1. Cellular Respiration
Chapter 9

2. Chemical Energy and Food
1 gram of sugar (glucose) when burned in the presence of O2 releases 3811 calories of heat.
Calorie: the amount of energy needed to raise the temp of 1 gram of water 1 degree C.
Cells gradually release energy from glucose and other compounds = glycolysis.
Glycolysis releases a small amount of energy at a time.

3. Overview Glycolysis Presence of Oxygen
(Cellular Respiration)
Krebs Cycle
Electron Transport Chain
Not in the Presence of Oxygen (Fermentation)
Alcoholic Fermentation
Lactic Acid Fermentation

4. Cellular Respiration
Cellular Respiration: the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.
6O2 + C6H12O6  6CO2 + 6H2O + energy
To avoid the energy from getting burned up all at once, the release of energy in respiration happens a little at a time in 3 steps:
1. glycolysis
2. Krebs Cycle
3. electron transport chain

5. Glycolysis
Glycolysis: the process in which one molecule of glucose (C6H12O6) is broken in half, producing 2 molecules of pyruvic acid (a 3-carbon compound). Takes place in the cytoplasm of the cell.
A. ATP Production-
2 ATP are used to make 4 ATP molecules; net gain is 2 ATP.
B. NADH Production-
4 high-energy electrons added to NAD+  NADH (electron carrier).
After pyruvic acid is formed through glycolysis, what happens next will depend upon whether or not oxygen is present or not.
oxygen present  Krebs Cycle, electron transport
no oxygen  fermentation (alcoholic or lactic acid)

6. Krebs Cycle (citric acid cycle)
Needs oxygen; occurs in mitochondrion.
The pyruvic acid (3 carbon compounds) from glycolysis is broken down into carbon dioxide in a series of energy-extracting reactions.
A. Pyruvic acid enters the mitochondrion.
One carbon goes off to make CO2 and is
released into the air. The other 2 are
added to a 4-C compound to make a 6
carbon molecule called citric acid.

7. Krebs (con’t) 2 carbons break off citric acid (6-C
compound) and released to atmosphere.
Two C then get added back to make a 6-C
compound again. Cycle starts again.
NAD and FAD are electron carriers that accept high-energy electrons = NADH & FADH. They are used to generate huge amounts of ATP.

8. Electron Transport
The electron transport chain uses the high-energy electrons from the Krebs Cycle to convert ADP to ATP.

9. Fermentation
Occurs after glycolysis if there is no oxygen (anaerobic).
The 2 main types of fermentation are alcoholic and lactic acid.

10. Alcoholic Fermentation
Pyruvic acid + NADH  alcohol + CO2 + NAD+
Occurs in yeast and a few other microorganisms.
Most common example is when yeast is added to dough. The CO2 is released and causes the dough to rise.

11. Lactic Acid Fermentation
Pyruvic acid + NADH  lactic acid + NAD+
In many cells, the pyruvic acid that accumulates as a result of glycolysis gets converted to lactic acid.
Lactic acid is produced in your muscles during rapid exercise when the body cannot supply enough oxygen to your tissues.
As you exercise and lose oxygen in your muscles, your body will try to make ATP through lactic acid fermentation and as a result, the lactic acid builds up in your muscles and makes them ache/burn.

12. (Krebs, Electron Transport)
Totals
Glycolysis
Oxygen- Respiration
(Krebs, Electron Transport)
36 ATP
Glycolysis
No Oxygen
(Fermentation)
2 ATP

13. Photosynthesis vs. Cellular Respiration
Function
Captures energy
Releases energy
Location
chloroplasts
mitochondrion
Reactants
CO2 & H2O
C6H12O6 & O2
Products
Equation
6CO2 + 6H2O  C6H12O6 + 6O2
6O2 + C6H12O6  6CO2 + 6H2O
Energy
Energy