1. Cellular Respiration: Obtaining Energy from Food
Chapter 6
Cellular Respiration: Obtaining Energy from Food
Laua Coronado Chap Bio 10

2. Biology and : Marathoners versuSocietys Sprinters
Sprinters do not usually compete at short and long distances.
Natural differences in the muscles of these athletes favor sprinting or long-distance running.
Laua Coronado Chap Bio 10

3. Muscle Fibers
The muscles that move our legs contain two main types of muscle fibers:
Slow twitch fibers
Generate less power
Last longer
Generate ATP using oxygen
Fast twitch fibers
Generate more power
Fatigue much more quickly
Can generate ATP without using oxygen
All human muscles contain both types of fibers but in different ratios.
Laua Coronado Chap Bio 10

4. ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE
Animals depend on plants to convert solar energy to:
Chemical energy of sugars
Other molecules we consume as food
Photosynthesis:
Uses light energy from the sun to power a chemical process that makes organic molecules.
Laua Coronado Chap Bio 10

5. Producers and Consumers
Plants and other autotrophs (self-feeders):
Make their own organic matter from inorganic nutrients.
Heterotrophs (other-feeders):
Include humans and other animals that cannot make organic molecules from inorganic ones.
Autotrophs are producers because ecosystems depend upon them for food.
Heterotrophs are consumers because they eat plants or other animals.
Laua Coronado Chap Bio 10

6. Figure 6.1 Figure 6.1 Producer and consumer
Laua Coronado Chap Bio 10
Figure 6.1

7. Chemical Cycling between Photosynthesis and Cellular Respiration
The ingredients for photosynthesis are carbon dioxide and water.
CO2 is obtained from the air by a plant’s leaves.
H2O is obtained from the damp soil by a plant’s roots.
Chloroplasts in the cells of leaves:
Use light energy to rearrange the atoms of CO2 and H2O, which produces
Sugars (such as glucose)
Other organic molecules
Oxygen
Laua Coronado Chap Bio 10

8. Cellular Respiration
Plant and animal cells perform cellular respiration, a chemical process that:
Primarily occurs in mitochondria
Harvests energy stored in organic molecules
Uses oxygen
Generates ATP
The waste products of cellular respiration are:
CO2 and H2O
Used in photosynthesis
Laua Coronado Chap Bio 10

9. Cellular Respiration Animals perform only cellular respiration.
Plants perform:
Photosynthesis and
Cellular respiration
Laua Coronado Chap Bio 10

10. Figure 6.2 Sunlight energy enters ecosystem Photosynthesis C6H12O6
Glucose O2
Oxygen
CO2
Carbon dioxide
H2O
Water
Figure 6.2 Energy flow and chemical cycling in ecosystems
Cellular respiration
ATP
drives cellular work
Heat energy exits ecosystem
Laua Coronado Chap Bio 10
Figure 6.2

11. CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY
Cellular respiration is:
The main way that chemical energy is harvested from food and converted to ATP
An aerobic process—it requires oxygen
Laua Coronado Chap Bio 10

12. CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY
Cellular respiration and breathing are closely related.
Cellular respiration requires a cell to exchange gases with its surroundings.
Cells take in oxygen gas.
Cells release waste carbon dioxide gas.
Breathing exchanges these same gases between the blood and outside air.
Laua Coronado Chap Bio 10

13. Figure 6.3 O2 CO2 Breathing Lungs O2 CO2 Muscle cells Cellular
Figure 6.3 How breathing is related to cellular respiration.
Cellular
respiration
Laua Coronado Chap Bio 10
Figure 6.3

14. Glucose loses electrons Oxygen gains electrons (and hydrogens)
Oxidation
Glucose loses electrons
(and hydrogens)
C6H12O6
 6 O2 6
CO2
 6
H2O
Glucose
Oxygen
Carbon
dioxide
Water
Figure 6.UN2 Redox reaction The Overall Equation for Cellular Respiration
A common fuel molecule for cellular respiration is glucose.
The overall equation for what happens to glucose during cellular respiration:
Reduction
Oxygen gains electrons (and hydrogens)
Laua Coronado Chap Bio 10
Figure 6.UN02

15. The Role of Oxygen in Cellular Respiration
Cellular respiration can produce up to 38 ATP molecules for each glucose molecule consumed.
During cellular respiration, hydrogen and its bonding electrons change partners.
Hydrogen and its electrons go from sugar to oxygen, forming water.
This hydrogen transfer is why oxygen is so vital to cellular respiration.
Laua Coronado Chap Bio 10

16. Redox Reactions
Chemical reactions that transfer electrons from one substance to another are called:
Oxidation-reduction reactions or
Redox reactions for short
The loss of electrons during a redox reaction is called oxidation.
The acceptance of electrons during a redox reaction is called reduction.
During cellular respiration glucose is oxidized while oxygen is reduced.
Laua Coronado Chap Bio 10

17. Citric Acid Cycle Electron Transport Glycolysis ATP ATP ATP
Figure 6.UN3 Glycosis orientation diagram
ATP
ATP
ATP
Laua Coronado Chap Bio 10
Figure 6.UN03

18. Why does electron transfer to oxygen release energy?
When electrons move from glucose to oxygen, it is as though the electrons were falling.
This “fall” of electrons releases energy during cellular respiration.
Cellular respiration is:
A controlled fall of electrons
A stepwise cascade much like going down a staircase
Laua Coronado Chap Bio 10

19. 1 H2 O2 2 Release of heat energy H2O
Figure 6.4 A simple redox reaction
H2O
Laua Coronado Chap Bio 10
Figure 6.4

20. NADH and Electron Transport Chains
The path that electrons take on their way down from glucose to oxygen involves many steps.
The first step is an electron acceptor called NAD+.
The transfer of electrons from organic fuel to NAD+ reduces it to NADH.
The rest of the path consists of an electron transport chain, which:
Involves a series of redox reactions
Ultimately leads to the production of large amounts of ATP
Laua Coronado Chap Bio 10

21. Electron transport chain
Electrons from food e e
Stepwise release
of energy used
to make
NAD
NADH
ATP 2 H 2 e
Electron transport chain
Figure 6.5 The role of oxygen in harvesting food energy. 2 e 2 1 2 H O2
Hydrogen, electrons,
and oxygen combine
to produce water
H2O
Laua Coronado Chap Bio 10
Figure 6.5

22. An Overview of Cellular Respiration
Is an example of a metabolic pathway, which is a series of chemical reactions in cells
All of the reactions involved in cellular respiration can be grouped into three main stages:
Glycolysis
The citric acid cycle
Electron transport
Laua Coronado Chap Bio 10

23. Figure 6.6 Mitochondrion Cytoplasm Cytoplasm Animal cell Plant cell
High-energy
electrons
carried
by NADH
High-energy
electrons carried
mainly by
NADH
Glycolysis
Citric
Acid
Cycle 2
Pyruvic
acid
Electron
Transport
Glucose
Figure 6.6 A road map for cellular respiration
ATP
ATP
ATP
Laua Coronado Chap Bio 10
Figure 6.6

24. The Three Stages of Cellular Respiration
Stage 1: Glycolysis
A six-carbon glucose molecule is split in half to form two molecules of pyruvic acid.
These two molecules then donate high energy electrons to NAD+, forming NADH.
Three steps
Uses two ATP molecules per glucose to split the six-carbon glucose
Makes four additional ATP directly when enzymes transfer phosphate groups from fuel molecules to ADP
Produces a net of two molecules of ATP per glucose molecule.
Laua Coronado Chap Bio 10

25. Energy investment phase
INPUT
OUTPUT
2 ATP
2 ADP
Glucose
Key
Figure 6.7 Glycolysis (Step 1)
Carbon atom
Phosphate
group
High-energy
electron
Energy investment phase
Laua Coronado Chap Bio 10
Figure 6.7-1

26. Energy investment phase
INPUT
OUTPUT
NADH
NAD
2 ATP
2 ADP
Glucose
Key
NAD
Figure 6.7 Glycolysis (Step 2)
Carbon atom
NADH
Phosphate
group
High-energy
electron
Energy investment phase
Energy harvest phase
Laua Coronado Chap Bio 10
Figure 6.7-2

27. Energy investment phase
INPUT
OUTPUT
NADH
2 ATP
NAD
2 ADP
2 ATP
2 ADP
2 Pyruvic acid
Glucose
2 ADP
NAD
2 ATP
Key
Figure 6.7 Glycolysis (Step 3)
Carbon atom
NADH
Phosphate
group
High-energy
electron
Energy investment phase
Energy harvest phase
Laua Coronado Chap Bio 10
Figure 6.7-3

28. Enzyme P ADP ATP P P Figure 6.8
Figure 6.8 ATP synthesis by direct phosphate transfer P P
Laua Coronado Chap Bio 10
Figure 6.8

29. Stage 2: The Citric Acid Cycle
Completes the breakdown of sugar.
In the citric acid cycle, pyruvic acid from glycolysis is first “prepped.”
The citric acid cycle:
Extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2
Uses some of this energy to make ATP
Forms NADH and FADH2
Laua Coronado Chap Bio 10

30. Figure 6.9 INPUT OUTPUT Oxidation of the fuel generates NADH
(from glycolysis)
(to citric acid cycle)
NAD
NADH
CoA
Pyruvic acid
loses a carbon
as CO2
Acetic acid
Acetic acid
attaches to
coenzyme A
Acetyl CoA
Pyruvic acid
Figure 6.9 The link between glycolysis and the citric acid cycle: the conversion of pyruvic acid to acetyl coA.
CO2
Coenzyme A
Laua Coronado Chap Bio 10
Figure 6.9

31. INPUT OUTPUT ATP Citric Acid Cycle Citric acid Acetic acid 2 CO2
ADP  P
ATP
Citric
Acid
Cycle
3 NAD
3 NADH
Figure 6.10 The citric acid cycle
FAD
FADH2
Acceptor
molecule
Laua Coronado Chap Bio 10
Figure 6.10

32. Stage 3: Electron Transport
Releases the energy your cells need to make the most of their ATP.
The molecules of the electron transport chain are built into the inner membranes of mitochondria.
The chain functions as a chemical machine that uses energy released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane.
These ions store potential energy.
Laua Coronado Chap Bio 10

33. Stage 3: Electron Transport
When the hydrogen ions flow back through the membrane, they release energy.
The hydrogen ions flow through ATP synthase.
ATP synthase:
Takes the energy from this flow
Synthesizes ATP
Laua Coronado Chap Bio 10

34. Electron transport chain
Space between
membranes H H H H H H H H
Electron
carrier H H H H H
Protein
complex
Inner
mitochondrial
membrane
FADH2
FAD
Figure 6.11 How electron transport drives ATP synthase machines
Electron
flow H 1 O2
 2 H
H2O 2
NADH
NAD
ADP  P
ATP H H H H H
Matrix
Electron transport chain
ATP synthase
Laua Coronado Chap Bio 10
Figure 6.11

35. ETC Inhibitor Cyanide is a deadly poison that:
Binds to one of the protein complexes in the electron transport chain
Prevents the passage of electrons to oxygen
Stops the production of ATP
Laua Coronado Chap Bio 10

36. The Versatility of Cellular Respiration
In addition to glucose, cellular respiration can “burn”:
Diverse types of carbohydrates
Fats
Proteins
Laua Coronado Chap Bio 10

37. Food Polysaccharides Fats Proteins Sugars Glycerol Fatty acids
Amino acids
Figure 6.12 Energy from food
Citric
Acid
Cycle
Acetyl
CoA
Glycolysis
Electron
Transport
ATP
Laua Coronado Chap Bio 10
Figure 6.12

38. Figure 6.13 Cytoplasm Mitochondrion 6 NADH 2 NADH 2 NADH 2 FADH2
Glycolysis 2
Acetyl
CoA 2
Pyruvic
acid
Citric
Acid
Cycle
Electron
Transport
Glucose
Maximum
per
glucose:
Figure 6.13 A summary of ATP yield during cellular respiration
Cellular respiration can generate up to 38 molecules of ATP per molecule of glucose. 2
ATP 2
ATP
About
34 ATP
About
38 ATP
by direct
synthesis
by direct
synthesis
by ATP
synthase
Laua Coronado Chap Bio 10
Figure 6.13

39. FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY
Some of your cells can actually work for short periods without oxygen.
Fermentation is the anaerobic (without oxygen) harvest of food energy.
After functioning anaerobically for about 15 seconds:
Muscle cells will begin to generate ATP by the process of fermentation
Fermentation relies on glycolysis to produce ATP.
Laua Coronado Chap Bio 10

40. Laua Coronado Chap Bio 10

41. FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY
Glycolysis:
Does not require oxygen
Produces two ATP molecules for each glucose broken down to pyruvic acid
Pyruvic acid, produced by glycolysis, is
Reduced by NADH, producing NAD+, which keeps glycolysis going.
In human muscle cells, lactic acid is a by-product.
Laua Coronado Chap Bio 10

42. Figure 6.14 INPUT OUTPUT 2 ADP 2 ATP  2 P Glycolysis 2 NAD 2 NAD
2 NADH
2 NADH
2 Pyruvic
acid
 2 H
Glucose
2 Lactic acid
Figure 6.14 Fermentation: Producing lactic acid
Laua Coronado Chap Bio 10
Figure 6.14

43. The Process of Science: Does Lactic Acid Buildup Cause Muscle Burn?
Observation: Muscles produce lactic acid under anaerobic conditions.
Question: Does the buildup of lactic acid cause muscle fatigue?
Hypothesis: The buildup of lactic acid would cause muscle activity to stop.
Experiment: Tested frog muscles under conditions when lactic acid could and could not diffuse away.
Laua Coronado Chap Bio 10

44. diffusion of lactic acid; diffusion of lactic acid
Battery
Battery
Force
measured
Force
measured
Frog muscle
stimulated by
electric current
Figure 6.15 A.V. Hill's apparatus for measuring muscle fatigue
Solution allows
diffusion of lactic acid;
muscle can work for
twice as long
Solution prevents
diffusion of lactic acid
Laua Coronado Chap Bio 10
Figure 6.15

45. The Process of Science: Does Lactic Acid Buildup Cause Muscle Burn?
Results: When lactic acid could diffuse away, performance improved greatly.
Conclusion: Lactic acid accumulation is the primary cause of failure in muscle tissue.
However, recent evidence suggests that the role of lactic acid in muscle function remains unclear.
Laua Coronado Chap Bio 10

46. Fermentation in Microorganisms
Fermentation alone is able to sustain many types of microorganisms.
The lactic acid produced by microbes using fermentation is used to produce:
Cheese, sour cream, and yogurt dairy products
Soy sauce, pickles, olives
Sausage meat products
Laua Coronado Chap Bio 10

47. Fermentation in Microorganisms
Yeast are a type of microscopic fungus that:
Use a different type of fermentation
Produce CO2 and ethyl alcohol instead of lactic acid
This type of fermentation, called alcoholic fermentation, is used to produce:
Beer
Wine
Breads
Laua Coronado Chap Bio 10

48. INPUT OUTPUT 2 ADP 2 ATP  2 P 2 CO2 released Glycolysis 2 NAD 2 NAD
2 NADH
2 NADH
2 Pyruvic
acid
 2 H
Glucose
2 Ethyl alcohol
Figure 6.16a Fermentation: Producing ethyl alcohol
Laua Coronado Chap Bio 10
Figure 6.16a

49. Evolution Connection: Life before and after Oxygen
Glycolysis could be used by ancient bacteria to make ATP when little oxygen was available, and before organelles evolved.
Today, glycolysis:
Occurs in almost all organisms
Is a metabolic heirloom of the first stage in the breakdown of organic molecules
Laua Coronado Chap Bio 10

50. Figure 6.17 Earth’s atmosphere O2 present in 2.1
Earth’s atmosphere
O2 present in
2.1
First eukaryotic organisms
2.2
Atmospheric oxygen reaches 10% of modern levels
2.7
Atmospheric oxygen
first appears
Billions of years ago
3.5
Oldest prokaryotic
fossils
4.5
Origin of Earth
Figure 6.17 A time line of oxygen and life on Earth
Laua Coronado Chap Bio 10
Figure 6.17

51. C6H12O6 Sunlight O2 Cellular respiration CO2 H2O
Heat
C6H12O6
Sunlight O2
ATP
Cellular
respiration
Photosynthesis
Figure 6.UN6 Summary: Chemical cycling
CO2
H2O
Laua Coronado Chap Bio 10
Figure 6.UN06

52. C6H12O6  6 O2 6 CO2  6 H2O  Approx. 38 ATP
Figure 6.UN7 Summary: Overall equation for cellular respiration
Laua Coronado Chap Bio 10
Figure 6.UN07

53. Glucose loses electrons (and hydrogens)
Oxidation
Glucose loses electrons
(and hydrogens)
C6H12O6
CO2
Electrons
(and hydrogens)
ATP O2
H2O
Figure 6.UN8 Summary: Role of oxygen in cellular respiration
Reduction
Oxygen gains
electrons (and
hydrogens)
Laua Coronado Chap Bio 10
Figure 6.UN08

54. Figure 6.UN09 Mitochondrion O2 6 NADH 2 NADH 2 NADH 2 FADH2 Glycolysis
Acetyl
CoA
Citric
Acid
Cycle 2
Pyruvic
acid
Electron
Transport
Glucose 2
CO2 4
CO2
H2O
Figure 6.UN9 Summary: Metabolic pathway of cellular respiration
About
34 ATP 2
ATP
by direct
synthesis
by direct
synthesis 2
ATP
by ATP
synthase
About
38 ATP
Laua Coronado Chap Bio 10
Figure 6.UN09