Microbial Metabolism Flashcards
What are the requirements for microbial survival and growth?
- source of energy for cellular work
- source of electrons to reduce CO2 to form organic molecules
- nutrients (carbon, hydrogen, and oxygen) to synthesize organic building blocks needed for cell maintenance and growth
What are the different sources of energy?
- organic or inorganic chemical compounds
- energy is harvested by oxidizing these compounds
- or sunlight
- energy is typically conserved in cells as ATP
What are phototrophs?
organisms that use light as an energy source
What are chemotrophs?
organisms that obtain energy from oxidizing chemical compounds
What are lithotrophs?
organisms that use reduced inorganic substances as a source of electrons
What are organotrophs?
organisms obtain electrons from organic compounds
What are heterotrophs?
- organisms that use organic molecules as carbon sources (which often serve as energy and electron sources as well)
- ex: glucose
What are autotrophs?
- organisms that use carbon dioxide as their sole or principle carbon source
- must obtain energy and electrons from other sources
- primary producers are autotrophs
What is metabolism?
the total of all chemical reactions occurring in the cell
What is catabolism?
- breaking things down
- fueling reactions
- energy conserving
- provide reducing power (electrons)
- generate precursors for biosynthesis
What is anabolism?
- the synthesis of complex organic molecules from simpler ones
- requires energy, electrons, and building blocks from fueling reactions (catabolism)
What is free energy (G)?
the amount of energy that is available to do useful work
What is standard free energy change (deltaG0’)?
the change in free energy during a chemical reaction for standard conditions (pH 7, 25 C, 1 atm, 1M concentrations of reactants and products)
What is an exergonic chemical reaction?
- a reaction that releases energy
- has a negative standard free energy change
- catabolism reactions
What is an endergonic chemical reaction?
- a reaction that requires energy
- has a positive standard free energy change
- anabolism reactions
What is the role of ATP in metabolism?
- releases 32kJ/mol of energy when hydrolyzed to ADP and Pi
- coupled to endergonic reactions to make them favorable
- made in respiration and used to do work
What are other energy rich compounds besides ATP?
- phosphoenolpyruvate (-51.6 kJ/mol)
- 1,3 biphosphoglycerate (-52.0 kJ/mol)
- acetyl phosphate (-44.8 kJ/mol)
- acetyl-CoA (-35.7 kJ/mol)
- ADP (-31.8 kJ/mol)
- AMP (-14.2 kJ/mol)
- glucose 6 phosphate (-13.8 kJ/mol)
What happens in a redox reaction?
- electron carriers are used to transfer electrons to an electron donor to an electron acceptor
- can result in energy release, which can be conserved as ATP or another energy-rich compound
What is oxidation?
the loss of electrons
What is reduction?
the gain of electrons
What is standard reduction potential (E’0)?
- the equilibrium constant for a redox reaction
- a measure of the tendency of the reducing agent to lose electrons
- more negative: better electron donor
- more positive: better electron acceptor
How are redox pairs ordered on an electron tower?
- better electron donors at the top (more negative E’0)
- better electron acceptors at the bottom (more positive E’0)
- oxidized form on the left
- reduced form on the right
What is the relationship between E’0 and deltaG0’?
the greater the difference between the E’0 of the donor and the E’0 of the receptor, the more negative deltaG0’ (more spontaneous)
How do electrons travel in the electron tower?
- down and to the left (releases energy)
- to go up the tower, light energy is used during photosynthesis
