7.2 Light Dependent Reaction

8/11/2019 7.2 Light Dependent Reaction

1/22

PhotosynthesisChapter

7.1 Introduction to photosynthesis

7.2 Light dependent reaction

7.3 Light independent reaction

7.4 Factors limiting the rate ofphotosynthesis


2/22

Explain the conversion of light energyinto ATP and NADPH

OBJECTIVE :

At the end of this lesson, students shouldbe able to :


3/22

KEYTERMS Light Dependent Reactions Photophosphorylation Non-cyclicphotophosphorylation Cyclic photophosphorylation


4/22

Overview:7.2 Light Dependent Reactions


5/22

7.2 Light Dependent Reactions

Light dependent reaction

Occurs in the presence of

light

Occurs in the grana

The light dependentreaction converts lightenergy to chemicalenergy (ATP andNADPH)


6/22

Photophosphorylation

The formation of ATP which occurs duringthe light dependent stage of photosynthesis(ATP production in photosynthesis)

2 types of photophosphorylation:-

(a) The non-cyclic photophosphorylation

(b) The cyclic photophosphorylation


7/22

THE NON-CYCLIC

PHOTOPHOSPHORYLATION


8/22

STEPS IN NON-CYCLICPHOTOPHOSPORYLATION

Step 1i) Light strikes photosystem II - causes

electrons to be ejected


9/22

ii) These electrons are accepted by electron

acceptor


10/22

Step 2

i) Electrons from the acceptor pass through aseries of electron transport chain


11/22

ii. The electrons lose energy until they reach for

the Photosystem I


12/22

iii) The energy released is used to form ATP-

photophosphorylation


13/22

Step 3

i) PSI absorbs light energyii) Electrons are ejected from PS1iii) PS1 receives electrons from PS1


14/22

iv) The ejected electron are accepted by electron

acceptorv) The electron and hydrogen ions (H +) are usedto NADP to NADPH

vi) Protons are produced by photolysis of water


15/22

Photolysis of water

i) Photolysis is the process of splitting watermolecules using light energy with the releaseof electrons and protons (H+) and oxygen.

ii) Proton from H 2O reduce NADP to NADPH 2iii) Electrons from H 2O used to replaced

electrons missing from photosystem IIiv) Oxygen atom is released as a by-product

that used in cellular respiration


16/22

NADPH & ATP produced are used inthe light independent reactions orCalvin Cycle


17/22


18/22


19/22

CYCLICPHOTOPHOSPORYLATION

The electrons from PS1 also be recycledto PSI

Produced only ATP known as cyclicphotophosphorylation


20/22


21/22

Electron from PSI may pass back tothe ETC and to PS1 after they areejected

As the electron pass along the ETC,

ATP is formed

CYCLIC

PHOTOPHOSPORYLATION


22/22

Light dependent reactions use light

energy to produce ATP & NADPH

Involves PSI & PSII

Conclusion

7.2 Light Dependent Reaction

Documents

Transcript of 7.2 Light Dependent Reaction