using chemical energy - only autotrophs can use energy of sunlight through photosynthesis
- heterotrophs - use autotrophs for food; accounts for 95% of earth's organisms
- digestion - 1st step of harvesting energy; breaks down large molecules into smaller ones
- catabolism - harvesting energy from C-H and other chemical bonds
cellular respiration - harvests energy by shifting electrons from 1 molecule to the next
- energy from electrons used for ATP, or lost as heat
- electrons at end of process lose most of their energy, get transferred to final electron acceptor
- aerobic respiration - where final acceptor is oxygen
- anaerobic respiration - where final acceptor is nonorganic molecule other than oxygen
- fermentation - where final acceptor is organic molecule
- C6H12O6 + 6O2 >> 6CO2 + 6H2O
- -720 kilocalorie change per mole in free energy
ATP synthase - enzyme that creates most of ATP
- uses energy in gradient of protons produced by pumping protons across the membrane
- energy used for reactions come from catabolism or light striking chlorophyll
- spins due to mov't of protons
- mechanical energy from spin used to attach 3rd phosphate to ADP
glucose catabolism - ATP from catabolism forms in 2 ways
- substrate-level phosphorylation - additional phosphate directly transferred
- glycolysis - glucose chemical bonds shifted to provide energy for ATP
- aerobic respiration - uses electrons from organic molecules to power ATP synthase
- electrons donated to oxygen gas in final stage
- used by eukaryotes, aerobic prokaryotes for majority of ATP
- organisms combine the 2 processes
- glycolysis - stage 1
- 10-reaction biochemical pathway that produces ATP through substrate-level phosphorylation
- catalyzed by free floating enzymes
- uses 2 ATP, produces 4 ATP, 4 electrons for NAD+, 2 pyruvate molecules
- aerobic respiration - stages 2-4
- pyruvate oxidation - stage 2
- pyruvate gets converted into CO2 and acetyl-CoA
- NADH forms for every pyruvate molecule that gets converted
- Krebs cycle - stage 3
- aka citric acid cycle or tricarboxylic acid cycle
- cycle of 9 reactions that produce 2 ATP from substrate-level phosphorylation
- lots of electrons removed to NADH
- electron transport chain - stage 4
- uses electrons from NADH to pump protons across the membrane
- ATP synthase uses proton gradient to make ATP
- procedure occurs in prokaryotes and mitochondria of eukaryotes
anaerobic respiration - occurs w/o O; replaced by S, NO3, other inorganic molecules
- methanogens - use CO2 as final electron acceptor, reducing it to CH4
- sulfur bacteria - reduces SO4 to H2S; set the stage for photosynthesis evolution
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