1. Cellular Respiration
Section 9-3

2. Glycolysis
1. The cells of most organisms transfer energy found in organic compounds, such as those in foods, to ATP.
2. The primary fuel for cellular respiration is glucose.
3. Fats can be broken down to make ATP. Proteins and nucleic acids can also be used to make ATP, but they are usually used for building important cell parts.

3. Glycolysis, continued
4. In glycolysis, enzymes break down one six-carbon molecule of glucose into two three-carbon pyruvate (3-carbon #5 answer) molecules.
6. The breaking of a sugar molecule by glycolysis results in a net gain of two ATP molecules.
7. This process of glycolysis is anaerobic, or takes place without oxygen.

5. Glycolysis, continued
Glycolysis is the only source of energy for some prokaryotes.
8. Other organisms use oxygen to release even more energy from a glucose molecule.
9. Metabolic processes that require oxygen are aerobic.
In aerobic respiration, the pyruvate product of glycolysis undergoes another series of reactions to produce more ATP molecules.

6. Glycolysis gives a net result of 2 ATP.

7. Krebs Cycle
10. Pyruvate (from glycolysis) is broken down and combined with other carbon compounds.
Each time the carbon-carbon bonds are rearranged during the Krebs cycle, energy is released.
The total yield of energy-storing products from the Krebs cycle is two ATP, 8 NADH, and 2 FADH2.

8. Electron Transport Chain
11. Up to 34 ATP molecules can be produced from one glucose molecule in aerobic respiration.
12. The second stage of aerobic respiration takes place in the inner membranes of mitochondria, and uses 2 charged particles hydrogen ions and electrons.
12. Energy from the electrons is used to actively transport hydrogen ions out of the inner mitochondrial compartment because of the attraction of opposite charges.
Electron carriers, produced during the Krebs cycle, transfer energy through the electron transport chain.

9. Glycolysis is anaerobic (no oxygen)
#11) aerobic part is the krebs cycle and electron transport

10. Aerobic Respiration, continued
Electron Transport Chain
13. Hydrogen ions diffuse through ATP synthase, providing energy to produce several ATP molecules from ADP.
14. At the end of the electron transport chain, the electrons combine with an oxygen atom and two hydrogen ions to form two water molecules.
15. If oxygen is not present, the electron transport chain stops. The electron carriers are not recycled, so the Krebs cycle also stops.

11. Fermentation
To make ATP during glycolysis, NAD+ is converted to NADH. Organisms must recycle NAD+ to continue making ATP through glycolysis.
16. The process in which carbohydrates are broken down in the absence of oxygen is called fermentation.
17. Fermentation continues supplying a cell with ATP in little to no oxygen (anaerobic) conditions.

12. 18. In lactic acid fermentation, pyruvate is converted to lactic acid.
19. During vigorous exercise, lactic acid fermentation also occurs in the muscles of animals, including humans.
20. During alcoholic fermentation, one enzyme removes carbon dioxide from pyruvate. A second enzyme converts the remaining compound to ethanol, recycling NAD+ in the process.

13. Respiration equation – balance it. C6H12O6 + O2 H2O + CO2 + ATP
Respiration equation – balance it! C6H12O6 + O H2O + CO2 + ATP (up to 36)

14. Two Types of Fermentation

15. Efficiency of Cellular Respiration
In the first stage of cellular respiration, glucose is broken down to pyruvate during glycolysis, an anaerobic process.
Glycolysis results in a net gain of two ATP molecules for each glucose molecule that is broken down without oxygen (anaerobic).
21. In the second stage, pyruvate either 1) passes through the Krebs cycle or 2) undergoes fermentation. Fermentation recycles NAD+ but does not produce ATP.

16. Efficiency of Cellular Respiration
22 a) Anaerobic respiration such as Glycolysis and fermentation, produce a net gain of only 2 ATP.
22 b) The Krebs cycle feeds NADH and FADH2 to the electron transport chain, which can produce up to 34 ATP molecules using oxygen (aerobic).

17. Summary
The breaking of a sugar molecule by glycolysis results in a net gain of two ATP molecules.
The total yield of energy-storing products from one time through the Krebs cycle is one ATP, three NADH, and one FADH2.

18. Summary, continued
Electron carriers transfer energy through the electron transport chain, which ultimately powers ATP synthase.
Fermentation enables glycolysis to continue supplying a cell with ATP in anaerobic conditions.