Steps of Photosynthesis - AP Biology (MRW)

Calvin cycle phase 2

1) 3-phosphoglycerate gets another phosphate group from ATP becoming 1,3-bisphosphoglycerate. 2) Then a pair of electrons donated from NADPH reduces 1,3-bisphosphoglycerate. 3) 1,3-bisphosphoglycerate loses a phosphate group becoming glyceraldehyde 3-phosphate (G3P) *** for every three molecules of CO2 that enter the cycle, 6 molecules of G3P are formed.....HOWEVER, only ONE molecule of G3P can be counted as a gain of carbohydrate because the rest are required to complete the cycle which began with 15 carbons (3 RuBP) and ends with 18 carbons (6 G3P).

Step 8 (Photosystem 1)

2 electrons are captured from Fd by NADP+ (catalyzed by NADP+ reductase), converting it into NADPH (the H atom used comes from the H2O that was split in Photosystem 2)

Calvin cycle phase 3

3 ATP are used to change 5 of the G3P into 3 molecules of RuBP which will be ready to receive CO2 again so the cycle can continue.

Calvin cycle phase 1

CO2 is attached to ribulose bisphosphate (a 5 carbon sugar abbreviated RuBP). This process is catalyzed by RuBP carboxylase-oxygenase (RUBISCO). A 6 carbon intermediate is formed that immediately splits forming 2 molecules of 3-phosphoglycerate

Fourth (Last) Process

Calvin Cycle (Dark Cycle or better called Light-independent cycle)

Phase 1 of Calvin cycle is called

Carbon Fixation

Step 5 (photosystem II)

Chemiosmosis: a process during which ADP + Pi become ATP using the enzyme ATP synthase as the hydrogen ions diffuse through the thylakoid space back to the stroma.

Step 2 (Photosystem II) Fig. 10.14 left middle

Excited electron is transferred from P680 to the "Primary Electron Acceptor" and P680 becomes P680+ because it has lost an electron.

Step 3 (Photosystem II) (Fig 10.14 left blue red)

H2O is taken in and split up (H, O, H, Electron) A pair of electrons are given back to P680+. H+ is released into thylakoid. Oxygen joins with another forming O2.

Step 6 (Photosystem I)

Light energy excites an electron of the P700 pair of chlorophyll a molecules. The electron is transferred to the PS(I) primary electron acceptor so that the P700 becomes P700+ which can act as an electron acceptor to accept the next electron from the bottom of the electron transport chain from PS (II)

Step 1 (Photosystem II) Figure 10.14 bottom left

Light strikes a pigment molecule boosting an electron to a higher energy level. This electron transfers its energy to a nearby electron in another pigment molecule which is repeated until the energy is transferred to the P680 pair of chlorophyll a molecules in the reaction center complex.

What are Photosystems II and I called together. Summarize them.

Linear electron flow (noncyclic): A route of electron flow during the light reactions of photosynthesis that involves both photosystems (I and II) and produces ATP, NADPH, and O2. The net electron flow is from H2O to NADP+.

Step 9 (Photosystem 1)

NADPH and ATP diffuse into the stroma and Photosystem 1 is done

Step 4 (Photosystem II) (Fig 10.14 middle)

Photoexcited electrons pass from Primary Electron Acceptor of PS II to PS I via electron transport chain made up of plastoquinone (Pq), a cytochrome complex, and plastocyanin (Pc). These release free energy that is used to pump protons (H+) into the thylakoid space causing a proton gradient across the thylakoid membrane.

Step 3 of Photosystem II is called (Fig. 10.14 left blue and red)

Photolysis

Second Process

Photosystem 1

First Process

Photosystem 2

Light Dependent reactions

Photosystem II, chemiosmosis, and Photosystem I

Phase 2 of the Calvin Cycle is called

Reduction

Phase 3 of the Calvin Cycle is called

Regeneration

Step 7 (Photosystem I)

The higher energy (photoexcited) electrons pass from PS I down a second electron transport chain through ferredoxin (Fd).