ENERGY METABOLISM
DEFINE:
• ASSIMILATION - BIOSYNTHESIS OR
CONVERSION OF NUTRIENTS TO CELL
MASS- ENERGY REQUIRING
• DISSIMILATION - ACT OF BREAKING
DOWN COMPONENTS TO SMALLER PARTS
- USUALLY ENERGY YIELDING
MOST COMMON ENERY PATHWAYS USED BY
MICROORGANISMS
•
•
•
•
FERMENTATION
AEROBIC RESPIRATION
ANAEROBIC RESPIRATION
PHOTOSYNTHESIS
ENZYMES
• CHARACTERISTICS
– BIOLOGICAL CATALYST
– CHEMICAL COMPOSITION IS PROTEIN
– LOWER ENERGY OF ACTIVIATION FOR
CHEMICAL REACTIONS
– NOT ALTERED IN THE REACTIONS
– INCREASE THE RATE OF THE REACTION
– HIGHLY SPECIFIC
FERMENTATION
• DEFINITION - THAT SERIES OF ENERGY
YIELDING BIOLOGICAL OX/RED
REACTIONS IN WHICH ORGANIC
CHEMICALS SERVE AS BOTH THE
ELECTRON DONOR AND THE FINAL
ELECTRON ACCEPTOR.
• CHARACTERISTICS OF THE PATHWAY
– LOW ENERGY YIELD - ONLY 2
MOLECULES OF ATP PRODUCED PER
MOLECULE OF CARBOHYDRATE
FERMENTTED- NO ETS
•
•
•
PRINCIPAL PRODUCTS
ORGANIC ACIDS
ALCOHOLS
GASES – CARBON DIOXIDE AND
HYDROGEN
• ATP
-MOST COMMON SUBSTRATES FERMENTED
ARE CARBOHYDRATES.
-PATHWAY OCCURS IN THE CYTOPLASM OF
CELLS AND NOT IN THE MITOCHONDRIA
-OXYGEN GAS IS NOT REQUIRED BUT DOES
NOT INTERFERE WITH FERMENTATION
-UNIQUELY MICROBIAL
• FERMENTATION CAN YIELD SINGLE
PRODUCTS (HOMOFERMENTATIONS) OR
MULTIPLE PRODUCTS
(HETEROFERMENTATIONS)
AEROBIC RESPIRATION
• DEFINITION - THE ENERGY YIELDING PROCESS IN
WHICH OXYGEN GAS SERVES AS THE FINAL
ELECTRON ACCEPTOR. USUALLY, A
CARBOHYDRATE SERVES AS THE INITIAL
ELECTRON DONOR.
• HIGH ENERGY PATHWAY - 36-38 ATP PRODUCED
PER MOLECULE OF CARBOHYDRATE RESPIRED
• PART OF THE PATHWAY OCCURS IN THE
CYTOPLASM AND PART IN THE MITOCHONDRIA.
• PRODUCTS OF THE PATHWAY ARE CARBON
DIOXIDE, WATER, AND ATP
• A CLOSER LOOK AT THE ETS
– CYTOCHROME C IS MISSING IN THE ETS
OF SOME BACTERIA.
– THESE BACTERIA ARE SAID TO BE
OXIDASE NEGATIVE.
– THOSE WHICH HAVE CYTOCHROME C IN
THEIR ETS ARE SAID TO BE OXIDASE
POSITIVE.
OXIDATION OF INORGANIC COMPOUNDS
• A SPECIAL MODIFIED TYPE OF AEROBIC
RESPIRATION
• CHEMOAUTOTROPHS USE THIS TYPE OF
RESPIRATION
• CHEMICAL COMPOUNDS SUCH AS H2, NH3,
AND H2S CAN BE RESPIRED AND ATP CAN
BE ACQUIRED BY THE ORGANISM.
• MANY OF THE ORGANISMS FOUND AT THE
DEEP THERMAL OCEAN VENTS ARE
CHEMOAUTOTROPHS. pp. 160 in text
• H2S AND CO2 ARE AVAILABLE THERE.
• H2S + O2
SO4-- + ENERGY
• CO2 + R
CH2O
ANAEROBIC RESPIRATION
• THERE IS NO SINGLE COMMON PATHWAY
• INITIAL ELECTRON DONOR CAN BE ORGANIC OR
INORGANIC
• FINAL ELECTRON ACCEPTOR IS ALWAYS AN
INORGANIC COMPOUND THAT IS RICH IN
ELEMENTAL OXYGEN.
• EXAMPLES ARE: NO3-, SO4--, C03-• THE AMOUNT OF ATP GENERATED PER
MOLECULE OF SUBSTRATE RESPIRED VARIES.
ANAEROBIC RESPIRATION (CONT.)
• THE ATP GENERATED IS NEVER AS MUCH
AS IN AEROBIC RESPIRATION BUT NEVER
AS LITTLE AS IN FERMENTATION.
PHOTOSYNTHESIS
• THIS ENERGY PATHWAY USES LIGHT AS THE
ENERGY SOURCE
• CLASSICAL PHOTOSYNTHESIS AS SEEN IN
PLANTS AND ALGAE
– WATER IS USED AS THE INITIAL ELECTRON
DONOR
– CARBON DIOXIDE IS THE FINAL ELECTRON
ACCEPTOR
– PRODUCTS ARE CARBOHYDRATE, OXYGEN
GAS AND WATER.
– THERE IS NO NET PRODUCTION OF ATP.
• CLASSICAL PHOTOSYNTHESIS CAN BE
SUMMARIZED AS FOLLOWS:
• 6CO2 + 12H2O + LIGHT ENERGY =
+ CHLOROPHYLL A
C6H1206 + 6O2 + 6H20
PHOTOAUTOTROPHS
• PLANTS, ALGAE AND SOME BACTERIA ARE
PHOTOAUTOTROPHS
• CLASSICAL PHOTOSYNTHESIS IS USED BY ALL
PLANTS, ALGAE, AND SOME BACTERIA
(CYANOBACTERIA).
• THERE ARE SOME BACTERIA IN THE
PHOTOAUTOTROPH GROUP THAT USE A
DIFFERENT TYPE OF PHOTOSYNTHESIS.
• ANAEROBIC, OXYGEN GAS IS NEVER
PRODUCED
•
•
•
•
•
H2S IS USED AS THE INITIAL ELECTRON DONOR,
NOT WATER
A BACTERIOCHLOROPHYLL IS USED AS THE
LIGHT CAPTURING PIGMENT
PRODUCTS ARE: CARBOHYDRATE, WATER, AND
ELEMENTAL SULFUR.
BC ABSORBS LIGHT OF LONGER WAVELENGHTHS
THAN CLASSICAL CHLOROPHYLL A. CHEMICAL
STRUCTURE IS SLIGHTLY DIFFERENT.
CALLED GREEN AND PURPLE SULFUR BACTERIA
• THIS TYPE OF PHOTOSYNTHESIS CAN BE
SUMMARIZED AS FOLLOWS:
• 2H2S + CO2 + LIGHT ENERGY = C6H1206 +
2S + H2O
• BACTERIOCHLOROPHYLL IS USED AS
LIGHT CAPTURING PIGMENT
PHOTOHETEROTROPHS
• ONLY A FEW BACTERIA IN THIS GROUP
• THEY USE ORGANIC ACIDS AND
ALCOHOLS AS THE INITIAL ELECTRON
DONORS.
• FINAL ELECTRON ACCEPTOR IS CARBON
DIOXIDE.
• PRODUCTS: CARBOHYDRATE, AND
OXIDIZED ORGANIC ACIDS AND
ALCOHOLS.
• CALLED GREEN AND PURPLE NONSULFUR BACTERIA
• THIS TYPE OF PHOTOSYNTHESIS CAN BE
SUMMARIZED AS FOLLOWS:
• CO2 + ORGANIC ACIDS AND ALCOHOLS=
C6H1206 +OXIDIXED ORGANIC ACIDS AND
ALCOHOLS
• BACTERIOCHLOROPHYLL IS USED AS
LIGHT CAPTURING PIGMENT