Download Archaea possess genes and several metabolic pathways

Archaea possess genes and several metabolic pathways that are more
closely related to those of eukaryotes than prokaryotes.
LEARNING OBJECTIVE [ edit ]
Describe the similarities between archaea, eukaryotes, and bacteria
KEY POINTS [ edit ]
Archaea exhibit a great variety of chemical reactions in theirmetabolism and use many sources of
energy.
The energy released generates adenosine triphosphate (ATP) through chemiosmosis, in the same
basic process that happens in the mitochondrion of eukaryotic cells.
The chromosomes replicate from multiple starting­points (origins of replication)
using DNA polymerases that resemble the equivalent eukaryotic enzymes.
TERMS [ edit ]
eukaryote
Any of the single­celled or multicellular organisms, of the taxonomic domain Eukaryota, whose
cells contain at least one distinct nucleus.
mitochondrion
a spherical or ovoid organelle found in the cytoplasm of eukaryotic cells, contains genetic material
separate from that of the host; it is responsible for the conversion of food to usable energy in the
form of ATP
archaea
a taxonomic domain of single­celled organisms lacking nuclei that are fundamentally from
bacteria.
metabolism
The complete set of chemical reactions that occur in living cells.
Give us feedback on this content: FULL TEXT [ edit ]
The evolutionary relationship
between archaea and eukaryotesremains
unclear. Aside from the similarities in cell
structure and function that are discussed
below, many genetic trees group the two .
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Archaea and other domains
Phylogenetic tree showing the relationship between the Archaea and other domains of life.
Eukaryotes are colored red, archaea green and bacteria blue.
Complicating factors include claims that the relationship between eukaryotes and the
archaeal phylum Crenarchaeotais closer than the relationship between
the Euryarchaeotaand the phylum Crenarchaeota, and the presence of archaean­
like genes in certain bacteria, such as Thermotoga maritima, from horizontal gene transfer.
The leading hypothesis is that the ancestor of the eukaryotes diverged early from the
Archaea, and that eukaryotes arose through fusion of an archaean and eubacterium, which
became the nucleus and cytoplasm. This explains various genetic similarities but runs into
difficulties when it comes to explaining cell structure.
Despite this visual similarity to bacteria, archaea possess genes and
several metabolic pathways that are more closely­related to those of eukaryotes, notably the
enzymes involved in transcription and translation.
Archaea exhibit a great variety of chemical reactions in their metabolism and use many
sources of energy. These reactions are classified into nutritional groups, depending on energy
and carbon sources. Some archaea obtain energy frominorganic compounds such as sulfur or
ammonia (they are lithotrophs). These include nitrifiers, methanogens
andanaerobic methane oxidisers. In these reactions, one compound passes electrons to
another (in a redox reaction), releasing energy to fuel the cell's activities. One compound acts
as an electron donor and another as an electron acceptor. The energy released generates
adenosine triphosphate (ATP) through chemiosmosis, in the same basic process that
happens in the mitochondrion of eukaryotic cells.
The chromosomes replicate from multiple starting­points (origins of replication) using DNA
polymerases that resemble the equivalent eukaryotic enzymes. However, the proteinsthat
direct cell division, such as the protein FtsZ, which forms a contracting ring around the cell,
and the components of theseptum that is constructed across the center of the cell, are similar
to their bacterial equivalents.