photosynthesis/respiration
Post on 04-Jan-2016
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Photosynthesis/respirationLiving things use energy to maintain homeostasis
Photosynthesis = the process by which autotrophs capture energy from the sun and store it in the chemical bonds of glucose. Occurs in chloroplast.
Sun energy + 6 CO2 + 12 H2O C6H12O6 + 6 O2 + 6 H2O Respiration = process by which living things break down glucose. The energy from the chemical bonds in glucose are captured in ATP molecules for use by an organism to do work.. Occurs in mitochondria.
C6H12O6 + 6 O2 6 CO2 + 6 H2O + ATP energy
Redox RXOxidation/reduction processes = transfer of energy by the loss/gain of electrons
OILRIGOxidation Is Losing Reduction Is Gaining
Photosynthesis and respiration use redox Rx to convert the suns energy into energy that is usable by living things
Electrons moved from carrier molecule to carrier molecule
PhotosynthesisPhotosynthesis captures energy from the sun and stores the energy in the chemical bonds of glucose.
Sun energy + 6 CO2 + 12 H2O C6H12O6 + 6 O2 + 6 H2O
Occurs in chloroplasts in mesophyll cells in leaves. CO2 and O2 enter/exit leaves via stomata on leaf surfaces.
Recall structure of chloroplast
Phospholipid bilayer outer membraneGrana = stacks of thylakoids
Stroma = space outside thylakoids
Inner thylakoid space = pace inside thylakoid
Chlorophyll = light sensitive pigment. Drives photosynthesis
Combined process of light dependant and light independent Rx
lightElectromagnetic radiation (ER) =
all the wavelengths () of electromagnetic energy
Wavelength () = distance between peak peak of trough trough
Higher frequency () = shorter () lower frequency () = longer ()
Visible light spectrum ROYGBIV
400-700 nm ()
Light reflected is what we ‘see’
Other are absorbed
Plants use red and blue in photosynthesis
Photon = ‘mass’ of energy contained by all of ER
Conversion of light energy into the chemical bonds of glucose occurs
In the light dependant (photosystem II and photosystem I)
and light independent (Calvin cycle)
reactions
Light dependant RX
Photosynthetic pigments Chlorophyll aChlorophyll bcarotenoids
Generate: NADPH, ATP (by photophosphorylation) and O2
Photosystem I and Photosystem II
P700 P680
Noncyclic light dependant Rx1. Light hits P680 in photosystem II.
2. Two excited electroms (e-) leave P680 (to a higher energy level) and are captured by a primary e- acceptor.3. The e- are passed ‘down’ to photosystem I via carrier molecules
Plastoquinone (Pq), a cytochrome complex, and plastocyanin.
4. Energy from e- is used to pump H+ from stroma into inner thylakoid space contributing to the production of ATP.
5. When e- reach photosystem I, they join P700 (fill in for missing e-)
IN THE MEANTIMEAn enzyme was used to split water to form
H+ ions in inner thylakoid space (2)
e- to replace those lost (2) in P680O2
Noncyclic light dependant Rx
6.. Light hits P700 in photosystem I
7. Two excited electroms (e-) leave P700 (to a higher energy level) and are captured by a primary e- acceptor.
Now to continue our story….
8. Electrons are passed from the primary acceptor to a carrier molecule Ferredoxin (Fd)
9. NADP+ reductase transfers the e- from Fd to NADP to form NADPH
What happens to all the H+ building up in the inner thylakoid space?
chemiosmosis H+ diffuse down [ ] gradient through ATP synthaseTo produce ATP (photophosphorylation)
Cyclic light dependant RxProduces ATP but no NADPH
1. Light hits P700 in photosystem I
2. Two excited electroms (e-) leave P700 (to a higher energy level) and are captured by a primary e- acceptor.3. Electrons are passed ‘down’ and returned to P700 via carrier molecules
Fd from photosystem I andcytochrome complex and Pc from photosystem II
Energy is used to produce ATP via chemiosmosis
ATP and NADPH are used in the carbon fixation pathwayknown as the light independent Rx or Calvin cycle
Light independent Rx
Calvin Cycle ATP and NADPH are used to produce glyceraldehyde 3-phosphate from CO2 (3)
Carbon fixation
3 CO2 + 3 RuBP (ribulose biphosphate) 6 3-phosphoglycerate
Reduction
(6) 3-phosphoglycerate + ATP (6) 1,3-biphosphoglycerate(6) 1,3-biphosphoglycerate + NADPH (6) G3P
(1) G3P become glucose or other compounds(5) G3P to regenerate RuBP
Regeneration (5) G3P + ATP 3 RuBP Calvin cycle ready to begin again
rubisco
Evolution in photosynthesis
C3 plants Carbon fixation involves rubisco
Hot dry weather CO2 as stomata close to reduce water loss via transpiration
O2 can combine with rubisco and be sent to Calvin cycle instead of CO2
Causing photorespiration = BAD
Photorespiration = product broken down with no ADP formation
Loss of G3P production
No RuBP generated
C4 plants
C4 plants Bundle sheath cells arranged around veins of leavesMesophyll cells between bundle sheaths and leaf surface
In mesophyl : CO2 + PEP (phosphoenolpyruvate) oxaloacetate (4C)
PEP carboxylase
Fixed carbon brought to bundle sheaths and released to Calvin cycle
Minimizes photorespiration and increases photosynthetic productivity
Efficient carbon fixation
CAM plants
CAM plants = crassulacean acid plants
succulents
As in C4 plants, CO2 is fixed into intermediate organic molecules
Carbon fixation takes place at night when stomata are open
Carbon released into Calvin cycle during the day (stomata closed) when light is available for
ATP, NADPH production
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