1. CHAPTER 8 PHOTOSYNTHESIS
SECTION 8-1
ENERGY and LIFE

2. AUTOTROPHS AND HETEROTROPHS
What is the key source of energy for most things?
THE SUN
Plants and other organisms such as blue-green algae use light energy from the sun to produce food.
These organisms are called AUTOTROPHS.
Use simple inorganic molecules to do this.

3. AUTOTROPHS and HETEROTROPHS
Heterotrophs are organisms that obtain energy from the food they consume.
Unable to use sunlight directly.
ALL organisms must release energy in sugars and other compounds.

4. CHEMICAL ENERGY and ATP
What are three forms of energy?
Light, heat, and electricity
Energy can be stored in compounds.
Electrons release energy when a piece of wood is set on fire.
When chemical bonds are broken and electrons shift from higher energy levels to lower energy levels, the extra energy is released as light and heat.

5. CHEMICAL ENERGY and ATP
How do organisms such as humans store and release energy?
Chemical compounds are used to do this.
What is ATP?
Adenosine Triphosphate (ENERGY storing molecule)
ATP consists of ADENOSINE, a 5-CARBON SUGAR, and
3 PHOSPHATE GROUPS

6. What is ATP?

7. RELEASING ENERGY
How is stored energy released from ATP to be used by the cell?
Energy stored in chemical bond between the second and third phosphate groups.
Breaking this bond releases the energy stored in it.

8. STORING ENERGY What is ADP? Key molecule used to store excess energy.
ADENOSINE DIPHOSPHATE
2 PHOSPHATE GROUPS
Partially charged battery
Key molecule used to store excess energy.
To store energy…
P + ADP  ATP
ATP is like a fully charged battery. WHY?

9. RELEASING ENERGY ATP is the basic energy source for all cells.
What are different cellular functions that ATP can power within the cell?
ACTIVE TRANSPORT
PROTEIN SYNTHESIS
MUSCLE CONTRACTION

10. USING BIOCHEMICAL ENERGY
What is a SODIUM – POTASSIUM Pump?
Used during Active Transport
Pumps Na- ions out of the cell and K+ ions in
Assists in transport of glucose into cell
Maintains muscle movement and control
Controls cell volume
Why do most cells only have a small amount of ATP?
Not a good molecule for storing large amounts of energy over a long period of time.
Cells regenerate ATP
How do cells store energy for long periods of time?
Glucose stores 90 times more energy than ATP

11. 8-2 Photosynthesis: An Overview
What is PHOTOSYNTHESIS?
Plants use the energy of sunlight to convert water and carbon dioxide into high energy carbohydrates
Sugars and starches
And Oxygen, a waste product.

12. Investigating Photosynthesis
As a tree grows bigger and bigger in size, where does the tree’s increase in mass come from?
SOIL, WATER, AIR?
This simple question asked hundreds of years ago began the research into photosynthesis.
Let’s take a closer look at some of the experiments that led to the discovery of photosynthesis…

13. Van HELMONT’S Experiment
1643, Belgian physician Jan van Helmont.
What did he do?
Experiment to investigate if plants grew by taking materials out of the soil.
His experiment?
1. Determined mass of a pot of dry soil and a seedling.

14. Van HELMONT Experiment
2. Planted the seedling in the pot of soil.
Watered regularly.
3. At the end of 5 years, the seedling had grown into a small tree. Mass gain of 75 grams.
4. Mass of soil remained almost unchanged.
His Conclusion
Mass of the tree came from the water – only thing he added.
Accounted for the “HYDRATE” portion of a CARBOHYDRATE
Where does the “CARBO” portion come from?
Carbon Dioxide

15. Priestley’s Experiment
1771, English minister Joseph Priestley
What did he do?
Lit a candle, placed a jar over it, and watched the flame gradually die out.
What did he reason about the candle flame?
Something in the air was necessary to keep the candle burning.

16. Priestley’s Experiment
What was his next step?
He placed a spring of mint underneath the jar with the candle.
After a few days, candle could be relit.
Burned for a longer period of time.
His conclusion?
The mint sprig released something needed to keep the candle flame burning.
What was this mystery substance?
OXYGEN

17. The Ingenhousz Experiment
1779, Dutch scientist Jan Ingenhousz
What did he do?
Showed the effect observed by Priestley only occurred when plant exposed to light.
What did these experiments show?
When a plant is exposed to light, it transforms carbon dioxide and water into carbohydrates and releases oxygen.

18. PHOTOSYNTHESIS EQUATION
What is the balanced equation of photosynthesis?
Compare the equation of photosynthesis with another cellular process.

19. Light and Pigments
White light - mixture of different wavelengths of light
visible spectrum
Different wavelengths = different colors.

20. Light and Pigments
What are colored substances that absorb or reflect light?
PIGMENTS
Why are plants green?
chlorophyll: principle pigment in green plants
Absorbs red and blue-violet light
Chlorophyll a and Chlorophyll b
Reflect green light which is why plants look green.

21. Absorption of Light B – carotene
Red and orange pigments that absorb light in other regions of the spectrum.

22. SECTION 8-3: The Reactions
Where do they occur?
The Chloroplast
Contains Thylakoids
Photosynthetic
membranes.
Arranged in stacks called
GRANA (GRANUM)
Photosystems: chlorophyll and pigments in the thylakoid
LIGHT-Collecting Units of the Chloroplast

23. 8-3: Reactions of Photosynthesis
1. Light-Dependent Reactions
In the thylakoid membranes
2. Light-Independent Reactions or The Calvin Cycle
Take place in the stroma

24. NADP+ AN ELECTRON CARRIER
Carries 2 High-energy electrons (e-) and a hydrogen ion (H+).
Converts NADP+ into NADPH
Sunlight energy is trapped in chemical form.
NADPH carries HE e- produced in chlorophyll to chemical reactions in the cell.

25. LIGHT DEPENDENT REACTIONS
PRODUCE Oxygen gas
CONVERT ADP and NADP+ into energy carriers ATP and NADPH
STEP A: Pigments in Photosystem II absorb light.
Electrons absorb light energy making them HIGH-Energy electrons
HIGH-Energy electrons passed to Electron Transport Chain (ETC)

26. LIGHT DEPENDENT REACTIONS
STEP A CONTINUED:
Does chlorophyll run out of electrons? No
Where do the new electrons come from?
WATER is broken down by enzymes.
1 WATER molecule  2 H+ ions and 1 O atom
2 H+ ions replace the HE electrons passed to the ETC
Oxygen is released into the atmosphere

27. LIGHT DEPENDENT REACTIONS
STEP B: HE e- move through ETC from Photosystem II to Photosystem I
Energy used in ETC to transport H+ ions from Stroma to Thylakoid.
STEP C: Pigments in Photosystem I use light energy to recharge electrons.
NADP+ picks up HE e- and H+ ions
NADP+ becomes NADPH

28. LIGHT DEPENDENT REACTIONS
STEP D: H+ ions are pumped across the thylakoid membrane.
Inside of membrane fills up with H+ ions
Outside of membrane becomes negatively charged.
This difference in charges provides the energy to make ATP.
What is the importance of H+ ions?

29. LIGHT DEPENDENT REACTIONS
STEP E: ENERGY MAKING STEP
ATP SYNTHASE found in cell membrane.
Allows H+ ions to pass through.
ATP Synthase rotates and binds ADP with a Phosphate making ATP.
LDR ETC produces HIGH-Energy electrons and ATP

30. ATP SYNTHASE

31. Photosynthesis Reactions

32. REVIEW of LDR What happens in LDR?
LDR traps sunlight energy in a chemical form (A).
HE e- give energy to ETC to move H+ ions into the thylakoid (B).
PHOTOSYSTEM I recharges e- and are picked up by NADP+ with H+ ions making NADPH (C).
H+ ions are pumped across the thylakoid membrane into the cell (D).
H+ ions diffuse back through the membrane using ATP Synthase (E).
Provides energy for ADP + P  ATP (FREE ENERGY)

33. The Calvin Cycle (Light-Independent Reactions)
Discovered by Melvin Calvin in 1948.
Involves an enzyme called RUBISCO
The Calvin Cycle uses ATP and NADPH from LDR to produce high energy sugars.

34. The Calvin Cycle STEP A: CO2 Enters the Cycle 12 (3-C molecules) made
STEP B: Energy Input
3-C molecules are converted into higher-energy forms.
Uses ATP and HE electrons
12 ATP and 12 NADPH are used
Returns 12 ADP and 12 NADP+

35. The Calvin Cycle STEP C: 6-Carbon Sugar Produced
3-C molecules produce SUGARS, lipids, amino acids, and other compounds.
STEP D: 5-Carbon Molecules Regenerated
5-C molecules are returned to beginning of cycle
6 ATP are used here.

36. The Calvin Cycle LDR traps sunlight energy in a chemical form
6 CO2 are used to create a single 6-C SUGAR molecule
Plants use the SUGARS to meet energy needs and build more macromolecules such as Cellulose.
LDR traps sunlight energy in a chemical form
ATP and NADHP
CC uses this chemical energy to produce stable, high energy SUGARS from CO2 and H2O.

37. REVIEW of CALVIN CYCLE
CO2 combines with 5-C molecules to make 3-C molecules (A)
3-C molecules converted into higher energy forms using ATP and NADPH (B)
Two 3-C molecules removed from CC to make Glucose and other molecules (C)
Ten 3-C molecules are converted back to Six 5-C molecules (D).
Cycle repeats itself.

38. Bozeman Science Video http://www.youtube.com/watch?v=g78utcLQrJ4
Start 2:13
Stop 8:35

39. LDR and CC Why are they called LIGHT DEPENDENT REACTIONS?
They require light energy to take place.
Let’s look at the bigger picture.
What would happen if plants do not get sunlight?
Plants could not perform photosynthesis.
They would not produce sugars or release Oxygen Gas
Organisms like you and me(heterotrophs) would not be able to survive.
Why is the Calvin Cycle called Light Independent Reactions?
When does the CC take place?

40. The CALVIN CYCLE

41. THE CALVIN CYCLE 1. Where does the Calvin Cycle take place?
2. What enters the CC from the atmosphere?
3. Where do ATP and NADPH come from?
4. What is the product of the CC?
5. How is the cycle completed? (Why is the CC called a cycle?)

42. Factors that Affect Photosynthesis
Water
Provides electrons to the LDR
How do plants in dry areas protect themselves from water loss?
Temperature
ENZYMES function best between 0 and 35 degrees C
What effect will extreme temperatures have on enzymes?
Intensity of Light
More Light = More Photosynthesis

43. Why do leaves change color in the fall?
Pigments carotene (red/orange) and xanthophyll (yellow)
Help absorb sunlight with chlorophyll for photosynthesis.
What major change occurs during winter?
Carotene and xanthophyll are responsible for supplying light energy to the plant.

44. Name: EXIT PASS Nov 4
1. What materials enter the chloroplast that are used in the light-dependent reactions?
2. What material comes into the chloroplast that is used in the Calvin Cycle?
3. What material exits the chloroplast from the light-dependent reactions?
4. How do plants receive electrons for use in Photosystem II?
5. What materials move from the L-D reactions to the Calvin Cycle?
Which steps produce these materials?
6. What materials move from the Calvin Cycle back to the LDR?