diversity Flashcards
(37 cards)
how are the metabolic types of bacteria determined?
by their energy source which is chemotroph (preformed molecules) or phototroph (sunlight)
their carbon source which is heterotroph (organic) or autotroph (inorganic)
and their electron source which is organo (organic for fermentation) or litho (inorganic for respiration)
what are the 3 most common metabolic types?
chemoorganotrophs, chemolithotrophs and phototrophs
how are electrons transferred?
from molecules with a low reduction potential (an electron donor) to molecules with a high reduction potential (electron acceptors)
how are electrons and protons used to generate ATP is respiration?
electrons are transferred which releases energy
this energy is used to secrete protons and form a proton gradient
this creates a proton motive force that generates ATP
what are the 2 main sources of energy for metabolism?
reducing power and ATP
which 2 metabolites are produced when organic compounds are used as a source of electrons?
acetyl-CoA and pyruvate
how do chemoorganotrophs respire?
some use oxygen as the final electron acceptor so they carry out aerobic respiration
other chemoorganotrophs that use a different final electron acceptor carry out anaerobic respiration
chemoorganotrophs that don’t use a final electron acceptor carry out fermentation
how do chemoorganotrophs respire aerobically?
they use proteins to shuttle electrons along an electron transfer chain from an electron donor to oxygen
the energy released from the ETC is used to pump protons across the membrane
the protons power ATPases to generate ATP
how do chemoorganotrophs respire anaerobically?
a different molecule such as cytochromes are used as final electron acceptors
the amount of energy generated from the ETC depends on the molecule used as the final acceptor
ATP is produced by oxidative phosphorylation using the proton motive force
how do chemoorganotrophs carry out fermentation?
organic molecules are used as electron acceptors but there is no transfer chain
ATP is produced by substrate-level phosphorylation in the cytoplasm
the energy yield is lower
how do chemolithotrophs produce organic molecules?
use carbon dioxide as a source of carbon
use the calvin cycle and TCA chain to fix carbon
they require NADF which needs protons for the reverse electron flow process
what electron donor and acceptors do chemolithotrophs use and what by-products are produced?
use hydrogen as an electron donor which has a wide range of acceptors
using oxygen as the acceptor produces water
using acetate as the acceptor generates carbon dioxide
using methane or chlorinated compounds as the acceptor forms ethene
how can iron be used as an acceptor?
when it accepts electrons it is oxidised from +2 to +3 and turns brown
what is nitrification and anammox?
nitrification: ammonium is oxidised to nitrate using 2 different bacteria in aerobic conditions
anammox: ammonium is oxidised to nitrogen gas by planctomycetes in anaerobic conditions
how can sulfur be used as an electron donor?
they are reduced to sulfuric acid by acid-producing microbes
how are acid-producing bacteria used in biomining?
they can extract elements such as iron and copper from rocks by oxidising them to form ions
they dissolve the rocks with the acid they produce from sulfur
how do archaea carry out photosynthesis?
they use a protein called bacteriorhodopsin which is a light-driven proton pump in their membranes
it contains a pigment called retinal that undergoes a conformational change when excited by light
retinal is complexed to rhodopsin which drives electron transfer and causes protons to move generating a proton gradient that is used to produce ATP
what is cyanobacteria?
bacteria that carry out photosynthesis
how do cyanobacteria carry out photosynthesis?
they don’t have chloroplasts but they have thylakoids containing a photosynthetic apparatus
they have light harvesting complexes containing pigments that capture light
energy is generated at a reaction centre
what is the oxygenic Z pathway?
it uses 2 direct photosystems with distinct absorption wavelengths that are excited by light
the energy from light is used to remove electrons from water producing protons
the flow of electrons is used to pump protons out of the cell and reduce NADP+
the proton gradient is used to generate ATP
NADPH and ATP are used to fix carbon dioxide and make glucose
how do purple bacteria carry out anoxygenic photosynthesis?
light is captured by antenna complexes in organelles called chromatophores and the light energy is transferred to the PSII reaction centre
PSII donates an electron to a cyclic electron transfer chain
the electron transfer chain pumps protons outside the cell and the gradient is used to generate ATP by cyclic phosphorylation
NADP+ is reduced by reverse electron flow which uses energy
electrons are transferred to NAD+ and are replenished by inorganic or organic compounds
what are archaea and what are the 2 main phyla of archaea?
prokaryotes, they are their own domain
the 2 phyla are euryarcheota and crenarcheaota
what are extremophiles?
archaea species that are adapted to survive in harsh conditions
how do green sulfur carry out anoxygenic photosynthesis?
light is captured by antenna complexes in organelles called chlorosomes
in chlorosomes there is a photon centre that transfers light to the PSI system
PSI donates an electron to the electron transfer chain and protons are pumped out of the cell
the protons reduce NADP+ using ferredoxin
the proton gradient generates ATP
PSI receives electrons from inorganic sulfur derivatives
