What Are Mitochondria and How Does Cellular Respiration Work?
Mitochondria are the 'powerhouses' of the cell, converting glucose and oxygen into usable energy (ATP) through cellular respiration. This process happens in three main stages, each releasing energy stored in chemical bonds.
Cellular respiration is the process by which cells break down glucose using oxygen to produce ATP, carbon dioxide and water; most of it occurs in the mitochondria's matrix and inner membrane (cristae).
- 1↓GlycolysisGlucose splits into 2 pyruvate in the cytoplasm, net gain of 2 ATP
- 2↓Pyruvate OxidationPyruvate enters the mitochondrial matrix and converts to Acetyl-CoA, releasing CO2
- 3↓Krebs CycleAcetyl-CoA is oxidized in the matrix, producing 2 ATP, NADH and FADH2 per glucose
- 4Electron Transport ChainNADH/FADH2 drive H+ pumping across the cristae, producing ~32-34 ATP via ATP synthase
Try it: interactive calculator
Step-by-step worked examples
One glucose molecule undergoes full cellular respiration and yields 36 ATP total. If glycolysis gives 2 ATP and the Krebs cycle gives 2 ATP, how many ATP come from the electron transport chain?
Total ATP = 36 ATP from glycolysis + Krebs = 2 + 2 = 4 ATP from ETC = 36 − 4 = 32 ATP
A muscle cell respires 5 glucose molecules aerobically, each yielding 36 ATP. How much total ATP is produced?
ATP per glucose = 36 Number of glucose = 5 Total ATP = 5 × 36 = 180 ATP
Without oxygen, a cell can only complete glycolysis (net 2 ATP) then fermentation. How much ATP does it lose per glucose compared to aerobic respiration (36 ATP)?
Aerobic ATP = 36, Anaerobic ATP = 2 ATP lost = 36 − 2 = 34 ATP per glucose This shows why oxygen dramatically increases energy yield
Flashcards
Quick quiz
Q1.Where does the Krebs cycle take place?
Q2.Approximately how much ATP does one glucose molecule yield in full aerobic respiration?
Q3.Which stage of respiration does NOT require oxygen?
Q4.What is the final electron acceptor in the electron transport chain?
The full card deck, worked steps and AI-tutor support for “What Are Mitochondria and How Does Cellular Respiration Work?” are in Notek — study by hand before your exam.
Common mistakes
Mitochondria only exist to store energy. — Correct: Mitochondria actively produce ATP by breaking down glucose, not just storing energy.
All of cellular respiration happens inside the mitochondria. — Correct: Glycolysis happens in the cytoplasm; only the Krebs cycle and ETC happen in mitochondria.
Cellular respiration and photosynthesis are the same process. — Correct: They are near-opposites: respiration breaks down glucose using O2, photosynthesis builds glucose using CO2 and light.
The Krebs cycle produces most of the ATP directly. — Correct: The Krebs cycle produces only 2 ATP directly; most ATP comes from the electron transport chain.
FAQ
What is cellular respiration?
The process cells use to convert glucose and oxygen into ATP, carbon dioxide and water.
What is the formula for cellular respiration?
C6H12O6 + 6O2 → 6CO2 + 6H2O + ~36-38 ATP.
What are examples of cellular respiration?
Muscle cells burning glucose during exercise, or any aerobic cell converting food into usable ATP energy.
How do you calculate total ATP from cellular respiration?
Multiply the number of glucose molecules respired by the ATP yield per glucose (about 36-38 ATP).