Photosynthesis HLPhotosynthesis HLMrs. Jackie

Draw the structure of a Draw the structure of a chloroplast chloroplast

About 2-10microm in diameter

Include ◦Circular DNA◦Ribosomes◦Starch grains◦Fat droplets

Inter granal lamella

grana

Photosynthesis consist of light Photosynthesis consist of light dependent and light independent dependent and light independent reactionsreactions

Light dependent rx and Light dependent rx and photophosphorilationphotophosphorilation

Energy level

PSII

H2O

2H++1/2O2

light

X

PSI

light

2e-

2e-

2e-

2e-

ADP +Pi

ATP

ADP +Pi

ATP

y

2e-

NADPHNADP +H

Non-CyclicPhotophosphorilation

Non cyclic photophosphorylationNon cyclic photophosphorylation

Light hits the pigments on PSII which are mainly found in the grana

Chlorophyll a involved absorbing light at the 680nm

Light absorption excites the electron which move to electron acceptor X.

Chlorophyll mol change to a positive because it looses e-.

The electrons are passed thorough a series of redox reactions to PSI

Non cyclic photophosphorylationNon cyclic photophosphorylation

The presence of Chl a+ induce the lysis of water so that oxygen, H and electrons are released

Electrons are taken by Chl a+ which turns into Chl a

The oxygen is released as a waste productThe H are pumped to the lumen of the

grana and accumulate until diffusion occurs though the channel of the APT synthethase and ADP +Pi are converted into ATP

Grana Thylakoid membraneGrana Thylakoid membrane

Lumen

ATP

ADP+ Pi

H+

light

2e-

NADP+H2e-

H+

H2O2H+1/2O2

Non-cyclic photophosphorilationNon-cyclic photophosphorilation

The light also hits the photosystem I which absorbs light at 700nm.

Electrons move away from the nucleus.Electrons move away from chl a to the

electron acceptor YElectron are then passed on to NADP

which combines with H to produced NADPH

The chl a+ receive electrons from the electron carrier chain and become chl a

Cyclic photophosphorilationCyclic photophosphorilation

Increasin energy level

X

Y

PSI

2e-

2e-

2e-

2e-

ADP +Pi ATP

ADP +Pi ATP

light

Light independent reactionsLight independent reactions

Calvin Cycle◦Takes place in the

stroma of the chloroplast

◦ATP provides energy and NADPH provides the reducing power needed for biosynthesis using CO2

◦RuBP- carbon dioxide acceptor

Calvin CycleCalvin Cycle

6 Glycerate-3-phosphate(GP) (6x3C)

6 Glycerate-1,3-diphosphate(6 x 3C)

6 triose-phosphate(TP) (6 x3C)

5 Triose-phosphate(TP) (5x3C)

3 Ribulosebiphosphate(RuBP) (3x5C)

3CO2(3X1C)

RuBP carboxylase

6ADP +6Pi

6ATP

6NADPH

6NADP+

1TP (1x3C

3ADP+3Pi

3ATP

Review of Calvin CycleReview of Calvin Cycle

The Calvin Cycle takes place in the stoma of the chloroplast.

RuBP take up CO2 with the aid of RuBP carboxylase forming GP (glycerate 3 phosphate)

GP will be reduced to TP (triose-phosphate) but this conversion needs energy from ATP and reducing power from NADPH.

TP can be converted to glucose, sucrose, starch, fatty acids and amino acids

TP is also converted to RuBP to keep the cycle going. This process requires ATP