Anabolisme

• Proses pembentukan senyawa kompleks dari senyawa sederhana dengan bantuan enzim.

• Memerlukan energi reaksi endergonik• Contoh : Fotosintesis

Fotosintesis

• Sintesis zat organik (glukosa) dari zat anorganik (air dan karbondioksida) dengan bantuan cahaya matahari

• Terjadi pada organ tumbuhan yang memiliki klorofil dalam kloroplas.

• Terdapat beberapa jenis pigmen : klorofil a (pigmen hijau mampu menyerap cahaya merah dan biru ungu serta memantulkan cahaya hijau), klorofil b (pigmen hijau kuning menyerap cahaya biru dan jingga), dan karotenoid (pigmen kuning jingga menyerap cahaya biru-hijau).

Penelitian Fotosintesis• Jan Ingenhouz (adanya gas oksigen)• Nicholas de Saussure (pertambahan berat)• Samuel Ruben dan Martin Kamen (Oksigen yang

dihasilkan berasal dari air)• Julius Robert Mayer (absorbsi energi dalam

bentuk energi cahaya energi kimia (ATP/NADH)

• Daniel Arnon organ fotosintesis (memisahkan kloroplas)

• Van Niel 2 reaksi fotosintesis (terang dan gelap)

Chloroplasts: The Sites of Photosynthesis in Plants

• The leaves of plants– Are the major sites of photosynthesis

Vein

Leaf cross section

Figure 10.3

Mesophyll

CO2 O2Stomata

• Chloroplasts– Are the organelles in which photosynthesis occurs– Contain thylakoids and grana

Chloroplast

Mesophyll

5 µm

Outermembrane

Intermembranespace

Innermembrane

Thylakoidspace

ThylakoidGranumStroma

1 µm

The Splitting of Water• Chloroplasts split water into– Hydrogen and oxygen, incorporating the electrons

of hydrogen into sugar molecules

6 CO2 12 H2OReactants:

Products: C6H12O66 H2O 6 O2

Figure 10.4

Reaksi Terang• Terjadi di grana• Disebut fotolisis karena menguraikan air oleh matahari.• Energi cahaya ditangkap molekul pigmen fotosintesis yang

tersusun dalam satu bagian yang disebut fotosistem (I dan II), partikel FS I di lamela intergrana, sedang FS II di membran grana.

• Tiap fotosistem mengandung molekul klorofil/ pigmen aksesori (karotenoid atau xantofil). Sedang molekul klorofil utama adalah klorofil a pigmen primer (FS I = P700 nm dan FS II = P680 nm).

• Pada reaksi terang terjadi fotofosforilasi (pelepasan elektron akibat cahaya matahari). Ada dua fotofosforilasi (siklik dan non siklik)

– Reflect light, which include the colors we see

Light

ReflectedLight

Chloroplast

Absorbedlight

Granum

Transmittedlight

Figure 10.7

• The electromagnetic spectrum– Is the entire range of electromagnetic energy, or radiation

Gammarays X-rays UV Infrared

Micro-waves

Radiowaves

10–5 nm 10–3 nm 1 nm 103 nm 106 nm1 m

106 nm 103 m

380 450 500 550 600 650 700 750 nm

Visible light

Shorter wavelength

Higher energy

Longer wavelength

Lower energyFigure 10.6

• The absorption spectra of three types of pigments in chloroplasts Three different experiments helped reveal which wavelengths of light are photosynthetically important. The results are shown below.

EXPERIMENT

RESULTSAb

sorp

tion

of li

ght b

ych

loro

plas

t pig

men

ts

Chlorophyll a

(a) Absorption spectra. The three curves show the wavelengths of light best absorbed by three types of chloroplast pigments.

Wavelength of light (nm)

Chlorophyll b

Carotenoids

Figure 10.9

• Chlorophyll a– Is the main photosynthetic pigment

• Chlorophyll b– Is an accessory pigment

C

CH

CH2

CC

CC

C

CNNC

H3C

C

CC

C C

C

C

C

N

CC

C

C N

MgH

H3C

H

C CH2 CH3

H

CH3C

HHCH2

CH2

CH2

H CH3

C O

O

O

O

O

CH3

CH3

CHO

in chlorophyll a

in chlorophyll b

Porphyrin ring:Light-absorbing“head” of moleculenote magnesiumatom at center

Hydrocarbon tail:interacts with hydrophobicregions of proteins insidethylakoid membranes ofchloroplasts: H atoms notshown

Figure 10.10

• When a pigment absorbs light– It goes from a ground state to an excited state,

which is unstable

Excitedstate

Ener

gy o

f ele

ction

Heat

Photon(fluorescence)

Chlorophyllmolecule

GroundstatePhoton

e–

Figure 10.11 A

• A photosystem– Is composed of a reaction center surrounded by a number of

light-harvesting complexes

Primary electionacceptor

Photon

Thylakoid

Light-harvestingcomplexes

Reactioncenter

Photosystem

STROMA

Thyl

akoi

d m

embr

ane

Transferof energy

Specialchlorophyll amolecules

Pigmentmolecules

THYLAKOID SPACE(INTERIOR OF THYLAKOID)Figure 10.12

e–

Fotofosforilasi non siklik

• Elektron yang tereksitasi diganti posisinya oleh elektron asal fotolisis air dan tidak bisa mereduksi pigmen lagi atau di bawa ke P700.

• Cahaya diserap oleh pigmen utama di FS I dan FS II.

• Elektron dari FS digunakan untuk mereduksi NADP

• Menghasilkan ATP, NADPH, dan oksigen

Fotofosforilasi Siklik

• Elektron yang tereksitasi dapat kembali ke P700 melalui rantai transfer elektron

• Hanya melibatkan FS I• Tidak mereduksi NADP• Hanya menghasilkan ATP

• Produces NADPH, ATP, and oxygen

Figure 10.13 Photosystem II(PS II)

Photosystem-I(PS I)

ATP

NADPH

NADP+

ADP

CALVINCYCLE

CO2H2O

O2 [CH2O] (sugar)

LIGHTREACTIONS

Light

Primaryacceptor

Pq

Cytochromecomplex

PC

e

P680

e–

e–

O2

+

H2O2 H+

Light

ATP

Primaryacceptor

Fd

ee–

NADP+

reductase

ElectronTransportchain

Electron transport chain

P700

Light

NADPH

NADP+

+ 2 H+

+ H+

1

5

7

2

3

4

6

8

• A mechanical analogy for the light reactions

Millmakes

ATP

ATP

e–

e–e–

e–

e–

Phot

on

Photosystem II Photosystem I

e–

e–

NADPH

Phot

on

Figure 10.14

• In cyclic electron flow– Only photosystem I is used– Only ATP is produced

Primaryacceptor

Pq

Fd

Cytochromecomplex

Pc

Primaryacceptor

Fd

NADP+

reductaseNADPH

ATPFigure 10.15

Photosystem II Photosystem I

NADP+

• The light reactions and chemiosmosis: the organization of the thylakoid membrane

LIGHTREACTOR

NADP+

ADP

ATP

NADPH

CALVINCYCLE

[CH2O] (sugar)STROMA(Low H+ concentration)

Photosystem II

LIGHTH2O CO2

Cytochromecomplex

O2

H2O O21

1⁄2

2

Photosystem ILight

THYLAKOID SPACE(High H+ concentration)

STROMA(Low H+ concentration)

Thylakoidmembrane

ATPsynthase

PqPc

Fd

NADP+

reductase

NADPH + H+

NADP+ + 2H+

ToCalvincycle

ADP

PATP

3

H+

2 H++2 H+

2 H+

Figure 10.17

Siklus Calvin

• Terjadi di stroma kloroplas• Menggunakan hasil dari reaksi terang (ATP

sebagai energi utama dan NADPH2 sebagai sumber energi pereduksi)

• Memerlukan CO2 • Tidak memerlukan cahaya• Ditemukan oleh Melvin Calvin.• Terdiri dari 4 tahap : karboksilasi, reduksi,

regenerasi, dan sintesis produk.

• The Calvin cycle

(G3P)

Input(Entering one

at a time)CO2

3

Rubisco

Short-livedintermediate

3 P P

3 P P

Ribulose bisphosphate(RuBP)

P

3-Phosphoglycerate

P6 P

6

1,3-Bisphoglycerate6 NADPH

6 NADPH+

6 P

P6

Glyceraldehyde-3-phosphate(G3P)

6 ATP

3 ATP

3 ADP CALVINCYCLE

P5

P1G3P

(a sugar)Output

LightH2O CO2

LIGHTREACTION

ATP

NADPH

NADP+

ADP

[CH2O] (sugar)

CALVINCYCLE

Figure 10.18

O2

6 ADP

Glucose andother organiccompounds

Phase 1: Carbon fixation

Phase 2:Reduction

Phase 3:Regeneration ofthe CO2 acceptor(RuBP)

The Importance of Photosynthesis: A Review

Light reactions:• Are carried out by molecules in the thylakoid membranes• Convert light energy to the chemical energy of ATP and NADPH• Split H2O and release O2 to the atmosphere

Calvin cycle reactions:• Take place in the stroma• Use ATP and NADPH to convert CO2 to the sugar G3P• Return ADP, inorganic phosphate, and

NADP+ to the light reactions

O2

CO2H2O

Light

Light reaction Calvin cycle

NADP+

ADP

ATP

NADPH

+ P 1

RuBP 3-Phosphoglycerate

Amino acidsFatty acids

Starch(storage)

Sucrose (export)

G3P

Photosystem IIElectron transport chain

Photosystem I

Chloroplast

Figure 10.21