Chapter 10: PHOTOSYNTHESIS

[Pages:30]Chapter 10: PHOTOSYNTHESIS

1. Overview of Photosynthesis 2. Light Absorption 3. The Light Reactions 4. The Calvin Cycle

1. Overview of Photosynthesis

Chapter Reading ? pp. 185-190, 206-207

What is Photosynthesis?

The process of converting light energy (kinetic) into energy stored in the covalent bonds of glucose molecules (potential).

6 CO2 + 6 H2O

Light energy

C6H12O6 + 6 O2

Carbon dioxide Water

Glucose Oxygen gas

PHOTOSYNTHESIS

? carried out by photoautotrophs

? plants, phytoplankton, cyanobacteria (any photosynthetic organism)

? the basis of almost all ecosystems

? all "food energy" ultimately comes from the sun ? source of all atmospheric oxygen (O2)

Photosynthetic Organisms

(a) Plants

(b) Multicellular alga

(c) Unicellular protist 10 ?m

(e) Purple sulfur bacteria

1.5 ?m

(d) Cyanobacteria 40 ?m

Photosynthesis occurs in Chloroplasts

Leaf cross section Vein

Mesophyll

Stomata

CO2 O2

Chloroplast

Mesophyll cell

5 ?m

Chloroplast Structure

Chloroplast

Thylakoid

Stroma Granum

Thylakoid space

Outer membrane

Intermembrane space

Inner membrane

1 ?m

The Fate of Atoms Involved in Photosynthesis

Reactants:

6 CO2

12 H2O

Products:

C6H12O6

6 H2O

6 O2

Revealed by experiments involving radioactive isotopes in key molecules:

? 14C in CO2 and 18O in H2O and CO2

Two Stages of Photosynthesis

H2O

CO2

Light

Light Reactions

NADP+ ADP

+P

i

ATP

NADPH

Calvin Cycle

Chloroplast O2

[CH2O] (sugar)

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