Light Energy & the Chloroplast
Light and Pigments
1. Light energy travels in waves of different lengths
- Different wavelengths can appear as different colors
2. Pigments give an object color
- The color of a pigment is due to the color of light it reflects
- Chlorophyll is a green pigment
Chloroplast Structure
1. Chloroplasts also have outer and inner membranes
Plus a thylakoid membrane
- A stack of thylakoids is called granum
2. Forms three scapes:
- Intermembrane space
- Stroma
- Thylakoid space
3. Within the thylakoid membrane are photosystems that contain chlorophyll
Photosynthesis: Light & Dark
Overview of Photosynthesis
1. Photosynthesis produces food using energy from the sun
2. CO2 + H2O + E → C6H12O6 + O2
- Carbon dioxide + Water + Energy → Glucose + Oxygen
Stages of Photosynthesis
1. The light reactions convert energy from the sun into usable energy
- Light hits photosystem I energizing electrons
- Electrons travel through an e- transport chain to NADP+ (NADPH)
- Light hits photosystem II energizing electrons
- Electrons travel through an e- transport chain pumping H+ into the thylakoid
- Electrons from photosystem II replace electrons from photosystem I
- Water is split to replace electrons from photosystems II (releases O2)
- ATP is produced by ATP Synthase through chemiosmosis
2. The Calvin cycle (Carbon Fixation) uses energy from the light reactions to convert CO2 into “glucose” independent light
- CO2 joins yo RuBP with electrons (& ATP) producing G3P
- RuBP is regenerated