Ch 8 Energy From Sunlight

8.1.2.3 Photosynthesis uses light energy to make food Where? Chloroplasts Grana Thylakoid

Structure of Leaf and Chloroplast Mesophyll is leaf layer Stomata (stoma) CO2 in O2 out Veins Carry H2O and nutrients Chloroplast in the mesophyll

Structure of Chloroplast cont’ Stroma Thick fluid that rxns occur in Photosynthesis takes place in the chloroplast Usually in leaves Chlorophyll Chemical that gives green color; uses light in photosynthesis Light hits plant – 3 things: Thylakoids (form stacks) Stacks of thylakoids (grana/granum) that rxns occur in Absorb

Overview of Photosynthesis Chloroplast use e-, CO2 and H+ Produce sugar Opposite of cellular respiration (Glucose + O2  CO2 + H2O + “energy”) e- are boosted “uphill” Sunlight energy CO2 + H2O  C6H12O6 + O2 6CO2 + 6H2O  C6H12O6 + 6O2 LIGHT

Light Reactions Chlorophyll in grana capture light Remove e- from H2O H+ used O2 is “waste product” e- and H+ used to make NADPH Chloroplast generate ATP Light energy stored as: NADPH and ATP Convert light energy to chemical energy

Calvin Cycle ATP made in L.R. provides energy Enzymes needed are in stroma Can complete in the dark Does not require light to begin Makes sugar from CO2, H+ and e- (from NADPH)

8.4 Photosynthesis has a global impact Carbon Cycle C moves from inorganic to organic compounds and back

Photosynthesis and Global Climate Key molecule of Carbon cycle: CO2 Most organisms (including plants) give off some CO2 Plants go through cellular respiration!! CO2 traps heat in Greenhouse effect About 10° C warmer

Photosynthesis and Global Climate cont’ Prior to ~1900 CO2 made up 300 ppm of atmosphere Now 360 ppm Pg 173 Issues to consider… Global Warming Deforestation Fossil Fuels Alternative Fuel Alternative Transportation

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