1. Chapter
Energy and Life

2. Energy makes the world go ‘round
Defined: the ability to do work, cause change or produce heat
Machines, cars, appliances and technology need energy to run
Living things, and their cells, need to obtain and use energy

3. The big picture
Autotrophs: make their own food using the sun’s energy in photosynthesis
Heterotrophs: obtain energy from the foods they consume
Root Words for Ch 8:
auto- = self
-troph = food
chloro- = green
-phyll = leaf (chlorophyll: photosynthetic pigment in chloroplasts) 
electro- = electricity
magnet- = magnetic (electromagnetic spectrum: all forms of radiation)
hetero- = other
meso- = middle (mesophyll: the middle layer of tissue inside a leaf) 
photo- = light (photosystem: cluster of pigment molecules) 

4. THE COMBUSTION REACTION: “FUELS” + O2 ⟶ CO2 + H2O + energy
The big picture
When organisms (organic, carbon-based compounds) decompose over many years they form fossil fuels deep in the earth.
When fossil fuels are “burned” in COMBUSTION REACTIONS the stored energy is released and used to run our machines:
THE COMBUSTION REACTION:
“FUELS” + O2 ⟶ CO H2O + energy
All of our “fuels” began with photosynthesis!

5. Photosynthesis and Respiration: Complementary Processes that drive the carbon cycle
Plants produce energy-rich carbohydrate molecules in photosynthesis using H2O, the carbon in CO2 and energy from the sun:
6 CO H2O + energy from sun ⟶ C6H12O O2
THINK OF ARROW AS “EQUALS”
LEFT SIDE = REACTANTS
RIGHT SIDE = PRODUCTS

6. Photosynthesis and Respiration: Complementary Processes that drive the carbon cycle
6 CO H2O + energy from sun ⟶ C6H12O O2
This energy has to go somewhere!
Where does this energy go???
After this reaction, the energy is stored in the glucose molecule

7. C6H12O6 + 6 O2 ⟶ 6 CO2 + 6 H2O + energy to live
Photosynthesis and Respiration: Complementary Processes that drive the carbon cycle
Living things use energy stored in the chemical bonds of carbohydrates in cellular respiration:
C6H12O O2 ⟶ 6 CO H2O + energy to live
The glucose molecule is our chemical fuel.
Respiration is a kind of combustion reaction.
Cellular respiration and photosynthesis are direct opposite reactions. 

8. Chemical Potential Energy and ATP
All organisms must release the energy stored in the bonds in sugars and other chemical compounds = our chemical fuel
ATP: Adenosine Triphosphate
one of the principal chemical compounds that cells use to store and release energy

9. ATP is like a fully charged battery ready to power the cell.
CONSISTS OF A NITROGENOUS BASE ADENINE, A SUGAR CALLED RIBOSE AND 3 PHOSPHATE GROUPS
THE KEY TO ATP’s ABILITY TO STORE AND RELEASE ENERGY ARE THE 3 PHOSPHATE GROUPS

10. Chemical Energy and ATP
Releasing Energy
Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates: ATP ⟶ ADP + P + ENERGY
2 Phosphate groups P
ADP = ADENOSINE DIPHOSPHATE

11. Chemical Energy and ATP
Storing Energy
ADP has two phosphate groups instead of three.
A cell can store small amounts of energy by adding a phosphate group to ADP.
ATP
ADP
Energy +
Energy
Adenosine Triphosphate (ATP)
Adenosine Diphosphate (ADP) + Phosphate
Partially charged battery
Fully charged battery

12. How cells use ATP
The energy from ATP is needed for many cellular activities including:
ACTIVE TRANSPORT across cell membranes
PROTEIN SYNTHESIS on the ribosomes
MUSCLE CONTRACTION in specialized muscle cells and tissues
Most cells have only a small amount of ATP because it is not a good way to STORE large amounts of energy
Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose:
ADP + P ⟶ATP

13. Van Helmont’s Experiment
8-2 Discovering Photosynthesis
Van Helmont massed the soil and the plant over five years.
The plant grew but the soil mass stayed the same.
He assumed the added mass came from the water he added.

14. Priestley’s Experiment
8-2 Discovering Photosynthesis
A burning candle which is covered with a glass jar will stop burning.
If a green plant is placed in the jar the candle will burn.
The plant produced the O2 needed to burn the candle.
Jan Ingenhousz showed that Priestley’s experiment only worked if LIGHT was present.

15. 6 CO2 + 6 H2O + energy from sun ⟶ C6H12O6 + 6 O2
Discovering Photosynthesis – The key cellular process identified with energy production
The experiments performed by van Helmont, Priestley, Ingenhousz and other scientists led to the discovery that….
In the presence of light, plants transform low-energy molecules of carbon dioxide and water into energy-rich molecules of carbohydrates and they also release oxygen gas.
6 CO H2O + energy from sun ⟶ C6H12O O2
carbon dioxide + water LIGHT sugars + oxygen

16. Light and Pigments
In addition to CO2 and H2O, photosynthesis requires light energy from the sun AND light –absorbing molecules called pigments.
The principal pigment in plants is chlorophyll.
Chlorophyll a – absorbs light mostly in the blue-violet and violet regions at either end of the visible spectrum
Chlorophyll b – absorbs light mostly in the blue and red regions of the visible spectrum

17. Electromagnetic Spectrum

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Light and Pigments
Chlorophyll absorbs light well in the blue-violet and red regions of the visible spectrum.
100 80 60 40 20
Chlorophyll b
Estimated Absorption (%)
Chlorophyll a
Photosynthesis requires light and chlorophyll. In the graph above, notice how chlorophyll a absorbs light mostly in the blue-violet and red regions of the visible spectrum, whereas chlorophyll b absorbs light in the blue and red regions of the visible spectrum.
Wavelength (nm)
Wavelength (nm)
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Light and Pigments
Chlorophyll does not absorb light well in the green region of the spectrum. Green light is reflected by leaves, which is why plants look green.
100 80 60 40 20
Chlorophyll b
Estimated Absorption (%)
Chlorophyll a
Photosynthesis requires light and chlorophyll. In the graph above, notice how chlorophyll a absorbs light mostly in the blue-violet and red regions of the visible spectrum, whereas chlorophyll b absorbs light in the blue and red regions of the visible spectrum.
Wavelength (nm)
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20. 8-3 The Reactions of Photosynthesis
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8-3 The Reactions of Photosynthesis
Photo Credit: ©Stone

21. 8-3 The Reactions of Photosynthesis Chloroplasts
Thykaloids: saclike photosynthetic membranes inside chloroplasts
Granum: a stack of thylakoids
Stroma: the region outside the thylakoid membranes

22. CHLOROPLASTS: where photosynthesis occurs
Inside a Chloroplast
CHLOROPLASTS: where photosynthesis occurs
Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, the light-collecting units of the chloroplast.
THYLAKOIDS: arranged in stacks called granum
STROMA: outside of thylakoids but inside chloroplast
Photosystems
Chloroplast
Saclike membranes of thylakoids

23. Light- dependent reactions
Inside a Chloroplast
Light & H2O enter the light-dependent reactions forming ATP + NADPH + O2
ATP + NADPH + CO2 enter Calvin Cycle forming sugars = light-ind. reactions
H2O
CO2
Light
NADP+
ADP + P
Light- dependent reactions
Calvin Cycle
Calvin cycle
The process of photosynthesis includes the light-dependent reactions as well as the Calvin cycle.
Chloroplast O2
Sugars

24. The Reactions of Photosynthesis include:
The light-dependent reactions – take place within the thylakoid membranes of the chloroplast.
The light-dependent reactions use energy from sunlight and H2O to produce ATP, NADPH, and O2.
The light-independent reactions – THE CALVIN CYCLE – take place in the stroma of the chloroplast
The Calvin cycle uses CO2 and ATP and NADPH from the light-dependent reactions to produce high-energy sugars.

25. Photosynthesis: the light cycle happens in the chloroplasts, the dark cycle happens in the stroma

26. Trapping & Storing the Sun’s Energy
The Sun’s energy is absorbed by e- in chlorophyll
Cells use electron carriers to transport these excited e- to other molecules
One carrier molecule is NADP+.
NADP+ accepts and holds 2 high-energy e- along with a hydrogen ion (H+). This converts the NADP+ into NADPH.
The conversion of NADP+ into NADPH is one way the energy of sunlight can be trapped in chemical form.
The NADPH carries high-energy e- to chemical reactions elsewhere in the cell.
These high-energy e- are used to help build energy-rich molecules cells need, including carbohydrates like glucose, from low-energy compounds.

27. Light-Dependent Reactions
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Light-Dependent Reactions
1. Photosynthesis begins when chlorophyll pigments in photosystem II absorb light, exciting the electrons.
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.

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2. Excited e- are passed along the electron transport chain.
Photosystem II
Electron carriers
High-energy electron

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3. Enzymes on the thylakoid membrane break two water molecules into: O2, 4 H+ and 2 excited e-.
Photosystem II
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
Electron carriers
High-energy electron

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4. The energized e- from water replace the e- 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

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5. O2 is left behind & 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

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6. H+ 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

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7. Energy from the e- 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.

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8. High-energy e- move through the electron transport chain from PS II to PS I.
Photosystem II
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
Photosystem I

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Pigments in PS I use light energy to re-energize the e-
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
Photosystem I

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10. NADP+ picks up the e- & 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

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11. As e- pass from chlorophyll to NADP+, more H+ are pumped across the membrane.
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH

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12. Inside the membrane fills with H+. Outside the membrane becomes negative.
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH

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13. The charge difference provides 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

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14. 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

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15. The protein ATP synthase in the membrane allows H+ ions to pass through.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH

42. 16. The protein rotates as H+ ions pass through.
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16. The protein rotates as H+ ions pass through.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
2 NADP+ 2 2
NADPH

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17. ATP synthase binds ADP and a phosphate group to produce ATP.
ATP synthase
+ O2
2H2O
The light-dependent reactions use energy from sunlight to produce ATP, NADPH, and oxygen.
ADP
2 NADP+ 2 2
NADPH

44. Light-Dependent Reactions
The light-dependent electron transport system produces 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

45. The Light Dependent Reactions-Summary
The light-dependent reactions use water, ADP, and NADP+.
The light-dependent reactions produce oxygen, ATP, and NADPH.
These compounds provide the energy to build energy-containing sugars from low-energy compounds.

46. The Calvin Cycle - Summary
ATP and NADPH formed by the light-dependent reactions contain an abundance of chemical energy, but are not stable enough to store that energy for more than a few minutes.
During the Calvin cycle plants use the energy in ATP and NADPH to build high-energy compounds that can be stored for a long time.
The Calvin cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars.
Because the Calvin cycle does not require light, these reactions are also called the light-independent reactions.

47. The Calvin Cycle
Six CO2 molecules enter the cycle 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.

48. The Calvin Cycle
The result is twelve 3-carbon molecules, which are then converted into higher-energy forms.
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.

49. The Calvin Cycle
The energy for this conversion comes from ATP and high-energy electrons from NADPH.
Energy Input 12
12 ADP 12
NADPH
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.
12 NADP+

50. Two of twelve 3-carbon molecules are removed from the cycle.
The Calvin Cycle
Two of twelve 3-carbon molecules are removed from the cycle.
Energy Input 12
12 ADP 12
NADPH
The Calvin cycle uses ATP and NADPH to produce high-energy sugars.
12 NADP+

51. The Calvin Cycle
The molecules are used to produce sugars, lipids, amino acids and other compounds. 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
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52. The Calvin Cycle
The 10 remaining 3-carbon molecules are converted back into six 5-carbon molecules, which are used to begin the next 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
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53. The two sets of photosynthetic reactions work together
The light-dependent reactions trap sunlight energy in chemical form.
The light-independent reactions use that chemical energy to produce stable, high-energy sugars from carbon dioxide and water.
Our atmosphere gets Oxygen Gas!

54. Factors Affecting Rate of Photosynthesis
A shortage of water will slow or stop photosynthesis.
Photosynthesis depends on enzymes that only work between 0°C and 35°C.
As light intensity increases the rate of photosynthesis increases up to a certain level; at this point the plant reaches its maximum rate.

55. ADP: Adenosine Diphosphate
SAME AS ATP EXCEPT IT HAS 2 PHOSPHATE GROUPS
When the bond between the 2nd & 3rd phosphate group in ATP is broken, energy is released. OR
A cell can store small amounts of energy by adding a phosphate group to ADP:
ADP + P ⟶ ATP

56. The Light Dependent Reactions
Photosynthesis begins when chlorophyll pigments in photosystem II absorb light, exciting the electrons (e-)
Excited e- are passed along the electron transport chain (ETC)
Enzymes on the thylakoid membrane break 2 H2O molecules into 4 H+, O2, and 2 energized e-
The 2 e- from water replace the e- that chlorophyll lost to the ETC
O2 is released to the air
H+ are released inside the thylakoid membrane

57. The Light Dependent Reactions
High energy e- move through the ETC to photosystem I.
Energy from the e- is used to transport H+ ions from the stroma into the inner thylakoid space.
Pigments in photosystem I use light energy to re-energize the e-
NADP+ picks up these high-energy e-, along with H+, and becomes NADPH.

58. The Light Dependent Reactions
As e- are passed from chlorophyll to NADP+, more H+ are pumped across the membrane.
Inside of membrane fills with H+, outside of membrane beomes negatively charged.
Charge difference across membrane provides energy to make ATP.
H+ cannot cross the membrane directly.
The cell membrane contains a protein called ATP synthase that allows H+ to pass through it.
As H+ pass through ATP synthase, the protein rotates.
As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP.