cellular respiration of protein - 1st broken down into amino acids
- deamination - process that removes the amino group
- reactions convert remaining carbon chain into parts that take place in glycolysis/Krebs cycle
- alanine converted to pyruvate
- glutamate converted into a-ketoglutarate
- aspartate converted into oxaloacetate
cellular respiration of fat - 1st broken down into fatty acids and glycerol
- beta oxidation - process that removes 2-carbon acetyl groups from fatty acids to convert them into acetyl groups
- takes place in mitochondrial matrix
- each acetyl group combines w/ coenzyme A to form acetyl-CoA
- produces 20% more ATP than glucose per 6-carbon molecule
- contains 2x as much kilocalories per gram
fermentation - process that recycles NAD+ in absence of oxygen
- uses organic compound as electron acceptor instead of oxygen
ethanol fermentation - occurs in yeast (single-celled fungi)
- pyruvate accepts hydrogen from NADH
- enzymes remove CO2 from pyruvate through decarboxylation, making acetaldehyde (2-carbon molecule)
- CO2 released causes bread to rise
- acetaldehyde + NADH >> ethanol + NAD+
- ethanol begins to kill yeast at 12% concentration
lactic acid fermentation - uses lactate dehydrogenase to transfer H from NADH to pyruvate
- pyruvate + NADH >> lactic acid + NAD+
- lactate - ionized form of lactic acid
- interferes w/ muscle function when circulating blood can't remove lactic acid fast enough
evolution of metabolism - changed stage by stage
- degradation - breaks down organic molecules abiotically produced
- started w/ origin of ability to use chemical bond energy
- glycolysis - initial breakdown of glucose
- captures a larger amount of chemical bond energy by breaking bonds in steps
- hasn't changed in over 2 billion years
- anaerobic photosynthesis - uses light to pump protons from cells
- still uses chemiosmosis to produce ATP
- evolved in absence of oxygen
- dissolved H2S provided hydrogen for procedure
- oxygen-forming photosynthesis - H2O replaced H2S
- generates oxygen instead of sulfur
- all oxygen in atmosphere from oxygen-forming photosynthetic reaction
- nitrogen fixation - obtaining nitrogen atoms from N2 gas by breaking triple bonds
- evolved in hydrogen rich atmosphere
- occurs in oxygen-free environments (oxygen poisons nitrogen-fixation)
- aerobic respiration - final event in history of metabolic evolution
- gets energy from electrons in organic molecules
- uses same proton pumps as photosynthesis
- 1st evolved among purple nonsulfur bacteria (obtained hydrogen from organic molecules)
- mitochondria thought to be descendents of nonsulfur bacteria
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