1. Unit 2: Metabolic Processes Photosynthetic Pigments
SBI4U – Ms. Richardson

2. Light Can behave as a particle (photon) or a wave
When light behaves as a wave, the shorter the wavelength, the more energetic the photon
Sunlight contains photons of every wavelength
Visible light: small part of the electromagnetic spectrum (380 – 750nm)

3. Photoelectric Effect
Formation of electrically charged particles in matter when illuminated by light

4. Leaves Function: Structure: photosynthesis
maximizes surface area exposed to light
limits distance for gases to travel to reach chloroplast

5. Leaves

6. Transpiration
Loss of water vapour in plants, primarily through stomata
Assists photosynthesis:
Transpiration pull
Evaporative cooling

7. Stomata Controls gas exchange
Guard cells swell when K+ ions and water move into guard cells
Stomata close (night)
When K+ ions and water move out of guard cells, they become flaccid
Stomata open (day)
CO2 absorbed

8. Chloroplasts Site of photosynthesis
Occurs mainly in stroma and thylakoid membrane
Contain their own DNA and ribosomes
May contain starch an lipids

9. Pigment Molecules Molecules that absorb light
Many different types of pigments in plants, each absorbing light of different wavelengths
Pigment molecules appear the colour that they reflect
Eg: chlorophyll reflects green light

10. Pigment Molecules Carotenoids Orange and yellow accessory pigments
B-carotene = orange in carrots/fall leaves
Trap energy that is passed to chlorophyll for use in photosynthesis
Allow plants to absorb wider range of light

11. Pigment Molecules Chlorophyll a and b Green pigment molecules
Absorb mainly blue and red light
Hydrophobic
Found in thylakoid membrane

12. Photosystems Located in thylakoid membrane
Network of chlorophyll a molecules (antenna pigments) grouped around a central chlorophyll b molecule (reaction centre)

13. Photosystems
Antenna pigments absorb light of various wavelengths and pass energy to reaction centre
When pigment molecules absorb light, they eject electrons
The energy from the electrons is used in photosynthesis
Two photosystems involved in photosynthesis:
PSI (P700) – driven by light around 700nm
PSII (P680) – driven by light around 680nm
Photosynthesis is most effective when PSI and PSII work together (non-cyclic photophosphorylation)