1. The Reaction of Photosynthesis
Chapter 8.3
The Reaction of Photosynthesis

2. The Chloroplast
 Site of photosynthesis

3. The Chloroplast Inner membrane  thylakoid
Highly folded so there is an increased surface area for absorption of sunlight
Stacks of thylakoids  grana
Clusters of chlorophyll and other pigments  photosystems
Liquid filling of chloroplast  stroma

4. Electron Carriers
A carrier molecule is a compound that can accept a pair of high-energy electrons and transfer them along with most of their energy to another molecule
Main electron carrier of photosynthesis  NADP+
 Turns into NADPH when it is carrying electrons

5. Photosystems
There are two different groupings of photosystems in photosynthesis
 Light dependent reactions
Happens on the  thylakoid membrane
Has 2 photosystems (II and I)
 Light independent reactions
Happens in the  stroma
Also known as the  Calvin cycle

6. Figure 8-7 Photosynthesis: An Overview
Section 8-3
Light O2
Sugars
CO2
Chloroplast
Chloroplast
NADP+
ADP + P
Light-
Dependent
Reactions
Calvin
Cycle
ATP
NADPH

7. Concept Map Photosynthesis Light- dependent reactions Calvin cycle
Section 8-3
Photosynthesis
includes
Light-
dependent
reactions
Calvin cycle
takes place in
uses
use
take place in
Thylakoid
membranes
Stroma
NADPH
ATP
Energy from
sunlight
to produce of
to produce
ATP
NADPH O2
Chloroplasts
High-energy
sugars

8. Light Dependent Reactions
 Part of photosynthesis that requires light
Use light energy to produce ATP and NADPH, as well as oxygen

9. Light Dependent Reactions
 Pigments of photosystem II absorb light
Energy is absorbed by electrons
High energy electrons are transferred to NADP+ (electron carrier molecule)
These electrons are replaced by electrons produced by the breakdown of water
Water is broken down into  2 electrons, 2 H+ ions, and 1 oxygen atom
Oxygen is released
Hydrogen is broken apart and released inside the thylakoid

10. Light Dependent Reactions
The high energy electrons are passed through the  electron transport chain between photosystem II to photosystem I
The energy from the electrons is used to transport H+ ions from  the stroma into the inner thylakoid space

11. Light Dependent Reactions
 Light hits the electrons that are now in photosystem I to excite them again
These high energy electrons are picked up by NADP+
The NADP+ also picks up the H+ ions to make NADPH

12. Light Dependent Reactions
As the electrons move onto the NADP+,  more H+ ions are pumped across the membrane
Eventually, the outside of the thylakoid becomes negatively charged and the inside becomes positively charged
Difference in charge provides the energy to make  ATP

13. Light Dependent Reactions
Thylakoid membrane contains an enzyme called ATP synthase
 H+ ions pass through it to synthesize ATP
This energy will be used to make energy-containing carbohydrates

14. Click the image to play the video segment.
Light-Dependent Reactions, Part 1
Click the image to play the video segment.
Video 3

15. Click the image to play the video segment.
Light-Dependent Reactions, Part 2
Click the image to play the video segment.
Video 4

16. Light Dependent Reactions
Figure 8-10 Light-Dependent Reactions
Light Dependent Reactions
Section 8-3
Hydrogen
Ion Movement
Photosystem II
Chloroplast
ATP synthase
Inner
Thylakoid
Space
Thylakoid
Membrane
Stroma
Electron
Transport Chain
Photosystem I
ATP Formation

17. Light Dependent Reactions

18. Light Independent Reactions
Also known as the  Calvin cycle
Plants use the energy that  ATP and NADPH contain to build high-energy compounds that can be stored for a long time
 Does not require light

19. Light Independent Reactions
 Six carbon dioxide molecules enter the cycle from the atmosphere to produce 1 6-carbon sugar
As the cycle continues,  12 3-carbon molecules are created
These 3-carbon molecules obtain energy from ATP and NADPH to become high energy 3-carbon molecules.

20. Light Independent Reactions
Two of the 12 3-carbon molecules are removed from the cycle
Used to make  sugars, lipids, amino acids, and other materials needed for plant metabolism and growth
Rest of the 3-carbon molecules combine to make  6 5-carbon molecules

21. Factors that Affect Photosynthesis
Presence of water
 Lack of water slows down photosynthesis
Plants also have evolved ways to help prevent water loss (waxy covering on leaves)
Temperature
 Enzymes function best at 0-35 degrees Celsius
Intensity of Light
 Increasing light intensity increases the rate of photosynthesis
There is a certain amount of light intensity where the amount of photosynthesis within a plant does not change

22. Click the image to play the video segment.
Calvin Cycle
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Video 5

23. Figure 8-11 Calvin Cycle Section 8-3 CO2 Enters the Cycle Energy Input
ChloropIast
5-Carbon
Molecules
Regenerated
6-Carbon Sugar
Produced
Sugars and other compounds