By Alex

PHOTOSYNTHESIS

Glucose

Light

Carbon Dioxide

Water

Oxygen

6CO2 + 6H2O + Energy (Light) C6H12O6 (glucose) + 6O2

Complex series of reactions that takes place in two stages:

1. Light reaction (light dependent) 2. The Calvin cycle - Carbon Fixation ( Light

independent)

Light reactions Calvin Cycle (Carbon Fixation)

• Trap the energy from sun & use it to form ATP + Hi energy electron

• Split water - replenish Electrons & H+ (carried by NADPH)

• and released Oxygen

IN OUT

• form ATP • NADPH • Oxygen

• Carbon dioxide in the air • Electrons & Hydrogen deliver by NADPH • powered by ATP • Carbon dioxide, H+, and electron are rearranged

in to glucose with high energy level

ATP supply

The nature of light • Light is energy emitted as photons which acts both particle and waves • Different wavelength of light carry different amount of energy • The shorter the wavelength, the higher the energy • Different wavelength= different color • Sunlight is a mixture of different wavelength;

R O Y G B I V Longer Wavelength shorter Lower Frequency higher Lower Energy higher

When the sunlight hit the plant, the energy is absorbed by the pigments. Different pigments absorbs different wavelength. If the wavelength not absorbed, it is reflectd. Chlorophyll is the major photosynthetic pigment. It i absorbing some wavelengh but reflecting green.

By Alex

Cyclic Electron Transfer

Non- Cyclic Electron Transfer

WHERE IS CHLOROPHYLL?

Chloroplast • are a double membrane bound organelle Thylakoid • The stacks of pillow shapped membranse are filled with

chlorophyll and enzymes where light reactions occur Stroma • The fluid filling the rest of the chloroplast contain certains

enzyme for the Calvin Cycle

Photosytem L i g h t h a r v e s t i n g c o m p l e x e s e m b e d e d i n t h e t h y l a k o i d m e m b r a n e s c l u s t e r s o f photopigment- chlorophyll a, chlorophyll b and carotenoids.

1. Photon strike electron (chlorophyll) 2. The energy is absorbed causing 3. The electrons to jumpp & bound in energy on the photosystem 4. Reach to reaction centre chlorophyll 5. Electron acceptor come in, pick the electron to the ETC

Photosystem I (P700)

Photosystem II (P680)

Reaction Centre Chlorophyll

Electron Transport Chain (ETC) • Series of enzymes embedded in a membrane • Electrons are passed slong from one molecule to the

next and energy is given off to make ATP*

• As electron is moved, it drives the pumping of Hydrogen ions onto one side of a membrane creating concentration and electrical gradient to build.

• It is this gradient that drives the production of ATP.

By Alex

Photosytem L i g h t h a r v e s t i n g c o m p l e x e s e m b e d e d i n t h e t h y l a k o i d m e m b r a n e s c l u s t e r s o f photopigment- chlorophyll a, chlorophyll b and carotenoids.

Occur in thylakoid membrane

Cyclic Electron Transfer

CYCLIC ELECTRON TRANSFER 1. When, light (photon) strike electron (chlorophyll), the energy is absorbed and boost the electron to high energy level. 2. This energized electrons jump & bound [in energy] around the photosystem. 3. The electron then reach special chlorophyll a [called the reaction centre] 4. The electron kept by electron acceptor. 5. The electron acceptor deliver the electron to the Electron Transport Chain 6. The electron will move down ETC in a series of Oxidation-Reduction reaction [Redox reaction] 7. As electron move down the ETC, energy given off to make ATP 8. By the time electron move down ETC, it is no longer high energy electron. 9. The electron then return to P700 [Photosystem I].

Since the electron getting back where it begun, so it is a cyclic electron transfer.

Photosystem I (P700)

1

2

43 e-

7

65

8

9

e-

Energy to make ATPATP

Photophosphorylation

By Alex

Non- Cyclic Electron Transfer

Photosystem II (P680)

P680 (PSII) P700 (PSI)

Energy to make ATPATPe-

e-

e-

e-

e-

NADP+ + e- + H -->NADPH

Photolysis H2O --> O2 + H + e-

Replinish electron lost from P680

NON- CYCLIC ELECTRON TRANSFER 1. When, light (photon) strike electron (chlorophyll), the energy is absorbed and boost the electron to high energy level.

• This energized electrons jump & bound [in energy] around the photosystem. • The electron then reach special chlorophyll a [called the reaction centre] • The electron kept by electron acceptor.

2. The electron acceptor deliver the electron to the Electron Transport Chain • The electron will move down ETC in a series of Oxidation-Reduction reaction [Redox reaction]

3. As electron move down the ETC, energy given off to make ATP 4. By the time electron move down ETC, it is no longer high energy electron. 5. The electron then enter to P700 [Photosystem I] and again, light strike the electron to boost it to high energy

electron. • The electron bound around PSI, and reach special chlorophyll a [reaction centre] • The electron then kept by electron receptor

6. Electron receptor deliver the electron to short ETC. 7. At the end, electron e- combine with H+ & NADP+ to form NADPH molecule.

Photolysis • Water supply is broken by photom to form e-, H+ and Oxygen molecule • E- replinish electron supply in PSII • H+ combine with NADP+ to form NADPH • Oxygen molecule released to atmospheric air

Since the e- doesn't back to P680,then it's known as NON-cyclic electron transfer.

23

5

4

1

7

6

1i

8

Photophosphorylation

Calvin Cycle

By Alex

Photophosphorylation

1

2 3

4

5

6

Light (photon) strike electron (chlorophyll), the energy is absorbed and

boost the electron to high energy level

The high energy electron is picked up by electron receptor called

plastiquinone[PQ] and brought to ETC

Electron need to grab proton [H+] to going down the ETC [Cytochrome complex], As electron go down, it pulls the proton

with it. And H+ ion pump to the inside thylakoid membranethrough. Electron back to ground state[no longer high

energy electron]. Non cyclic pathway. Enter to PS1.

The electron is brought by PC [ ] to P700 [PS1]

The high energy electron is picked up by electron receptor called ferrodoxin[Fd]

and brought to ETC

The electron again strike by light, boost the electron to high energy level

The electron deliver to ETC pickup by NADP+. The ETC not only transport foe

electrom but also reduce NADP reductase.

Hydrogen ion (H+) pump into the thylakoid membrane derived from: • Hydrogen ion grabbed by electron to paass through ETC ( cytochrome complex) • From photolysis in which water break donating electron to PS11 and giving H+ to thylakoid

membrane The hydrogen ion cant pass through the phospholipid bilayer. The accumulate hydrogen ion cause the gradient of hydrogen ion inside the thylakoid membrane became high. A special tunnel in membrane, ATP synthase is a s special for pumping the hydrogen ion out by using the gradient different between inside the thylakoid membrane and stroma. The hydrogen ion taht pump out via ATP synthase used as energy to combine ADP and Pi to form ATP.