1. Chapter 4
Cells and Energy

2. Background: Autotrophs and Heterotrophs
Energy
Living things need energy to survive
What is the source of this energy?

3. Background: Autotrophs and Heterotrophs
Energy
Plants and some other types of organisms (i.e, some bacteria, algae, etc.) are able to use light energy from the sun to produce food.
Autotrophs
Produce their own food using the sun’s energy
AKA: producers!
Heterotrophs
Cannot make their own food/have to obtain the energy they need from the food they consume
AKA: consumers!
Feeding, decomposition

4. Background: Autotrophs and Heterotrophs

5. Section 4.1 Chemical Energy and ATP
Forms of Energy
Light, heat, electrical…
Also stored in chemical bonds in the molecules of the food we eat
Starch molecule
Glucose molecule

6. Section 4.1 Chemical Energy and ATP
Adenosine Triphosphate (ATP)
A molecule used to store and release energy in living beings
Energy from the breakdown of food molecules is used to carry out cell functions.

7. Section 4.1 Chemical Energy and ATP
Why do we need ATP to provide energy?
This energy is needed for many cellular activities, including active transport, protein synthesis, and muscle contraction.
Where does the energy come from?
Energy is released for the cell to use when a bond between two phosphate groups is broken.
Energy is stored in the cell to use at a later time when a phosphate bond is created.

8. Section 4.1 Chemical Energy and ATP
ATP v. ADP
phosphate removed

9. Section 4.1 Chemical Energy and ATP
ATP v. ADP

10. Section 4.1 Chemical Energy and ATP
ATP vs. ADP
ATP: 3 phosphate groups
ADP: 2 phosphate groups
Why is this important?
The more bonds to break…the more energy this molecule has to release!
Storing ATP
While ATP is a great molecule for transferring energy, it is not very good for storing large amounts of energy over a long period of time.
Therefore, cells regenerate ATP from ADP as needed by using the energy in foods like glucose!

11. Section 4.1 Chemical Energy and ATP
Carbohydrates are the molecules most commonly broken down to make ATP.
not stored in large amounts
up to 36 ATP from one glucose molecule
triphosphate
adenosine
diphosphate
tri=3
di=2

12. Section 4.1 Chemical Energy and ATP
Fats store the most energy.
80 percent of the energy in your body
about 146 ATP from a triglyceride
Proteins are least likely to be broken down to make ATP.
amino acids not usually needed for energy
about the same amount of energy as a carbohydrate

13. Section 4.1 Chemical Energy and ATP
A few types of organisms do not need sunlight and photosynthesis as a source of energy.
Some organisms live in places that never get sunlight.
In chemosynthesis, chemical energy is used to build carbon-based molecules.
similar to photosynthesis
uses chemical energy instead of light energy

14. Section 4.1 Chemical Energy and ATP
REVIEW
Organisms that make their own food are called
autotrophs.
heterotrophs.
decomposers.
consumers.

15. Section 4.1 Chemical Energy and ATP
REVIEW
Most autotrophs obtain their energy from
chemicals in the environment.
sunlight.
carbon dioxide in the air.
other producers

16. Section 4.1 Chemical Energy and ATP
REVIEW
How is energy released from ATP?
A phosphate is added.
An adenine is added.
A phosphate is removed.
A ribose is removed.

17. Section 4.1 Chemical Energy and ATP
REVIEW
How is it possible for most cells to function with only a small amount of ATP?
Cells do not require ATP for energy.
ATP can be quickly regenerated from ADP and P.
Cells use very small amounts of energy.
ATP stores large amounts of energy.

18. Section 4.1 Chemical Energy and ATP
REVIEW
Compared to the energy stored in a molecule of glucose, ATP stores
much more energy.
much less energy.
about the same amount of energy.
more energy sometimes and less at others.

19. Section 4.2: Overview of Photosynthesis
Photosynthesis: the process in which green plants use the energy of sunlight to convert water and carbon dioxide into high-energy carbohydrates and oxygen

20. Section 4.2: Overview of Photosynthesis
Van Helmont (mid 1600’s)
Question:
Do plants grow by taking material out of the soil?
Experiment:
Measured mass of a pot of dry soil and a seedling, planted the seedling, and watered it regularly.
After five years, the seedling was a small tree and had gained 75 kg, but the soil’s mass was almost unchanged.
Conclusion:
The gain in mass came from water because water was the only thing he had added.
This accounts for the “hydrate,” or water, portion of the carbohydrate produced by photosynthesis.
Follow Up Question:
Where does the carbon of the “carbo-” portion come from?

21. Section 4.2: Overview of Photosynthesis
Van Helmont (mid 1600’s)

22. Section 4.2: Overview of Photosynthesis
Van Helmont (mid 1600’s)
Although van Helmont did not realize it, CO2 made a major contribution to the mass of his tree.
In photosynthesis, the carbon in CO2 is used to make sugars and other carbohydrates.

23. Section 4.2: Overview of Photosynthesis
Priestley (late 1700’s)
Experiment:
Took a candle, placed a glass jar over it, and watched as the flame gradually died out
Conclusion:
The flame needed something in the air to keep burning and when it was used up, the flame died.
That substance was oxygen.
Follow-Up Experiment:
Placed a live sprig of mint under the jar and for a few days
Discovered the candle could be relit and would remain lighted for a while
The mint plant had produced the substance required for burning.
In other words, it had released oxygen.

24. Section 4.2: Overview of Photosynthesis
Priestley (late 1700’s)

25. Section 4.2: Overview of Photosynthesis
Ingenhousz (late 1700’s)
Showed that the effect observed by Priestley occurred only when the plant was exposed to light.
The results of both Priestley’s and Ingenhousz’s experiments showed that light is necessary for plants to produce oxygen.

26. Section 4.2: Overview of Photosynthesis
The equation for photosynthesis is:
6CO2 + 6H2O C6H12O6 + 6O2
carbon dioxide + water sugars + oxygen
Light
Light

27. Section 4.2: Overview of Photosynthesis

28. Section 4.2: Overview of Photosynthesis
How do plants capture the energy of sunlight?
In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll.
Pigments
Molecules that plants use to gather the sun’s energy
Primary Pigment in plants: chlorophyll
chlorophyll a
chlorophyll b

29. Section 4.2: Overview of Photosynthesis
Pigments
Chlorophyll does not absorb light well in the green region of the spectrum; therefore, green light is reflected

30. Section 4.2: Overview of Photosynthesis
chloroplast
leaf cell
leaf
Chlorophyll is a molecule that absorbs light energy.
In plants, chlorophyll is found in organelles called chloroplasts.

31. Section 4.2: Overview of Photosynthesis
Photosynthesis takes place in two parts of chloroplasts.
grana (thylakoids)
stroma
chloroplast
stroma
grana (thylakoids)

32. Section 4.2: Overview of Photosynthesis
The light-dependent reactions capture energy from sunlight.
take place in thylakoids
water and sunlight are needed
chlorophyll absorbs energy
energy is transferred along thylakoid membrane to
light-independent
reactions
oxygen is released

33. Section 4.2: Overview of Photosynthesis
The light-independent reactions make sugars.
take place in stroma
needs carbon dioxide from atmosphere
use energy to build a sugar in a cycle of chemical reactions

34. Section 4.2: Overview of Photosynthesis
Again, HOW do plants capture the energy of sunlight?
Light is a form of energy, so any compound that absorbs light also absorbs the energy from that light!
When chlorophyll absorbs light, much of the energy is transferred directly to electrons in the chlorophyll molecule, raising the energy levels of these electrons.
These high-energy electrons are what make photosynthesis “go.”

35. Section 4.2: Overview of Photosynthesis
REVIEW
In van Helmont's experiment, most of the added mass of the tree came from
soil and carbon dioxide.
water and carbon dioxide.
oxygen and carbon dioxide.
soil and oxygen.

36. Section 4.2: Overview of Photosynthesis
REVIEW
The raw materials required for plants to carry out photosynthesis are
carbon dioxide and oxygen.
oxygen and sugars.
carbon dioxide and water.
oxygen and water.

37. Section 4.2: Overview of Photosynthesis
REVIEW
The principal pigment in plants is
chloroplast.
chlorophyll.
carotene.
carbohydrate.

38. Section 4.3: Photosynthesis in Detail

39. Section 4.3: Photosynthesis in Detail
Chloroplasts contain thylakoids—saclike photosynthetic membranes.
Thylakoids are arranged in stacks known as grana. A singular stack is called a granum.
Single
thylakoid
Granum
Chloroplast

40. Section 4.3: Photosynthesis in Detail
Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, which are the light-collecting units of the chloroplast.
Photosystems
Chloroplast

41. Section 4.3: Photosynthesis in Detail
CO2
Light
NADP+
ADP + P
Light- dependent reactions
Calvin Cycle
Calvin cycle O2
Sugars

42. Section 4.3: Photosynthesis in Detail
High Energy Electrons Require a Carrier
When electrons in chlorophyll absorb sunlight, electrons gain a great deal of energy.
Cells use electron carriers to transport these high- energy electrons from chlorophyll to other molecules.
NADP+
Accepts and holds 2 high-energy electrons along with a hydrogen ion (H+).
This converts the NADP+ into NADPH.

43. Section 4.3: Photosynthesis in Detail (LDR)
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. The light-dependent reactions take place within the thylakoid membranes of chloroplasts.

44. Section 4.3: Photosynthesis in Detail (LDR)
Photosynthesis begins when the pigments in photosystem II absorb light, increasing their energy.
Photosystem II
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. The light-dependent reactions take place within the thylakoid membranes of chloroplasts.

45. Section 4.3: Photosynthesis in Detail (LDR)
These high-energy electrons are passed on to the electron transport chain (ETC).
Photosystem II
Electron carriers
High-energy electron

46. Section 4.3: Photosynthesis in Detail (LDR)
Enzymes on the thylakoid membrane break water molecules into:
Photosystem II
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
Electron carriers
High-energy electron

47. Section 4.3: Photosynthesis in Detail (LDR)
hydrogen ions
oxygen atoms
energized electrons
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
Electron carriers
High-energy electron

48. Section 4.3: Photosynthesis in Detail (LDR)
The energized electrons from water replace the high- energy electrons that chlorophyll lost to the ETC.
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
High-energy electron

49. Section 4.3: Photosynthesis in Detail (LDR)
As plants remove electrons from water, oxygen is left behind and is released into the air.
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen. The light-dependent reactions take place within the thylakoid membranes of chloroplasts.
High-energy electron

50. Section 4.3: Photosynthesis in Detail (LDR)
The hydrogen ions left behind when water is broken apart are released inside the thylakoid membrane.
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
High-energy electron

51. Section 4.3: Photosynthesis in Detail (LDR)
Energy from the electrons is used to transport H+ ions from the stroma into the inner thylakoid space.
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.

52. Section 4.3: Photosynthesis in Detail (LDR)
High-energy electrons move through the ETC from photosystem II to photosystem I.
Photosystem II o
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
Photosystem I

53. Section 4.3: Photosynthesis in Detail (LDR)
Pigments in photosystem I use energy from light to re-energize the electrons.
LDR
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
Photosystem I

54. Section 4.3: Photosynthesis in Detail (LDR)
NADP+ then picks up these high-energy electrons, along with H+ ions, and becomes NADPH.
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH

55. Section 4.3: Photosynthesis in Detail (LDR)
As electrons are passed from chlorophyll to NADP+, more H+ ions are pumped across the membrane.
LDR
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH

56. Section 4.3: Photosynthesis in Detail (LDR)
The inside of the membrane fills up with positively charged H+ ions, which makes the outside of the membrane negatively charged.
LDR
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH

57. Section 4.3: Photosynthesis in Detail (LDR)
The difference in charges provides the energy to make ATP.
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH

58. Section 4.3: Photosynthesis in Detail (LDR)
H+ ions cannot cross the membrane directly.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH

59. Section 4.3: Photosynthesis in Detail (LDR)
The cell membrane contains ATP synthase, which allows H+ ions to pass through it.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH

60. Section 4.3: Photosynthesis in Detail (LDR)
As H+ ions pass through ATP synthase, the protein rotates.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH

61. Section 4.3: Photosynthesis in Detail (LDR)
As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP.
ATP synthase
LDR
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
ADP
2 NADP+ 2 2
NADPH

62. Section 4.3: Photosynthesis in Detail (LDR)
Light-dependent electron transport produce not only high-energy electrons, but ATP as well.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
ADP
2 NADP+ 2 2
NADPH

63. Section 4.3: Photosynthesis in Detail

64. Section 4.3: Photosynthesis in Detail (LIR)
Better known as the CALVIN CYCLE
Uses ATP and NADPH from the LDR to produce high- energy sugars
Does NOT require light

65. Section 4.3: Photosynthesis in Detail (Calvin Cycle)
Six CO2 molecules enter from the atmosphere and combine with six 5- carbon molecules
CO2 Enters the Cycle
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.

66. Section 4.3: Photosynthesis in Detail (Calvin Cycle)
This creates twelve 3-C molecules, which are converted into higher-energy forms
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.

67. Section 4.3: Photosynthesis in Detail (Calvin Cycle)
The energy for this comes from ATP.
NADPH provides the high-energy electrons.
Energy Input 12
12 ADP 12
NADPH
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.
12 NADP+

68. Section 4.3: Photosynthesis in Detail (Calvin Cycle)
The Calvin Cycle
Section 4.3: Photosynthesis in Detail (Calvin Cycle)
Two of the twelve 3- C molecules are removed.
Energy Input 12
12 ADP 12
NADPH
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.
12 NADP+

69. Section 4.3: Photosynthesis in Detail (Calvin Cycle)
The Calvin Cycle
Section 4.3: Photosynthesis in Detail (Calvin Cycle)
They are used to produce sugars, lipids, amino acids, etc. 12
12 ADP 12
NADPH
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.
12 NADP+
6-Carbon sugar produced
Sugars and other compounds

70. Section 4.3: Photosynthesis in Detail (Calvin Cycle)
The Calvin Cycle
Section 4.3: Photosynthesis in Detail (Calvin Cycle)
Leftover 3-C molecules are converted back into 5-C molecules, to be used in the next turn of the cycle. 12
12 ADP
6 ADP 12
NADPH 6
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.
12 NADP+
5-Carbon Molecules Regenerated
Sugars and other compounds

71. Section 4.3: Photosynthesis in Detail

72. Section 4.3: Factors Affecting Photosynthesis
Water
Water shortage can slow or STOP P/S
Adaptations in Dry Climates
Waxy coating on leaves
Temperature
Enzymes for P/S function best between 0 ◦ C and 35◦C
Temps above or below this range can damage enzymes, slowing rate of P/S
Light Intensity
Increasing light intensity increases rate of P/S
There is a maximum light intensity that affects the rate of P/S though and after this point, it doesn’t change it

73. Section 4.3: Factors Affecting Photosynthesis

74. Section 4.3: Photosynthesis in Detail
REVIEW
In plants, photosynthesis takes place inside the
thylakoids.
chloroplasts.
photosystems.
chlorophyll.

75. Section 4.3: Photosynthesis in Detail
REVIEW
Energy to make ATP in the chloroplast comes most directly from
hydrogen ions flowing through an enzyme in the thylakoid membrane.
transfer of a phosphate from ADP.
electrons moving through the electron transport chain.
electrons transferred directly from NADPH.

76. Section 4.3: Photosynthesis in Detail
REVIEW
NADPH is produced in light-dependent reactions and carries energy in the form of
ATP.
high-energy electrons.
low-energy electrons.
ADP.

77. Section 4.3: Photosynthesis in Detail
REVIEW
What is another name for the Calvin cycle?
light-dependent reactions
light-independent reactions
electron transport chain
photosynthesis

78. Section 4.3: Photosynthesis in Detail
REVIEW
Which of the following factors does NOT directly affect photosynthesis?
wind
water supply
temperature
light intensity