1. Photosynthesis
Chapter 7

2. Photosynthesis Occurs in green plants, algae, and some bacteria
Transforms light E into chemical E
Stored in sugar bonds
Also produces O2

3. Anatomy of a Leaf Exterior of stoma (pl. stomata) for gas exchange
Veins carry water from roots and sugars from leaves
Mesophyll is interior leaf tissue
Filled with chloroplasts, site of photosynthesis
Stroma, thylakoids with chlorophyll, grana
All green areas of plants, concentrated in leaves

4. The Electromagnetic Spectrum
Electromagnetic (light) energy travels in waves
Wavelength from crest to crest
Energy levels vary
Low energy = long waves
Microwaves, radio waves
High energy = short waves
Gamma rays, x-rays
Visible spectrum
Colors seen are those that are reflected, not absorbed
White reflects all light
Black absorbs all light
Green plants reflect green

5. Light Energy Exists as photons, discrete units of energy
Pigments absorb specific photons
Energy elevates e-s of pigments to higher orbital ( PE)
Unstable in upper orbital so ‘fall’ back quickly
Releases energy as heat
White vs black cars/clothing in the South

6. Plant Pigments Leaves contain a variety of pigments
Chlorophyll a: reflects green
Direct photosynthetic reaction
Chlorophyll b: reflects green
Absorbs E and transfers to chlorophyll a
Carotenoids: reflects yellow and orange
Behaves like chlorophyll b
Expand system capabilities
Photoprotection: absorbs excess E to prevent damage
Similar mechanism in retina “Carrots for good eyes”
Anthocyanins: reflects red and purple
Cherries and flowers
Fall foliage change b/c other pigments outlast chlorophyll’s

7. Overview of Photosynthesis
Light reaction
In the thylakoids
Light E to ATP and NADPH
Fuels the dark cycle
Oxygen atoms escape
Dark reaction
In the stroma
Assembles sugars
Carbon fixation: incorporate CO2 to organic compounds
NADPH reduces carbon
Electron mov’t?
ATP provides chemical E to run the cycle
No direct need for light

8. Light Capturing In thylakoids Electron transfer chain in photosystem
Clusters of chlorophyll, pigments, and proteins
Light-gathering “antennae”
Photosystem I (P680)—absorbs red light at 680nm
Photosystem II (P700)—absorbs far-red light at 700nm

9. Light-Dependent (Light) Reaction
Starts with:
Sunlight
Water
Ends with:
ATP and NADPH
Important products in this process:
Oxygen
e-’s from water to PS II/PS I to NADP+
ETC between photosystems set up [H +]
gradient in thylakoid space
H + out to stroma through ATP synthase
Photophosphorylation
Where do you recognize this process from?

10. Light-Independent (Dark) Reaction
Starts with:
6 CO2
ATP and NADPH
Ends with:
2 G3P (3C) = sugar precursor
Important products in this process:
NADP+ and ADP + Pi
3 RuBP

11. Review of Photosynthesis