1. Agenda 2/5 Review of Photosynthesis so far
Who, what, when, where, why activity
Photosynthesis POGIL
Homework:
1. Plant Adaptations Video and Notes
2. Create your own concept map for photosynthesis
Turn in: Children’s books and video notes

2. ATP H+ H+ H+ H+ H+ H+ ADP H+ P thylakoid membrane thylakoid space
stroma
ATP synthase e-
NADPH
NADP+ e-
Photosystem I (P700)
Photosystem II (P680)
5000 e-
4999 e-
5000 e-
5000 e-
5000 e-
4999 e- H+
This “animation” walks through the steps of noncyclic electron flow, as outlined on the previous 3 slides. The “5000 e-” is meant for illustrative purposes only; no matter how many electrons were contained in photosystems II and I, if there was no way to replace those electrons, eventually the number of electrons would be 0. If that were to occur, there would no electrons to be excited by light, and the light reactions would grind to a halt. The electron that was “excited away” from photosystem I is replaced by the electron that was “excited away” from photosystem II; photosystem II’s lost electron is replaced through photolysis – the splitting of water – which releases ½ a molecule of O2 as a byproduct. This is where the oxygen comes from that is produced during photosynthesis, and is why autotrophs need water to perform photosynthesis! The oxygen is released through the stomata. The electron that was excited away from Photosystem I ends up reducing [adding an electron to] NADP+ to form NADPH, an important electron carrier that is needed in the Calvin Cycle.
Make sure to point out to students the coupled reactions that occur; as the electron travels down the electron transport chain, its “lost energy” is used to pump protons from the stroma to the thylakoid space to build a concentration gradient. Then, as those protons diffuse back across the thylakoid membrane through ATP synthase to achieve equilibrium, they cause ATP synthase to spin (like a turbine), which forces ADP and the phosphate group together, forming ATP.
Don’t forget to point out that the membrane is key here! If there was no thylakoid membrane (or if its integrity was disrupted and therefore “leaky”), it would be impossible to build this concentration gradient – not to mention that the cytochromes, photosystems, and ATP synthase would not exist/be functional!
Make sure to make the connection with “osmosis” when discussing “chemiosmosis;” for students who understand the idea of the movement of molecules from an area of high concentration to an area of low concentration (as in osmosis), discuss the idea that this is essentially the same process, just with protons (H+) instead of water molecules. H+ H H H+ O H+ H+ H+ H+ e- H+ O H+
(2 H+ & ½ O2)

3. Simplified Steps- Calvin Cycle
1. Carbon dioxide combines with RuBP with assistance by an enzyme called rubisco
2. That new molecule is very unstable and will split in half to form G3P/PGAL
This uses NADPH and ATP
3. Some of the G3P/PGAL will combine to form organic compounds
4. Some of the G3P/PGAL will combine to recreate RuBP (Remember it is a cycle!)
This also needs ATP

4. Phase 2: The Calvin Cycle
Quick recap:
In the Calvin Cycle, energy and electrons from the Light Reactions (in the form of ATP and NADPH) and carbon dioxide from the atmosphere are used to produce organic compounds.
The Calvin Cycle occurs in the stroma inside the chloroplasts (inside the cells…).
Carbon dioxide, ATP, and NADPH are required (reactants).
Organic compounds (G3P) are produced (products).

5. Photosynthesis: A Recap
So, as a broad overview of photosynthesis,
The Light Reactions (Phase 1) capture the energy in sunlight and convert it to chemical energy in the form of ATP and NADPH through the use of photosystems, electron transport chains, and chemiosmosis.
The Calvin Cycle (Phase 2) uses the energy transformed by the light reactions along with carbon dioxide to produce organic compounds.

6. Photosynthesis: A Recap
Based on this equation, how could the rate of photosynthesis be measured?
The photosynthetic equation:
Provides the carbon to produce organic compounds during the Calvin Cycle
The organic compound ultimately produced during the Calvin Cycle
light
6 H2O
6 CO2
6 O2
C6H12O6
Emphasize to students the importance of understanding how and when each component of the photosynthetic equation is used; this is much more valuable (and less intimidating!) than simply having them memorize the equation!
Most realistically, the rate of photosynthesis could be measured by using the:
Decrease in environmental CO2 (in a closed system)
Increase in environmental O2 (in a closed system)
Increase in glucose (perhaps measured using radioactive carbon)
Split during the light reactions to replace electrons lost from Photosystem II
Produced as a byproduct of the splitting of water during the light reactions
Excites electrons during the light reactions

7. Review
Identify the main players in the light dependent reactions of photosynthesis:
Example:
Who- ATP
What- Energy needed for the Calvin Cycle
When- After ETC in light dependent reactions
Where- Thylakoid membrane in ATP synthase protein
Do this for ATP, Light, Oxygen, NADPH, Water, CO2, Glucose