AP Biology

Photosynthesis: Life from Light

Adapted from Ms. Lisa Miller’s AP Biology Notes.

AP Biology

How are they connected?

glucose + oxygen carbon + water + energydioxide

C6H12O6 6O2 6CO2 6H2O ATP+ + +

Heterotrophs and Autotrophs

+ water + energy glucose + oxygencarbondioxide

6CO2 6H2O C6H12O6 6O2light

energy + ++

Autotrophsmaking energy & organic molecules from light energy

making energy & organic molecules from ingesting organic molecules

Where’s the ATP?

AP Biology 2005-2006

Plant Structure Obtaining Raw Materials

Sunlight Leaves = solar collectors Mesophyll cells have a

large number of chloroplasts.

CO2

Stomata= gas exchange Found under leaves

H2O: uptake from roots. Nutrients: uptake from

roots.

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Chloroplasts Double membrane Stroma Thylakoid sacs Grana stacks

Part of photosynthesis occurs in the thylakoid membrane.

Plant Structure

H+ H+

H+

H+

H+H+

H+ H+

H+H+

H+

AP Biology 2005-2006

Pigments of Photosynthesis

Chlorophyll and Accessory Pigments Embedded in thylakoid

membrane. Structure Function

Why does this structure make sense?

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Light: Absorption Spectra Photosynthesis gets energy by absorbing

wavelengths of light. Chlorophyll a (dominant pigment)

Absorbs best in red & blue wavelengths. Absorbs least in green.

Other pigments with different structures absorb light of different wavelengths.

Why areplants green?

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Photosynthesis

Light Reactions Light-dependent Reactions Energy production reactions.

Convert solar energy to chemical energy.

Calvin Cycle Light-independent Reactions Sugar production reactions.

It’s the Dark Reactions!

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Photosystems 2 photosystems in

thylakoid membrane. Act as light-gathering

“antenna complex.” Photosystem II:

chlorophyll a Photosystem I:

chlorophyll b

reactioncenter

Energy is passed to the primary electron acceptor, which removes an excited electron form the chlorophyll.

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The Light Reaction

2005-2006

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From Light Reactions to Calvin Cycle Calvin cycle

Location: chloroplast stroma.

Need products of light reactions to drive synthesis reactions. ATP NADPH

What is there

left to do?

Make sugar!

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From CO2 C6H12O6

CO2 has very little chemical energy. C6H12O6 contains a lot of chemical energy.

The reaction of CO2 C6H12O6 proceeds in many small uphill steps. Each catalyzed by specific enzyme. Using energy stored in ATP and NADPH.

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Calvin Cycle

2005-2006

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Summary Light Reactions:

produced ATP produced NADPH consumed H2O produced O2 as by product

Calvin Cycle: consumed CO2

produced glucose regenerated ADP regenerated NADP ADP NADP

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Factors that affect Photosynthesis Enzymes are a part of photosynthesis,

therefore, temperature and pH can affect the rate of photosynthesis.

The amount and type of light can affect the rate.

A shortage of any of the reactants,CO2 and/or H2O, can affect the rate.

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Supporting a biosphere

On global scale, photosynthesis is the most important process for the continuation of life on Earth.

Each year photosynthesis synthesizes 160 billion tons of carbohydrate.

Heterotrophs are dependent on plants as food source for fuel & raw materials.

AP Biology

Energy cycle

Photosynthesis

Cellular Respiration

glucose O2H2OCO2

ATP

sun

The Great Circleof Life!

Where’s Mufasa?

AP Biology 2005-2006

Summary of photosynthesis

Where did the CO2 come from? Where did the CO2 go? Where did the H2O come from? Where did the H2O go? Where did the energy come from? What’s the energy used for? Where did the O2 come from? Where will the O2 go?

6CO2 6H2O C6H12O6 6O2light

energy + ++