrane-bound organelles such as the nucleus.
Prokaryotes include two of the three domains of life, bacteria and
DNA of a prokaryotic cell consists of a single chromosome
that is in direct contact with the cytoplasm. The nuclear region in
the cytoplasm is called the nucleoid. Most prokaryotes are the
smallest of all organisms ranging from 0.5 to 2.0 µm in
A prokaryotic cell has three architectural regions:
Enclosing the cell is the cell envelope – generally consisting of a
plasma membrane covered by a cell wall which, for some bacteria, may
be further covered by a third layer called a capsule. Though most
prokaryotes have both a cell membrane and a cell wall, there are
exceptions such as
Mycoplasma (bacteria) and
which only possess the cell membrane layer. The envelope gives
rigidity to the cell and separates the interior of the cell from its
environment, serving as a protective filter. The cell wall consists of
peptidoglycan in bacteria, and acts as an additional barrier against
exterior forces. It also prevents the cell from expanding and bursting
(cytolysis) from osmotic pressure due to a hypotonic environment. Some
eukaryotic cells (plant cells and fungal cells) also have a cell wall.
Inside the cell is the cytoplasmic region that contains the genome
(DNA), ribosomes and various sorts of inclusions. The genetic
material is freely found in the cytoplasm.
Prokaryotes can carry
DNA elements called plasmids, which are usually
circular. Linear bacterial plasmids have been identified in several
species of spirochete bacteria, including members of the genus
Borrelia burgdorferi, which causes Lyme disease.
Though not forming a nucleus, the
DNA is condensed in a nucleoid.
Plasmids encode additional genes, such as antibiotic resistance genes.
On the outside, flagella and pili project from the cell's surface.
These are structures (not present in all prokaryotes) made of proteins
that facilitate movement and communication between cells.
Main article: Eukaryote
Structure of a typical animal cell
Structure of a typical plant cell
Plants, animals, fungi, slime moulds, protozoa, and algae are all
eukaryotic. These cells are about fifteen times wider than a typical
prokaryote and can be as much as a thousand times greater in volume.
The main distinguishing feature of eukaryotes as compared to
prokaryotes is compartmentalization: the presence of membrane-bound
organelles (compartments) in which specific metabolic activities take
place. Most important among these is a cell nucleus, an organelle
that houses the cell's DNA. This nucleus gives the eukaryote its name,
which means "true kernel (nucleus)". Other differences include:
The plasma membrane resembles that of prokaryotes in function, with
minor differences in the setup. Cell walls may or may not be present.
DNA is organized in one or more linear molecules,
called chromosomes, which are associated with histone proteins. All
DNA is stored in the cell nucleus, separated from the
cytoplasm by a membrane. Some eukaryotic organelles such as
mitochondria also contain some DNA.
Many eukaryotic cells are ciliated with primary cilia. Primary cilia
play important roles in chemosensation, mechanosensation, and
Cilia may thus be "viewed as a sensory cellular
antennae that coordinates a large number of cellular signaling
pathways, sometimes coupling the signaling to ciliary motility or
alternatively to cell division and differentiation."
Motile eukaryotes can move using motile cilia or flagella. Motile
cells are absent in conifers and flowering plants. Eukaryotic
flagella are less complex than those of prokaryotes.
All cells, whether prokaryotic or eukaryotic, have a membrane that
envelops the cell, regulates what moves in and out (selectively
permeable), and maintains the electric potential of the cell. Inside
the membrane, the cytoplasm takes up most of the cell's volume. All
cells (except red blood cells which lack a cell nucleus and most
organelles to accommodate maximum space for hemoglobin) possess DNA,
the hereditary material of genes, and RNA, containing the information
necessary to build various proteins such as enzymes, the cell's
primary machinery. There are also other kinds of biomolecules in
cells. This article lists these primary cellular components, then
briefly describes their function.
Main article: Cell membrane
Detailed diagram of lipid bilayer cell membrane
The cell membrane, or plasma membrane, is a biological membrane that
surrounds the cytoplasm of a cell. In animals, the plasma membrane is
the outer boundary of the cell, while in plants and prokaryotes it is
usually covered by a cell wall. This membrane serves to separate and
protect a cell from its surrounding environment and is made mostly
from a double layer of phospholipids, which are amphiphilic (partly
hydrophobic and partly hydrophilic). Hence, the layer is called a
phospholipid bilayer, or sometimes a fluid mosaic membrane. Embedded
within this membrane is a variety of protein molecules that act as
channels and pumps that move different molecules into and out of the
cell. The membrane is semi-permeable, and selectively permeable, in
that it can either let a substance (molecule or ion) pass through
freely, pass through to a limited extent or not pass through at all.
Cell surface membranes also contain receptor proteins that allow cells
to detect external signaling molecules such as hormones.
Main article: Cytoskeleton
A fluorescent image of an endothelial cell. Nuclei are stained blue,
mitochondria are stained red, and microfilaments are stained green.
The cytoskeleton acts to organize and maintain the cell's shape;
anchors organelles in place; helps during endocytosis, the uptake of
external materials by a cell, and cytokinesis, the separation of
daughter cells after cell division; and moves parts of the cell in
processes of growth and mobility. The eukaryotic cytoskeleton is
composed of microfilaments, intermediate filaments and microtubules.
There are a great number of proteins associated with them, each
controlling a cell's structure by directing, bundling, and aligning
filaments. The prokaryotic cytoskeleton is less well-studied but is
involved in the maintenance of cell shape, polarity and
cytokinesis. The subunit protein of microfilaments is a small,
monomeric protein called actin. The subunit of microtubules is a
dimeric molecule called tubulin. Intermediate filaments are
heteropolymers whose subunits vary among the cell types in different
tissues. But some of the subunit protein of intermediate filaments
include vimentin, desmin, lamin (lamins A, B and C), keratin (multiple
acidic and basic keratins), neurofilament proteins (NF–L, NF–M).
Two different kinds of genetic material exist: deoxyribonucleic acid
(DNA) and ribonucleic acid (RNA). Cells use
DNA for their long-term
information storage. The biological information contained in an
organism is encoded in its
RNA is used for
information transport (e.g., mRNA) and enzymatic functions (e.g.,
ribosomal RNA). Transfer
RNA (tRNA) molecules are used to add amino
acids during protein translation.
Prokaryotic genetic material is organized in a simple circular DNA
molecule (the bacterial chromosome) in the nucleoid region of the
Eukaryotic genetic material is divided into different,
linear molecules called chromosomes inside a discrete nucleus, usually
with additional genetic material in some organelles like mitochondria
and chloroplasts (see endosymbiotic theory).
A human cell has genetic material contained in the cell nucleus (the
nuclear genome) and in the mitochondria (the mitochondrial genome). In
humans the nuclear genome is divided into 46 linear
called chromosomes, including 22 homologous chromosome pairs and a
pair of sex chromosomes. The mitochondrial genome is a circular DNA
molecule distinct from the nuclear DNA. Although the mitochondrial DNA
is very small compared to nuclear chromosomes, it codes for 13
proteins involved in mitochondrial energy production and specific
Foreign genetic material (most commonly DNA) can also be artificially
introduced into the cell by a process called transfection. This can be
transient, if the
DNA is not inserted into the cell's genome, or
stable, if it is. Certain viruses also insert their genetic material
into the genome.
Main article: Organelle
Organelles are parts of the cell which are adapted and/or specialized
for carrying out one or more vital functions, analogous to the organs
of the human body (such as the heart, lung, and kidney, with each
organ performing a different function). Both eukaryotic and
prokaryotic cells have organelles, but prokaryotic organelles are
generally simpler and are not membrane-bound.
There are several types of organelles in a cell. Some (such as the
nucleus and golgi apparatus) are typically solitary, while others
(such as mitochondria, chloroplasts, peroxisomes and lysosomes) can be
numerous (hundreds to thousands). The cytosol is the gelatinous fluid
that fills the cell and surrounds the organelles.
Human cancer cells, specifically HeLa cells, with
DNA stained blue.
The central and rightmost cell are in interphase, so their
diffuse and the entire nuclei are labelled. The cell on the left is
going through mitosis and its chromosomes have condensed.
Cell nucleus: A cell's information center, the cell nucleus is the
most conspicuous organelle found in a eukaryotic cell. It houses the
cell's chromosomes, and is the place where almost all
RNA synthesis (transcription) occur. The nucleus is spherical and
separated from the cytoplasm by a double membrane called the nuclear
envelope. The nuclear envelope isolates and protects a cell's
various molecules that could accidentally damage its structure or
interfere with its processing. During processing,
DNA is transcribed,
or copied into a special RNA, called messenger
RNA (mRNA). This mRNA
is then transported out of the nucleus, where it is translated into a
specific protein molecule. The nucleolus is a specialized region
within the nucleus where ribosome subunits are assembled. In
DNA processing takes place in the cytoplasm.
Mitochondria and Chloroplasts: generate energy for the cell.
Mitochondria are self-replicating organelles that occur in various
numbers, shapes, and sizes in the cytoplasm of all eukaryotic
cells. Respiration occurs in the cell mitochondria, which generate
the cell's energy by oxidative phosphorylation, using oxygen to
release energy stored in cellular nutrients (typically pertaining to
glucose) to generate ATP.
Mitochondria multiply by binary fission,
Chloroplasts can only be found in plants and algae,
and they capture the sun's energy to make carbohydrates through
Diagram of an endomembrane system
Endoplasmic reticulum: The endoplasmic reticulum (ER) is a transport
network for molecules targeted for certain modifications and specific
destinations, as compared to molecules that float freely in the
cytoplasm. The ER has two forms: the rough ER, which has ribosomes on
its surface that secrete proteins into the ER, and the smooth ER,
which lacks ribosomes. The smooth ER plays a role in calcium
sequestration and release.
Golgi apparatus: The primary function of the
Golgi apparatus is to
process and package the macromolecules such as proteins and lipids
that are synthesized by the cell.
Lysosomes and Peroxisomes:
Lysosomes contain digestive enzymes (acid
hydrolases). They digest excess or worn-out organelles, food
particles, and engulfed viruses or bacteria.
Peroxisomes have enzymes
that rid the cell of toxic peroxides. The cell could not house these
destructive enzymes if they were not contained in a membrane-bound
Centrosome: the cytoskeleton organiser: The centrosome produces the
microtubules of a cell – a key component of the cytoskeleton. It
directs the transport through the ER and the Golgi apparatus.
Centrosomes are composed of two centrioles, which separate during cell
division and help in the formation of the mitotic spindle. A single
centrosome is present in the animal cells. They are also found in some
fungi and algae cells.
Vacuoles: Vacuoles sequester waste products and in plant cells store
water. They are often described as liquid filled space and are
surrounded by a membrane. Some cells, most notably Amoeba, have
contractile vacuoles, which can pump water out of the cell if there is
too much water. The vacuoles of plant cells and fungal cells are
usually larger than those of animal cells.
Eukaryotic and prokaryotic
Ribosomes: The ribosome is a large complex of
RNA and protein
molecules. They each consist of two subunits, and act as an
assembly line where
RNA from the nucleus is used to synthesise
proteins from amino acids. Ribosomes can be found either floating
freely or bound to a membrane (the rough endoplasmatic reticulum in
eukaryotes, or the cell membrane in prokaryotes).
Structures outside the cell membrane
Many cells also have structures which exist wholly or partially
outside the cell membrane. These structures are notable because they
are not protected from the external environment by the semipermeable
cell membrane. In order to assemble these structures, their components
must be carried across the cell membrane by export processes.
Many types of prokaryotic and eukaryotic cells have a cell wall. The
cell wall acts to protect the cell mechanically and chemically from
its environment, and is an additional layer of protection to the cell
membrane. Different types of cell have cell walls made up of different
materials; plant cell walls are primarily made up of cellulose, fungi
cell walls are made up of chitin and bacteria cell walls are made up
A gelatinous capsule is present in some bacteria outside the cell
membrane and cell wall. The capsule may be polysaccharide as in
pneumococci, meningococci or polypeptide as
Bacillus anthracis or
hyaluronic acid as in streptococci. Capsules are not marked by normal
staining protocols and can be detected by India ink or methyl blue;
which allows for higher contrast between the cells for
Flagella are organelles for cellular mobility. The bacterial flagellum
stretches from cytoplasm through the cell membrane(s) and extrudes
through the cell wall. They are long and thick thread-like appendages,
protein in nature. A different type of flagellum is found in archaea
and a different type is found in eukaryotes.
A fimbria also known as a pilus is a short, thin, hair-like filament
found on the surface of bacteria. Fimbriae, or pili are formed of a
protein called pilin (antigenic) and are responsible for attachment of
bacteria to specific receptors of human cell (cell adhesion). There
are special types of specific pili involved in bacterial conjugation.
Growth and metabolism
Cell growth and Metabolism
Between successive cell divisions, cells grow through the functioning
of cellular metabolism. Cell metabolism is the process by which
individual cells process nutrient molecules.
Metabolism has two
distinct divisions: catabolism, in which the cell breaks down complex
molecules to produce energy and reducing power, and anabolism, in
which the cell uses energy and reducing power to construct complex
molecules and perform other biological functions. Complex sugars
consumed by the organism can be broken down into simpler sugar
molecules called monosaccharides such as glucose. Once inside the
cell, glucose is broken down to make adenosine triphosphate (ATP),
a molecule that possesses readily available energy, through two
Bacteria divide by binary fission, while eukaryotes divide by mitosis
Main article: Cell division
Cell division involves a single cell (called a mother cell) dividing
into two daughter cells. This leads to growth in multicellular
organisms (the growth of tissue) and to procreation (vegetative
reproduction) in unicellular organisms.
Prokaryotic cells divide by
binary fission, while eukaryotic cells usually undergo a process of
nuclear division, called mitosis, followed by division of the cell,
called cytokinesis. A diploid cell may also undergo meiosis to produce
haploid cells, usually four.
Haploid cells serve as gametes in
multicellular organisms, fusing to form new diploid cells.
DNA replication, or the process of duplicating a cell's genome,
always happens when a cell divides through mitosis or binary fission.
This occurs during the S phase of the cell cycle.
In meiosis, the
DNA is replicated only once, while the cell divides
DNA replication only occurs before meiosis I.
does not occur when the cells divide the second time, in meiosis
II. Replication, like all cellular activities, requires
specialized proteins for carrying out the job.
An overview of protein synthesis.
Within the nucleus of the cell (light blue), genes (DNA, dark blue)
are transcribed into RNA. This
RNA is then subject to
post-transcriptional modification and control, resulting in a mature
RNA (red) that is then transported out of the nucleus and into the
cytoplasm (peach), where it undergoes translation into a protein. mRNA
is translated by ribosomes (purple) that match the three-base codons
of the m
RNA to the three-base anti-codons of the appropriate tRNA.
Newly synthesized proteins (black) are often further modified, such as
by binding to an effector molecule (orange), to become fully active.
Cells are capable of synthesizing new proteins, which are essential
for the modulation and maintenance of cellular activities. This
process involves the formation of new protein molecules from amino
acid building blocks based on information encoded in DNA/RNA. Protein
synthesis generally consists of two major steps: transcription and
Transcription is the process where genetic information in
DNA is used
to produce a complementary
RNA strand. This
RNA strand is then
processed to give messenger
RNA (mRNA), which is free to migrate
through the cell. m
RNA molecules bind to protein-
RNA complexes called
ribosomes located in the cytosol, where they are translated into
polypeptide sequences. The ribosome mediates the formation of a
polypeptide sequence based on the m
RNA sequence. The m
directly relates to the polypeptide sequence by binding to transfer
RNA (tRNA) adapter molecules in binding pockets within the ribosome.
The new polypeptide then folds into a functional three-dimensional
Main article: Motility
Unicellular organisms can move in order to find food or escape
predators. Common mechanisms of motion include flagella and cilia.
In multicellular organisms, cells can move during processes such as
wound healing, the immune response and cancer metastasis. For example,
in wound healing in animals, white blood cells move to the wound site
to kill the microorganisms that cause infection. Cell motility
involves many receptors, crosslinking, bundling, binding, adhesion,
motor and other proteins. The process is divided into three steps
– protrusion of the leading edge of the cell, adhesion of the
leading edge and de-adhesion at the cell body and rear, and
cytoskeletal contraction to pull the cell forward. Each step is driven
by physical forces generated by unique segments of the
Staining of a
Caenorhabditis elegans which highlights the nuclei of
Multicellular organisms are organisms that consist of more than one
cell, in contrast to single-celled organisms.
In complex multicellular organisms, cells specialize into different
cell types that are adapted to particular functions. In mammals, major
cell types include skin cells, muscle cells, neurons, blood cells,
fibroblasts, stem cells, and others. Cell types differ both in
appearance and function, yet are genetically identical. Cells are able
to be of the same genotype but of different cell type due to the
differential expression of the genes they contain.
Most distinct cell types arise from a single totipotent cell, called a
zygote, that differentiates into hundreds of different cell types
during the course of development. Differentiation of cells is driven
by different environmental cues (such as cell–cell interaction) and
intrinsic differences (such as those caused by the uneven distribution
of molecules during division).
Origin of multicellularity
Multicellularity has evolved independently at least 25 times,
including in some prokaryotes, like cyanobacteria, myxobacteria,
actinomycetes, Magnetoglobus multicellularis or Methanosarcina.
However, complex multicellular organisms evolved only in six
eukaryotic groups: animals, fungi, brown algae, red algae, green
algae, and plants. It evolved repeatedly for plants
(Chloroplastida), once or twice for animals, once for brown algae, and
perhaps several times for fungi, slime molds, and red algae.
Multicellularity may have evolved from colonies of interdependent
organisms, from cellularization, or from organisms in symbiotic
The first evidence of multicellularity is from cyanobacteria-like
organisms that lived between 3 and 3.5 billion years ago. Other
early fossils of multicellular organisms include the contested
Grypania spiralis and the fossils of the black shales of the
Francevillian Group Fossil
Francevillian Group Fossil B Formation in Gabon.
The evolution of multicellularity from unicellular ancestors has been
replicated in the laboratory, in evolution experiments using predation
as the selective pressure.
Main article: Evolutionary history of life
The origin of cells has to do with the origin of life, which began the
history of life on Earth.
Origin of the first cell
Stromatolites are left behind by cyanobacteria, also called blue-green
algae. They are the oldest known fossils of life on Earth. This
one-billion-year-old fossil is from Glacier National Park in the
Abiogenesis and Evolution of cells
There are several theories about the origin of small molecules that
led to life on the early Earth. They may have been carried to Earth on
meteorites (see Murchison meteorite), created at deep-sea vents, or
synthesized by lightning in a reducing atmosphere (see Miller–Urey
experiment). There is little experimental data defining what the first
self-replicating forms were.
RNA is thought to be the earliest
self-replicating molecule, as it is capable of both storing genetic
information and catalyzing chemical reactions (see
hypothesis), but some other entity with the potential to
self-replicate could have preceded RNA, such as clay or peptide
Cells emerged at least 3.5 billion years ago. The current
belief is that these cells were heterotrophs. The early cell membranes
were probably more simple and permeable than modern ones, with only a
single fatty acid chain per lipid. Lipids are known to spontaneously
form bilayered vesicles in water, and could have preceded RNA, but the
first cell membranes could also have been produced by catalytic RNA,
or even have required structural proteins before they could form.
Origin of eukaryotic cells
Further information: Evolution of sexual reproduction
The eukaryotic cell seems to have evolved from a symbiotic community
of prokaryotic cells. DNA-bearing organelles like the mitochondria and
the chloroplasts are descended from ancient symbiotic oxygen-breathing
proteobacteria and cyanobacteria, respectively, which were
endosymbiosed by an ancestral archaean prokaryote.
There is still considerable debate about whether organelles like the
hydrogenosome predated the origin of mitochondria, or vice versa: see
the hydrogen hypothesis for the origin of eukaryotic cells.
History of research
Main article: Cell theory
Hooke's drawing of cells in cork, 1665
Antonie van Leeuwenhoek
Antonie van Leeuwenhoek teaches himself to make lenses,
constructs basic optical microscopes and draws protozoa, such as
Vorticella from rain water, and bacteria from his own mouth.
Robert Hooke discovers cells in cork, then in living plant
tissue using an early compound microscope. He coins the term cell
Latin cella, meaning "small room") in his book Micrographia
Theodor Schwann and
Matthias Jakob Schleiden
Matthias Jakob Schleiden elucidate the
principle that plants and animals are made of cells, concluding that
cells are a common unit of structure and development, and thus
founding the cell theory.
Rudolf Virchow states that new cells come from pre-existing
cells by cell division (omnis cellula ex cellula).
1859: The belief that life forms can occur spontaneously (generatio
spontanea) is contradicted by
Louis Pasteur (1822–1895) (although
Francesco Redi had performed an experiment in 1668 that suggested the
Ernst Ruska builds the first transmission electron microscope
(TEM) at the University of Berlin. By 1935, he has built an EM with
twice the resolution of a light microscope, revealing previously
1953: Watson and Crick made their first announcement on the double
helix structure of
DNA on February 28.
Lynn Margulis published
Symbiosis in Cell Evolution detailing
the endosymbiotic theory.
Molecular and cellular biology portal
Outline of cell biology
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MBInfo – Descriptions on Cellular Functions and Processes
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Inside the Cell – a science education booklet by National Institutes
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Biology in "The
Biology Project" of University of Arizona.
Centre of the Cell online
The Image & Video Library of The American Society for Cell
Biology, a collection of peer-reviewed still images, video clips and
digital books that illustrate the structure, function and biology of
HighMag Blog, still images of cells from recent research articles.
Microscope Produces Dazzling 3D Movies of Live Cells, March 4,
2011 – Howard Hughes Medical Institute.
WormWeb.org: Interactive Visualization of the C. elegans Cell lineage
– Visualize the entire cell lineage tree of the nematode C. elegans
Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2014).
Biology of the Cell (6th ed.). Garland.
ISBN 9780815344322. ; The fourth edition is freely available
National Center for Biotechnology Information
National Center for Biotechnology Information Bookshelf.
Lodish H, Berk A, Matsudaira P, Kaiser CA, Krieger M, Scott MP,
Zipurksy SL, Darnell J (2004). Molecular Cell
Biology (5th ed.). WH
Freeman: New York, NY. ISBN 978-0-7167-4366-8.
Cooper GM (2000). The cell: a molecular approach (2nd ed.).
Washington, D.C: ASM Press. ISBN 0-87893-102-3.
Structures of the cell / organelles
Spindle pole body
Hierarchy of life
Biosphere > Ecosystem > Biocoenosis >
Population > Organism > Organ system >
Organ > Tissue > Cell > Organelle >
Biomolecular complex > Macromolecule > Biomolecule