Overview of Respiration
- aerobic = requires oxygen to occur (ex: cellular respiration)
vs.
anaerobic = does not require oxygen to occur (ex: glycolysis and fermentation)
Organic Compounds
Glycolysis
Oxygen Present
Cellular Respiration
(aerobic)
ATP
ATP
Oxygen Absent
Fermentation
(anaerobic)
No ATP
Glycolysis
- takes place in the cytoplasm of cells
- always occurring and does not require oxygen
- occurs before cellular respiration or fermentation
- 2 ATP are used to start process
- breaks down glucose into a net of 2 ATP, 2 pyruvate, and 2 NADH
- Why is there a net of 2 ATP?
- products (pyruvate and NADH) enter either cellular respiration or fermentation
- Efficiency = 3.5 % (only 2 ATP are made)
Overview of Cellular Respiration
= releases chemical energy from sugars and other organic compounds to make ATP when oxygen is present
- occurs in the mitochondria of cells
Cellular Respiration – 2 Stages
- occurs in the mitochondria
1) Krebs Cycle
= produces molecules that carry energy to the second stage of cellular respiration
- occurs in the matrix of the mitochondria
- pyruvate from glycolysis is broken down
- some ATP and other energy forms are made
- carbon dioxide is given off as a waste product
2) Electron Transport Chain
- occurs in the inner membrane of a mitochondria
- made of proteins
- uses energy from Krebs cycle and oxygen to make ATP
- water and heat are given off as waste products
Efficiency of Cellular Respiration = 66% (38 ATP are made)
Equation for Cellular Respiration
C6H12O6
+
(sugar = glucose)
6O2
(oxygen)

6CO2
(carbon dioxide)
+
6 H2O
(water)
Fermentation
- starts with glycolysis
- does not make ATP (but allows glycolysis to continue)
Types
1) Lactic Acid Fermentation
- occurs in your muscle cells
- produces lactic acid, results in muscle fatigue and cramps
- produces NAD+ that goes back to glycolysis
2) Alcoholic Fermentation
- produces alcohol (ethyl) and carbon dioxide
- produces NAD+ that goes back to glycolysis
Lactic Acid Fermentation
Alcoholic Fermentation
Importance of Fermentation
- produces food products we use (bread, cheese, yogurt)
- allows glycolysis to continue
- microorganisms in digestive tract break down food (allows more nutrients to be absorbed)