Transcript Photosynthesis/respiration

Photosynthesis/respiration
Living 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 RX
Oxidation/reduction processes =
transfer of energy by the loss/gain of electrons
OILRIG
Oxidation Is Losing
Reduction Is Gaining
Electrons moved from carrier molecule to carrier molecule
Photosynthesis and respiration use redox Rx to convert the
suns energy into energy that is usable by living things
Photosynthesis
Photosynthesis 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.
Combined process of light dependant and light independent Rx
Recall structure of chloroplast
Inner thylakoid space =
Phospholipid bilayer outer membrane
pace inside thylakoid
Grana = stacks of thylakoids
Stroma = space outside thylakoids
Chlorophyll = light sensitive
pigment. Drives photosynthesis
light
Electromagnetic radiation (ER) =
all the wavelengths () of electromagnetic energy
Wavelength () = distance between peak  peak of trough  trough
Higher frequency () = shorter () lower frequency () = longer (
Photon = ‘mass’ of energy contained by all  of ER
Visible light spectrum
ROYGBIV
 400-700 nm ()
Light reflected is what  we ‘see’
Other  are absorbed
Plants use red and blue  in photosynthesis
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
Generate: NADPH, ATP (by photophosphorylation) and O2
Photosynthetic pigments
Photosystem I
P700
Chlorophyll a
Chlorophyll b
carotenoids
and
Photosystem II
P680
Noncyclic light dependant Rx
1. 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 MEANTIME
An enzyme was used to split water to form
H+ ions in inner thylakoid space (2)
e- to replace those lost (2) in P680
O2
Noncyclic light dependant Rx
Now to continue our story….
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.
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 synthase
To produce ATP (photophosphorylation)
Cyclic light dependant Rx
Produces 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 and
cytochrome complex and Pc from photosystem II
Energy is used to produce ATP via chemiosmosis
ATP and NADPH are used in the carbon fixation pathway
known 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
rubisco
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
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 leaves
Mesophyll cells between bundle sheaths and leaf surface
PEP carboxylase
In mesophyl : CO2 + PEP (phosphoenolpyruvate)  oxaloacetate (4C)
Efficient carbon fixation
Fixed carbon brought to bundle sheaths and released to Calvin cycle
Minimizes photorespiration and increases photosynthetic productivity
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