Photosynthesis.a2ppt

41

description

 

Transcript of Photosynthesis.a2ppt

Page 1: Photosynthesis.a2ppt
Page 2: Photosynthesis.a2ppt

                                  

Page 3: Photosynthesis.a2ppt
Page 4: Photosynthesis.a2ppt
Page 5: Photosynthesis.a2ppt

Can you label the plant cell?

Page 6: Photosynthesis.a2ppt
Page 7: Photosynthesis.a2ppt
Page 8: Photosynthesis.a2ppt

The location and structure of chloroplasts

Figure 7.2

LEAF CROSS SECTION MESOPHYLL CELLLEAF

Chloroplast

Mesophyll

CHLOROPLAST Intermembrane space

Outermembrane

Innermembrane

ThylakoidcompartmentThylakoidStroma

Granum

StromaGrana

Stoma (pl. stomata)

Page 9: Photosynthesis.a2ppt
Page 10: Photosynthesis.a2ppt
Page 11: Photosynthesis.a2ppt
Page 12: Photosynthesis.a2ppt

© Pearson Education Ltd 2009This document may have been altered from the original

Week 10

A photosystem

Page 13: Photosynthesis.a2ppt

Two photo systems named by time of discovery PS I and PS II PSI has a light absorption peak of 700nm and appears mainly on inter-granal lamellae PSII has a light absorption peak of 680nm and appears mainly on granal lamellae

Capture solar power in form of photons

Act as light harvesters

Accessory pigments make up antenna complex which absorbs photons of light energy

This energy is channeled to the reaction centre of each photo system

Page 14: Photosynthesis.a2ppt
Page 15: Photosynthesis.a2ppt

Light-absorbing molecules

Absorb some wavelengths and reflect others

Color you see are the wavelengths NOT absorbed

Wavelength (nanometers)

chlorophyll b

chlorophyll a

Q: what wavelengths are NOT absorbed?

Page 16: Photosynthesis.a2ppt

ATP- ENERGY ‘CURRENCY’

Page 17: Photosynthesis.a2ppt

An overview of photosynthesis

Figure 7.5

Light

Chloroplast

LIGHTREACTIONS

(in grana)

CALVINCYCLE

(in stroma)

Electrons

H2O

O2

CO2

NADP+

ADP+ P

Sugar

ATP

NADPH

Page 18: Photosynthesis.a2ppt

• Each of the many photosystems consists of:

–an “antenna” of chlorophyll and other pigment molecules that absorb light

–a primary electron acceptor that receives excited electrons from the reaction-center chlorophyll

–P680 (in PS II)

–P700 (in PS I)

Page 19: Photosynthesis.a2ppt

Figure 7.7C

Primaryelectron acceptor

Photon

Reaction center

PHOTOSYSTEM

Pigmentmoleculesof antenna

Page 20: Photosynthesis.a2ppt

Fluorescence of isolated chlorophyll in solution. Excited electrons have no place to go.

Figure 7.7A

Heat

Photon(fluorescence)Photon

Chlorophyllmolecule

Page 21: Photosynthesis.a2ppt

Figure 7.7B

Excitation of chlorophyll in a chloroplast

The electrons are then passed to other molecules in an electron transport chain

Primaryelectron acceptor

Othercompounds

Chlorophyllmolecule

Photon

Page 22: Photosynthesis.a2ppt
Page 23: Photosynthesis.a2ppt

The energy changes of electrons as they flow through the light reactions are analogous to the cartoon. As complicated as the scheme is, don’t lose track of its functions:The light reactions use solar power to generate ATP and NADPH which provide chemical energy and reducing power to the sugar making reactions.

Page 24: Photosynthesis.a2ppt
Page 26: Photosynthesis.a2ppt

© Pearson Education Ltd 2009This document may have been altered from the original

Week 10

(a) The distribution of photosystems on granal and intergranal lamellae; (b) Formation of ATP during non-cyclic photophosphorylation

(a)

(b)

Page 27: Photosynthesis.a2ppt

Light reactions

Figure 7.8

Primaryelectron acceptor

Primaryelectron acceptor

Electron transport chain

Electron transport

Photons

PHOTOSYSTEM I

PHOTOSYSTEM II

Energy forsynthesis of

by chemiosmosis

Page 28: Photosynthesis.a2ppt

© Pearson Education Ltd 2009This document may have been altered from the original

Week 10

The Z-scheme

Page 29: Photosynthesis.a2ppt
Page 30: Photosynthesis.a2ppt

Light strikes photo system II and the energy is absorbed and passed along until it reaches P680 chlorophyll.

The excited electron is passed to the primary electron acceptor. Photolysis in the thylakoid takes the electrons from water and replaces the P680 electrons that were passed to the primary electron acceptor. ( O2 is released as a waste product)

The electrons are passed to photo system I via the electron transport chain (ETC) and in the process used to pump protons across the thylakoid membrane into the lumen.

The stored energy in the proton gradient is used to produce ATP which is used later in the Calvin-Benson Cycle.

Page 31: Photosynthesis.a2ppt

P700 chlorophyll then uses light to excite the electron to its second primary acceptor.

The electron is sent down another ETC and used to reduce NADP+ to NADPH.

The NADPH is then used later in the Calvin-Benson Cycle.

Page 32: Photosynthesis.a2ppt

Where do the electrons come from that keep the light reactions running?

Photosystem II regains electrons by splitting water molecules and releasing oxygen The reaction center pigment (P680) that gave up

electrons gets replacement electrons Photosystem I receives electrons from the

bottom of the cascade of the ETC from PS II and passes it to the P700 chlorophyll

Page 33: Photosynthesis.a2ppt

Light dependent phase

Page 34: Photosynthesis.a2ppt
Page 35: Photosynthesis.a2ppt

© Pearson Education Ltd 2009This document may have been altered from the original

Week 10

The Calvin cycle

Page 36: Photosynthesis.a2ppt
Page 37: Photosynthesis.a2ppt
Page 38: Photosynthesis.a2ppt
Page 39: Photosynthesis.a2ppt
Page 40: Photosynthesis.a2ppt
Page 41: Photosynthesis.a2ppt

LIGHT AS A LIMITING FACTOR