Photosynthesis

Page
8

Slide 64

In mitochondria, protons are pumped to the intermembrane space and drive ATP synthesis as they diffuse back into the mitochondrial matrix

In chloroplasts, protons are pumped into the thylakoid space and drive ATP synthesis as they diffuse back into the stroma

Slide 65

Fig. 10-16

Key

Mitochondrion

Chloroplast

CHLOROPLAST

STRUCTURE

MITOCHONDRION

STRUCTURE

Intermembrane

space

Inner

membrane

Electron

transport

chain

H+

Diffusion

Matrix

Higher [H+]

Lower [H+]

Stroma

ATP

synthase

ADP + P

i

H+

ATP

Thylakoid

space

Thylakoid

membrane

Slide 66

ATP and NADPH are produced on the side facing the stroma, where the Calvin cycle takes place

In summary, light reactions generate ATP and increase the potential energy of electrons by moving them from H2O to NADPH

Slide 67

Fig. 10-17

Light

Fd

Cytochrome

complex

ADP

+

i

H+

ATP

P

ATP

synthase

To

Calvin

Cycle

STROMA

(low H+ concentration)

Thylakoid

membrane

THYLAKOID SPACE

(high H+ concentration)

STROMA

(low H+ concentration)

Photosystem II

Photosystem I

4 H+

4 H+

Pq

Pc

Light

NADP+

reductase

NADP+ + H+

NADPH

+2 H+

H2O

O2

e–

e–

1/2

1

2

3

Slide 68

Concept 10.3: The Calvin cycle uses ATP and NADPH to convert CO2 to sugar

The Calvin cycle, like the citric acid cycle, regenerates its starting material after molecules enter and leave the cycle

The cycle builds sugar from smaller molecules by using ATP and the reducing power of electrons carried by NADPH

Slide 69

Carbon enters the cycle as CO2 and leaves as a sugar named glyceraldehyde-3-phospate (G3P)

For net synthesis of 1 G3P, the cycle must take place three times, fixing 3 molecules of CO2

The Calvin cycle has three phases:

Carbon fixation (catalyzed by rubisco)

Reduction

Regeneration of the CO2 acceptor (RuBP)

Slide 70

Fig. 10-18-1

Ribulose bisphosphate

(RuBP)

3-Phosphoglycerate

Short-lived

intermediate

Phase 1: Carbon fixation

(Entering one

at a time)

Rubisco

Input

CO2

P

3

6

3

3

P

P

P

P

Slide 71