1. Cellular Respiration
Chapter 5
Section 3

2. Cellular Energy All of the energy you use comes from the food you eat
Before you can use that energy, the food is broken down and the energy is stored as ATP.
The transfer of the energy in organic compounds (particularly glucose) to ATP is called RESPIRATION.
Aerobic vs. anaerobic

3. The Stages of Respiration
Balanced chemical Equation for Cellular Respiration (aerobic)

4. Stages of Respiration 1. Glucose is broken down to pyruvate
during glycolysis

5. Glycolysis 2
Glycolysis-the first stage of cellular respiration in which glucose is broken down in the cytoplasm.
Glycolysis is an enzyme-assisted anaerobic process that breaks down 1 six-carbon sugar(glucose) into 2 three carbon pyruvate molecules
Net Yield vs. Net Gain?

6. Stages of Respiration 1. Glucose is broken down to pyruvate
during glycolysis
2. Krebs Cycle

7. The Krebs Cycle
Named for Hans Krebs, who first described the cycle in 1937.
When O₂ is present, the pyruvate produced by glycolysis enters the mitochondrion and is converted to a 2-carbon compound Acetyl CoA.
Also called the Citric Acid Cycle

8. Krebs Cycle Net Gain for the Krebs Cycle is 2 ATP’s.
Remember that Glycolysis produces 2 pyruvate molecules, thus providing 2 rounds of the Krebs Cycle.

9. Electron Transport Chain
In eukaryotic organisms, the ETC is located in the inner membranes of the mitochondria.
Hydrogen ions accumulate in the outer compartment producing a concentration gradient across the inner membrane.
H+ ions diffuse back into the inner compartment through a carrier protein that adds a phosphate group to ADP→ATP.

10. Electron Transport Chain

11. Stages of Respiration

12. Respiration in the Absence of O₂
Fermentation-The recycling of NAD+ (nicotinamide adenine dinucleotide phosphate-oxidase ion) using an organic hydrogen acceptor.
Two Important types:
1. Lactic Acid Fermentation
2. Alcoholic Fermentation

13. Lactic Acid Fermentation
Three Carbon Pyruvate molecule (glycolysis product) is converted to 3-carbon lactate.
Lactate is the ion of an organic acid called lactic acid.
Allows glycolysis to continue in the absence of O₂
During vigorous exercise, pyruvate in muscles is converted to lactate when muscles must operate without enough O₂, causing soreness.
Blood removes most lactate

14. Lactic Acid Fermentation

15. Alcoholic Fermentation
Used by some bacteria, fungi and prokaryotes.
Occurs in a two-step process:
The three carbon pyruvate is broken down into a , a two-carbon compound, releasing carbon dioxide.
Electrons are transferred from a molecule of NADH to the two-carbon compound, producing ethyl alcohol.
As in lactic acid fermentation, the NAD+ is recycled and glycolysis continues.

16. Alcoholic Fermentation

17. In the Presence of O₂…

18. Without the Presence of O₂
Alcohol Fermentation
Lactic Acid Fermentation