1. Cellular Respiration

2. The cell obtains most of its energy requirements through the
The cell obtains most of its energy requirements through the of glucose (glycogen, glycerol & amino acids may also be used)
Releases the energy that is stored in
Glucose is to form
( ), ( ) and energy

3. Releasing Stored Energy
There are 3 ways of releasing the energy stored in food:
Aerobic cellular respiration is carried out by organisms that live in
environments( )
Examples: fungi, bacteria, plants, animals
2. Anaerobic cellular respiration is carried out by organisms that live in anaerobic environments( )
Examples: nitrogen fixing bacteria, deep ocean producers
3. Fermentation - modified form of cellular respiration
Examples: Yeast, bacteria that cause milk to sour

4. Aerobic Cellular Respiration
The controlled process of respiration can be divided into three groups:
1. Glycolysis process which converts ( )to (aka pyruvate)
2. Kreb's ( ) cycle process in which the of acid yields energy in the form of and
3. Respiratory ( ) Chain - an electron transfer system that produces

5. Aerobic Cellular Respiration

6. Glycolysis Anaerobic reaction that occurs in the
Occurs in all living cells
Does not provide enough energy to sustain life
Location: occurs outside the mitochondria in the cytoplasm of the cell
in glycolysis the cell supplies the activation energy which is needed to initiate the reaction
net result is 2 ATP

7. Stage of Glycolysis Summary
1. Glucose ( ) enters respiration pathway
2. Two from provide the activation energy to begin the reaction ( ) which converts glucose to (6 carbon molecule)

8. Stages of Glycolysis Summary
3. Glucose phosphate is split into (phosphoglyceraldehyde) (3 carbon molecule)
4. Each continues through glycolysis to yield: , & forming the

10. Stage 1 of Glycolysis

11. Stage 2 Glycolysis

12. Energy Gained from Glycolysis
Glycolysis nets:

13. The Fate of Pyruvate
Pyruvate can proceed to processes dependent on the availability of oxygen:
Aerobic Cellular Respiration
Pyruvate is transported from the into the
Anaerobic Cellular Respiration -
Pyruvate remains in the
The fate of pyruvate, the final product of glycolysis, depends on the availability of oxygen and on the type of organism.
When oxygen is available, pyruvate enters the matrix of the mitochondrion. A series of reactions yield carbon dioxide and acetyl-CoA. NAD+ is reduced to NADH.

14. Preparation for the Kreb’s Cycle Transition Reaction (aka oxidative decarboxylation)
Occurs in the
Pyruvate combines with coenzyme A ( )
Loses a carbon atom in the form of CO2
Remaining 2 carbon molecule attaches to CoA to form
Coenzyme A “tows” the acetyl group (2 carbon compound) into the Krebs cycle
During the Krebs cycle, carbon atoms are fully oxidized to carbon dioxide, NAD+ and FAD are to and , and a is produced.

15. Krebs Cycle
The and from the Krebs cycle their to the electron carriers in the electron transport chain.
As are passed from one carrier to the next, the energy that is is used to pump hydrogen ions( ) across the mitochondrial inner membrane into the intermembrane space( ), creating a concentration( ) gradient.
The energy stored in the gradient is used to by

17. Krebs Cycle Citric Acid Cycle
Occurs in the mitochondria
Cycle must be completed per glucose molecule
Net gains per glucose molecule:
2 ATP
6 NADH
2 FADH2
Occurs in the mitochondrial matrix
for each glucose ---> 2 pyruvate molecules therefore giving 2 turns of Krebs cycle
yields of Krebs cycle
ATP - 1 molecule/cycle -> 2 ATP/glucose molecule
NADH - 3 molecules/cycle -> 6 NADH/glucose molecule
FADH - 1 molecule/cycle -> 2 FADH/glucose molecule

18. Kreb’s Cycle Steps
The 2 C group from the transition reaction combines with a 4 C to produce a 6 C called
Citric acid steps through a number of reactions, and to become a 5C -

19. Kreb’s Cycle
Ketoglutaric acid proceeds through a number of reactions losing CO2 and producing NADH and ATP to become a 4C -
Succinyl acid becomes (4 C) producing FADH
Fumeric acid is transformed to forming NADH

20. Kreb’s Cycle
The oxaloacetic acid molecule the cycle ends with is not the same molecule with which the cycle began
[proven using radioactive markers in glucose entering - markers end up in oxaloacetic acid]

22. Video – The Kreb’s Cycle

23. Electron Transport Provides during aerobic cellular respiration
Electrons are passed down a chain of protein complexes imbedded in the inner membrane
Energy is pump hydrogen ions, H+, from the matrix into the intermembrane space
Against concentration gradient
Requires oxygen to function
Oxygen is the of the electron transport system producing water
Electron transport system occurs on the inner membrane in the cristae
Kreb’s cycle and glycolysis convert some of glucose’s energy to produce ATP from ADP
most energy from the first two stages of respiration is held as high energy electrons in the electron carriers NAD and FAD

24. Electron Transport System
Oxidative has these high energy electrons being passed step by step to a lower energy acceptor -> oxygen
In oxidative phosphorylation a series of electron carriers, each holding the electron at a slightly energy level, pass the electrons along the pathway to
At the top of the energy hill, the electrons are held by and

25. Cytochromes
The principle components of the electron transport chain are
Composed of a protein enclosing an atom of iron each with a different capacity for holding electrons at different energy levels
The enclosed iron atom alternately and an electron passing it along to the next cytochrome at a slightly lower level of energy

26. Electron Transport System
At the end of each chain the electrons are by
which then combines with protons (H+) from the solution to produce
For each entering the electron transport chain a yield of is realized

27. Role of Oxygen
Video – Oxidative Phosphorylation

28. C/R - Energy Harvest

29. C/R - Energy Harvest

30. Aerobic Cellular Respiration
Net gain of per 1 glucose during cellular respiration
Majority of ATP is produced using Electron Transport System and Chemiosmosis

31. Wrap Up

32. Anaerobic Cellular Respiration
No available
Only produces the amount of ATP generated by
Converts that cannot be processed in the Krebs cycle to or
Fermentation – pathway taken by pyruvate to produce ATP in anaerobic conditions
Two types:
Lactate Fermentation
Ethanol Fermentation
The type of organism and oxygen availability determines the pathway of pyruvic acid
process which occurs in the absence of oxygen [anoxia v hypoxia] and converts glucose to lactic acid (in animals) or alcohol and carbon dioxide (fermentation in yeast)
Using only glycolysis the net result is 2 ATP

33. Lactate Fermentation Occurs in the Occurs when energy demands
oxygen supply
Cells convert pyruvate molecules into lactate or
Use as energy source
Lactate is stored
When oxygen levels increase lactate is converted back to pyruvate
Pyruvate proceeds to Krebs cycle
animals and some micro-organisms form lactic acid if there is an oxygen deficiency
uses H+ from NADH to convert pyruvic acid -> lactic acid

34. Ethanol Fermentation Anaerobic process Occurs in the of cells
Process in which yeasts and some bacteria convert pyruvate to and CO2
Used to produce alcoholic beverages and aid in the rising of bread
in most plants and many micro-organisms oxygen deficiency leads to alcoholic fermentation
carbon dioxide is removed from pyruvic acid & H+ from NAD+

35. Anaerobic Respiration
Both types of fermentation but free NAD+ to accept H+ supplying a small amount of energy and preventing the cell from becoming acidic
Various other chemical pathways exist which allow some organisms to thrive in anoxic and hypoxic conditions

36. Summary

37. Cellular Respiration Releases Energy from Organic Compounds - Review
Three metabolic pathways make up aerobic cellular respiration. B. C.

38. Cellular Respiration Releases Energy from Organic Compounds - Review
The first set of reactions in aerobic cellular respiration is called glycolysis.
It is an anaerobic process.
During glycolysis, a small amount of ATP is generated, and NAD+ is reduced to NADH.

39. ↓ (ATP -> ADP) [phosphorylation]
Stage 1 of Glycolysis
glucose
↓ (ATP -> ADP) [phosphorylation]
glucose phosphate
↓ [rearranged]
fructose phosphate
fructose diphosphate
↓ [split]
PGAL  PGAL a. b. c. d.

40. Stage 2 Glycolysis a. b. c. PGAL PGAL DPGA DPGA PGA PGA
↓ NAD -> NADH ↓ NAD -> NADH
DPGA DPGA
↓ ADP -> ATP ↓ ADP -> ATP
PGA PGA
Pyruvate Pyruvate a. b. c.

41. Cellular Respiration Releases Energy from Organic Compounds - Review
The fate of pyruvate, the final product of glycolysis, depends on the availability of oxygen and on the type of organism.
When oxygen is available, pyruvate enters the matrix of the mitochondrion. A series of reactions yield carbon dioxide and acetyl-CoA. NAD+ is reduced to NADH.
Transition Reaction

42. Cellular Respiration Releases Energy from Organic Compounds - Review
Acetyl-CoA enters the Krebs cycle by combining with a four-carbon compound.
During the Krebs cycle, two carbon atoms are fully oxidized to carbon dioxide, NAD+ and FAD are reduced to NADH and FADH2, and a small amount of ATP is produced.
citrate

43. Cellular Respiration Releases Energy from Organic Compounds - Review
The NADH and FADH2 from the Krebs cycle donate their electrons to the electron carriers in the electron transport chain.
As electrons are passed from one carrier to the next, the energy that is released is used to pump hydrogen ions across the mitochondrial inner membrane into the intermembrane space, creating a concentration gradient.
The energy stored in the gradient is used to generate ATP by chemiosmosis.

44. Cellular Respiration Releases Energy from Organic Compounds - Review
Organisms that carry out anaerobic cellular respiration use inorganic chemicals other than oxygen as the final electron-acceptor. This produces ATP for the cell, but not as much as in aerobic respiration.
breakdown of glucose in the presence of oxygen
36 ATP
breakdown of glucose by lactate or ethanol fermentation
2 ATP

45. Cellular Respiration Releases Energy from Organic Compounds - Review
In muscle that is functioning anaerobically, pyruvate is converted to lactate and the reduced NADH is reoxidized so that glycolysis can continue. This process is called lactate fermentation.

46. Cellular Respiration Releases Energy from Organic Compounds - Review
In yeast growing anaerobically, pyruvate is converted to carbon dioxide and ethanol. This process is known as ethanol fermentation.

47. Cellular Respiration Releases Energy from Organic Compounds - Review
Fermentation is used on an industrial scale to produce ethanol.
Ethanol is used as an additive to gasoline to reduce some environmental contaminants.
Selected Fermentation Products and their Uses

48. Chapter 5 Concept Organizer

49. Chapter 5 Summary
P/S and C/R proceed through many different rxns to produce energy-rich compounds and break them down to release their stored energy (ATP)
When the bond to the last phosphate group is broken, leaving ADP and a free phosphate group, the energy released is available to do cellular work.
In P/S the CO2 and H2O are involved in two separate sets of reactions:
H2O is split into hydrogen ions, electrons, and oxygen in the light-dependent reactions
CO2 is incorporated into carbohydrates in the light-independent reactions.

50. Chapter 5 Summary (cont’d)
light-dependent rxns (thylakoid membranes) capture light energy and use it to excite electrons to produce ATP and NADPH.
light-independent reactions (stroma) use the chemical potential energy of ATP and the reducing power of NADPH to reduce carbon dioxide and form glucose via the Calvin-Benson cycle.
Glucose is processed to release energy through glycolysis, the Krebs cycle, and electron transport
Glycolysis is an anaerobic process that occurs in the cytoplasm and breaks down glucose into pyruvate
Pyruvate enters the mitochondria, where it is broken down into carbon dioxide and acetyl CoA.

51. Chapter 5 Summary (cont’d)
Acetyl CoA enters the Krebs cycle (matrix) and energy released from breakdown of compounds in the Krebs cycle is used to reduce NAD -> NADH and FAD -> FADH
NADH & FADH donate electrons to the ETC on the inner mitochondrial membranes
Energy, released as electrons, is passed along the chain & used to create a hydrogen ion gradient that powers chemiosmosis, which generates ATP.
Glycolysis is the only source of energy for some organisms. Pyruvate is broken down into carbon dioxide and alcohol (ethanol fermentation) or lactate (lactate fermentation). This process occurs anaerobically.

52. Chapter 5 Review
What molecule provides energy for most cellular processes?
Would photosynthesis and respiration be able to proceed without enzymes? Why or why not?
Where are chlorophyll molecules found?
What happens when a compound is oxidized? Reduced? Which form contains more energy?
What occurs during chemiosmosis? Where does it occur?
What metabolic pathways are involved in cellular respiration? Where do they occur?