1. Cellular Respiration: Harvesting Chemical Energy

2. Bacteria are used to produce yogurt, sour cream, pepperoni, and cheese
Both carbon monoxide and cyanide kill by disrupting cellular respiration

3. All the energy in all the food you eat can be traced back to sunlight
If you exercise too hard, your muscles shut down from a lack of oxygen

4. BIOLOGY AND SOCIETY: FEELING THE “BURN”
When you exercise
Muscles need energy in order to perform work
Your cells use oxygen to release energy from the sugar glucose

5. Aerobic metabolism Anaerobic metabolism
When enough oxygen reaches cells to support energy needs
Anaerobic metabolism
When the demand for oxygen outstrips the body’s ability to deliver it

6. Anaerobic metabolism
Without enough oxygen, muscle cells break down glucose to produce lactic acid
Lactic acid is associated with the “burn” associated with heavy exercise
If too much lactic acid builds up, your muscles give out

7. Physical conditioning allows your body to adapt to increased activity
The body can increase its ability to deliver oxygen to muscles
Long-distance runners wait until the final sprint to exceed their aerobic capacity
Figure 6.1

8. ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE
Fuel molecules in food represent solar energy
Energy stored in food can be traced back to the sun
Animals depend on plants to convert solar energy to chemical energy
This chemical energy is in the form of sugars and other organic molecules

9. Producers and Consumers
Photosynthesis
Light energy from the sun powers a chemical process that makes organic molecules
This process occurs in the leaves of terrestrial plants

10. Autotrophs Heterotrophs “Self-feeders”
Plants and other organisms that make all their own organic matter from inorganic nutrients
Heterotrophs
“Other-feeders”
Humans and other animals that cannot make organic molecules from inorganic ones

11. Producers
Biologists refer to plants and other autotrophs as the producers in an ecosystem
Consumers
Heterotrophs are consumers, because they eat plants or other animals
Figure 6.2

12. 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 rearrange the atoms of these ingredients to produce sugars (glucose) and other organic molecules
Oxygen gas is a by-product of photosynthesis

13. Both plants and animals perform cellular respiration
Cellular respiration is a chemical process that harvests energy from organic molecules
Cellular respiration occurs in mitochondria
The waste products of cellular respiration, CO2 and H2O, are used in photosynthesis

14. Sunlight
energy
Ecosystem
Photosynthesis
(in chloroplasts)
Glucose
Carbon dioxide
Oxygen
Water
Cellular respiration
(in mitochondria)
for cellular work
Heat energy
Figure 6.3

15. CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY
The main way that chemical energy is harvested from food and converted to ATP
This is an aerobic process—it requires oxygen

16. The Relationship Between Cellular Respiration and Breathing
Cellular respiration and breathing are closely related
Cellular respiration requires a cell to exchange gases with its surroundings
Breathing exchanges these gases between the blood and outside air

17. Breathing Lungs Muscle cells Cellular respiration
Figure 6.4

18. The Overall Equation for Cellular Respiration
A common fuel molecule for cellular respiration is glucose
This is the overall equation for what happens to glucose during cellular respiration
Glucose
Oxygen
Carbon
dioxide
Water
Energy
Unnumbered Figure 6.1

19. The Role of Oxygen in Cellular Respiration
During cellular respiration, hydrogen and its bonding electrons change partners
Hydrogen and its electrons go from sugar to oxygen, forming water

20. Redox Reactions
Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions
Redox reactions for short

21. The loss of electrons during a redox reaction is called oxidation
The acceptance of electrons during a redox reaction is called reduction

22. [Glucose loses electrons (and hydrogens)]
Oxidation
[Glucose loses electrons (and hydrogens)]
Glucose
Oxygen
Carbon
dioxide
Water
Reduction
[Oxygen gains electrons (and hydrogens)]
Unnumbered Figure 6.2

23. RS IS NECESSARY IN ALL LIVING CELLS.
PLANTS ARE WELL KNOWN FOR PS, BUT THEY MUST ALSO REPIRE IN ORDER TO SURVIVE.
PS - OCCURS ONLY IN PLANT CELLS CONTAINING CHLOROPHYLL DURING THE DAYLIGHT HOURS.
RS - OCCURS IN ALL OF A PLANT’S LIVING CELLS

24. PLANTS NEED ENERGY TO PERFORM MANY ESSENTIAL FUNCTIONS OF LIFE:
WHY IS RS NECESSARY?
PLANTS NEED ENERGY TO PERFORM MANY ESSENTIAL FUNCTIONS OF LIFE:
GROWTH,
REPAIR,
NUTRIENT MOVEMENT,
REPRODUCTION, &
NUTRIENT TRANSPORT.

25. The *Metabolic Pathway of Cellular Respiration
Cellular respiration is an example of a metabolic pathway
A series of chemical reactions in cells –building or degradation process
All of the reactions involved in cellular respiration can be grouped into three main stages
Glycolysis
The Krebs cycle
Electron transport
* WHAT IS METABOLISM?

26. A Road Map for Cellular Respiration
Cytosol
Mitochondrion
High-energy
electrons
carried
by NADH
High-energy
electrons carried
mainly by
NADH
Glycolysis 2
Pyruvic
acid
Krebs
Cycle
Electron
Transport
Glucose
Figure 6.7

27. Glycolysis

28. Evolutionarily more advanced
Cellular Respiration
Evolutionarily more advanced
Requires oxygen provided from photosynthesis
Occurs as a second step AFTER glycolysis
Much more efficient - more ATPs produced per molecule of glucose
GLYCOLYSIS occurs alone or can be followed by CELLULAR REPIRATION, but cellular respiration cannot occur unless glycolysis happens first!

29. Glycolysis Occurs in the cytoplasm
Anaerobic, not really a part of respiration
Glucose molecule  2 pyruvic acid molecules
2 ATP used up, 4 ATP formed (net gain 2 ATP)
2 NADH formed
Pyruvic acid and NADH enter mitochondria

30. In animal cells this byproduct is LACTIC ACID.
What happens next???
If glycolysis ONLY occurs (no oxygen available), then pyruvate rapidly breaks down into byproducts:
In animal cells this byproduct is LACTIC ACID.
This is known as lactic acid fermentation.
In plant cells this byproduct is ETHANOL and CO2
This is known as alcoholic fermentation.
If oxygen IS available, then cellular respiration can occur.

32. Preparation for cellular respiration
NADH and pyruvic acid enter the mitochondria
(Coenzyme A)
pyruvic acid (3 carbons)  acetyl CoA (2 carbons) + CO2
©©©  ©© ©
Coenzyme A is required for this step!
And you have to have oxygen in this step too!
1 NADH is formed for every pyruvate conversion.

33. Krebs Cycle

34. Stage 2: The Krebs Cycle
The Krebs cycle completes the breakdown of sugar

35. In the Krebs cycle, pyruvic acid from glycolysis is first “prepped” into a usable form, Acetyl-CoA2 1
Acetic
acid 3
Pyruvic
acid
Acetyl-CoA
(acetyl-coenzyme A)
CO2
Coenzyme A
Figure 6.10

36. The Krebs cycle extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2
The cycle uses some of this energy to make ATP
The cycle also forms NADH and FADH2

37. Krebs Cycle Input Output Acetic acid 2 CO2 ADP 3 NAD FAD 2 1 3 4 5 6
Figure 6.11

38. Electron Transport

39. Stage 3: Electron Transport
Electron transport releases the energy your cells need to make the most of their ATP

40. The molecules of electron transport chains 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

41. Electron transport chain
Protein
complex
Electron
carrier
Inner
mitochondrial
membrane
Electron
flow
Electron transport chain
ATP synthase
Figure 6.12

42. The Versatility of Cellular Respiration
Cellular respiration can “burn” other kinds of molecules besides glucose
Diverse types of carbohydrates
Fats
Proteins

43. Food Polysaccharides Fats Proteins Sugars Glycerol Fatty acids
Amino acids
Amino groups
Acetyl-
CoA
Krebs
Cycle
Glycolysis
Electron
Transport
Figure 6.13

44. Adding Up the ATP from Cellular Respiration
Cytosol
Mitochondrion
Glycolysis 2
Acetyl-
CoA 2
Pyruvic
acid
Krebs
Cycle
Electron
Transport
Glucose
Maximum
per
glucose: by
direct
synthesis by
ATP
synthase
by direct
synthesis
Figure 6.14

45. FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY
Some of your cells can actually work for short periods without oxygen
For example, muscle cells can produce ATP under anaerobic conditions
Fermentation
The anaerobic harvest of food energy

46. Fermentation in Human Muscle Cells
Human muscle cells can make ATP with and without oxygen
They have enough ATP to support activities such as quick sprinting for about 5 seconds
A secondary supply of energy (creatine phosphate) can keep muscle cells going for another 10 seconds
To keep running, your muscles must generate ATP by the anaerobic process of fermentation

47. Glycolysis is the metabolic pathway that provides ATP during fermentation
Pyruvic acid is reduced by NADH, producing NAD+, which keeps glycolysis going
In human muscle cells, lactic acid is a by-product

48. (a) Lactic acid fermentation
2 ADP+ 2
Glycolysis
2 NAD
2 NAD
Glucose
2 Pyruvic
acid
+ 2 H
2 Lactic
acid
(a) Lactic acid fermentation
Figure 6.15a

49. Fermentation in Microorganisms
Various types of microorganisms perform fermentation
Yeast cells carry out a slightly different type of fermentation pathway
This pathway produces CO2 and ethyl alcohol

50. (b) Alcoholic fermentation
2 ADP+ 2
2 CO2 released
2 ATP
Glycolysis
2 NAD
2 NAD
Glucose
2 Ethyl
alcohol
2 Pyruvic
acid
+ 2 H
(b) Alcoholic fermentation
Figure 6.15b

51. The food industry uses yeast to produce various food products
Figure 6.16

52. EVOLUTION CONNECTION: LIFE ON AN ANAEROBIC EARTH
Ancient bacteria probably used glycolysis to make ATP long before oxygen was present in Earth’s atmosphere
Glycolysis is a metabolic heirloom from the earliest cells that continues to function today in the harvest of food energy

53. SUMMARY OF KEY CONCEPTS
Chemical Cycling Between Photosynthesis and Cellular Respiration
Heat
Sunlight
Cellular
respiration
Photosynthesis
Visual Summary 6.1

54. The Overall Equation for Cellular Respiration
Oxidation:
Glucose loses electrons
(and hydrogens)
Glucose
Carbon dioxide
Electrons
(and hydrogens)
Energy
Reduction:
Oxygen gains
electrons (and
hydrogens)
Oxygen
Visual Summary 6.2

55. The Metabolic Pathway of Cellular Respiration
Glucose
Oxygen
Water
Energy
Visual Summary 6.3