Ch. 8 Cellular Respiration Flashcards
the evolution of metabolic pathways of cellular respiration
when life originated, there was little oxygen in the atmosphere
- anaerobic respiration was used by earliest organisms
later, non-cyclic pathway of photosynthesis increased atmospheric O2
-cells arose that used oxygen as the final acceptor in the ETC
ATP
universal energy source for all cells
-photosynthesizers get energy from the sun
-animals get energy second- or third- hand
regardless, energy is converted to the chemical bonds of ATP before it’s used
cellular respiration equation
C6H12O6 + 6O2—> 6O2 + 6H2O + 36ATP
main type of energy releasing pathways
- anaerobic
- aerobic
anaerobic respiration
- evolved first
- doesn’t require oxygen
- produces less ATP
- starts with glycolysis in cytoplasm
- completed in cytoplasm
aerobic respiration
- evolved later
- needs oxygen
- starts with glycolysis in cytoplasm
- completed in mitochondria
types of anaerobic respiration
- alcoholic fermentation
- lactic acid fermentation
alcoholic fermentation
occurs in yeast of beer, wine, and bread
produces: ethyl alcohol, CO2
lactic acid fermentation
occurs in bacteria, and muscles
produces lactic acid = sore muscles, cheese
fermentation pathways
begins with glycolysis
does not break glucose down completely to CO2 and H2O
- only a yield of 2 ATP
steps that follow just regenerate NAD+
3 steps of the aerobic respiration
- glycolysis
- Krebs cycle (citric acid cycle)
- electron transport chain/ phosphorylation
glycolysis
net yield of 2 ATP and 2 NADH
glycolysis equation
C6H12O6—> C3H4O3
Prep steps
yields 2 NADH, 2 CO2
krebs cycle
- takes 2 pyruvates and converts it into 2 acetyl co-a
- oxaloacetate, a 4-carbon molecule, is produced at the end of the cycle
- cycle repeats for a second time
results of the krebs cycle
-all of carbon molecules in pyruvate end up in CO2
-coenzymes are reduced (they pick up hydrogen and electrons
yields 4 CO2, 2 ATP, 6 NADH, 2 FADH
role of coenzymes/ electron carriers
-NAD+ and FAD accept hydrogen and electrons
- becomes NADH and FADH2
delivers hydrogens to ETC
- provides energy for ADP+P to convert to ATP
electron transport chain/ phosphorylation
-occurs in mitochondria
-coenzymes deliver electrons to electron transport chains
-electron transport sets up a H+ gradient
-H+ flows down concentration gradient and powers ATP formation
after ATP, O2 is the final acceptor of H+ forming H2O
importance of oxygen
electron transport phosphorylation requires presence of oxygen because the final electron acceptor at the end of cellular respiration is O2
what happens if there are no carbs?
- body will use carbs first
- need 500-600 carbs a day to fuel the brain
- body will next use fatty acids and glycerol in fats
- body will use amino acids and carbon backbones of proteins as a final resort
