1. Aerobic Cellular Respiration
Process that extracts energy from food (mainly glucose, but also proteins and lipids) in the presence of oxygen –obligate aerobes
The energy that is extracted is used to synthesize ATP
ATP is used to supply energy directly to cells to drive chemical reactions

2. Why Make ATP? Referred to as energy currency of the cell
Provide energy for chemical reactions to take place in our body (cells)

3. Mitochondria Site of cellular respiration (where ATP is made)
Conists of
Outer membrane
Inner membrane
Matrix
Cristae

4. Aerobic Cellular Respiration
Divided into 4 stages
Glycolysis
Pyruvate oxidation
Citric acid cycle
Electron transport chain and oxidative phosphorylation
Each Stage involves the transfer of FREE ENERGY
ATP is produced in two different ways
Substrate-level phosphorylation
Oxidative phosphorylation

5. Aerobic Respiration Location of each Stage Glycolysis
Cytosol
Pyruvate Oxidation
Mitochondrial matrix
Citric Acid Cycle
Electron Transport
Inner mitochondrial membrane

6. Glycolysis
This process is for the conversion of only ONE glucose molecule!!!
Primitive
Process found in almost all organisms
Both prokaryotes and eukaryotes
Does not require O₂
Involves
Soluble enzymes
(10 sequential enzyme-catalyzed reactions)
Oxidation of a 6-carbon sugar glucose
Produces
2 molecules of pyruvate (3-carbon molecule)
4 ATP and 2 NADH
Two Phases in which this occurs
Initial energy investment phase
Energy payoff phase

7. Glycolysis Overview

8. Glycolysis Overview Initial energy investment phase
2 ATP are consumed
Energy payoff phase
4 ATP produced
2 NADH molecules are synthesized
Overall NET reaction;
Glucose + 2 ADP + 2 Pi + 2 NAD⁺ → 2 pyruvate + 2 ATP + 2 NADH + 2H⁺
62 kJ of energy is stored by the synthesis of 2 ATP molecules
Rest of the free energy is stored in the 2 pyruvate molecules

9. Substrate-Level Phosphorylation
Phosphate groups are attached to ADP from a substrate forming ATP (enzyme catalyzed reaction)
ALL ATP molecules are produced this way in Glycolysis

10. Pyruvate Pyruvate can take 2 paths from this point:
Aerobic Respiration (with oxygen)
Pyruvate moves into mitochondria and ATP is made via Krebs Cycle and Electron Transport Chain
Anaerobic Respiration (without oxygen)
Pyruvate stays in cytoplasm and is converted into lactic acid
-Lactic Acid Fermentation

11. Pyruvate Oxididation
Remember glycolysis occurs in the cytosol of the cell
The Citric Acid Cycle (next step) occurs in the mitochondrial matrix
Pyruvate must pass through the inner and outer membrane of the mitochondrion

12. Pyruvate Oxidation Outer membrane
Pyruvate diffuses across the outer membrane through large pores of mitochondrion
Inner membrane
Pyruvate-specific membrane carrier is required
Inside Matrix
Pyruvate is converted into an acetyl group
Acetyl group is bonded to coenzyme A
Produces an acetyl-CoA complex

13. Pyruvate Oxidation Decarboxylation reaction Dehydrogenation reaction
Conversion of pyruvate to acetyl-CoA
Involves 2 Reactions
Catalyzed by pyruvate dehydrogenase
Decarboxylation reaction
Carboxyl group (-COO⁻) of pyruvate is removed
Produces
CO₂
Dehydrogenation reaction
2 electrons and a proton are transferred
NADH
H⁺ in solution
Net reaction
2 pyruvate + 2 NAD⁺ + 2 CoA → 2 acetyl-CoA + 2 NADH + 2 H⁺ + 2 CO₂

14. Pyruvate Oxidation
Acetyl group reacts with the sulfur atom of coenzyme A
Acetyl-CoA is the molecule that will start the Citric Acid Cycle

15. Citric Acid Cycle Discovered by Sir Hans Krebs (1900-1981)
Consists of 8 enzyme catalyzed reaction
ALL ATP are produced by substrate-level phosphorylation

16. Citric Acid Cycle Overview
2 molecules of pyruvate are converted to Acetyl-CoA
Citric Acid Cycle goes through two turns for every single glucose molecule that is oxidized
1 Turn
Acetyl-CoA + 3 NAD⁺ + FAD + ADP + Pi → 2 CO₂ + 3 NADH + 3 H⁺ + FADH₂ + ATP + CoA
ATP is synthesized by substrate level phosphorylation coupled by GTP

17. Citric Acid Cycle Overview

18. Citric Acid Cycle
ALL of the carbon atoms that make up a glucose molecule are converted into CO₂
oxidation of pyruvate
acetyl groups
6CO₂

19. Oxidation of ONE Glucose Molecule
Total # of NET Molecules Produced
NADH
FADH₂
CO₂
ATP
Glycolysis 2
Pyruvate Oxidation
Citric Acid Cycle 6 4

20. Electron Transport Chain (Chemiosmosis)
Process that extracts potential energy that is stored in NADH and FADH₂
These molecules were formed during glycolysis, pyruvate oxidation, and citric acid cycle
Redox reactions – transfer of electrons
This energy is used to synthesize additional ATP (A lot more) via oxidative phosphorylation

21. The Electron Transport Chain
Occurs on the inner mitochondrial membrane
Facilitates the transfer of electrons from NADH and FADH₂ to O₂

22. The Electron Transport Chain
Composed of
4 Complexes
Complex I, NADH dehydrogenase
Complex II, succinate dehydrogenase
Complex III, cytochrome complex
Complex IV, cytochrome oxidase
2 Electron shuttles
Ubiquinone (UQ)
Hydrophobic molecule – shuttles electrons from complex I and II to complex III
Cytochrome C (cyt c)
Shuttles electrons from complex III to complex IV

23. The Driving Force Behind Electron Transport
Complexes I, III, IV
Each has a cofactor
Each cofactor has increasing electronegativity
Alternate between reduced and oxidized states
Electrons move towards more electronegative molecules (downstream)
Final electron acceptor – OXYGEN (most electronegative)
Pulls electrons from complex IV

24. How a Single Oxygen Atom Works (O)
Final electron acceptor
Removes two electrons from complex IV
Reacts with 2 H⁺ to produce H₂O
BUT WE BREATH IN O₂ NOT A SINGLE O
So for every O₂ molecule
Pulls a total of 4 electrons through the electron transport chain
2 H₂O molecules are produced
Pulling 4 electrons from complex IV triggers a chain reaction between other complexes!!

25. What happens in this chain of reactions?
Starts with O₂
Pulls electrons through the chain of complexes
NADH is least electronegative but contains most free energy
O₂ has highest electronegativity but contains least amount of free energy

26. Proton Gradient
Electron Transport from NADH or FADH₂ to O₂ does not produce any ATP!!
What does?
Proton Gradient
Transport of H⁺ ions across the inner mitochondrial membrane from the matrix into the inter-membrane space
Creates
Proton-Motive Force
Chemical gradient (difference in concentrations)
Electro potential gradient is created (because of the positive charge on Hydrogen atom)

27. Proton Gradient

28. Chemiosmosis 34 ATP are Produced!
The ability of cells to use the proton-motive force to do work
Synthesizes ATP using electrochemical gradient
Uses ATP synthase enzyme
ATP is synthesized using oxidative phosphorylation
34 ATP are Produced!

29. Oxidative Phosphorylation
Relies on ATP synthase
Forms a channel which H⁺ ions can pass freely
H⁺ ions cause the synthase to rotate harnessing potential energy to synthesize ATP

30. NADH from Glycolysis NADH produced during glycolysis is in cytosol
Transported into mitochondria via two shuttle systems
Malate-aspartate shuttle
Glycerol-phosphate shuttle

31. NADH and FADH₂ NADH and FADH₂ are involved in REDOX reactions
Considered Cosubstrates
For every NADH that is oxidized
About 3 ATP are synthesized
10 NADH x 3 ATP = 30 ATP
NADH is derived from vitamin niacin
For every FADH₂
About 2 ATP are synthesized
2 FADH₂ x 2 ATP = 4 ATP
FADH₂ is derived from vitamin riboflavin (B₂)
Total of 34 ATP synthesized by electron transport chain

32. Efficiency of Cellular Respiration

33. Efficiency of Cellular Respiration
38 ATP produced
Hydrolysis of ATP yields 31kJ/mol
31 kJ/mol x 38 ATP = 1178 kJ/mol
Oxidation of Glucose contains 2870 kJ/mol of energy
Only 41% of the energy in oxidation of glucose in converted into ATP
The rest is lost as thermal energy

34. Cells that need a constant supply of ATP
Brain cells, muscle cells
Need burst of ATP during periods of activity
Creatine phosphate pathway
Immediate source of energy
Creatine phosphate splits (high energy)
Donated directly to ADP to re-form ATP
Stored within cell (3 to 5 times more than ATP)
Provides enough energy for minute walk or short distance sprint
creatine + ATP → creatine phosphate + ADP
creatine phosphate → creatine + ATP

35. Cellular Respiration Regulated Enzyme used Inhibited by Activated by
Feedback inhibition
Enzyme used
Phosphofructokinase
Inhibited by
High levels of ATP
High levels of citrate
Activated by
High levels of ADP
High levels of AMP
Glucose
Stored as glycogen