Martian meteorite may have held life
Feb. 10 2006, NewScientist.com news service Kimm Groshong
A mix of carbon compounds filling the miniscule veins in a Martian meteorite
has refuelled the debate on the possibility of life on Mars. Similarities between
the carbon-rich filler and that found in fractured volcanic samples from the
Earth's ocean floor dangle the possibility that life produced the Martian material,
say scientists. A team of researchers led by David McKay and Everett Gibson
of the Johnson Space Center in Houston, US, raise the scenario as just one
possibility after extensively analysing new samples of the Nakhla meteorite.
The UK’s Natural History Museum recently provided the team with fresh
samples from the interior of the meteorite, which broke into many pieces upon
landing in Egypt in 1911. Near the tube-like veins in the rock, researchers
found iddingsite – a mineral also formed on Earth, mainly through alteration of
an iron-based mineral called olivine by water. And within the cracks, they found
carbon-rich material that appears dark brown or black.
Astrobiologists look for carbon and water in their search for extraterrestrial life.
Carbon is the building block of terrestrial life, forming the basis for organic
chemistry, and water is necessary to support all forms of life on Earth. The
team outlined possible sources of the carbon-containing components. Either a
carbon-bearing impactor introduced them to Mars between 600,000 and
700,000 years ago or they are "products of biogenic activity and introduced by
groundwater into the fracture features in Nakhla.
Enzymes convert substrates to products – reactions that make up “steps” in metabolic pathways
Enzymes are catalysts that decrease activation energy of a reaction, bringing reactants together at physiological
Enzymes often require cofactors or coenzymes.
Coenzymes serve to transfer functional groups from one reaction to another, for example NAD is a coenzyme that
Enzymes “control” whether or not reactions occur.
Enzyme activity can be regulated via binding of a regulatory molecule to the enzyme allosteric site. Some
enzymes have allosteric sites. In Feedback inhibition the end product of the pathway serves as a regulator to an
enzyme early in the pathway. When the endproduct is present the endproduct binds to the allosteric site,
inhibiting the enzyme from binding to the substrate. The metabolic pathway cannot proceed past this reaction.
Reactions that generate energy are coupled to the phosphorylation of ATP. This is substrate level
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