1. Cellular Respiration
Honors Biology

2. Why is food important?
Provides us with the chemical building blocks we need to grow and reproduce
Energy
All living things need energy

3. How much energy is in food?
1 gram of glucose releases 3811 calories of heat energy
calorie: amount of energy needed to raise the temperature of 1 gram of water 1 ºC
Calorie (also called kilocalories)= 1000 calories

4. Overview
Cellular Respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

5. The energy in glucose is released a little bit at a time through 3 steps
Glycolysis
Krebs Cycle
Electron Transport Chain

6. Glycolysis
Overview: process by which one molecule of glucose is broken into 2 3-C molecules called pyruvic acid (Pyruvate)
Takes place in the cytosol of the cell
Does not require oxygen

15. Balance Sheet 4 ATP are made 2 ATP are used Net yield = 2 ATP
Even though not a lot of energy is produced this process is so fast that cells can produce thousands of ATP in a few milliseconds

16. Why do we need the other steps?
In a few seconds all the cells NAD+ are filled up with electrons and glycolysis can not continue

17. What’s the next step?
After glycolysis 90% of the energy that was available in glucose is still stored in the pyruvic acid
To use this energy, it requires a powerful electron acceptor
Oxygen

18. What’s the next step?
It depends on whether or not oxygen is present or not
no oxygen = Fermentation
Oxygen present = cellular respiration

19. Aerobic Respiration Take place only if oxygen is present 2 stages
Kreb’s Cycle
Electron Transport Chain
Intermediate step

20. The Kreb’s Cycle Named after Hans Krebs a British Biochemist
Overview: acetyl CoA is broken down into CO2 while energy is released
AKA: The Citric Acid Cycle

28. Balance Sheet
Each glucose is broken into 2 pyruvic acids so one glucose results in 2 turns of the Kreb’s cycle
This produces a total of
6 NADH
2 FADH2
2 ATP
4 CO2

29. What have we made so far? Glycolysis produced
Net 2 ATP
2 NADH
Added with Kreb’s Cycle products
Total of 10 NADH
Total of 2 FADH2
Net total 4 ATP

30. Electron Transport Chain

31. Chemiosmosis

32. Balance Sheet Glycolysis Aerobic Respiration
2 ATP
Aerobic Respiration
Kreb’s cycle= 2 ATP
ETC: every NADH produces 3 ATP and each FADH2 produces 2 ATP = 34
Grand total per glucose = 38 ATP
In the presence of oxygen the cell can generate 18X as much ATP from one glucose molecule

33. Some ATP is used to “pump” the NADH from glycolysis into the mitochondria
Net ATP 36
This represents about 36 percent of the total energy in glucose, the rest is lost as heat

34. Fermentation AKA Anaerobic Respiration
Takes place in the cytosol of the cell
ATP is NOT produced BUT it does allow NAD+ to be regenerated so that glycolysis can continue

35. Lactic Acid Fermentation

36. Microrganisms carry out lactic acid fermentation
This lactic acid is used to manufacture food products such as yogurt, cheese, pickles, sour cream and buttermilk

37. During exercise your muscles can use Lactic Acid fermentation when oxygen is not available
Feel the burn
Oxygen debt
Eventually lactic acid is carried by the blood to the liver where it is converted back into pyruvic acid once oxygen is available

38. Alcoholic Fermentation
Some plant cells and unicellular organisms (yeast) convert pyruvic acid into ethyl alcohol

39. 2 steps

40. Alcoholic Fermentation is how beer and wine and bread are made
Yeast is added to the mixture to produce the alcohol
Wine the CO2 in step one is released
Champagne the CO2 is not released
Bread also uses yeast to produce CO2 which causes the bread to rise
The alcohol evaporates during baking

41. Glycolysis and Fermentation
Together these “release” enough energy to many unicellular organisms to survive
Larger multicellular organisms require more energy thus a different pathway

42. Energy and Exercise We have 3 main sources of ATP
Stored ATP in muscles
ATP made by Glycolysis via Lactic Acid Fermentation
ATP made by Cellular Respiration

43. Quick Energy Running from a bear Provided by 1st stored ATP
Only lasts a few seconds
2nd Lactic Acid Fermentation
90 seconds

44. Long Term Energy 3rd Cellular Respiration Produces energy more slowly
Must pace yourself
Stored Glycogen broken down to glucose
15-20 minutes
After that we begin to break down fat

46. Step 1
2-C acetyl CoA combines with 4-C oxaloacetic acid to form 6-C citric acid
This reaction regenerates coenzyme A

47. Step 2
Citric Acid releases a CO2, an electron and a H to from a 5-C compound
NAD+ is reduced into NADH

48. Step 3
The 5-C compound releases another CO2 and an electron and a H atom forming a 4-C compound
NAD+ is reduced to NADH
ADP gains a P to become ATP

49. Step 4
4-C compound releases a H atom and an electron to form a different 4-C compound
FAD (flavin adenine dinucleotide) is reduced to FADH2

50. Step 5
4-C compound releases another H atom and an electron to regenerate oxaloacetic acid to keep the cycle going
NAD+ is once again reduced to NADH