Cellular respiration involves three main stages - glycolysis, the Krebs cycle, and the electron transport chain. Glycolysis breaks down glucose in the cytoplasm, producing pyruvate. Pyruvate then enters the mitochondria and is converted to acetyl-CoA to feed into the Krebs cycle, where more ATP is generated. In the electron transport chain, electrons are passed through protein complexes in the mitochondrial membrane, establishing a proton gradient used to power ATP synthase and produce large amounts of ATP through chemiosmosis. The overall process is the reverse of photosynthesis and harvests energy from food to produce ATP for cellular work.

1. Cellular Respiration

2. Cellular Respiration
Photosynthesis
CO2 + H2O + energy  sugars + O2
Cell Respiration
Sugars + O2  CO2 + H2O + energy

3. Cellular
Respiration

4. • You breathe air into your lungs. The oxygen in the air you breathe is absorbed into the blood in the capillaries that
surround your lungs and then transported via the pulmonary vein into the left side of your heart.
• The oxygenated blood is pumped out of the left side of your heart and into the arteries that deliver it throughout
your body to your muscles.
• When the oxygenated blood reaches your muscles the oxygen is absorbed into your muscle cells. . At the same
time that your blood is providing oxygen to your muscles, it is also removing carbon dioxide
• The de-oxygenated and carbon dioxide rich blood is pumped out of the right side of your heart to your lungs via
your pulmonary artery. Once in the lungs, your blood releases the carbon dioxide into the air that you breathe out
and absorbs more oxygen from the air that you breathe in, and the entire process begins again.
Glucose + O2 → CO2 + H2O (l) + ATP

5. Cellular Respiration
Generate ATP

6. How Do cells make ATP
• Fermentation—NO oxygen
• Anaerobic Respiration—no oxygen
• Aerobic Respiration—OXYGEN
– Reverse process of photosynthesis
– Takes place in mitochondria
– Harvest potential energy in food, use it to make ATP
• ALL organisms do some sort of ATP generation
C6H12O6 + 6O2 6CO2 + 6H2O + 36 ATP

7. Aerobic Respiration
• Redox reaction
– Oxidize glucose and reduce oxygen
• Carried out in 3 steps
1. Glycolysis—breaking a 6-carbon glucose into 2
3-carbon pyruvate molecules, use NADH to
catch electrons
2. Krebs Cycle—oxidize pyruvate, release C02 ,and
FADH2
3. Electron Transport Chain—transfers electrons
from NADH and FADH2 down a gradient using
ATP synthase to make ATP

8. Aerobic
Respiration

9. Mitochondria
• Glycolysis takes place in cell’s cytoplasm
• Rest of the reactions take place in mitochondria
– Cristae—folds to increase surface area of inner
membrane
– Intermembrane compartment—area between 2
membranes
• Electron transport chains
– Matrix—space within the inner membrane
• Krebs Cycle

11. Structure of Mitochondrion

12. Glycolysis
• Can be done with or without oxygen
• Done in cell’s cytoplasm
• 10 Steps
– First 5 steps “prepare” glucose
– Last 5 steps get the energy out
• Produces 2 molecules of ATP
– Substrate level phosphorylation
– Does NOT need proton gradient or ATP synthase
(like chemiosmotic phosphorylation)

14. First 5 Steps

15. Last 5 Steps

16. Stages of Cellular Respiration
Glycoysis

17. Formation of Acetyl CoA
• Before we can start Krebs Cycle have to
convert pyruvate
• In mitochondrial matrix
• Pyruvate loses CO2 molecule
• NADH reduced to NADH
• Acetyl CoA = 2 Carbon molecule

18. Acetyl CoA

19. Krebs Cycle
• Occurs mitochondria matrix
• Cycle turns 2 times for every glucose molecule
1. Acetyl CoA loses coenzyme = 2 Carbon
molecule
2. 2-Carbon + oxaloacetate = citrate
3. CO2 released
4. Electrons transferred to NADH and FADH2
5. ATP made by substrate level phosphorylation

20. Outputs of Krebs Cycle
• 4 CO2
• 2 ATP
• 6 NADH
• 2 FADH2
• Heat
• Intermediate molecules in cycle can be used
to make other organic molecules, amino acids,
fats

21. Cellular Respiration: NADH

22. Cellular Respiration: NADH
Electron Transport Chain
http://media.pearsoncmg.com/bc/bc
_0media_bio/bioflix/bioflix.htm?cc7r
espiration
Just first subsection: overview

23. (Krebs Cycle)

24. Electron Transport Chain
• Takes place across the inner mitochondrial
membrane
• Uses /electrons from NADH and FADH2
• NADH and FADH2 donate electrons to enzymes in
membrane to create H+ gradient
• In AEROBIC respiration final electron acceptor is
O2
– O2 combines with H+ to make water
• ATP finally made by chemiosmotic
phosphorylation
– Protons through ATP synthase to turn ADP to ATP

25. Electron Transport Chain

26. Stages of Cellular Respiration:
Chemiosmosis
http://www.youtube.com/watch?v=zfvVvC4-u_A&feature=related

27. Final Outputs of Respiration
Aerobic
Respiration
Per 1
Glucose Molecule
• 10 NADH
• 2 FADH2
• 36 ATP

28. Alternate Energy Pathways
Anaerobic Respiration
• No oxygen
• Different terminal
electron acceptor
– NO3-, SO4-, CH4
• Amount of ATP
produced depends on
terminal electron
acceptor
• Fermentation
• No oxygen
• Only uses glycolysis
• Only generates 2 ATP
• Can use sugar, alcoholic,
lactic acid

29. Different Types of Fermentation
Pyruvic acid CO2 + acetaldehyde + NADH
ethanol + NAD+

30. Photosynthesis v. Cellular Respiration
Photosynthesis Cellular Respiration
Energy source Light Food
Energy released No, stored Yes
Reactants H2O, CO2
Glucose, O2
Products Glucose, O2 CO2, H2O

31. Connections Among
Metabolic Pathways