1. CELLULAR
RESPIRATION

2. Energy
Energy is the ability to do work
All living thing livings (organisms) need energy to live
Directly or indirectly nearly all the energy for life comes from the Sun
Some organisms make their own food (autotrophs)
While others must obtain it from other organisms (heterotrophs)

3. The chemical bonds between atoms of food molecules provide the energy used by all living organisms to sustain life
Respiration is the life process in which this energy is released for use in the cell
Once released, it becomes available to the cell in the operation of all other life functions
Remember that we referred to all the chemical reactions in a cell as the cell’s metabolism.

4. Where Does All This Energy Come From?
Complex carbohydrates are the major source of energy for most organisms
But – before the energy in those carbohydrates can be used by cells, the carbohydrates are broken down into simple sugars such as glucose
C6H12O6
FYI: How much energy is in glucose?
Lots
One gram of the sugar glucose (C6H12O6), when burned in the presence of oxygen, releases 3811 calories of heat energy.

5. The process where these glucose molecules are broken down to release energy is cellular respiration
Cellular respiration is a series of enzyme catalyzed chemical reactions which produces ATP (adenosine triphosphate)
Most of the processes that occur in cells use the ATP for their energy source

6. ATP ATP is an energy-transfer compound or “energy-carrier”
Cell can use ATP because (in part) of it’s unique structure
It makes ATP PERFECT for the storage and release of energy

7. High Energy Bond ~

8. The high energy bonds contain a large amount of energy
ATP releases energy when the bond between the second and third phosphate groups is broken, forming a molecule called adenosine diphosphate (ADP)
ATP and ADP can be interchanged by the addition or removal of a phosphate group
Sometimes ADP becomes adenosine monophosphate (AMP) by losing an additional phosphate group but there is less energy released in this reaction

10. Overview of Cellular Respiration
6O2 + C6H12O CO2 + 6H2O + Energy
ENZYMES
(ATP)

11. Glycolysis and aerobic respiration
Cellular respiration occurs in 2 main parts
Glycolysis and aerobic respiration
The 1st stage, glycolysis, is an anaerobic process
Anaerobic metabolic processes do not require oxygen
The 2nd stage – aerobic respiration – includes the Krebs cycle and electron transport and is an aerobic process
Aerobic metabolic processes require oxygen.

13. Remember: This is occurring in the cytoplasm in the
Glycolysis
Glucose (6 carbon molecule) is broken down in the cytoplasm into two 3-carbon molecules called pyruvic acid
It takes 2 molecules of ATP to split each molecule of glucose
At the end of glycolysis, however, 4 molecules of ATP are produced
Glucose + 2 ATP
2 Pyruvic Acid + 4 ATP or
C-C-C-C-C-C + 2ATP
C-C-C + C-C-C + 4ATP
Remember: This is occurring in the cytoplasm in the
absence of oxygen

14. In the absence of Oxygen
In some cells lacking the enzymes necessary for aerobic respiration Or
In cells when oxygen is lacking,
Anaerobic respiration will go to fermentation

15. Lactic Acid Fermentation
Glucose is gradually broken down in a series of enzyme controlled reaction to lactic acid (anaerobic respiration)
Glucose
2 Lactic Acid ATP

16. Lactic Acid Fermentation
Lactic acid is produced in animals and is associated with muscle fatigue when the muscle cells are using oxygen faster than the circulatory system can supply it.
Lactic acid is also produced by some bacteria and is important in the production of cheeses, buttermilk, and yogurt
As a result of anaerobic respiration, there is a net gain of 2 ATP

17. Another End Product of Anaerobic Respiration
Depending on the organism (like yeast and some bacteria in the baking and brewing industries), anaerobic respiration can also produce the end products ethyl alcohol and carbon dioxide
enzymes
2 ATP
glucose
2 alcohol +
2CO2 +

18. Aerobic Respiration
Many of the enzymes involved in aerobic cellular respiration are located in the mitochondria
In the process with the presence of oxygen, the chemical energy of glucose is released gradually in a series of enzyme-controlled reactions
Aerobic respiration is much more efficient than anaerobic respiration

19. Glucose + Oxygenwater + carbon dioxide + 36ATP
SUMMARY EQUATION
Glucose + Oxygenwater + carbon dioxide + 36ATP or
enzymes
C6H12O6 +
6O2
6H2O +
6CO2 +
36ATP

20. Krebs Cycle
Glycolysis has a net result of 2 ATP and 2 pyruvate (pyruvic acid)
In the presence of oxygen, pyruvate is transported into the mitochondrial matrix where it is converted to carbon dioxide.
The series of reactions that does this called the Krebs cycle (or citric acid cycle)
For each glucose molecule, there are two turns of the Krebs cycle
The net yield from the Krebs is six carbon dioxide molecules & 2 ATP

22. The Electron Transport Chain
The final step in the breakdown of glucose
High-energy electrons and hydrogen ions produced in the Krebs cycle are used to convert ADP to ATP
Electrons move along the mitochondrial membrane and are released
H+ ions are released and diffuse into the matrix
Oxygen is the final electron acceptor
(H+ plus O = H2O one of the by-products)
In total 32 molecules of ATP are formed for each molecule of glucose

24. Total ATP Production in Aerobic Respiration2
From Glycolysis 2
From the Krebs Cycle 32
From the Electron Transport Chain 36
GRAND TOTAL

25. Only 2 molecules of ATP are produce in anaerobic respiration
Efficiencies
Only 2 molecules of ATP are produce in anaerobic respiration
While 36 molecules of ATP are produced in aerobic respiration

26. Prokaryotic cellular respiration
Some prokaryotes also undergo aerobic respiration
They do not, however, have a mitochondria
Main difference – use of cell membrane as electron transport site
The movement of pyruvate to mitochondria not necessary, saving prokaryotic cell two ATP molecules
Increases net total of ATP to 38

27. During a race, runners rely on the energy supplied by ATP to make it to the finish line.
To obtain energy, the body uses ATP already in muscles and new ATP made by lactic acid fermentation and cellular respiration
At the beginning of a race, the body uses all three ATP sources, but stored ATP and lactic acid fermentation can only supply energy for a limited time

28. When the gun goes off in a footrace, the muscles of the runners contain only enough of this ATP for a few seconds of intense activity
Before most of the runners have passed the e50-meter mark, that store of ATP is nearly gone
At this point, their muscle cells are producing most of their ATP by lactic acid fermentation
These sources can usually supply enough ATP to last about 90 seconds
In a 200 or 300-meter sprint, this may be just enough to reach the finish line

29. What happens if the race is longer?
For exercise longer than 90 seconds, cellular respiration is the only way to generate a continuing supply of ATP
Cellular respiration release energy more slowly than fermentation, which is why even well-conditioned athletes have to pace themselves
Your body stores energy in muscle and other tissues in the form of the carbohydrate glycogen
These stores of glycogen are usually enough to last for 15 or 20 minutes of activity
After that, your body begins to break down other stored molecules, including fats, for energy
This is one reason why aerobic forms of exercise such as running, dancing and swimming are so beneficial for weight control

30. Comparing Photosynthesis and Cellular Respiration