PhotosynthesisPhotosynthesis

The process of capturing, converting The process of capturing, converting and storing energy from the sun by and storing energy from the sun by

green plants.green plants.

In simple terms:In simple terms:

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

This is the This is the OPPOSITE OPPOSITE reaction to cell respiration.reaction to cell respiration.

Plants do BOTH photosynthesis and cell respiration.Plants do BOTH photosynthesis and cell respiration.

3 Steps in Photosynthesis3 Steps in Photosynthesis1.1. Absorption of sunlightAbsorption of sunlight2.2. Conversion of sunlight energy (TO ENERGY Conversion of sunlight energy (TO ENERGY

CARRIERS)CARRIERS)3.3. Storage of energy in sugar (carbon “fixing”)Storage of energy in sugar (carbon “fixing”)

**Steps 1 + 2Steps 1 + 2 MUST take place in the light MUST take place in the light( ( LIGHT DEPENDENT REACTIONS)LIGHT DEPENDENT REACTIONS)

**Step 3Step 3 Can happen in the light or in the dark Can happen in the light or in the dark (LIGHT INDEPENDENT REACTIONS)(LIGHT INDEPENDENT REACTIONS)

Light Dependent Reactions Light Dependent Reactions Absorption by PigmentsAbsorption by Pigments

Requires Requires pigments pigments to absorb lightto absorb light Chlorophyll AChlorophyll A (absorbs red, orange and violet) (absorbs red, orange and violet)

Chlorophyll BChlorophyll B (extends range of absorption to (extends range of absorption to include more blue light)include more blue light)

CarotenoidsCarotenoids (absorbs blue and green light) (absorbs blue and green light)

Light Dependent Reactions Light Dependent Reactions Conversion to Energy CarriersConversion to Energy Carriers

Electrons in the pigments are Electrons in the pigments are excited excited and passed and passed (“transferred”) to other molecules (NADPH)(“transferred”) to other molecules (NADPH)

Water is split into Hydrogen and OxygenWater is split into Hydrogen and Oxygen The oxygen from water is releasedThe oxygen from water is released

Electrons (from Hydrogen) are used to power the Electrons (from Hydrogen) are used to power the creation of ATP and NADPHcreation of ATP and NADPH

Like ATP, NADPH can be used to make reactions Like ATP, NADPH can be used to make reactions happenhappen

The ATP and NADPH is used to make The ATP and NADPH is used to make molecules of glucose (Cmolecules of glucose (C66 H H1212 O O66) from carbon ) from carbon dioxide (COdioxide (CO22))

This process is called This process is called carbon fixing carbon fixing or the or the CALVIN CYCLE.CALVIN CYCLE.

Light Independent ReactionsLight Independent ReactionsCarbon FixingCarbon Fixing

Summary of PhotosynthesisSummary of Photosynthesis

InputInput OutputOutput

Stage 1 Stage 1 (light dependent)(light dependent)

Stage 2Stage 2(light dependent)(light dependent)

Stage 3Stage 3(LIGHT (LIGHT

INDEPENDENT)INDEPENDENT)

Sunlight & waterSunlight & water

ElectronsElectrons

NADPH, CO2NADPH, CO2

Oxygen & Oxygen & electronselectrons

ATP & NADPHATP & NADPH

GlucoseGlucose(C6 H12 O6)(C6 H12 O6)