3. Microbial Metabolism Flashcards
catabolism
fueling reactions
energy-conserving reactions
provide ready source or reducing power (electrons)
generate precursors for biosynthesis
anabolism
the synthesis of complex organic molecules from simpler ones
requires energy from fueling reactions
nutrients
supply of monomers (or precursors of) required by cells for growth
macronutrients
nutrients required in large amounts
micronutrients
nutrients required in minute amounts
trace metals and growth factors
requirements for nutrition in cells
carbon
hydrogen
oxygen
phosphorous
sulfur
nitrogen
carbon
major element in all classes of macromolecules
most microbes (heterotrophs) use
organic carbon
autotrophs use
carbon dioxide
nitrogen
proteins, nucleic acids, and many more cell consituents
phosphorous
nucleic acids and phospholipids
sulfur
sulfur containing amino acids (cysteine and methionine)
vitamins (thiamine, biotin, lipoic acid)
potassium
required by enzymes for activity
iron (Fe)
cellular respiration
trace metals
enzyme cofactors
active transport
how cells accumulate solutes against concentration gradient
three classes of transporters:
simple transport
group translocation
ABC system
simple transport
driven by the energy in the proton motive force
group translocation
chemical modification of the transported substance driven by phosphoenolpyruvate
ABC transporter
periplasmic binding proteins are involved and energy comes from ATP
phosphotransferase system in E.coli
-best studied group translocation system
-glucose, fructose, mannose
-five proteins required
-energy derived from phosphoenolpyruvate (from glycolysis)
ABC (ATP-binding cassette) systems
200+ different systems identified in prokaryotes for organic and inorganic compounds
high substrate affinity (very specific to what they are transporting)
ATP drives uptake
requires trans-membrane and ATP-hydrolyzing proteins plus:
-gram negatives employ periplasmic binding proteins
-gram positive and archaea employ substrate-binding proteins on external surface of cytoplasmic membrane
activation energy
minimum energy required for molecules to become reactive
-a catalyst is usually required to overcome activation energy barrier
electron donor
the substance is oxidized (glucose)