Cellular respiration is the enzymatic breakdown of glucose (C6H12O6) in the presence of oxygen to produce ATP.
Three Stages of Cellular Respiration
Three stages occur during cellular respiration; glycolysis, citric acid or TCA cycle, and the electron transport system. The net equation for cellular respiration is as follows:
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C6H12O6 + 6O2 –> 6 CO2 + 6H2O + 38 ATP |
Glycolysis is a ten-step process that occurs in the cytoplasm. Each molecule of glucose is converted into two units of pyruvic acid. Each glucose molecule yields 2 ATP and 2 NADH.
The citric acid cycle or TCA cycle occurs in the mitochondrial matrix. Each glucose molecule that enters the TCA cycle through acetyl CoA produces 2 ATP, 6 NADH, and 2 FADH2
The electron transport chain occurs in the inner mitochondrial matrix. Using the electrons of the NADH and FADH2 from the TCA cycle, they give up energy used to fuel H+ ions to flow through the mitochondrial membrane. Each glucose molecule produces 34 ATP.
Practice Questions
Khan Academy
MCAT Official Prep (AAMC)
Practice Exam 2 B/B Section Passage 2 Question 7
Key Points
• The three stages of cellular respiration are glycolysis, citric acid or TCA cycle, and the electron transport chain
• The net equation of cellular respiration is: C6H12O6+6O2→6CO2+6H2O+38 ATP
• Glycolysis yields 2 ATP and 2 NADH
• Citric acid or TCA cycle produces 2 ATP, 6 NADH, and 2 FADH2
• The electron transport chain produces 34 ATP
Key Terms
glycolysis: the cellular metabolic pathway of the simple sugar glucose to yield pyruvic acid and ATP as an energy source
glucose: a simple monosaccharide with a molecular formula of C6H12O6
adenosine triphosphate: a multifunctional nucleoside triphosphate used in cells as a coenzyme
NADH: nicotinamide adenine dinucleotide (NAD) carrying two electrons and bonded with a hydrogen (H) ion
TCA cycle: a series of enzymatic reactions that occurs in all aerobic organisms to generate energy