1. Cellular Respiration

2. Cellular Respiration Objectives:
Summarize how glucose is broken down in the first stage of cellular respiration.
Describe how ATP is made in the second stage of cellular respiration.
Identify the role of fermentation in the second stage of cellular respiration.
Evaluate the importance of oxygen in aerobic respiration.

4. How Cells Harvest Chemical Energy
Introduction to Cell Metabolism
Glycolysis
Aerobic Cell Respiration
Anaerobic Cell Respiration

5. Breathing and Cell Respiration are related
CO2
Lungs
Muscle cells carrying out
CO2
Bloodstream O2
CELLULAR RESPIRATION
Sugar + O2  ATP + CO2 + H2O

6. Cellular Respiration uses oxygen and glucose to produce
Carbon dioxide, water, and ATP.
Glucose
Oxygen gas
Carbon dioxide
Water
Energy

7. How efficient is cell respiration?
Energy released from glucose banked in ATP
Energy released from glucose (as heat and light)
Gasoline energy converted to movement
100%
About 40%
25%
Burning glucose in an experiment
“Burning” glucose in cellular respiration
Burning gasoline in an auto engine

8. Reduction and Oxidation OILRIG
Oxidation is losing electrons
Reduction is gaining electrons
Loss of hydrogen atoms
Energy
Glucose
Gain of hydrogen atoms
Glucose gives off energy and is oxidized

9. Reduction and Oxidation OILRIG
Gain or loss of electrons is often in the form of hydrogen. The hydrogen is then passed to a coenzyme such as NAD+

10. Reduction and Oxidation
What are some common co-enzymes?
NAD+ and FAD
NAD H  NADH + H+
FAD H  FADH2
Remember that H = 2 electrons and 2H+

11. Reduction and Oxidation
These co-enzymes are very important for cell respiration because they transfer high-energy electrons to electron transport systems (ETS).

12. Reduction and Oxidation
As the electrons move from carrier to carrier, energy is released in small quantities.
Electron transport system (ETS)

13. Generation of ATP
There are two ways to generate ATP
Chemiosmosis
Substrate-Level Phosphorylation

14. Generation of ATP
Chemiosmosis
Cells use the energy released by “falling” electrons in the ETS to pump H+ ions across a membrane
Uses the enzyme ATP synthase.

15. Generation of ATP
Chemiosmosis

16. Generation of ATP
Substrate Level Phosphorylation
Enzyme
ATP can also be made by transferring phosphate groups from organic molecules to ADP
Adenosine
substrate
Adenosine
product
Figure 6.7B

17. Glycolysis General Outline No Oxygen Anaerobic Oxygen Aerobic
Glucose
Glycolysis
No Oxygen
Anaerobic
Oxygen
Aerobic
Pyruvic Acid
Transition Reaction
Fermentation
Krebs Cycle
ETS
36 ATP

18. Glycolysis
Where? The cytosol
What? Breaks down glucose to pyruvic acid

20. Glycolysis Energy In: 2 ATP Energy Out: 4 ATP NET 2 ATP
Steps – A fuel molecule is energized, using ATP.
Glucose 1 3
Step
Glycolysis 1
Glucose-6-phosphate 2
Fructose-6-phosphate
Energy In: 2 ATP 3
Fructose-1,6-diphosphate
Step A six-carbon intermediate splits into two three-carbon intermediates. 4 4
Glyceraldehyde-3-phosphate (G3P) 5
Step A redox reaction generates NADH. 5
1,3-Diphosphoglyceric acid (2 molecules) 6
Steps – ATP and pyruvic acid are produced.
3-Phosphoglyceric acid (2 molecules)
Energy Out: 4 ATP 6 9 7
2-Phosphoglyceric acid (2 molecules) 8
2-Phosphoglyceric acid (2 molecules)
NET 2 ATP 9
Pyruvic acid
(2 molecules per glucose molecule)

21. General Outline of Aerobic Respiration
Glycolysis
Transition Reaction
Krebs Cycle
Electron Transport System

22. Transition Reaction
Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle
Pyruvic Acid
Acetyl CoA

23. General Outline of Aerobic Respiration
Glycolysis
Transition Reaction
Krebs Cycle
Electron Transport System

24. Krebs Cycle
Where? In the Mitochondria
What? Uses Acetyl Co-A to generate ATP, NADH, FADH2, and CO2.

26. Krebs Cycle

27. Krebs Cycle

28. General Outline of Aerobic Respiration
Glycolysis
Krebs Cycle
Electron Transport System

30. ELECTRON TRANSPORT CHAIN
Electron Transport System
Protein complex
Intermembrane space
Electron carrier
Inner mitochondrial membrane
Electron flow
Mitochondrial matrix
ELECTRON TRANSPORT CHAIN
ATP SYNTHASE
Figure 6.12

31. Electron Transport System

32. Electron Transport System
For each glucose molecule that enters cellular respiration, chemiosmosis produces up to 38 ATP molecules

33. Overview of Aerobic Respiration

34. Fermentation
Requires NADH generated by glycolysis.
Where do you suppose these reactions take place?
Yeast produce carbon dioxide and ethanol
Muscle cells produce lactic acid
Only a few ATP are produced per glucose

35. Fermentation

36. Fermentation in the Absence of Oxygen
Fermentation When oxygen is not present, fermentation follows glycolysis, regenerating NAD+ needed for glycolysis to continue.
Lactic Acid Fermentation In lactic acid fermentation, pyruvate is converted to lactate.

37. Each molecule of glucose can generate molecules of ATP in aerobic respiration but only 2 ATP molecules in respiration without oxygen (through glycolysis and fermentation).