Photosynthesis

Comparing Photosynthesis & Respiration Cellular Respiration Function Energy Storage Energy Release Location Chloroplasts Mitochondria Reactants CO2 and H2O C6H12O6 and O2 Products Equation 6CO2 + 6H2O  C6H12O6 + 6O2 C6H12O6 + 6O2 6CO2 + 6H2O

Mitochondrion and Chloroplast structure

Photosynthesis overview Process of storing energy in sugar molecules from the energy initially in the sun (radiant energy) 1st step: Capture radiant energy and use it to generate our “energy currency” 2nd step: Use “energy currency” to convert CO2 to glucose Oxygen is released as a byproduct Happens in the chloroplast

WHY ARE PLANTS GREEN? It has to do with sunlight! Sunlight is a form of electromagnetic energy, which travels in waves.

WHY ARE PLANTS GREEN? Different wavelengths of visible light are seen by the human eye as different colors. Gamma rays Micro- waves Radio waves X-rays UV Infrared Visible light Wavelength (nm)

The feathers of male cardinals are loaded with carotenoid pigments The feathers of male cardinals are loaded with carotenoid pigments. These pigments absorb some wavelengths of light and reflect others. Reflected light Sunlight minus absorbed wavelengths or colors equals the apparent color of an object.

Plant pigments Pigments are materials that absorb particular wavelengths of light and reflect others When chlorophyll absorbs light, energy is transferred to electrons and “boosts” them to a higher state. Plant pigments

Chloroplast Pigments Chloroplasts contain several pigments Chlorophyll a: absorbs mainly violet and red light the best Chlorophyll b: absorbs blue and orange light the best Carotenoids: absorbs blue and green best Figure 7.7

Different pigments absorb light differently

Photosystems: Clusters of pigments in thylakoid membrane Photosystem I Traps light energy and transfers the light-excited electrons to an electron transport chain. Those excited electrons are replaced by splitting a molecule of water, which releases oxygen. The electron transport chain releases energy, which is used to make ATP Photosystem II Produces NADPH by transferring excited electrons and hydrogen ions to NADP+.

Light Reactions Photosystem I and Photosystem II SUMMARY: In the light reactions, electron transport chains generate ATP, NADPH, & O2 Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons The excited electrons are passed from the primary electron acceptor to electron transport chains The light reactions convert light energy to the chemical energy of ATP and NADPH Watch the following animation: http://www.youtube.com/watch?v=eY1ReqiYwYs

Two types of photosystems cooperate in the ight reactions Inputs: Water Sunlight energy Outputs: Oxygen ATP NADPH Photon ATP mill Photon Water-splitting photosystem NADPH-producing photosystem

Plants produce O2 gas by splitting H2O The O2 liberated by photosynthesis is made from the oxygen in water (H+ and e-)

ELECTRON TRANSPORT CHAIN The production of ATP in photosynthesis Thylakoid compartment (high H+) Light Light Thylakoid membrane Antenna molecules Stroma (low H+) ELECTRON TRANSPORT CHAIN PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE

A Photosynthesis Road Map Chloroplast Light Stroma NADP Stack of thylakoids ADP + P Calvin cycle Light reactions Sugar used for cellular respiration

Light reactions Role of chlorophyll: Photosystem Role of chlorophyll: Capture energy from light Role of an electron carrier: transport electrons Tracking electrons and energy NADP+ + 2e- + H+  NADPH

Calvin Cycle Location- Purpose- Input – Output – Tracing carbon Factors affecting photosynthesis

Calvin Cycle Called a cycle because the starting material, RuBP, is regenerated. Uses carbon from carbon dioxide, the energy from ATP, and high energy electrons and hydrogen ions from NADPH to make a small sugar named G3P. The plant uses G3P to make glucose and other organic molecules. Overall input: CO2, ATP, NADPH Overall output: Glucose

Calvin Cycle Watch the following animation: http://www.youtube.com/watch?v=mHU27qYJNU0&NR=1

Review: Photosynthesis uses light energy to make food molecules Light reactions use water and produce oxygen. The Calvin Cycle uses ATP and NADPH created in the the light reactions to convert carbon dioxide to glucose. Chloroplast Light Photosystem II Electron transport chains Photosystem I CALVIN CYCLE Stroma Electrons Cellular respiration Cellulose Starch Other organic compounds LIGHT REACTIONS CALVIN CYCLE

Fill out the following chart to compare Photosynthesis and Cellular Respiration Function Location Reactants Products Equation

Photosynthesis – Cellular Respiration comparison Function Energy capture Energy release Location Chloroplasts Mitochondria Reactants CO2 and H2O C6H12O6 and O2 Products Equation 6CO2 + 6H2O light> C6H12O6 + 6O2 6O2 + C6H12O6  6CO2 +6H2O + energy