PhotosynthesisPhotosynthesis

Materials needed:Materials needed:Carbon dioxideCarbon dioxideWaterWater

Product:Product:Sugar (glucose)Sugar (glucose)Oxygen (waste product)Oxygen (waste product)

Energy source:Energy source: LightLight

Photosynthesis Photosynthesis Autotrophs Autotrophs

Self feedersSelf feeders Make their own foodMake their own food

Heterotrophs Heterotrophs feed on autotrophs feed on autotrophs each other &each other & organic wasteorganic waste

Photosynthesis occurs in the chloroplastPhotosynthesis occurs in the chloroplast 2 main reactions:2 main reactions:

• Light reaction Light reaction • Calvin cycleCalvin cycle

PhotosynthesisPhotosynthesis Organisms use light energy to make sugar Organisms use light energy to make sugar

from carbon dioxide and waterfrom carbon dioxide and water In the process they also make OxygenIn the process they also make Oxygen

6CO6CO22 + 6H + 6H22O O + C + C66HH1212OO66 + 6O + 6O22

Carbon dioxide + water yields sugar (glucose) + oxygenCarbon dioxide + water yields sugar (glucose) + oxygen

Plants make OPlants make O2 2 by splitting waterby splitting water

Light Dependent ReactionLight Dependent Reaction

Convert light energy to chemical energyConvert light energy to chemical energy OO2 2 gas produced as a waste productgas produced as a waste product

Occurs in the Occurs in the thylakoidthylakoid membranes membranes Light energy absorbed by Light energy absorbed by cholorphyllcholorphyll

1.1. Reactants: water, sun, ADP, NADPReactants: water, sun, ADP, NADP++

2.2. Products: OProducts: O22, ATP, NADPH, ATP, NADPH

PhotosystemPhotosystem Light harvesting pigments absorb light energy and pass the energy from Light harvesting pigments absorb light energy and pass the energy from

molecule to molecule until it reaches the reaction centermolecule to molecule until it reaches the reaction center The primary electron acceptor captures the light excited electron from the The primary electron acceptor captures the light excited electron from the

reaction center chlorophyll and passes it to the electron transport chainreaction center chlorophyll and passes it to the electron transport chain

Light dependent reactionLight dependent reaction Requires lightRequires light

energyenergy Chlorophyll Chlorophyll absorbs all wave length’s except green.absorbs all wave length’s except green. Photosystem IIPhotosystem II

1.1. Energy from the light is absorbed by electrons, increasing their Energy from the light is absorbed by electrons, increasing their energy level.energy level.

2.2. Electrons enter the electron transport chain which generates Electrons enter the electron transport chain which generates ATPATP

3.3. Water molecules are broken apart into – 2 electrons, 2 H Water molecules are broken apart into – 2 electrons, 2 H++ ions ions and 1 oxygen.and 1 oxygen.

• Electron supplyElectron supply

Use light energy to break water apart and forms ATP Use light energy to break water apart and forms ATP and oxygen.and oxygen.

Light Dependent Reaction Light Dependent Reaction (Continued)(Continued)

Photosystem IPhotosystem I Light energy excites electron in the reaction Light energy excites electron in the reaction

centercenter Electron raised energy level, electrons from Electron raised energy level, electrons from

the bottom of the electron transport chain the bottom of the electron transport chain supply electronssupply electrons

Electrons pass through a short ETC Electrons pass through a short ETC producing NADPHproducing NADPH• NADP+ NADP+ NADPH NADPH

Energy from the light reactions drive the Dark reactions

Light-independent reactionLight-independent reaction Calvin cycle Calvin cycle

Does not require lightDoes not require light Uses the energy from ATP and NADPH.Uses the energy from ATP and NADPH. Carbon dioxide enters the cycle. (attaches to Carbon dioxide enters the cycle. (attaches to

RuBP)RuBP) Carbon dioxide molecule is broken apart.Carbon dioxide molecule is broken apart. Oxygen is released.Oxygen is released. Carbon molecules start a cycle (six times)Carbon molecules start a cycle (six times) Use 6 molecules of carbon dioxide to produce a Use 6 molecules of carbon dioxide to produce a

single 6 –carbon sugar molecule (glucose) single 6 –carbon sugar molecule (glucose)

Calvin Cycle

ChloropIast

CO2 Enters the Cycle

Energy Input

5-CarbonMoleculesRegenerated

Sugars and other compounds

6-Carbon SugarProduced

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