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 NON-SULFUR 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