Photosynthesis Flashcards
What is the equation for photosynthesis?
6CO^2 + 6H^2O ——> C^6H^12O^6 + 6O^2
What is the overall outcome of the dark reaction?
Chemical energy is stored as glucose sugar
What is the overall outcome of the light reaction?
Light energy is transformed into chemical energy in the form of NADPH and ATP.
What does the light reaction produce?
6 water ——> Oxygen + Hydrogen Ions
Produces 12 NADP+ —-> NADPH
Produces 12 ADP —-> ATP
What happens in the light reaction?
Chlorophyll and other pigments (carotenoids) in the thylakoid absorb light energy to split water molecules into hydrogen ions and oxygen. The oxygen gas is released to the atmosphere and the light energy is stored as chemical energy in the form of ATP and NADPH for the Dark Reaction.
Where does the light reaction happen?
Thylakoid membranes
What happens in Photosystem 2?
Step 1: Chlorophyll and pigments (besides chlorophyll a) absorb light energy and transfer it to chlorophyll a within each of the photo systems.
Step 2: Light energy is used to split water into oxygen, hydrogen, ions & energized electrons. Oxygen is released through stomates in the leaves. The concentration of hydrogen ions increases inside the thylakoid membrane to create a concentration gradient.
What happens in the electron transport chain/system?
Step 1: Electron carriers transport the energized electrons through the ETC towards Photosystem 1.
Step 2: The energized electrons (-) attract hydrogen ions (+), in the stroma outside the thylakoid membrane, losing energy as they pull them across further increasing the concentration of hydrogen ions in the thylakoid.
What happens in Photosystem 1?
At the end of the electron transport system, electrons are re-energized. Enzymes in the membrane use 2 electrons and a hydrogen ions from the split water to combine with an energy carrier NADP+ forming NADPH. This compound is used as the energy source to drive the dark reactions (Calvin Cycle).
What happens in ATP Synthase?
Hydrogen ions travel down the concentration gradient through synthase enzymes in the membrane regenerating ATP from ADP as they cross over the thylakoid membrane back into the stroma.
Where does the dark reaction occur?
The Stroma
What goes in/out of the Dark Reaction?
In: 6 CO^2, 12 NADPH, 18 ATP
Uses: RuBP, PGA/PGAL, and G3P
Out: NADP+, ADP, 1 molecule of glucose (C^6 H^12 O^6)
When does the Dark Reaction happen?
Anytime fuel (ATP and NADPH) is available. Sunlight is not required.
What happens in Carbon Fixation (DR)?
Step 1: Carbon dioxide combines with RuBP (ribulose biphosphate) catalysed by the enzyme Rubisco.
Rubisco=Ribulose Biphosphate Carboxylase
Rubisco fixes carbon from the air and is the most abundant protein/enzyme on Earth.
Step 2: Each 6-carbon molecule is highly unstable and breaks down into 2-3 carbon molecules called 3-phosphoglycerate = PGA
What happens in G3P Reduction (DR)?
Step 1: Each 3-carbon PGA molecule receives a phosphate from ATP and 2 electrons from NADPH to form 3-carbon sugars (G3P= Glyceraldehyde 3 Phosphate)
Step2:One of the sugars leaves the Calvin Cycle to start building a glucose molecule.
