1. Aerobic Respiration
SBI4U1

2. C6H12O6 (s) + 6O2 (g)  6CO2 (g) + 6H2O (l) + energy
Aerobic Respiration: catabolic pathway that requires oxygen
C6H12O6 (s) + 6O2 (g)  6CO2 (g) + 6H2O (l) + energy
Plants and animals rely on it to form ATP
Obligate anaerobes (organisms that must have oxygen)
Energy from food molecules is transferred to ATP
Cells use ATP to power endergonic rxns

3. Goals of Cellular Respiration
Break bonds b/t C-atoms in glucose to form 6CO2
Move H atom electrons from glucose to oxygen, to form 6H2O
Trap free energy released in the process in form of ATP

4. C6H12O6 (s) + 6O2 (g)  6CO2 (g) + 6H2O (l) + energy
Cellular respiration decreases potential energy and increases entropy
Yields 2870kJ of free energy per mol of glucose
ΔG = kJ per mol of glucose

5. 4 Steps in Cellular Respiration
Glycolysis (cytoplasm, 10 steps)
Pyruvate Oxidation (mitochondrial matrix, 1 step)
Krebs Cycle (mitochondrial matrix, 8 steps)
Oxidative Phosphorylation/Electron Transport Chain (cristae, most ATP generation)

6. #1 #2 #4 #3

7. Glycolysis glykos = sweet, lysis = splitting
Breaks down glucose into 2 molecules of pyruvate
There are two stages (each w/ 5 steps, 10 total)
Does not require oxygen (essential anaerobic)
Animation:

8. 1st Stage: Glucose Split into Two Phosphorylation of glucose by ATP
2-3. Molecule is rearranged and 2nd ATP phosphorylation
C molecule split into two 3-C molecules
One glyceraldehyde 3-phosphate (G3P) and one that will be converted later

9. 2nd Stage: Forms Pyruvate
6. Oxidation then phosphorylation to produce NADH to 2 BPG (NAD+ reduced)
7. 2 ADP removes high energy phosphates, leaving 2 3PG molecules
8-9. H2O removed leaving 2 PEP molecules
10. 2 ADP removes high energy phosphates, leaving 2 pyruvate molecules

10. Net Reaction for Glycolysis:
Glucose + 2 NAD ADP + 2Pi  2 pyruvate + 2H2O + 2NADH + 2ATP
Reactants C6H12O6 2 NAD+ 2 ADP 2 Pi Products 2 C3H4O3 (pyruvate) 2 NADH + H+ 2 ATP (net) 2 H2O
Animation (one more time!):

11. Pyruvate Oxidation Carboxyl group removed from pyruvate as CO2
C2 fragment is oxidized into acetic acid (as NAD+ is reduced to NADH)
Coenzyme A (a sulfur containing vitamin B derivative) forms an unstable bond with acetic acid
Two molecules of Acetly-CoA and NADH produced

12. Acetyl CoA Acetyl CoA is a pivotal molecule in cellular metabolism
Most molecules used to provide an organism with energy are converted to acetyl CoA(reversible)

13. Krebs Cycle A.k.a. Citric Acid Cycle Cyclic metabolic pathway
Acetyl CoA is oxidized to CO2
Regenerates compound that picks up more acetyl CoA
Converts released energy to ATP, NADH, and FADH2

14. For each turn of the cycle:
2 C atoms enter as acetyl group and 2 C leave as CO2
much of acetyl group’s energy is transferred as high energy electrons to reduce 3NAD+ → 3NADH and 1 FAD → 1 FADH2

15. there are 2 turns of the Kreb’s cycle for each 1 glucose
some of acetyl group’s energy is used in the substrate level phosphorylation of ADP → 1ATP
for each glucose molecule oxidized 2 acetyl CoA are produced
there are 2 turns of the Kreb’s cycle for each 1 glucose

16. Reactants and Products of the Krebs Cycle:
Reactants 2 acetyl CoA 2 oxaloacetate 6 NAD+ 2 ADP 2 FAD 2 Pi Products 2 CoA 4 CO2 6 NADH 6 H+ 2 FADH2 2 ATP (net)
Animation:

17. Oxidative Phosphorylation
During glycolysis and 2 rounds of the Krebs cycle carbon from glucose  CO2
Very few ATP molecules have been produced at this point
Energy is in NADH and FADH2
Oxygen is used here to produce majority of ATP
Animation:

18. Electron Transport Chain (ETC)
System of enzymes (with cofactors) embedded in the inner mitochondrial membrane
Enzymes pass electrons from NADH and FADH2 to O2 in a series of redox reactions

19. Each component of the ETC is more electronegative than the previous
Final electron acceptor, O2, is one of the most electronegative substances on earth

20. Electron transfer from NADH to O2 is highly exergonic
Intermediate steps help release the energy in
manageable amounts to accommodate the change in
energy form

21. FADH2 enters the ETC after the first part of the
multi-enzyme complex
Therefore yields 1/3 less energy

22. NADH from cytosol cannot move into the mitochondrial matrix
Electrons must be shuttled, usually via an FADH2
Therefore usually yields 1/3 less energy then NADH produced in the mitochondrial matrix

23. ETC Animation (one more time!):

24. Chemiosmosis
H+ ions pumped using energy released in the electron cascade through the ETC
Creates a high [H+] in the inner membrane space
This gradient drives phosphorylation of ADP  ATP

26. ATP Synthase ATP is formed (oxidative phosphorylation)
As the H+ re-enter the matrix through special protein channels that are coupled with ATP synthase

27. Yield of ATP from Aerobic Respiration
It is possible to generate 36 or 38 molecules of ATP from one glucose molecule
38 for prokaryotes b/c they do not need to use 2 ATP transport NADH from glycolysis across mitochondrial membrane
These #’s are theoretical
Experimental yields are lower. Why?
(read text for reasons to account for lower values)

29. Interconnections of Metabolic Pathways
Humans eat more than just glucose. So what happens to the other molecules?
Compounds from all nutrients can be broken down
They can enter glycolysis and the Krebs cycle
E.g. Glycerol from fatty acids can be converted to G3P
E.g. Amino acid alanine is directly converted to pyruvate

31. Things You Should Know... Aerobic respiration 4 stages in respiration
Know where they occur
Know the basic steps (not all intermediates, but major molecules)
Know electron carriers (NAD+ and FAD)
Reactants/products for each (esp. ATP)
Examples of common intermediates between fat, carbohydrates, protein and stages in respiration.