1. Chapter 7 Cellular Respiration Notes

2. Metabolism Crash Course
The idea of metabolism is broken down into two parts:
Anabolism – using monomers to construct polymers using energy
Catabolism – breaking down polymers into monomers and releasing energy

3. Cells Use Redox Reactions to Extract Energy
Redox reactions are catalyzed by enzymes
Electrons carry energy from one molecule to another
Cofactors serve as electron carriers
Example: Nicotinamide adenosine dinucleotide (NAD+)
NAD+ accepts 2 electrons and 1 proton to become NADH
Reaction is reversible
In chemical reactions, there is a transfer of one or more electron. These electrons move from one reactant to another reactant. This transfer of electrons is called an oxidation-reduction reaction.
The loss of electrons from one substance is called oxidation
The addition of electrons to another substance is known as reduction

4. NAD+ Accepts Electrons to Form NADH
When glucose is being oxidized during cellular respiration, each electron that is being passed down during the oxidation, travels with a proton. These protons do not get directly transferred to the oxygen, as it is the final electron acceptor. Instead, the protons get passed on to an electron carrier, called a coenzyme, called nicotinamide adenine dinucleotide.
This coenzyme is utilized as an electron carrier because it can cycle easily between the oxidized form (NAD+) and the reduced form (NADH).
Enzymes called dehydrogenases remove a pair of hydrogen atoms (2 electrons and 2 protons) from the glucose molecule, oxidizing it. This enzyme delivers the 2 electrons along with 1 proton to NAD+, creating NADH.

5. Types of Respiration Aerobic respiration
Final electron acceptor is oxygen (O2)
Anaerobic respiration
Final electron acceptor is an inorganic molecule (not O2)
Fermentation
Final electron acceptor is an organic molecule
All three types of cellular respiration are catabolic pathways, however, aerobic cellular respiration is considered the most efficient catabolic pathway.

6. The Aerobic Respiration of Glucose
C6H12O O2  6CO H2O + energy
Energy must be harvested in small steps
These small steps involve electron carriers

7. Glucose Oxidation Proceeds in Four Stages
Glycolysis
Pyruvate oxidation
Krebs cycle
Electron transport chain & chemiosmosis

8. Glycolysis Converts One Glucose to Two Pyruvates

9. Glucose is First Converted into Two G3P Molecules

10. Each G3P Molecule is Converted into Pyruvate

11. The Fate of Pyruvate and NADH

12. Pyruvate Oxidation Pyruvate is oxidized in the presence of oxygen
Occurs in:
mitochondria of eukaryotes
plasma membrane of prokaryotes
Catalyzed by pyruvate dehydrogenase

13. Pyruvate Oxidation

14. The Krebs Cycle

15. The Electron Transport Chain (ETC)

16. Chemiosmosis

17. Calculating the Energy Yield of Respiration

18. Oxidation without O2: Anaerobic Respiration
Inorganic molecules (not O2) used as final electron acceptor

19. Oxidation without O2: Anaerobic Respiration
Example 1: Sulfur bacteria
Inorganic sulphate (SO4) is reduced to hydrogen sulfide (H2S)
Early sulfate reducers set the stage for evolution of photosynthesis

20. Oxidation without O2: Fermentation
Example 2: Alcohol acid fermentation
Occurs in yeast
Electrons are transferred from NADH to pyruvate to produce ethanol

21. Oxidation without O2: Fermentation
Example 2: Lactic acid fermentation
Occurs in animal cells (especially muscles)
Electrons are transferred from NADH to pyruvate to produce lactic acid

22. Catabolism of Protein

23. Catabolism of Fats

24. Extraction of Energy from Macromolecules