A report on Organelle

(A) Electron micrograph of Halothiobacillus neapolitanus cells, arrows highlight carboxysomes. (B) Image of intact carboxysomes isolated from H. neapolitanus. Scale bars are 100 nm.
Structure of Candidatus Brocadia anammoxidans, showing an anammoxosome and intracytoplasmic membrane

Organelle is a specialized subunit, usually within a cell, that has a specific function.

- Organelle
(A) Electron micrograph of Halothiobacillus neapolitanus cells, arrows highlight carboxysomes. (B) Image of intact carboxysomes isolated from H. neapolitanus. Scale bars are 100 nm.

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Onion (Allium cepa) root cells in different phases of the cell cycle (drawn by E. B. Wilson, 1900)

Cell (biology)

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Basic structural and functional unit of life forms.

Basic structural and functional unit of life forms.

Onion (Allium cepa) root cells in different phases of the cell cycle (drawn by E. B. Wilson, 1900)
Structure of a typical prokaryotic cell
Structure of a typical animal cell
Structure of a typical plant cell
Detailed diagram of lipid bilayer of cell membrane
A fluorescent image of an endothelial cell. Nuclei are stained blue, mitochondria are stained red, and microfilaments are stained green.
Deoxyribonucleic acid (DNA)
Human cancer cells, specifically HeLa cells, with DNA stained blue. The central and rightmost cell are in interphase, so their DNA is diffuse and the entire nuclei are labelled. The cell on the left is going through mitosis and its chromosomes have condensed.
Diagram of the endomembrane system
Prokaryotes divide by binary fission, while eukaryotes divide by mitosis or meiosis.
An outline of the catabolism of proteins, carbohydrates and fats
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 mRNA (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 mRNA 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.
Staining of a Caenorhabditis elegans highlights the nuclei of its cells.
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 United States.
Robert Hooke's drawing of cells in cork, 1665

They are simpler and smaller than eukaryotic cells, and lack a nucleus, and other membrane-bound organelles.

Eukaryote

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Eukaryotes are organisms whose cells have a nucleus enclosed within a nuclear envelope.

Eukaryotes are organisms whose cells have a nucleus enclosed within a nuclear envelope.

The endomembrane system and its components
Simplified structure of a mitochondrion
Longitudinal section through the flagellum of Chlamydomonas reinhardtii
Structure of a typical animal cell
Structure of a typical plant cell
Fungal Hyphae cells: 1 – hyphal wall, 2 – septum, 3 – mitochondrion, 4 – vacuole, 5 – ergosterol crystal, 6 – ribosome, 7 – nucleus, 8 – endoplasmic reticulum, 9 – lipid body, 10 – plasma membrane, 11 – spitzenkörper, 12 – Golgi apparatus
This diagram illustrates the twofold cost of sex. If each individual were to contribute the same number of offspring (two), (a) the sexual population remains the same size each generation, where the (b) asexual population doubles in size each generation.
Phylogenetic and symbiogenetic tree of living organisms, showing a view of the origins of eukaryotes and prokaryotes
One hypothesis of eukaryotic relationships – the Opisthokonta group includes both animals (Metazoa) and fungi, plants (Plantae) are placed in Archaeplastida.
A pie chart of described eukaryote species (except for Excavata), together with a tree showing possible relationships between the groups
The three-domains tree and the Eocyte hypothesis
Phylogenetic tree showing a possible relationship between the eukaryotes and other forms of life; eukaryotes are colored red, archaea green and bacteria blue
Eocyte tree.
Diagram of the origin of life with the Eukaryotes appearing early, not derived from Prokaryotes, as proposed by Richard Egel in 2012. This view implies that the UCA was relatively large and complex.

Eukaryotic cells typically contain other membrane-bound organelles such as mitochondria and Golgi apparatus; and chloroplasts can be found in plants and algae.

Two mitochondria from mammalian lung tissue displaying their matrix and membranes as shown by electron microscopy

Mitochondrion

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Two mitochondria from mammalian lung tissue displaying their matrix and membranes as shown by electron microscopy
Simplified structure of a mitochondrion.
Cross-sectional image of cristae in a rat liver mitochondrion to demonstrate the likely 3D structure and relationship to the inner membrane
Electron transport chain in the mitochondrial intermembrane space
Transmission electron micrograph of a chondrocyte, stained for calcium, showing its nucleus (N) and mitochondria (M).
Typical mitochondrial network (green) in two human cells (HeLa cells)
Model of the yeast multimeric tethering complex, ERMES
Evolution of MROs
The circular 16,569 bp human mitochondrial genome encoding 37 genes, i.e., 28 on the H-strand and 9 on the L-strand.

A mitochondrion is a double-membrane-bound organelle found in most eukaryotic organisms.

Diagram of a typical prokaryotic cell

Prokaryote

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Diagram of a typical prokaryotic cell
Phylogenetic ring showing the diversity of prokaryotes, and symbiogenetic origins of eukaryotes
Phylogenetic and symbiogenetic tree of living organisms, showing the origins of eukaryotes and prokaryotes
Diagram of the origin of life with the Eukaryotes appearing early, not derived from Prokaryotes, as proposed by Richard Egel in 2012. This view, one of many on the relative positions of Prokaryotes and Eukaryotes, implies that the universal common ancestor was relatively large and complex.
Comparison of eukaryotes vs. prokaryotes
Phylogenetic tree showing the diversity of prokaryotes. 
This 2018 proposal shows eukaryotes emerging from the archaean Asgard group which represents a modern version of the eocyte hypothesis. Unlike earlier assumptions, the division between bacteria and the rest is the most important difference between organisms.

A prokaryote is a single-celled organism that lacks a nucleus, and other membrane-bound organelles.

This fluid lipid bilayer cross section is made up entirely of phosphatidylcholine.

Lipid bilayer

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Thin polar membrane made of two layers of lipid molecules.

Thin polar membrane made of two layers of lipid molecules.

This fluid lipid bilayer cross section is made up entirely of phosphatidylcholine.
The three main structures phospholipids form in solution; the liposome (a closed bilayer), the micelle and the bilayer.
Schematic cross sectional profile of a typical lipid bilayer. There are three distinct regions: the fully hydrated headgroups, the fully dehydrated alkane core and a short intermediate region with partial hydration. Although the head groups are neutral, they have significant dipole moments that influence the molecular arrangement.
TEM image of a bacterium. The furry appearance on the outside is due to a coat of long-chain sugars attached to the cell membrane. This coating helps trap water to prevent the bacterium from becoming dehydrated.
Diagram showing the effect of unsaturated lipids on a bilayer. The lipids with an unsaturated tail (blue) disrupt the packing of those with only saturated tails (black). The resulting bilayer has more free space and is, as a consequence, more permeable to water and other small molecules.
Illustration of a GPCR signaling protein. In response to a molecule such as a hormone binding to the exterior domain (blue) the GPCR changes shape and catalyzes a chemical reaction on the interior domain (red). The gray feature is the surrounding bilayer.
Transmission Electron Microscope (TEM) image of a lipid vesicle. The two dark bands around the edge are the two leaflets of the bilayer. Historically, similar images confirmed that the cell membrane is a bilayer
Human red blood cells viewed through a fluorescence microscope. The cell membrane has been stained with a fluorescent dye. Scale bar is 20μm.
3d-Adapted AFM images showing formation of transmembrane pores (holes) in supported lipid bilayer
Illustration of a typical AFM scan of a supported lipid bilayer. The pits are defects in the bilayer, exposing the smooth surface of the substrate underneath.
Structure of a potassium ion channel. The alpha helices penetrate the bilayer (boundaries indicated by red and blue lines), opening a hole through which potassium ions can flow
Schematic illustration of pinocytosis, a type of endocytosis
Exocytosis of outer membrane vesicles (MV) liberated from inflated periplasmic pockets (p) on surface of human Salmonella 3,10:r:- pathogens docking on plasma membrane of macrophage cells (M) in chicken ileum, for host-pathogen signaling in vivo.
Schematic showing two possible conformations of the lipids at the edge of a pore. In the top image the lipids have not rearranged, so the pore wall is hydrophobic. In the bottom image some of the lipid heads have bent over, so the pore wall is hydrophilic.
Illustration of lipid vesicles fusing showing two possible outcomes: hemifusion and full fusion. In hemifusion, only the outer bilayer leaflets mix. In full fusion both leaflets as well as the internal contents mix.
Schematic illustration of the process of fusion through stalk formation.
Diagram of the action of SNARE proteins docking a vesicle for exocytosis. Complementary versions of the protein on the vesicle and the target membrane bind and wrap around each other, drawing the two bilayers close together in the process.

The cell membranes of almost all organisms and many viruses are made of a lipid bilayer, as are the nuclear membrane surrounding the cell nucleus, and membranes of the membrane-bound organelles in the cell.

SEM micrograph of the cilia projecting from respiratory epithelium in the trachea

Cilium

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SEM micrograph of the cilia projecting from respiratory epithelium in the trachea
Eukaryotic motile cilium
Illustration depicting motile cilia on respiratory epithelium.
Tracheal respiratory epithelium showing cilia and much smaller microvilli on non-ciliated cells in scanning electron micrograph.
Scanning electron micrograph of nodal cilia on a mouse embryo

The cilium, plural cilia is a membrane-bound organelle found on most types of cell, and certain microorganisms known as ciliates.

Plant cells with visible chloroplasts.

Plastid

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Plant cells with visible chloroplasts.
Plastid types
Leucoplasts in plant cells.
There is an illustration of stages depicted by the diagram mentioned above in which it is shown inter-conversion of Plastids

The plastid (Greek: πλαστός; plastós: formed, molded – plural plastids) is a membrane-bound organelle found in the cells of plants, algae, and some other eukaryotic organisms.

Micrograph of rough endoplasmic reticulum network around the nucleus (shown in the lower right-hand area of the picture). Dark small circles in the network are mitochondria.

Endoplasmic reticulum

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The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding.

The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding.

Micrograph of rough endoplasmic reticulum network around the nucleus (shown in the lower right-hand area of the picture). Dark small circles in the network are mitochondria.
1 Nucleus
2 Nuclear pore
3 Rough endoplasmic reticulum (RER)
4 Smooth endoplasmic reticulum (SER)
5 Ribosome on the rough ER
6 Proteins that are transported
7 Transport vesicle
8 Golgi apparatus
9 Cis face of the Golgi apparatus
10 Trans face of the Golgi apparatus
11 Cisternae of the Golgi apparatus
3D rendering of endoplasmic reticulum
A 2-minute animation showing how a protein destined for the secretory pathway is synthesized into the rough endoplasmic reticulum, which appears at the upper right approximately halfway through the animation.
Electron micrograph showing smooth ER (arrow) in mouse tissue, at 110,510× magnification.
Skeletal muscle fiber, with sarcoplasmic reticulum colored in blue.
Ca2+-antagonized transport into the endoplasmic reticulum (CaATiER) model

It is a type of organelle made up of two subunits – rough endoplasmic reticulum (RER), and smooth endoplasmic reticulum (SER).

Structure of bacterial flagellum.

Flagellum

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Hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility.

Hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility.

Structure of bacterial flagellum.
Prokaryotic (bacterial and archaeal) flagella run in a rotary movement, while eukaryotic flagella run in a bending movement. The prokaryotic flagellum uses a rotary motor, and the eukaryotic flagellum uses a complex sliding filament system. Eukaryotic flagella are ATP-driven, while prokaryotic flagella can be ATP-driven (Archaea) or proton-driven (Bacteria).
Different flagellar arrangements in bacteria
Eukaryotic flagella. 1–axoneme, 2–cell membrane, 3–IFT (IntraFlagellar Transport), 4–Basal body, 5–Cross section of flagella, 6–Triplets of microtubules of basal body
Cross section of an axoneme
Longitudinal section through the flagella area in Chlamydomonas reinhardtii. In the cell apex is the basal body that is the anchoring site for a flagellum. Basal bodies originate from and have a substructure similar to that of centrioles, with nine peripheral microtubule triplets (see structure at bottom center of image).
The "9+2" structure is visible in this cross-section micrograph of an axoneme.
Beating pattern of eukaryotic "flagellum" and "cillum", a traditional distinction before the structures of the two are known.
thumb|Multiple flagella in lophotrichous arrrangement on surface of Helicobacter pylori
thumb|right|Physical model of a bacterial flagellum

In some bacteria the flagellum can also function as a sensory organelle, being sensitive to wetness outside the cell.

Micrograph of Golgi apparatus, visible as a stack of semicircular black rings near the bottom. Numerous circular vesicles can be seen in proximity to the organelle.

Golgi apparatus

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Micrograph of Golgi apparatus, visible as a stack of semicircular black rings near the bottom. Numerous circular vesicles can be seen in proximity to the organelle.
3D rendering of Golgi apparatus
Diagram of a single "stack" of Golgi
The Golgi apparatus (salmon pink) in context of the secretory pathway
Diagram of secretory process from endoplasmic reticulum (orange) to Golgi apparatus (magenta). 1. Nuclear membrane; 2. Nuclear pore; 3. Rough endoplasmic reticulum (RER); 4. Smooth endoplasmic reticulum (SER); 5. Ribosome attached to RER; 6. Macromolecules; 7. Transport vesicles; 8. Golgi apparatus; 9. Cis face of Golgi apparatus; 10. Trans face of Golgi apparatus; 11. Cisternae of the Golgi apparatus.
Two Golgi stacks connected as a ribbon in a mouse cell. Taken from the movie.
Three-dimensional projection of a mammalian Golgi stack imaged by confocal microscopy and volume surface rendered using Imaris software. Taken from the movie.

The Golgi apparatus, also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells.