A report on Mitochondrion

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.

Double-membrane-bound organelle found in most eukaryotic organisms.

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

162 related topics with Alpha

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Three-dimensional representations of several fatty acids. Saturated fatty acids have perfectly straight chain structure. Unsaturated ones are typically bent, unless they have a trans configuration.

Fatty acid

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Carboxylic acid with an aliphatic chain, which is either saturated or unsaturated.

Carboxylic acid with an aliphatic chain, which is either saturated or unsaturated.

Three-dimensional representations of several fatty acids. Saturated fatty acids have perfectly straight chain structure. Unsaturated ones are typically bent, unless they have a trans configuration.
Comparison of the trans isomer Elaidic acid (top) and the cis isomer oleic acid (bottom).
Arachidic acid, a saturated fatty acid.
Numbering of carbon atoms. The systematic (IUPAC) C-x numbers are in blue. The omega-minus "ω−x" labels are in red. The Greek letter labels are in green. Note that unsaturated fatty acids with a cis configuration are actually "kinked" rather than straight as shown here.

Pyruvate is then decarboxylated to form acetyl-CoA in the mitochondrion.

A top-down view of skeletal muscle

Skeletal muscle

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Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton.

Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton.

A top-down view of skeletal muscle
3D rendering of a skeletal muscle fiber
Muscle types by fiber arrangement
Types of pennate muscle. A – unipennate; B – bipennate; 
C – multipennate
ATPase staining of a muscle cross section. Type II fibers are dark, due to the alkaline pH of the preparation. In this example, the size of the type II fibers is considerably less than the type I fibers due to denervation atrophy.
Structure of muscle fibre showing a sarcomere under electron microscope with schematic explanation.
Diagram of sarcoplasmic reticulum with terminal cisternae and T-tubules.
Human embryo showing somites labelled as primitive segments.
When a sarcomere contracts, the Z lines move closer together, and the I band becomes smaller. The A band stays the same width. At full contraction, the thin and thick filaments overlap.
Contraction in more detail
(a) Some ATP is stored in a resting muscle. As contraction starts, it is used up in seconds. More ATP is generated from creatine phosphate for about 15 seconds. (b) Each glucose molecule produces two ATP and two molecules of pyruvic acid, which can be used in aerobic respiration or converted to lactic acid. If oxygen is not available, pyruvic acid is converted to lactic acid, which may contribute to muscle fatigue. This occurs during strenuous exercise when high amounts of energy are needed but oxygen cannot be sufficiently delivered to muscle. (c) Aerobic respiration is the breakdown of glucose in the presence of oxygen (O2) to produce carbon dioxide, water, and ATP. Approximately 95 percent of the ATP required for resting or moderately active muscles is provided by aerobic respiration, which takes place in mitochondria.
Exercise-induced signaling pathways in skeletal muscle that determine specialized characteristics of slow- and fast-twitch muscle fibers
Jogging is one form of aerobic exercise.
In muscular dystrophy, the affected tissues become disorganized and the concentration of dystrophin (green) is greatly reduced.
Prisoner of war exhibiting muscle loss as a result of malnutrition.

Muscle fibers also have multiple mitochondria to meet energy needs.

Diagram of ion concentrations and charge across a semi-permeable cellular membrane.

Electrochemical gradient

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Gradient of electrochemical potential, usually for an ion that can move across a membrane.

Gradient of electrochemical potential, usually for an ion that can move across a membrane.

Diagram of ion concentrations and charge across a semi-permeable cellular membrane.
Diagram of the Na+-K+-ATPase.
Diagram of the conformational shift in retinal that initiates proton pumping in bacteriorhodopsin.
Simplified diagram of photophosphorylation.
Detailed diagram of the electron transport chain in mitochondria.

In mitochondria and chloroplasts, proton gradients generate a chemiosmotic potential used to synthesize ATP, and the sodium-potassium gradient helps neural synapses quickly transmit information.

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.

In contrast, eukaryotes have a range of organelles including the nucleus, mitochondria, lysosomes and endoplasmic reticulum.

Voltage-dependent anion channel

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Voltage-dependent anion channels, or mitochondrial porins, are a class of porin ion channel located on the outer mitochondrial membrane.

NAD+ to NADH.

Respiratory complex I

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Not found in eukaryotes.

Not found in eukaryotes.

NAD+ to NADH.
FMN to FMNH2.
CoQ to CoQH2.

It catalyzes the transfer of electrons from NADH to coenzyme Q10 (CoQ10) and translocates protons across the inner mitochondrial membrane in eukaryotes or the plasma membrane of bacteria.

The redox reactions of nicotinamide adenine dinucleotide.

Nicotinamide adenine dinucleotide

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Coenzyme central to metabolism.

Coenzyme central to metabolism.

The redox reactions of nicotinamide adenine dinucleotide.
UV absorption spectra of NAD and NADH.
Some metabolic pathways that synthesize and consume NAD in vertebrates. The abbreviations are defined in the text.
Salvage pathways use three precursors for NAD+.
Rossmann fold in part of the lactate dehydrogenase of Cryptosporidium parvum, showing NAD in red, beta sheets in yellow, and alpha helices in purple.
In this diagram, the hydride acceptor C4 carbon is shown at the top. When the nicotinamide ring lies in the plane of the page with the carboxy-amide to the right, as shown, the hydride donor lies either "above" or "below" the plane of the page. If "above" hydride transfer is class A, if "below" hydride transfer is class B.
A simplified outline of redox metabolism, showing how NAD and NADH link the citric acid cycle and oxidative phosphorylation.
The structure of cyclic ADP-ribose.
Arthur Harden, co-discoverer of NAD

In eukaryotes the electrons carried by the NADH that is produced in the cytoplasm are transferred into the mitochondrion (to reduce mitochondrial NAD) by mitochondrial shuttles, such as the malate-aspartate shuttle.

Mitochondrial proteins encoded from the nuclear genome need to be targeted and transported appropriately into the mitochondria.

Mitochondrial biogenesis

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Mitochondrial proteins encoded from the nuclear genome need to be targeted and transported appropriately into the mitochondria.
The processes of fusion and fission allow for mitochondrial reorganization.

Mitochondrial biogenesis is the process by which cells increase mitochondrial numbers.

A sucrose specific porin from Salmonella typhimurium, a gram-negative bacterium.

Porin (protein)

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Porins are beta barrel proteins that cross a cellular membrane and act as a pore, through which molecules can diffuse.

Porins are beta barrel proteins that cross a cellular membrane and act as a pore, through which molecules can diffuse.

A sucrose specific porin from Salmonella typhimurium, a gram-negative bacterium.

They are present in the outer membrane of gram-negative bacteria and some gram-positive mycobacteria (mycolic acid-containing actinomycetes), the outer membrane of mitochondria, and the outer chloroplast membrane.

Translocase of the outer membrane

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The translocase of the outer membrane (TOM) is a complex of proteins found in the outer mitochondrial membrane of the mitochondria.