Introduction • Autotrophs: • Photoautotrophs : • Chemoautotrophs
Important structures • Chloroplast • Thylakoids: • Grana: • Stroma:
Chloroplast two outer membranes thylakoid membrane system Organelle of photosynthesis in plants and algae stroma thylakoid compartment
a A look inside the leaf b One of the photosynthetic cells inside leaf leaf’s upper epidermis photosynthetic cell in leaf leaf vein Leaf Structure leaf’s lower epidermis
Properties of Light • White light from the sun is composed of a range of wavelengths. • All colors
Chlorophyll • Chlorophyll is the main pigment that absorbs sunlight. • Chlorophyll absorbs blue light and to a lesser extent, red light. • It reflects green light
Photosynthesis: Light-Dependent • Photosystems - chlorophyll a molecule....
Photosynthesis: Light-Dependent • pigment absorbs light energy
Two Potential Fates of Excited Electrons Electron returns to resting, unexcited state. Excited electrons are passed to other atoms.
Photosynthesis: Light-Dependent • electrons in the pigments become excited • energy (but not the electrons) is transferred • excites the electrons in a chlorophyll a molecule at the center of the photosystem.
The Passing of Electrons in Their Excited State Molecules that gain electrons always carry greater energy than before receiving them
Photosynthesis: Light-Dependent • chlorophyll that is the reaction center • Splits water
Photosynthesis: Light-Dependent • chlorophyll a continually loses its excited electrons to a nearby molecule, • replacement electrons come from water.
Photosynthesis: Light-Dependent • Protons rush out of the thylakoid sacs with great force—to build energy-storing ATP molecules
Photosynthesis: Light-Dependent • Product #1 of the “Photo” Portion of Photosynthesis: ATP • Product #2: NADPH • Product #3 (waste): O2
Photosynthesis Equation LIGHT ENERGY 6H2O + 6CO2 6O2 + C6H12O6 6 water + 6 carbon dioxide 6 oxygen + glucose
Suppose a large meteor hit the earth. How could smoke and soot in the atmosphere wipe out life far beyond the area of direct impact?
Photosynthesis • Two stages:
Light-dependent Reactions • require light to work
Light-independent Reactions • do not require light
Two Steps in Photosynthesis sunlight H2O O2 CO2 Where the two stages of photosynthesis occur inside the chloroplast NADPH, ATP light-dependent reactions light-independent reactions NADP+, ADP sugars
Photosynthesis: Light-inDependent • Calvin Cycle • whether or not light is present. • Occur in the stroma
Light-inDependent • take the energy from ATP + energized ions from NADPH + carbon dioxide to make glucose or sugar. • carbon dioxide into CH2O.
Summary of Photosynthesis sunlight Light Dependent Reactions 6O2 12H2O ATP ADP + Pi NADP+ NADPH 6CO2 Calvin- Benson cycle Light Independent Reactions 6 RuBP 12 PGAL 6H2O phosphorylated glucose P end products (e.g., sucrose, starch, cellulose)