electron shuttle

Examples of electron shuttle in the following topics:

• Electrons and Energy

  • In living systems, a small class of molecules functions as electron shuttles: they bind and carry high-energy electrons between compounds in cellular pathways.
  • These compounds can be easily reduced (that is, they accept electrons) or oxidized (they lose electrons).
  • It is noteworthy that NAD+must accept two electrons at once; it cannot serve as a one-electron carrier .
  • When electrons are added to a compound, the compound is reduced.
  • When electrons are removed from a compound, the compound is oxidized.

• Glow of Space Shuttles

  • The glow observed as a space shuttle re-enters the atmosphere is due to excited NO2 releasing light to return to its ground state.
  • When space shuttles return from space and being to re-enter the Earth's atmosphere, a glow, especially around the tail end of the shuttle, can often be observed.
  • The lining of the space shuttle is no exception; specifically, the glow on the space shuttle forms when atomic oxygen reacts with the nitric oxide (NO) on the exterior of the shuttle.
  • where NO2* represents the excited state of electrons in NO2.
  • It is the relaxation of these electrons from the excited state back to the ground state that produces the glow that is visible around the space shuttle (see the concept about the emission spectra for more information).

• Electron Transport Chain

  • The electron transport chain uses the electrons from electron carriers to create a chemical gradient that can be used to power oxidative phosphorylation.
  • Once it is reduced to QH2, ubiquinone delivers its electrons to the next complex in the electron transport chain.
  • This enzyme and FADH2 form a small complex that delivers electrons directly to the electron transport chain, bypassing the first complex.
  • Cytochrome c is the acceptor of electrons from Q; however, whereas Q carries pairs of electrons, cytochrome c can accept only one at a time.
  • The electron transport chain is a series of electron transporters embedded in the inner mitochondrial membrane that shuttles electrons from NADH and FADH2 to molecular oxygen.

• ATP Yield

  • The process of glycolysis only produces two ATP, while all the rest are produced during the electron transport chain.
  • Clearly, the electron transport chain is vastly more efficient, but it can only be carried out in the presence of oxygen.
  • Another source of variance occurs during the shuttle of electrons across the membranes of the mitochondria.
  • Thus, electrons are picked up on the inside of mitochondria by either NAD+ or FAD+.
  • NAD+ is used as the electron transporter in the liver, and FAD+ acts in the brain.

• Nitrogen Fixation Mechanism

  • Note this is a reduction reaction which means that electrons must be added to the N2 to reduce it to NH4.
  • Thus, the role of component II is to supply electrons, one at a time to component I.
  • B) ATP binds to component II, which receives electrons from an electron donor (ferredoxin or flavodoxin); binding of ATP induces an allosteric conformational change which allows association of the two proteins.
  • Electrons flow from the [4Fe-4S] cluster on II to the P cluster on I.
  • C) Electrons are further shuttled to the iron-molybdenum cofactor (FeMoco), and ATP is hydrolised to ADP.

• Shuttle Vectors and Expression Vectors

  • A shuttle vector is a vector that can propagate in two different host species, hence, inserted DNA can be tested or manipulated in two different cell types.
  • Shuttle vectors can be used in both eukaryotes and prokaryotes.
  • Shuttle vectors are frequently used to quickly make multiple copies of the gene in E. coli (amplification).
  • One of the most common types of shuttle vectors is the yeast shuttle vector that contains components allowing for the replication and selection in both E. coli cells and yeast cells.
  • The yeast component of a yeast shuttle vector includes an autonomously replicating sequence (ARS), a yeast centromere (CEN), and a yeast selectable marker.

• Shuttle Diplomacy

  • Shuttle diplomacy is the action of a thrid party in serving as an intermediary between principals in a dispute.
  • Originally and usually, the process entails successive travel ("shuttling") by the intermediary, from the working location of one principal, to that of another.
  • Negotiators often use shuttle diplomacy when one or both of the two principals refuses to recognize the other.
  • Shuttle diplomacy became an important part of Kissinger's diplomatic efforts in the Middle East during the Nixon and Ford administrations.
  • Kissinger developed the practice of "shuttle diplomacy" as Nixon's National Security Adviser, and later, Ford's Secretary of State.

• Nitrogen Compounds

  • The reddish and poisonous nitrogen dioxide (NO2) contains an unpaired electron and is an important component of smog.
  • Nitrogen molecules containing unpaired electrons show a tendency to dimerize (thus pairing the electrons), and are, in general, highly reactive.
  • These engines were extensively used on spacecraft such as the space shuttle and those of the Apollo Program because their propellants are liquids at room temperature and ignition occurs on contact without an ignition system, allowing many precisely controlled burns.

• Circular Motion

  • Consider a space shuttle that orbits around the earth.
  • Since the space shuttle is undergoing uniform circular motion, there must be a force that prevents the space shuttle from flying out of orbit.
  • The relationship between the gravitational pull on the satellite from the Earth ($g'$) and the velocity of the space shuttle is: $mg'= \frac{mv^{2}}{r}$ where $m$ is the mass of the space shuttle, $v$ is the velocity at which it orbits around the earth, and $r$ is the radius of its orbit.

• Productivity Gains from Hardware

  • Later in the Industrial Revolution came the flying shuttle, a simple device that doubled the productivity of weaving.
  • Early electric data processing was done by running punched cards through tabulating machines, the holes in the cards allowing electrical contact to incremental electronic counters.
  • By the 1960s, thousands of transistors and other electronic components were being manufactured on silicon semiconductor wafers as integrated circuits, which are universally used in today's computers.
  • In 1973, IBM introduced point of sale (POS) terminals in which electronic cash registers were networked to the store's mainframe computer.