Download Stage 2: Aerobic Respiration

Cellular Respiration
I. Harvesting Chemical Energy
• Breaking down complex organic compounds into simpler molecules,
releasing energy to make ATP.
C6H12O6 + 6O2 Æ 6CO2 + 6 H2O + Energy (ATP)
Stage 1: Glycolysis
• Initial breakdown of glucose into two 3-carbon sugars (pyruvic acid)
occurs in the cytoplasm
• can lead either to (1) Fermentation or
(2) Aerobic Respiration
depending on availability of O2
• produces 2 ATP molecules (actually 4, but 2 used)
Stage 2: Aerobic Respiration
I. Overview of Aerobic Respiration (O2 required)
•Instead of going into fermentation, PYRUVIC ACID (that 3-carbon
molecule) diffuses INTO the mitochondria.
NOTE: Aerobic respiration produces nearly 20 TIMES as much ATP as is
produced by GLYCOLYSIS alone.
• Aerobic respiration occurs in 2 parts:
(1) Krebs cycle
(2) Electron Transport Chain (ETC)
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The Krebs Cycle (aka Citric Acid Cycle):
•Occurs inside the matrix, where enzymes needed to catalyze these
reactions are found.
• Carbon dioxide is released as the sugars are further broken down
• Energy from the bonds is transferred to 2 temporary molecules (NADH
and FADH2)
NOTE: So far, we have ONLY 2 ATP made during GLYCOLYSIS,
and 2 ATP made during KREBS CYCLE.
• Electrons from NADH & FADH2 are then transferred to an
e- transport chain
Electron Transport Chain
(occurs in INNER mitochondrial membrane)
•NADH and FADH2 supply e- and H+ to the electron transport chain.
•The e- are PASSED ALONG, RELEASING energy to PUMP H+ OUTSIDE,
building a concentration gradient.
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Electron Transport Chain cont’d
As the H+ RETURN to the matrix through protein channels, they RELEASE energy,
driving the SYNTHESIS of 30-32 ATP !!!
• The FINAL e- ACCEPTOR of the chain is oxygen (O2), which also accepts
H+ in a reaction forming WATER as a product.
O2
H2O
2
2
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Anaerobic Pathways (operate in absence of O2)
• Alcohol or Lactic Acid Fermentation
• Produces significantly less ATP than aerobic processes.
• Basically just converts pyruvic acid to a
less toxic compound.
•Used by bacteria, yeast, mammalian muscle
cells
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Critical Thinking
How does the folding of the inner mitochondrion membrane benefit aerobic
respiration?
Critical Thinking
A person will breathe deeply and rapidly for some time after a period of
very strenuous exercise. The longer and more intense the exercise was,
the longer the deep breathing will continue after the exercise stops. Using
your understanding of cellular respiration, explain why strenuous exercise
stimulates deep breathing that continues after the end of exercise.
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