Photosynthesis

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Leaves are the major locations of photosynthesis

Their green color is from chlorophyll, the green pigment within chloroplasts

Light energy absorbed by chlorophyll drives the synthesis of organic molecules in the chloroplast

CO2 enters and O2 exits the leaf through microscopic pores called stomata

Slide 14

Chloroplasts are found mainly in cells of the mesophyll, the interior tissue of the leaf

A typical mesophyll cell has 30–40 chloroplasts

The chlorophyll is in the membranes of thylakoids (connected sacs in the chloroplast); thylakoids may be stacked in columns called grana

Chloroplasts also contain stroma, a dense fluid

Slide 15

Fig. 10-3

Leaf cross section

Vein

Mesophyll

Stomata

CO2

O2

Chloroplast

Mesophyll cell

Outer

membrane

Intermembrane

space

5 µm

Inner

membrane

Thylakoid

space

Thylakoid

Granum

Stroma

1 µm

Slide 16

Fig. 10-3a

5 µm

Mesophyll cell

Stomata

CO2

O2

Chloroplast

Mesophyll

Vein

Leaf cross section

Slide 17

Fig. 10-3b

1 µm

Thylakoid

space

Chloroplast

Granum

Intermembrane

space

Inner

membrane

Outer

membrane

Stroma

Thylakoid

Slide 18

Tracking Atoms Through Photosynthesis: Scientific Inquiry

Photosynthesis can be summarized as the following equation:

6 CO2 + 12 H2O + Light energy  C6H12O6 + 6 O2 + 6 H2O

Slide 19

The Splitting of Water

Chloroplasts split H2O into hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules

Slide 20

Reactants:

Fig. 10-4

6 CO2

Products:

12 H2O

6 O2

6 H2O

C6H12O6

Slide 21

Photosynthesis as a Redox Process

Photosynthesis is a redox process in which H2O is oxidized and CO2 is reduced

Slide 22

The Two Stages of Photosynthesis: A Preview

Photosynthesis consists of the light reactions (the photo part) and Calvin cycle (the synthesis part)

The light reactions (in the thylakoids):

Split H2O

Release O2

Reduce NADP+ to NADPH

Generate ATP from ADP by photophosphorylation