A review of metabolism
First consider the three processes in which a molecule of glucose can
be degraded to obtain ATP and remember that the basis for distinguishing
them is their terminal electron acceptor
- aerobic respiration - terminal electron acceptor = oxygen
- anaerobic respiration - terminal electron acceptor = inorganic
compound other than oxygen
- fermentation - terminal electron acceptor = organic compound
Consider how ATP is synthesized:
- substrate-level phosphorylation (SLP) occurs when ATP
is produced when a pathway (such as glycolysis) or cycle (such as the Krebs
cycle is occurring.
- oxidative phosphorylation (OP) occurs when ATP is produced
in the electron transport system
Consider the pathways and cycles that cells use when they carry out
energy metabolism .
- glycolysis
- Krebs cycle
- electron transport system
Consider which pathways and cycles are used in the three processes noted
above:
- Aerobic respiration - glycolysis, Krebs cycle, electron transport system
- Anaerobic respiration - glycolysis, Krebs cycle, electron transport
system
- Fermentation - glycolysis
Consider what happens in each of these pathways and cycles:
- glycolysis
- glucose is partially oxidized
- ATP is formed via SLP
- reduced NAD is formed
- oxidation/reduction occurs
- Krebs cycle
- the oxidation of glucose is completed
- ATP is formed via SLP
- carbon dioxide is produced (the carbons were originally in glucose)
- reduced NAD and reduced FAD are produced
- oxidation/reduction occurs
- Electron transport system (ETS)
- ATP is produced via OP
- reduced coenzymes give up their hydrogens (protons and electrons) to
the system
- the electrons move down the ETS releasing energy
- the energy is captured by the cell by pushing protons across the membrane
- when the protons come back across the membrane (at very specific locations)
ATP is synthesized
- oxidation/reduction occurs