Presence of Oxygen in mitochondria is called Aerobic conditions and under this aerobic conditions Pyruvic acid is converted into Acetyl Co.A which enters Krebs' cycle
while in absence of oxygen which called Anaerobic conditions pyruvic acid is converted into Lactic acid to avoid accumulation of NADH⁺ which inhibit glycolysis and provide NAD⁺ required for glycolysis
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Street: 1. Cars 2. People 3. Wind in the trees 4. Birds 5. Car horn
School: 1. School bell 2. Students laughing 3. Teacher talking 4. Footsteps 5. Lockers
Church: 1. Priest talking 2. People talking 3. Church music 4. Kids crying 5. Benches creaking