1. Cellular Respiration

2. Chemical Energy and Food
PHOTOSYNTHESIS
___________ + _________ + ___________ →_______________ + __________
6 CO2
6 H2O
C6H12O6
6O2
CELLULAR RESPIRATION
C6H12O6
6 CO2
_____________ + _________ →________ + __________ + __________
6O2
6 H2O
The two equations are exact opposites!
Discovery School - The Mitochondria (2:44)

3. Comparing Photosynthesis & Cellular Respiration:
Which type(s) of organisms carry out photosynthesis?
Autotroph Heterotroph
Which type(s) of organisms carry out cellular respiration?

4. Organisms that do CELLULAR RESPIRATION:
Bacteria
Protists
Fungi
Plants
Animals
In short – almost ALL organisms undergo cellular respiration (also known as AEROBIC RESPIRATION)!

5. EXCEPT FOR…
SOME bacteria, who undergo a similar process called ANAEROBIC RESPIRATION, which does NOT require oxygen.
Instead, this process may use nitrate, sulfate, or carbonate…
HOWEVER, it does not result in as much ATP production as when oxygen is used

6. Energy (Adenosine triphosphate)
Reactants
Products
O C6H12O6 → CO H2O + ATP
Oxygen
Carbon Dioxide
Water
Glucose/sugar
Energy (Adenosine triphosphate)
Yields/ produces
Cellular respiration is the process that releases energy from food in the presence of oxygen.

7. Structure of the Mitochondria:

8. Chemical Energy and Food
Cellular respiration happens slowly and in many steps.
If all the energy was release in one step… Most would be lost as light and heat!
Cellular respiration breaks down glucose molecules and banks their energy in ATP

9. Chemical Energy and Food
Unit for measuring energy in food = Calorie
1 Calorie = 1 kilocalorie = 1,000 calories
Energy Consumption - Virtual Cell Animation (4:41)

10. Anaerobic Vs Aerobic Respiration
Anaerobic Respiration
Does NOT require oxygen
Makes less ATP (than aerobic)
Ex:Glycolysis
Aerobic Respiration
Requires oxygen
Makes more ATP
Ex: Krebs cycle and electron Transport chain

11. 3 Stages of Cellular Respiration
Glycolysis
Krebs Cycle (Citric Acid Cycle)
Electron Transport Chain (ETC)

12. Glycolysis ATP (Glykos = sweet, Lysis = split apart)
The first step in cellular respiration
Happens in the CYTOPLASM outside the mitochondria
Does not require oxygen, BUT it needs some energy to get it started.
What molecule is going to supply the energy?
ATP
Glycolysis Overview - Virtual Cell Animation (3:00)

13. Glycolysis Reactions - Virtual Cell Animation (5:00)
Produces pyruvic acid (pyruvate = 3-carbon compound)
Cell needs to invest some energy to get a higher return (2 ATP gained)
Occurs quickly, in milliseconds to respond to increased energy demand
Produces 2 NADH
Glycolysis Reactions - Virtual Cell Animation (5:00)

14. Put in 2 ATP and get back 4 ATP
Glycolysis
________ ↓
___________ → → _____________
____________________ + _______________
GLUCOSE
2 PYRUVIC ACID
ATP ATP ATP ATP
NADH NADH
Put in 2 ATP and get back 4 ATP
Net gain of 2 ATP and 2 NADH

15. The Advantages of Glycolysis
Glycolysis produces ATP very fast, which is an advantage when the energy demands of the cell suddenly increase.
Glycolysis does not require oxygen, so it can quickly supply energy to cells when oxygen is unavailable.

16. Mitochondria Structure
Has a double membrane, with an intermembrane space between the two layers.
Cristae are folds of the inner membrane
The matrix is the innermost compartment, which is filled with a gel-like fluid.

17. Citric Acid Cycle An Overview (3:17)
The Krebs Cycle
2nd stage of cellular respiration
also known as the Citric Acid Cycle (The Krebs Cycle is because citric acid is the first compound formed in this series of reactions.)
Citric Acid Cycle An Overview (3:17)

18. Kreb’s Cycle (preparation stage)
Pyruvic acid from glycolysis enters the matrix
NAD+ accepts 2 high- energy electrons to form NADH.
One molecule of CO2 is also produced.
The remaining 2 carbon atoms react to form acetyl- CoA.
Diagram by Riedell
The Citric Acid Cycle The Reactions (4:13)

19. The Citric Acid Cycle The Reactions (4:13)
The Krebs Cycle
Acetyl-CoA combines with a 4-carbon molecule (oxaloacetic acid) to produce citric acid.
The Citric Acid Cycle The Reactions (4:13)
Diagram by Riedell

20. The Citric Acid Cycle The Reactions (4:13)
The Krebs Cycle
Citric acid is broken down into a 5-carbon compound and then a 4-carbon compound.
Two molecules of CO2 are released.
The 4-carbon compound can then start the cycle again by combining with acetyl-CoA.
The Citric Acid Cycle The Reactions (4:13)

21. KREBS CYCLE
KREBS CYCLE PRODUCES
____ 3 1 1 4
Krebs Cycle Animation

22. Energy Extraction
Remember! Each molecule of glucose results in 2 molecules of pyruvic acid, which enter the Krebs cycle. So each molecule of glucose results in 2 complete “turns” of the Krebs cycle.

23. Electron Transport Chain
Final step in the breakdown of glucose
Where occurs across the inner membrane of the mitochondria.
Energy Yield Total of 32 ATP
H2O
NAD+
NADH
ATP H+
Controlled release of energy for synthesis of ATP
Electron transport chain 2 O2
2e + 1
Electron Transport Chain (2:00)

24. Electron Transport Chain
Most of the energy in glucose is stored in electron carriers NADH and FADH2
Only 4 total ATP produced per glucose after complete breakdown in the Krebs Cycle

25. Electron Transport Chain
NADH and FADH2 deposit electrons into electron transport chains in the inner mitochondrial membrane
Electrons join with oxygen gas and hydrogen ions to made H2O at the end of the ETCs

26. FIGURE 8-8 The electron transport chain of mitochondria
NADH and FADH2 donate their energetic electrons to the carriers of the transport chain. As the electrons pass through the transport chain, some of their energy is used to pump hydrogen ions from the matrix into the intermembrane space. This creates a hydrogen ion gradient that is used to drive ATP synthesis. At the end of the electron transport chain, the energy-depleted electrons combine with oxygen and hydrogen ions in the matrix to form water.

27. Chemiosmosis
Energy is released from electrons as they are passed down the electron transport chain
Released energy used to pump hydrogen ions across the inner membrane
Hydrogen ions accumulate in intermembrane space

28. Chemiosmosis
Hydrogen ions form a concentration gradient across the membrane, a form of stored energy
Hydrogen ions flow back into the matrix through an ATP synthesizing enzyme
Process is called chemiosmosis

29. Chemiosmosis
Flow of hydrogen ions provides energy to link molecules of ADP with phosphate, forming ATP
ATP then diffuses out of mitochondrion and used for energy-requiring activities in the cell

30. Overview of Cellular Respiration

31. Cellular Respiration Glycolysis, Krebs cycle, Electron Transport (6:01)

32. Fermentation When pyruvic acid moves to the next step,
if there is no oxygen = anaerobic
if there is oxygen = aerobic

34. Fermentation
Fermentation – process by which cells release energy in the absence of oxygen
Glycolysis produces ATP quickly and does not require O2
Without O2 the ETC does not run – no where for NADH to deposit its electrons
Without NAD+ the cell cannot keep glycolysis going and ATP production stops.

35. Two types of fermentation:
Alcoholic Fermentation
Lactic Acid Fermentation

36. Alcoholic Fermentation
Occurs in yeast cells:
Yeast is added to bread– CO2 produced in fermentation make air spaces in bread and therefore bread rises.
Alcohol evaporates during cooking
Alcohol is toxic to cells. If too much fermentation occurs, alcohol will kill yeast cells.
Happens when:
Yeast make beer
Bacteria make wine
How Stuff Works - Bread (2:35)
How Stuff Works - Whiskey (2:32)

37. Lactic Acid Fermentation
Happens in muscles during exercise when body can’t get oxygen to tissues fast enough.
Lactic acid builds up in muscles causing soreness.
Bacteria use lactic acid fermentation to make: yogurt, cheese, sour cream, pickles, sauerkraut

40. The Totals Cellular Respiration (aerobic: with oxygen)
1 glucose → 36 ATP
Fermentation (anaerobic: without oxygen)
1 glucose → 2 ATP