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Cell and it’s structure
Def. of cell.
Mitochondria
Cell theory.
Golgi body
Sizes &Shapes of cell.
Endoplasmic reticulum
Multi cellular Organism.
Plastids
Unicellular organism.
Vacuoles
Structure of cell.
Division of cells
Structure of nucleus.
Eukaryotic cells
Prokaryotic cells
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What is cell?
The cell is the basic structural, functional and biological unit of all known living organisms. Cells are
the smallest unit of life that is classified as a living thing, and are often called the "building blocks of
life".
The cell was discovered by Robert Hooke in 1665. The cell theory, first developed in 1839 by Matthias
Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells,
that all cells come from preexisting cells, that vital functions of an organism occur within 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
Cell Theory
In biology, cell theory is a scientific theory that describes the properties of cells, and the basic unit of
structure in every living thing. The initial development of the theory, during the mid-17th century, was
made possible by advances in microscopy; the study of cells is called cell biology. Cell theory is one of
the foundations of biology.
The three parts to the cell theory are as described below:
All living organisms are composed of one or more cells.
The cell is the basic unit of structure, function, and organization in all organisms.
All cells come from pre-existing, living cells.
Size of cells
The smallest objects that the unaided human eye can see are about 0.1 mm long. That means that
under the right conditions, you might be able to see an ameoba, a human egg, and a paramecium
without using magnification. A magnifying glass can help you to see them more clearly, but they will
still look tiny.
Smaller cells are easily visible under a light microscope. It's even possible to
make out structures within the cell, such as the nucleus, mitochondria and chloroplasts. Light
microscopes use a system of lenses to magnify an image. The power of a light microscope is limited
by the wavelength of visible light, which is about 500 nm. The most powerful light microscopes can
resolve bacteria but not viruses.
To see anything smaller than 500 nm, you will need an electron microscope. Electron microscopes
shoot a high-voltage beam of electrons onto or through an object, which deflects and absorbs some
of the electrons. Resolution is still limited by the wavelength of the electron beam, but this wavelength
is much smaller than that of visible light. The most powerful electron microscopes can resolve
molecules and even individual atoms.
Shape of the cells
All cells are similar to each other because they all have the same basic structure inside. They all have
a membrane that encloses the jelly-like cytoplasm and a nucleus that controls the cell. But apart from
these similarities, cells can be very different from each other. There are more than 200 different
shapes and sizes of cell in our body doing many different jobs.
Multi cellular & Unicellular organism
Multicellular organisms are organisms that consist of more than one cell, in contrast to singlecelled organisms. To form a multicellular organism, these cells need to identify and attach to
the other cells.Only a dozen or so unicellular species have cells that can be seen individually
with the naked eye. The rest of the nearly two
million[citation needed] visible species are multicellular. In particular all species
of animals, land plants and filamentous fungi are multicellular, as are many algae. Some
organisms are partially uni- andmulticellular, like Dictyostelium..
Multicellular organisms —like plants, animals and brown algae— arise from a single
cell and generate a multi-celledorganism. Pluricellular organisms are the result of manycelled individuals joining together through colony formation, filament formation or
aggregation. Pluricellularity has evolved independently in Volvox and some flagellated green
algae
A unicellular organism, also known as a single-celled organism, is an organism that consists
of only one cell, unlike a multicellular organism that consists of multiple cells. Historically the
simple single celled organisms have sometimes been referred to as monads. The main groups
of unicellular organisms are bacteria,
archaea, protozoa, unicellular algae and unicellular fungi. Unicellular organisms fall into two
general categories:prokaryotic organisms and eukaryoticorganisms..Unicellular organisms are
believed to be the oldest form of life, possibly existing 3.8 billion years ago
Structure of the cell
The cell membrane, or plasma membrane, 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 .
Nucleus
In cell biology, the nucleus pl. nuclei; from Latin nucleus is a membrane-enclosed organellefound in eukaryotic
cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in
complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these
chromosomes are the cell's nuclear genome. The function of the nucleus is to maintain the integrity of these
genes and to control the activities of the cell by regulating gene expression — thenucleus is, therefore, the
control center of the cell.
Nucleus
-Large Oval body near the centre of the cell.
-The control centre for all activity.
-Surrounded by a nuclear membrane.
Nucleo plasm
-is the protoplasm in the nucleus.
-contains genetic material --->
CHROMOSOMES (DNA)
Nucleolus
-is found in the nucleus.
-contains
more geneticinformation (RNA)
A chromosome is an organized structure of DNA, protein, and RNA found in cells. It is a single piece of coiled
DNA containing many genes, regulatory elementsand other nucleotide sequences.
Chromosomes also contain DNA
bound proteins, which serve to package the DNA and control its functions. Chromosomal DNA encodes most or
all of an organism's genetic information; some species also contain plasmids or other extra chromosomal
genetic elements.
Cell Organelles
Mitochondria : the power generators: Mitochondria are self- replicating organelles that occur in various
numbers, shapes, and sizes in the cytoplasm of all eukaryotic cells. Mitochondria play a critical role in
generating energy in the eukaryotic cell. 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, like
prokaryotes.
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 lipidsthat are synthesized by the cell.
A vacuole is a membrane-boundorganelle which is present in all plant and fungal cells and
some protist, animal and bacterialcells.Vacuoles are essentially enclosed compartments which are filled with
water containing inorganic and organic molecules including enzymes in solution, though in certain cases they
may contain solids which have been engulfed.
Plastids
The plastid is a major organellefound in the cells of plants and algae. Plastids are the site of
manufacture and storage of important chemical compounds used by the cell. They often
contain pigments used in photosynthesis.
Chloroplasts green plastids: for photosynthesis; see alsoetioplasts, the predecessors of chloroplasts
Chromoplasts coloured plastids: for pigment synthesis and storage Leucoplasts colourless plastids:
for monoterpene synthesis;
Lysosomes
Lysosomes are the cell's waste disposal system and can digest some compounds. They are used for the
digestion of macromolecules from phagocytosis (ingestion of other dying cells or larger extracellular material,
like foreign invading microbes),
endocytosis (where receptor proteinsare recycled from the cell surface), and autophagy (wherein old or
unneeded organelles or proteins, or microbes that have invaded the cytoplasm are delivered to the lysosome).
Other functions include digesting bacteria (or other forms of waste) that invade a cell and helping repair damage
to the plasma membrane by serving as a membrane patch, sealing the wound.
Prokaryotes & Eukaryotes
Prokaryotic cells were the first form of life on Earth. They are simpler and smaller than eukaryotic cells, and
lack membrane-bound organelles such as the nucleus. Prokaryotes include two of the domains of life,
bacteria and archaea. The 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.
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 compartments in which specific metabolic activities take place. Most important among
these is a cell nucleus, a membrane- delineated compartment that houses the eukaryotic cell's DNA. This
nucleus gives the eukaryote its name, which means "true nucleus." Other differences include:
Plant & Animal cell
Plant cell
Animal cell
Nucleus
Nucleus
Nucleolus (within the nucleus)
Nucleolus (within the nucleus)
Rough endoplasmic reticulum
Rough endoplasmic reticulum (ER)
Smooth endoplasmic reticulum
Smooth endoplasmic reticulum
Ribosomes
Ribosomes
Cytoskeleton
Cytoskeleton
Golgi apparatus ((dictiosomes)
Golgi apparatus
Cytoplasm
Cytoplasm
Mitochondria
Mitochondria
Plastids and their derivatives
Vesicles
Vacuole(s)
Lysosomes
Cell wall
Centrosome
Centrioles
Plant & Animal cell
Plant Cell
Animal Cell
Cell division
Cell division is the process by which a parent cell divides into two or more daughter cells.Cell
division usually occurs as part of a larger cell cycle. In eukaryotes,there are two distinct type
of cell division: a vegetative division, whereby each daughter cell is genetically identical to the
parent cell ((mitosis),.. and a reductive cell division,
whereby the number of chromosomes in the daughter cells is reduced by half, to produce
haploid gametes ((meiosis). Both of these cell division cycles are required in sexually
reproducing organisms at some point in their life cycle, and both are believed to be present in
the last eukaryotic common ancestor. Prokaryotes also undergo a vegetative cell division
known as binary fission, where their genetic material is segregated equally into two daughter
cells. All cell divisions, regardless of organism, are preceded by a single round of DNA
replication.