Photosynthesis Flashcards
Photosynthesis overall equation
6CO2 and 6H2O and light energy to 6O2 and C6H12O6, anabolism
Photosynthesis as redox reaction
Electrón flow in opposite direction, H2O is plot and electrons form more polar H-O bonds are transferred along with the protons to CO2 reducing it to a sugar and generating less polar C-H bonds, energy required for this process is derived form sunlight, it is stored at PE in the C-H bonds of sugar
Chloroplast structure
Double membrane, stroma, granulated made of thylakoid discs
Two overall processes in photosynthesis
Light reaction that splits H2O to release O2, electrons form this reaction are captured by chlorophyll and raised to a higher energy level, they are moved down ETC similar to those in mitochondria, released energy is used to generate ATP and. Reduced electron carrier- NADPH and then a DARK reaction that fixes CO2 called the Calvin cycle
Electromagnetic spectrum
Shorter wavelength has higher energy, longer wavelength has lower energy
Why are leaves green?
Green wavelength is reflected while other wavelengths are absorbed, high transmittance of green light in chlorophyll solution low transmittance of blue
Types of chlorophyll
Chlorophyll a and b, CHO in b and CH3 in a
Absorbance of chlorphyll a, b , and carotenoids
LOOK UP
Carotenoids
Alter the absorbance properties of photosynthetic mechanisms
Light absorbing pigments with other proteins
To form two photosystems locate din thylakoid membrane
Photo system I absorbance wavelength
700nm
Photo system II wavelength absorbance
680nm
Excitation of isolated chlorophyll by light
Photo excited electrons which released heat and the photon as energy, then once energy is released returns to the ground state
Photo system structure
In membrane, light harvesting complexes have pigment molecules where energy is transferred, and reaction center complex has a primary electron acceptor with a special pair of chlorophyll a molecules
P680 (photosystem II)
When excited electron is passed form chlorophyll P680 it leaves the chlorophyll molecule oxidized, the loss of electron is idled by the splitting of water, which released 2O2, 2 proton, and 2 electrons (water reduced the chlorophyll), hydrogen is released to thylakoid lumen creating a proton gradient across thylakoid membrane, energy from electrons is also used to maintain this proton gradient which generates ATP
PS II to PS I
Light to pigments to P680, o primary acceptor, to Pq, to cytochrome complex, to Pc to P70 where light excites their pigment molecules and primary acceptor in PS I takes place
PS I to NADPH
Primary acceptor in PS I, Fd (Ferredoxin) , to NADP plus re-educates, which produces NADOH to NADP plus and H plus
Non cyclic electron transfer
Can generate ATP and NADPH
Cyclic electron transfer
Generates ATP, not NADH (Calvin cycle uses more ATP and NADPH), and provide the extra ATP
Chemiomosis in chloroplast
FINDDDD
End products of light reactions
NADPH and ATP (goes to Calvin cycle)
3 intermediate proteins for electrons in light rxns
Plastoquinone, plastocyanin, ferredoxin
Calvin cycle phases
Carbon fixation, reduction, regeneration of CO2 acceptor (RuBP)
Calvin cycle outputs for light reactions
ADP and inorganic phosphate and NADP+, other output from CO2 is CH2O (sugar)
Carbon fixation
3CO2 in rubisco form 6 3-phophoglycerate and produces 6 ADP from using ATP, fixes one CO2 into a five carbon compound (RuBP), unstable and forms 2 3-carbon molecule (3-phosphoglycerate) RUBISCO (enzyme) catalyzes fixation of carbon dioxide (lots in leaf plants)
Reduction
Phosphorylation 3-phosphoglycerateto form 3-bisphosphoglyerate using ATP (3 carbons, 2 phosphates per, 6 total), then NADPH (reduces previous molecule) is used to make glyceraldehyde 3-phosphate (G3P) (3 carbons, 1 phosphate, 6 total), ONE G3P triose sugar is produced (glucose and others)
G3P two pathways
- Could be used to generate other sugars for storage and energy 2. Used to generate more ribulose biphosphate (RuBP) that can be used to maintain the Calvin Cycle, FROM 3 CO2, 1 G3P used for sugar, 5 G3P used to synthesize more RuBP
Regeneration of RuBP
5 G3P react with 3 ATP (which produces 3ADP) to make 3 RuBP (5 carbon, 2 phosphate each, 3 total)
Two fates for G3P
One third ends up as starch, two thirds converted o disaccharide sucrose for glucose and fructose energy
Carbon numbers in calvin cycle
18 with addition of 3 CO2, when one G3P is removed later on, 15 carbons remain
