cellular respiration: a catabolic process that breaks apart glucose and strips it of its electrons

process of cellular respiration

equation: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

GOAL: take one glucose molecule and make 38 molecules of ATP (dismantle)

3 steps:

1. glycolysis

   • no oxygen needed

   • occurs in cytoplasm

   • glucose broken down into 3-carbon molecules called pyruvate

   • produces 2 ATP, 2 NADH

2. link

   • if oxygen is present, pyruvic acid broken down further into 2 acetyl COA (+2 NADH, releases CO2)

3. krebs [citric acid] cycle

   • acetyl coa broken down

   • CO2 released

   • +2 ATP, 6 NADH, 2 FADH2

   • occurs in mitochondria

   • most of remaining energy is hydrogen attached to NADH + FADH2

4. electron transport chain

   • occurs in inner membrane of the mitochondria

   • electrons from NAD(H) passed to carrier molecules embedded in inner membrane; allows H+ protons to diffuse from matrix → inner membrane space

   • forms steep proton gradient - H+ protons diffuse back down the gradient through ATP synthase; ATP is made as ADP picks up its third phosphate

   • hydrogen electrons land on oxygen - final electron acceptor, makes water

   • each hydrogen from NADH can make 3 ATP, each hydrogen from FADH2 makes 2 ATP

   • 10 moles of NADH = 30 ATP

   • 2 moles of FADH2 = 4 ATP

   • glycolysis/krebs cycle = 4 ATP
     → total: 38 ATP