Cellular Respiration
Cellular Respiration
The process that releases energy from food in the
presence of oxygen
Aerobic v. Anaerobic
Oxygen is required at the very end of respiration in the
electron transport chain. Cellular processes that require
oxygen are aerobic
Processes that do NOT require oxygen are considered
anaerobic
The three stages of Cellular respiration are:
1. Glycolysis, 2. The Krebs Cycle, and 3. Electron
Transport & ATP Synthesis
Glycolysis
1 molecule of glucose (a 6 carbon compound) is
transformed into 2 molecules of pyruvic acid (a 3 carbon
compound)
ATP Production
2 ATP molecules used to “get things going”
4 ATP molecules produced = gain of 2 ATP molecules
NADH Production
NAD+ accepts 2 electrons =the 2NADH and holds them until they can be
transferred to electron chain
Glycolysis does NOT require oxygen
Happens in the CYTOPLASM of the cell
The Krebs Cycle
 Pyruvic Acid is broken down into carbon dioxide in a
series of energy extracting reactions (AEROBIC)
Happens in the MATRIX of the Mitochondria
FOR EACH PYRUVIC ACID Molecule (there are 2)
Citric acid is broken down is a series of reactions
3 molecules of carbon dioxide
1 ATP, 4 NADH & 1 FADH2 (go to electron transport chain)
Electron Transport Chain & ATP Synthesis
 Uses high energy electrons from glycolysis and the Krebs
cycle to convert ADP to ATP
Electron Transport
• NADH and FADH2 pass their high energy electrons to the electron transport
chain (electron carriers located in the inner membrane of mitochondria)
• At the end of the chain an enzyme combines electrons with hydrogen ions
and oxygen to form water
• Oxygen is the final electron acceptor and the chain can’t function without it
• Forms a proton gradient used is ATP production (H+ from the NADH and
FADH2)
ATP Production
• ATP synthase located in the inner membrane wall
• ADP molecules are turned into ATP molecules
Together
Glycolysis, the
Krebs Cycle,
and the
Electron
Transport chain
results in
about 36
molecules of
ATP per 1
molecule of
glucose.
https://www.youtube.com/watch?v=-Gb2EzF_XqA
Stage
Glycolysis
Krebs Cycle
Electron
Transport Chain
& ATP synthase
Where does it
happen
Inputs
Outputs