1. Photosynthesis Intro
Chapter 9 & 10

2. What you need to know!
How chemiosmosis generates ATP in the light reactions
How photosystems convert solar energy into chemical energy

3. Physics of Light Light, like all radiation, has energy
Radiation can be sorted into an electromagnetic wave spectrum according to its wavelength
Visible light can be broken up into: red, orange, yellow, green, blue, indigo, violet

4. Colored Solid Objects
The color of solid objects is a result of absorbing and reflecting parts of the visible light spectrum
Example: Green object
Reflects green
Absorbs: red, orange, yellow, blue, purple
Absorbance spectrum of plants
Reflected light is useless to plants. Plants cannot grow under green light
It has the same affect as total darkness

5. Structure of a Chloroplast
Chloroplasts have a double membrane (endosymbiotic theory)
Inner membrane builds thylakoids: hollow membrane compartments that form stacks called grana.

6. Thylakoid Membrane
Molecules embedded in the phospholipid bilayer of the thylakoid membrane:
ATPase
Thylakoid space is used for H+ gradient and ATP synthase in the membrane
Pigments
Chlorophyll a, b, carotenoids, and xantophylls are the main pigments serving photosynthesis are embedded in the membrane
Electron transport chain molecules:
Ubiquinones, and cytochromes are embedded in the membrane

7. Structure of Cholorophyll

8. Structure of Chlorophyll
Magnesium Porphyrine Ring
Chlorophyll is a molecule that contains nitrogen (present in fertilizer, decaying compost, and proteins) or has to bound out of the air’s N2 (by nitrobacteria)
Expensive molecule: is recycled in fall in temperate climates
Chlorophyll has a hydrocarbon tail to make it lipophilic for membrane attachment

9. Structure of Cholorophyll
Chlorophyll exists in two different versions: chlorophyll a and b. Absorbance spectrums for both pigments maximize absorbance in the red and blue range

10. Leaf Structure and Photosynthesis
Photosynthesis takes place in the mesophyll of a plant’s leaf.
Gas exchange will take place through the stomata, during photosynthesis, stomata need to be open. Plants inevitably transpire through open stomata, which also helps to keep plants cool, but:
Only turgid stomata cells are open; if they become flaccid, they close, and photosynthesis stops.

11. Leaf Structure and Photosynthesis
Cuticle
Mesophyll
Vein
Stomata

12. Paper Chromatography
Technique for separating and identifying pigments from cell extracts.
The solvent moves up chromatography paper by capillary action
Pigments (solutes) are dissolved in the solvent and are carried up the paper

13. Paper Chromatography Differing pigments have different properties:
Solubility, size/shape, polarity
Different bands form as the solutes separate while they migrate up the paper

14. Rf Values of Pigments
Rf is a ratio of the migration of the pigment (B) over the migration of the solvent (F)
Rf = B/F
B = distance (mm) from the bottom of the pigment origin to the bottom of the pigment migration
If more than one pigment molecule is tested the highest band is B1, the next band is B2, etc.
F = distance from the bottom of the pigment origin to the bottom of the solvent front

15. Rf Values of Pigments Solvent Front B4
Band #
Distance migrated
Rf value
Identification of substance 1 2 B4
Rf values of substances are specific to the chromatography system used. If paper or solvent is changed, Rf values change
Rf values do not change with migration length in a system
Rf values are always between 0 & 1 B3 B2 B1
Pigment Origin