Energy From Sunlight (Chapter 8 Lesson) 

Light Energy & the Chloroplast

Light and Pigments

1. Light energy travels in waves of different lengths

1. Different wavelengths can appear as different colors

2. Pigments give an object color

1. The color of a pigment is due to the color of light it reflects

2. Chlorophyll is a green pigment

Chloroplast Structure

1. Chloroplasts also have outer and inner membranes

1. Plus a thylakoid membrane

   1. A stack of thylakoids is called granum

2. Forms three scapes:

1. Intermembrane space

2. Stroma

3. 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

1. Carbon dioxide + Water + Energy → Glucose + Oxygen

Stages of Photosynthesis

1. The light reactions convert energy from the sun into usable energy

1. Light hits photosystem I energizing electrons

2. Electrons travel through an e- transport chain to NADP+ (NADPH)

3. Light hits photosystem II energizing electrons

4. Electrons travel through an e- transport chain pumping H+ into the thylakoid

5. Electrons from photosystem II replace electrons from photosystem I

6. Water is split to replace electrons from photosystems II (releases O2)

7. 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

1. CO2 joins yo RuBP with electrons (& ATP) producing G3P

2. RuBP is regenerated