Photosynthesis Flashcards
What supplies energy for chemical reactions
ATP, NADH, NADPH, FADH2
Cellular Respiration
the oxidation of organic molecules to generate ATP
- CO2 is byproduct
- Performed by all living cells
Redox Reactions
Reaction involving transfer of electrons
Redox Reagent
chemical that catalyzes redox reactions
-come in oxidized and reduced forms
Oxidized forms of redox reagents
NADP+ NAD+ FAD
Reduced forms of redox reagents
NADPH, NADH, FADH2
-Reactive forms b/c have an extra electron at a high energy level
Steps of redox reaction
- Reduction of redox reagent
- Subsequent oxidation of the reagent
- Leaves behind a proton (that gets used later)
How to make ATP
ADP+Pi
-Requires energy and ATP-synthase
Photosynthesis
Conversion of light energy into chem energy (carbs)
- Uses CO2 and H2O, creates carbs and gives off O2 and H2O
- Light reactions and Calvin Cycle
Light Reactions
Uses light energy to make NADPH and H+
- Reagent is H2O
- Produces ATP (sent to calvin cycle)
- O2 is byproduct
Calvin Cycle
Fixes CO2 to create sugars
-needs NADPH and ATP for energy
Visible Light
Band along electromagnetic spectrum
-sufficient energy to excite molecules and cause reactions
Pigments
Substances that absorb some wavelength of light and reflect others
Absorption Spectrum
Range of absorbed and reflected wave lengths
- specific for each pigment
- Chlorophyll and accessory pigments
Chlorophyll
Absorbs blue and red light
- Reflects green light
- Main pigment of photosynthesis
Accessory Pigments
Chlorophyll b, carotenoids
-Different absorption spectrum than chlorophyll
Chloroplast Structure
- Outer membrane
- Inner membrane: thylakoid and grana
- Stroma:plastid goo
Grana Membranes
Binds chlorophyll, accessory pigments, photosystems, electron transport proteins, ATP synthase
-Runs light reactions
Photosystems
Group of pigment molecules whose purpose is to absorb light
- 250-400 pigment molecules
- Antenna complex and reaction center
Antenna Complex
Pass light energy to reaction center
-All but 2 of the pigment molecules
Resonance Energy Transfer (RET)
Light energy is absorbed by a pigment molecule in antenna complex
- Energy is passed to a neighboring molecule
- Energy hits reaction center
Reaction Center
An electron is energized–> jumps off a chlorophyll a
PSII structures
Antenna complex
- reaction center
- Oxygen Evolving complex (OEC)
PSII Functions
Phosphorylation and photolysis
PSII Phosphorylation
- Light energy excites pigment molecules in PSII
- RET
3 Reaction center loses an electron - Electron is passed down electron transport proteins
- Energy is used to pump H+ against gradient
- Photophosphorylation (Protons flow through ATP-synthase to make ATP)
Photolysis
Water splits to create Oxygen, electrons, protons
- electrons go to PSII
- Protons go through ATP-synthase
PSI Reduction
- Light energy excites pigment in PSI
- RET
- Reaction center loses an electron
- Electron travels down electron transport proteins
- Electron reduces NADP+ to NADPH
Where does PSII get electrons replaced from?
Photolysis
Where does PSI get electrons replaced from?
PSII
Energy products from light reactions
6 ATP from PSII
6 NADPH from PSI
-Goes to Calvin Cycle
Cyclic Electron Flow
Electrons lost by PSI can be used to pump protons across the membrane
- Generates extra ATP needed for Calvin Cycle
- Doesn’t reduce NADP+
- The electron is passed back to PSI
