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