Photosynthesis• Using light E to produce food

• Autotrophs

• Producers– Food for

entire biosphere

Where in plants does photosynthesis occur?

another redox reaction…

• Water is split apart– Lose e- or oxidized, leaving O2

• CO2 is reduced to sugar– Gain e-

• Opposite of cellular respiration?

Photosynthesis occurs in two stages

• Light Reactions– Convert light E to

chemical E and O2 waste

– Thylakoid membranes– Cellular respiration

• NADP+ is reduced to NADPH as e- carrier

• Calvin Cycle

• Stage 2 – Calvin Cycle

– In stroma

– Builds sugarsfrom CO2 and E converted in Stage 1

– NADPH provides the e- to reduce CO2

– ATP provides the E to drive the Calvin cycle

What is solar or light energy??

Pigments– Light absorbing molecules

– In thylakoid membranes

• Absorb wavelengths of light (some is reflected or transmitted)

Chlorophyll ablue-violet & red

Chlorophyll bblue & orange

Carotenoidsaccessoryprotect from excessXanthophylls

Filters, greenhouses, & global warming?

• How do filters work?

• What color filter is best suited for growing green plants?

• What are the effects of varying levels of CO2?

• How does a greenhouse affect plant growth?

• What is the greenhouse effect?

• Measure photosynthetic rate by CO2 assimilation– difference in CO2 input to

CO2 output

• Manipulate light and CO2

• Measure surface area• Set parameters• Collect data• Analyze…

whiteblue

red

green

How does a greenhouse affect plant growth?

• When its too cold outside

• Light passes inside• Reflective heat is

trapped inside

What is the greenhouse effect?

• Solar radiation passes in through atmosphere

– Ozone filters out most of UV

– Sunlight passes inside– Reflective heat is

trapped inside by atmospheric gases

Good thing; keeps Earth warm

Global Warming• CO2 production and release to the

atmosphere increases?– Burning more fossil fuels

• Carbon based (coal, oil, gasoline)

– Widespread deforestation• Less plants to consume or recycle CO2

• Thus… temperature increases– Melting polar ice– Rising sea level– Extreme weather patterns

“Who speaks for the trees?”