Metabolisms Flashcards
What is metabolism
all biochemical processes within a cell
what are the two main types parts of metabolism and describe them
1 - Anabolism: formation of biomass (growing)
2 - Catabolism: formation of energy from substrate (getting smaller but producing energy)
Describe Anabolism and give an example
use of chemical energy to convert nutrients and simple compounds into complex molecules
example: photosynthese
what are the two main types of Catabolism
and
describe it
fermentation and respirations are the two mains types
oxidation of organic or inorganic compounds, accompanied by the release of energy (ATP) and waste
What is ATP
Adenosine triphosphate is a nucletide
it carries energy in a form that cells can use
Which process produces ATP and which process uses it
Anabolism uses ATP and Catabolism produces it
What is a PED
primary electron donor
What is a TEA
terminal electron acceptor
what causes more energy to be conserved (less lost as heat) in the ETC (electron transport chain)
-when there is a greater difference in the electrode potential between the PED and the TEA
-there are more steps in the chain
-the more steps there are the more energy is conserved
What is an enzyme
a biological catalyst
(without which most biological reactions would occur too slowly for life)
Why might fermentation occur instead of respiration?
no need for external TEA, so redox reactions can occur internally regardless of exturnal environments
why might respiration occur instead of fermentation?
- more efficient: more ATP produced
- the electrode potential is bigger between the products meaning a bigger chain and less energy loss
- fermentation end products are still relatively complex molecules containing usable energy
What are the TEAs for aerobic and anaerobic respiration
aerobic TEA - Oxygen
anaerobic TEA - Sulfate, ferric iron (3+), arsenate, nitrate (any oxidised species that can accept electrons
what is a facultative anaerobe
respire aerobically but can use other TEA when no oxygen is available
which type of respiration is more favourable aerobic or anaerobic
aerobic
What does photo or chemo refer to
energy source
photo: sunlight
chemo: preformed molecules
What is an obligate anaerobe
can only survive in an environment that is oxygen depleted
what does hetero or litho refer to
electron donor
hetero: organic compounds
litho: inorganic compounds
what does hetero or auto refer to
carbon source
hetero: organic compound
auto: inorganic compound
what are two examples of chemoheterotrophy and
what produces more ATP
Fermentation and Respiration
Respiration produces more ATP
What is the process of chemoheterotrophy
uses chemical energy sources and organic carbon
what is the generalised equation for AEROBIC chemoheterotrophic respiration
C6H12O6 + 602 = 6CO2 + 6H2O
- organic C is oxidised by O2
- oxygen is reduced by organic C
- produces more ATP than other respiration pathways
Types of ANAEROBIC chemoheterotrophy
Reductions of other TEAs
including:
- Dissimilatory nitrate reduction
- Dissimilatory manganese reduction
- Dissimilatory iron reduction
- Dissimilatory reduction of other metals or
metalloids
- Dissimilatory sulfate reduction
- Methanogenesis
Dissimilatory nitrate reduction: who does it and where is it important
- bacteria only
- important role in soils and freshwaters subject to agricultural pollution or sewage
Dissimilatory iron reduction
- Fe-oxides ubiquitous in soils and sediments
- Implicated in release of Fe 2+ in anoxic
groundwaters, degration of org matter in
deeply buried sediments + formation of
variegated red beds in sedimentary rocks - some used in BIOREMEDIATION to degrage contaminants
- e- shuttling used
Dissimilatory manganese reduction
- some Mn-reducers are facultative anaerobes
- some prefer Fe(III) - reduction but will reduce
Mn if its available - mineral oxides cannot cross cell membrane so
cells either attach to mineral surface or use e-
shuttling molecules
What are electron shuttles
organic compounds that speed up dissimilatory metal reduction reactions
dissimilatory reduction of other metals and metalloids
- major interest to bioremediation
- lots of radioactive and toxic contaminants (As, Se, Cr, U, Tc, Pu)
- Some bacteria can reduce U as a byproduce of other activites (not for energy) but Geobacter and Shewanella (Fe reducers) can derive energy from it ALTHOUGH it is not as energetically favourable as Fe reduction
Dissimilatory sulfate reduction
- wide variety of bacteria can do this (usually obliagte anaerobes)
- found in water logged soils, brackish waters, sewage, mine waste, hot springs, oil and gas wells, deep sea hydrothermal vents and deep marine sediments (ANYWHERE ANOXIC WITH ENOUGH ORGANIC MATTER AND SULPHATE)
Methanogenesis
- methanogens
- Strict anaerobic Archaea
- there is chemoHETEROtrophic methanogeneis and chemolithoAUTOtrophic methanogensis
- occupy niches in anoxic, SO4 deficient environments: swamps, water-logged soils, tundra, marine sediments, hydrothermal vents, landfill and sewage
- PRODUCES VERY LITTLE ENERGY
what is chemolithoautotrophy
and
how is it different to chemoautotrophy
- rock eaters
- chemo = chemical energy souce
- litho = inorganic chemicals
- auto = CO2
different because it oxidises inorganic compounds not organics
Differences between chemoheterotrophy and chemolithoautotrophy
- litho uses inorganic sources of Carbon
- litho is less energetically favourable (the delta E is greater for hetero)
- electron donors required for both ATP generation and CO2 fixation
What do chemolithoautotrophs use as PED to produce biomass
inorganic species:
- H2 <—- most wide spread
-CH4 <—- methanotrophs
-H2S
-S0
-S2O3
-Fe (II)
-Mn (II)
-NH4
-NO2
and inorganic carbon
-CO2
-HCO3
What is the TEA for chemolithoautotrophy
usually oxygen but not always
Difference between methanogens and Methanotrophs
Methanogens - form methane
Methanotrophs - consume (oxidise) methane
-widespread wherever there is a stable source of CH4 eg:
polar regions
continental margins
where are the two types of sulfur oxidisers found
Gradient organisms:
sulfur springs, microbial mats, low O2 seawater, sewage polluted freshwaters
Acidophilic organims:
acid rich environments - AMD
Where do the two types of iron oxidisers exist
Neutrophiles:
-microaerophilic environments (require O2 but not too much)
Acidophiles:
- mine waste, very hot acid springs e.g. volcanic areas
What are the most common PED and TEA for nitrogen oxidisers
and
where are they found
PED = NH4
TEA = O2
found in marine sediments, below chemocline of water column in anoxic basins
What are the two major types of photosynthesis and
who does them
- Oxygenic photosythesis:
plants, algae, cyanobacteria - Anoxygenic photosythesis:
green and purple bacteria, heliobacteria
What are phototrophs
light eaters!
they use sunlight as their energy source
examples:
plants
algae
some bacteria
What is the main pigment used in photosynthesis to transform light energy into chemical energy
Chloropyhll
What are the two categories of chlorophyll (chl)
- light harvesting chl
- reaction-centre chl: transforms light energy (photons) into chemical energy (PEDs)
What are the light and dark parts of photosynthes
light - initial stage where light energy is absorbed and transformed into ATP
dark - dont require light, include: CO2 (autotrophy) and N2 fixation
Oxygenic phototrophs
- Algae (eukaryotic)
- Cyanobacteria (prokaryotic)
- green sulfur bacteria
strictly anaerobic
Anoxygenic phototrophs
- green sulfur bacteria
- green nonsulfur bacteria
- purple bacteria
- purple nonsulfur bacteria
- Heliobacteria
- green nonsulfur bacteria
aerobic or anaerobic
- purple bacteria
can live in deeper waters where IR radiation is flitered out
- purple nonsulfur bacteria
similar to purple sulfur bacteria but cant handle too much H2S
- heliobacteria
obligate anaerobic photoheterotrophs
common in rice paddies
