1. Respiration
Cellular respiration is the process by which cells transfer chemical energy from sugar molecules to ATP molecules.
As this happens cells release CO2 and use up O2
Respiration can be AEROBIC or ANAEROBIC

2. Breathing supplies oxygen to our cells and removes carbon dioxide
Breathing supplies oxygen to our cells and removes carbon dioxide
Breathing provides for the exchange of O2 and CO2
Between an organism and its environment
CO2 O2
Bloodstream
Muscle cells carrying out
Cellular Respiration
Breathing
Glucose + O2
CO2 +H2O +ATP
Lungs
Figure 6.2

3. . The human body uses energy from ATP for all its activities.
ATP powers almost all cellular and body activities .

4. CELLULAR RESPIRATION
Cellular respiration is an energy- releasing process. It produces ATP
ATP is the universal energy source
Making ATP
Plants make ATP during photosynthesis
Cells of all organisms make ATP by breaking down carbohydrates, fats, and protein

5. The energy in an ATP molecule
Lies in the bonds between its phosphate groups
Phosphate groups
ATP
Energy P
Hydrolysis
Adenine
Ribose
H2O
Adenosine diphosphate
Adenosine Triphosphate +
ADP
Figure 5.4A

6. REDOX REACTIONS The loss of electrons is called oxidation.
The addition of electrons is called reduction

7. Overview of Aerobic Respiration
C6H12O6 + 6O2  6CO2 + 6H2O +ATP
glucose oxygen carbon water
dioxide

8. When glucose is converted to carbon dioxide
It loses hydrogen atoms, which are added to oxygen, producing water
C6H12O6
6 O2
6 CO2
6 H2O
Loss of hydrogen atoms (oxidation)
Gain of hydrogen atoms (reduction)
Energy
(ATP)
Glucose +
Figure 6.5A

9. STAGES OF CELLULAR RESPIRATION
Overview: Cellular respiration occurs in three main stages
Glycolysis
Krebs Cycle or Citric Acid Cycle
Electron Transport Chain or Phosphorylation

10. No oxygen needed. It is universal
Stage 1:
Glycolysis
No oxygen needed. It is universal
Occurs in the cytoplasm
Breaks down glucose into pyruvate, producing a small amount of ATP (2)

11. GLYCOLYSIS Where?: In the cytosol of all cells.
Both aerobic and anaerobic respiration begin with glycolysis.
What happens?: The cell harvests energy by oxidizing glucose to pyruvate.
One molecule of glucose (6 carbons) is converted to two pyruvate molecules (3 carbons) through a series of 10 reactions mediated by enzymes.
Result:
2 pyruvate molecules (each with a 3 carbon backbone)
2 NADH molecules. Carrier that picks up hydrogens stripped from glucose.
2 ATP molecules. 4 are made but cells use 2 to start glycolysis so net gain is 2

12. An overview of cellular respiration

13. Preparatory steps to enter the Krebs cycle
The 2 pyruvate molecules enter the mitochondrion and an enzyme strips one carbon from each pyruvate.
This two carbon molecule is picked up by Co-enzyme A in preparation for the Krebs cycle.
This is acetyl CoA. This is what enters the Krebs cycle: C-C-CoA (oxaloacetate)

14. The citric acid cycle or Krebs cycle
Stage 2 :
The citric acid cycle or Krebs cycle
Takes place in the mitochondria
Completes the breakdown of glucose (catabolism), producing a small amount of ATP (2ATP)
Pyruvate is broken down to carbon dioxide
More coenzymes are reduced .Supplies the third stage of cellular respiration with electrons (hydrogen carriers such as NADH)

15. KREBS CYCLE or citric acid cycle
This cycle involves a series of 8 steps forming and rearranging. Each time it releases CO2 and NADH carries hydrogen to the last step. 6 CO2 are given off as waste (this is the most oxidized form of Carbon) In total:
6 CO2
6 NADH are produced and
2 FADH and only
2 ATP

16. An overview of cellular respiration

17. Oxidative phosphorylation or electron transport chain
Stage 3:
Oxidative phosphorylation or electron transport chain
Occurs in the mitochondria (inner membrane)
Uses the energy released by “falling” electrons to pump H+ across a membrane
Harnesses the energy of the H+ gradient through chemiosmosis, producing ATP

18. Chemiosmosis
Chemiosmosis is an energy coupling mechanism that uses energy stored on H+
Chemiosmosis is the coupling of the REDUX reactions of the electron transport chain to ATP synthesis

19. Electron transport chain
NADH passes electrons to an electron transport chain
As electrons “fall” from carrier to carrier and finally to O2
Energy is released in small quantities
H2O
NAD+
NADH
ATP H+
Controlled release of energy for synthesis of ATP
Electron transport chain 2 O2
2e + 1
Figure 6.5C

20. ELECTRON TRANSPORT CHAIN
Electron transport systems are embedded (protein molecules) in inner mitochondrial membranes (cristae)
NADH and FADH2 give up electrons that they picked up in earlier stages to electron transport system
Electrons are transported through the system
The final electron acceptor is oxygen. The hydrogen combines with the oxygen to form water

21. Electron transport chain
Intermembrane space
Inner mitochondrial membrane
Mitochondrial matrix
Protein complex
Electron flow
Electron carrier
NADH
NAD+
FADH2
FAD
H2O
ATP
ADP
ATP synthase H+ + P O2
Electron Transport Chain
Chemiosmosis .
OXIDATIVE PHOSPHORYLATION
+ 2 1 2
Figure 6.10

23. HOW MUCH TOTAL ATP(ENERGY) WAS PRODUCED?
Glycolysis
2 ATP formed by substrate-level phosphorylation
Krebs cycle and preparatory reactions
Electron transport phosphorylation
32-34 ATP formed
2+2+34=38
Most ATP production occurs by oxidative phosphorylation or electron transport chain

24. Electron transport phosphorylation requires the presence of oxygen
WHY OXYGEN?
Electron transport phosphorylation requires the presence of oxygen
Oxygen withdraws spent electrons from the electron transport system, then combines with H+ to form water

25. Web site tutorials to check:

26. An overview of cellular respiration

27. An overview of cellular respiration

29. Animation: Cell Respiration Overview

30. How efficient is cellular respiration?
Only about 40% efficient.
In other words, a call can harvest about 40% of the energy stored in glucose.
Most energy is released as heat

31. Evolution of cellular respiration
When life originated, atmosphere had little oxygen
Earliest organisms used anaerobic pathways
Later, photosynthesis increased atmospheric oxygen
Cells arose that used oxygen as final acceptor in electron transport (without oxygen to act as the final hydrogen acceptor the cells will die)

32. Fermentation
Fermentation allows some cells to produce ATP without oxygen.
This is Anaerobic respiration

33. Produce less ATP( 2) than aerobic pathways
ANAEROBIC RESPIRATION Fermentation is an anaerobic alternative to cellular respiration
Do not use oxygen
Produce less ATP( 2) than aerobic pathways
Two types. One produces alcohol and the other lactic acid as waste products
Fermentation pathways
Anaerobic electron transport

34. Fermentation Begin with glycolysis
Under anaerobic conditions, many kinds of cells
can use glycolysis alone to produce small amounts of ATP
Begin with glycolysis
Do not break glucose down completely to carbon dioxide and water
Yield only the 2 ATP from glycolysis
Steps that follow glycolysis serve only to regenerate NAD+

35. Carry out alcoholic fermentation Saccharomyces cerevisiae
Yeast
Single-celled fungi
Carry out alcoholic fermentation
Saccharomyces cerevisiae
Baker’s yeast
Carbon dioxide makes bread dough rise
Saccharomyces ellipsoideus
Used to make beer and wine

36. Our muscle cells…
In the absence of oxygen our muscles can carry out fermentation, but the pyruvate from glycolysis is turned into lactic acid instead of alcohol

37. In alcohol fermentation
NADH is oxidized to NAD+ while converting pyruvate to CO2 and ethanol
NAD+
NADH 2
GLYCOLYSIS
2 ADP + 2 P
ATP
Glucose
2 Pyruvate
released
CO2
2 Ethanol
Figure 6.13B
Figure 6.13C

38. More details…

39. Two stages of glycolysis
Energy-requiring steps
ATP energy activates glucose and its six-carbon derivatives
Energy-releasing steps
The products of the first part are split into three-carbon pyruvate molecules
ATP and NADH form

40. Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
In glycolysis, ATP is used to prime a glucose molecule
Which is split into two molecules of pyruvate
NAD+
NADH H+
Glucose
2 Pyruvate
ATP 2 P
2 ADP +
Figure 6.7A

41. PREPARATORY PHASE (energy investment)
In the first phase of glycolysis
ATP is used to energize a glucose molecule, which is then split in two
 Steps      –   A fuel molecule is energized, using ATP. 1 3
Glucose
PREPARATORY PHASE (energy investment)
ATP
Step 1
ADP P
Glucose-6-phosphate 2 P
Fructose-6-phosphate
ATP 3
ADP P P
Fructose-1,6-diphosphate
 Step      A six-carbon intermediate splits into two three-carbon intermediates. 4 4
Figure 6.7C

42. In the second phase of glycolysis
ATP, NADH, and pyruvate are formed P P
Glyceraldehyde-3-phosphate (G3P)
 Step     A redox reaction generates NADH. 5 6 9
NAD  5
NAD 
ENERGY PAYOFF PHASE
NADH P 6
NADH P 6
+H
+H P P P P
1,3 -Diphosphoglycerate
 Steps     –      ATP and pyruvate are produced. 6 9
ADP
ADP 6 7 7
ATP
ATP P P
3 -Phosphoglycerate 7 P P 8 8
2-Phosphoglycerate 8
H2O
H2O P P
Phosphoenolpyruvate (PEP)
ADP 9
ADP 9 9
ATP
ATP
Pyruvate

43. Net Energy Yield from Glycolysis
Energy requiring steps:
2 ATP invested
Energy releasing steps:
2 NADH formed
4 ATP formed
Glycolysis net yield is 2 ATP and 2 NADH

44. Preparatory reactions before the Krebs cycle
Pyruvate is oxidized into two-carbon acetyl units and carbon dioxide
NAD+ is reduced
pyruvate + coenzyme A + NAD+
acetyl-CoA + NADH + CO2
One of the carbons from pyruvate is released in CO2
Two carbons are attached to coenzyme A and continue on to the Krebs cycle

45. Acetyl CoA (acetyl coenzyme A)
Pyruvate is gets ready for the citric acid cycle
Prior to the citric acid cycle
Enzymes process pyruvate, releasing CO2 and producing NADH and acetyl CoA
CO2
Pyruvate
NAD+
NADH
+ H+
CoA
Acetyl CoA (acetyl coenzyme A)
Coenzyme A
Figure 6.8 2 1 3

46. Krebs cycle Products: Coenzyme A 2 CO2 3 NADH FADH2 ATP
The acetyl units are oxidized to carbon dioxide
NAD+ and FAD are reduced
Products:
Coenzyme A
2 CO2
3 NADH
FADH2
ATP

47. The citric acid cycle (Krebs)completes the oxidation of organic fuel (glucose), generating many NADH and FADH2 molecules
In the citric acid cycle
The two-carbon acetyl part of acetyl CoA is oxidized
CoA
CO2
NAD+
NADH
FAD
FADH2
ATP P
CITRIC ACID CYCLE
ADP + 3 +
3 H+
Acetyl CoA 2
Figure 6.9A

48. Krebs Cycle or Citric Acid Cycle

49. For each turn of the Krebs cycle
Two CO2 molecules are released (All of the carbon molecules in pyruvate end up in carbon dioxide)
Three NADH and one FADH2 (Coenzymes are reduced, they pick up electrons and hydrogen)
One molecule of ATP is formed for each turn so the net yield of ATP for the Krebs or Citric Acid cycle is 2 ATP molecules.

50. What happened to co-enzymes (NAD and FAD) during the first two stages?
Co-enzymes were reduced (gained electrons)
Glycolysis 2 NADH
Preparatory
reactions NADH
Krebs cycle FADH NADH
Total FADH NADH

51. Most ATP production occurs by oxidative phosphorylation or electron transport chain
Electrons from NADH and FADH2
Travel down the electron transport chain to oxygen, which picks up H+ to form water
Energy released by the redox reactions
Is used to pump H+ into the space between the mitochondrial membranes

52. ELECTRON TRANSPORT CHAIN OR PHOSPHORYLATION
Takes place in the mitochondria
Coenzymes deliver electrons to electron transport systems
Electron transport sets up H+ ion gradients
Flow of H+ down gradients powers ATP formation
The net yield from oxidative phosphorilation is 32 to 34 ATP molecules

53. Making ATP : Chemiosmotic model

54. In chemiosmosis, the H+ diffuses back through the inner membrane through ATP synthase complexes
Driving the synthesis of ATP
Intermembrane space
Inner mitochondrial membrane
Mitochondrial matrix
Protein complex
Electron flow
Electron carrier
NADH
NAD+
FADH2
FAD
H2O
ATP
ADP
ATP synthase H+ + P O2
Electron Transport Chain
Chemiosmosis .
OXIDATIVE PHOSPHORYLATION
+ 2 1 2
Figure 6.10

55. Certain poisons interrupt critical events in cellular respiration
Certain poisons interrupt critical events in cellular respiration
Various poisons
Block the movement of electrons
Block the flow of H+ through ATP synthase
Allow H+ to leak through the membrane H+ O2
H2O P
ATP
NADH
NAD+
FADH2
FAD
Rotenone
Cyanide, carbon monoxide
Oligomycin
DNP
ATP Synthase + 2
ADP
Electron Transport Chain
Chemiosmosis 1
Figure 6.11

56. OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis)
Review: Each molecule of glucose yields many molecules of ATP
Oxidative phosphorylation, using electron transport and chemiosmosis
Produces up to 38 ATP molecules for each glucose molecule that enters cellular respiration
Electron shuttle across membrane
Mitochondrion
Cytoplasm 2
NADH 2
NADH
(or 2 FADH2) 2
NADH 6
NADH 2
FADH2
GLYCOLYSIS
OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis)
Glucose 2
2 Acetyl CoA
CITRIC ACID CYCLE
Pyruvate
+ 2 ATP
+ 2 ATP
+ about 34 ATP
by substrate-level phosphorylation
by substrate-level phosphorylation
by oxidative phosphorylation
About 38 ATP
Maximum per glucose:
Figure 6.12

57. Anaerobic Electron Transport
Carried out by certain bacteria
Electron transport system is in bacterial plasma membrane
Final electron acceptor is compound from environment (such as nitrate), NOT oxygen
ATP yield is almost as good as from aerobic respiration

58. INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS
Cells use many kinds of organic molecules as fuel for cellular respiration

59. OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis)
Carbohydrates, fats, and proteins can all fuel cellular respiration
When they are converted to molecules that enter glycolysis or the citric acid cycle
OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis)
Food, such as peanuts
Carbohydrates
Fats
Proteins
Sugars
Glycerol
Fatty acids
Amino acids
Amino groups
Glucose
G3P
Pyruvate
Acetyl CoA
CITRIC ACID CYCLE
ATP
GLYCOLYSIS
Figure 6.14

60. How is energy obtained from proteins?
Proteins are broken down to amino acids
Amino acids are broken apart
Amino group is removed, ammonia forms, is converted to urea and excreted
Carbon backbones can enter the Krebs cycle

61. How do we get energy from fats?
Most stored fats are triglycerides
Triglycerides are broken down to glycerol and fatty acids
Glycerol is converted to PGAL, an intermediate of glycolysis
Fatty acids are broken down and converted to acetyl-CoA, which enters Krebs cycle

62. Carbohydrates Fats Amino acids Sugars Glycerol Fatty acids Glycolysis
LE 9-19
Proteins
Carbohydrates
Fats
Amino
acids
Sugars
Glycerol
Fatty
acids
Glycolysis
Glucose
Glyceraldehyde-3- P
NH3
Pyruvate
Acetyl CoA
Citric
acid
cycle
Oxidative
phosphorylation

63. Food molecules provide raw materials for biosynthesis
Cells use some food molecules and intermediates from glycolysis and the citric acid cycle as raw materials
This process of biosynthesis
Consumes ATP
ATP needed to drive biosynthesis
ATP
CITRIC
ACID
CYCLE
GLUCOSE SYNTHESIS
Acetyl
CoA
Pyruvate
G3P
Glucose
Amino
groups
Amino acids
Fatty
acids
Glycerol
Sugars
Carbohydrates
Fats
Proteins
Cells, tissues, organisms
Figure 6.15

64. The fuel for respiration ultimately comes from photosynthesis
All organisms
Can harvest energy from organic molecules
Plants, but not animals
Can also make these molecules from inorganic sources by the process of photosynthesis
Figure 6.16

65. Electrons “fall” from organic molecules to oxygen during cellular respiration
In cellular respiration, glucose and other fuels are oxidized, releasing energy.
In the summary equation of cellular respiration: C6H12O6 + 6O2  6CO2 + 6H2O+ ATP
Glucose is oxidized (loses electrons), oxygen is reduced ( gains electrons)
Cellular respiration does not oxidize glucose in a single step that transfers all the hydrogen in the fuel to oxygen at one time.
glucose is broken down gradually in a series of steps, each catalyzed by a specific enzyme