PHOTOSYNTHESIS

Photosynthesis:Photosynthesis:LifeLife fromfrom Light Light andand

AirAir

CAPTURING THE ENERGYIN LIGHT

The process by which organisms obtain energy directly from sunlight is called photosynthesis.

CO2 + H2O → C6H12O6 + O2

ENERGY FOR LIFEPROCESSES

Autotrophs: most Plants, Autotrophs: most Plants, Algae, and some Bacteria.Algae, and some Bacteria.

Autotrophs store energy in various organic compounds, primarily carbohydrates.

Photosynthesis involves a complex series of chemical reactions: Biochemical Pathway

Products used in cellular Products used in cellular respiration in respiration in bothboth plants plants and animals.and animals.

The BasicBy McGraw

Hill

oror

Oxidation is loss of hydrogen.Oxidation is loss of hydrogen.

Reduction is gain of hydrogen.Reduction is gain of hydrogen.

OIL RIGOIL RIGOxidation is LossOxidation is Loss

Reduction is Gain (of e-)Reduction is Gain (of e-)

Redox Reactions:

How are they connected?How are they connected?

glucose + oxygen carbon + water + energydioxide

C6H12O6 6O2 6CO2 6H2O ATP+ + +

+ water + energy glucose + oxygencarbondioxide

6CO2 6H2O C6H12O6 6O2light

energy + ++

oxidation = exergonic

reduction = endergonic

Heterotroph and….

Autotroph

NPK

…

H2O

What does it mean to be a What does it mean to be a plantplant Need to…

collect light energy transform it into chemical energy

store light energy in a stable form to be moved around

the plant or stored need to get building block atoms

from the environment C,H,O,N,P,K,S,Mg

produce all organic molecules needed for growth carbohydrates, proteins, lipids, nucleic acids

ATP

glucose

CO2

LIGHT ABSORPTION INCHLOROPLASTS

Light Reactions or Light Dependent Reactions

They begin with the absorption of lightin chloroplasts.

Review of theLight Reaction

With AllDetails!

CHLOROPLASTSCHLOROPLASTS

LIGHT AND PIGMENTS

chlorophylls accessory pigments carotenoids

Photosynthesis gets energy by absorbing wavelengths of light.

Accessory pigments with different structures absorb light of different wavelengths: chlorophyll a & b, carotenoids, xanthophylls, antenna pigments

What is Photosynthesis?What is Photosynthesis? Light reactions

light-dependent reactions convert solar energy to chemical energy

ATP & NADPH

Calvin cycle light-independent reactions sugar building reactions

uses chemical energy (ATP & NADPH) to reduce CO2 & synthesize C6H12O6

It’s not theDark Reactions!

Virtual CellPhoto.

LIGHT REACTIONSLIGHT REACTIONS

1.1. ELECTRON TRANSPORT CHAIN: ELECTRON TRANSPORT CHAIN: PHOTOSYSTEMS II AND I. PHOTOSYSTEMS II AND I.

1.1. chlorophyll chlorophyll aaPP680680 = absorbs 680nm = absorbs 680nm

wavelength red light wavelength red light chlorophyll chlorophyll bbPP700700 = absorbs 700nm = absorbs 700nm

wavelength red lightwavelength red light

2.2. REPLENISHING PHOTOSYSTEM IIREPLENISHING PHOTOSYSTEM II3.3. CHEMIOSMOSISCHEMIOSMOSIS

Photosystem

I

Go to: D-DriveYoutube Streaming Video

Photosystem I file bVirtual Cell:Photosynthesis

ELECTRON TRANSPORT CHAINELECTRON TRANSPORT CHAIN

The BasicBiochemical

Pathway

RESTORING PHOTOSYSTEM IIRESTORING PHOTOSYSTEM II

CHEMIOSMOSISCHEMIOSMOSIS

What is Photophosphorylation? What is Photophosphorylation?

NONcyclicphotophosphorylation

cyclicphotophosphorylation

ATP

NADP

Why Cyclic Phosphorolation?Why Cyclic Phosphorolation?

Calvin cycle uses more ATP than NADPH

18 ATP +12 NADPH

1 C6H12O6

PUTTING IT ALL TOGETHERPUTTING IT ALL TOGETHER

Review of theLight Reaction

With AllDetails!

OverviewOf the

Light Reaction

Photosynthesis AnimationPhotosynthesis Animation

http://www.stolaf.edu/people/giannini/flashanimat/metabolism/photosynthesis.swf

6CO2 6H2O C6H12O6 6O2light

energy + ++

Experimental evidenceExperimental evidence

Where did the OWhere did the O22 come from? come from? radioactive tracer = radioactive tracer = OO1818

6CO2 6H2O C6H12O6 6O2light

energy + ++

Experiment 1

6CO2 6H2O C6H12O6 6O2light

energy + ++

Experiment 2

Proved O2 came from H2O not CO2 = plants split H2O!

Photosynthesis summary Photosynthesis summary Where did the energy come from?Where did the energy come from?

Where did the electrons come from? Where did the electrons come from?

Where did the HWhere did the H22O come from?O come from?

Where did the OWhere did the O22 come from? come from?

Where did the OWhere did the O22 go? go?

Where did the HWhere did the H++ come from? come from?

Where did the ATP come from?Where did the ATP come from?

What will the ATP be used for? What will the ATP be used for?

Where did the NADPH come from?Where did the NADPH come from?

What will the NADPH be used for?What will the NADPH be used for?

So where does COSo where does CO22 fit in? fit in?

How do plants use it? How do plants use it?

Why do they need it?Why do they need it?

LIGHT INDEPENDENT LIGHT INDEPENDENT REACTIONSREACTIONS

KNOWN AS THE KNOWN AS THE CALVIN CYCLE CALVIN CYCLE = = C3 Photosynthesis.C3 Photosynthesis.

COCO2 2 IS FIXED INTO ORGANIC IS FIXED INTO ORGANIC COMPOUNDS: CARBON FIXATION.COMPOUNDS: CARBON FIXATION.

THREE MAJOR STEPS, WHICH OCCUR WITHIN THE STROMA.

Reduction Reaction= C gains H+ Calvin

Cycle

How do Plants

CaptureCO2?

Welcome to the Dark Side, Lord Calvin

P.S. The Dark Cycle Does P.S. The Dark Cycle Does Not Happen in the DarkNot Happen in the Dark

It is dependent on the products of the light It is dependent on the products of the light reaction (ATP and NADPH) So when the reaction (ATP and NADPH) So when the

lights go out…it has no energy to continue.lights go out…it has no energy to continue.

NOVACapturing C

Think…Think…

Why can’t we blow carbon emissions into Why can’t we blow carbon emissions into forests and solve global warming?forests and solve global warming?

ALTERNATIVE PATHWAYS TO FIX CARBON These alternative pathways are

generally found in plants that evolved in hot, dry climates.

Stomata: passageways FOR CO2 and O2.

C-4: PhotosynthesisC-4: Photosynthesis

Intense Sunlight and Hot (e.g. corn and Intense Sunlight and Hot (e.g. corn and crabgrass)crabgrass)

Stomata are Partly Closed During Day= CO2 Stomata are Partly Closed During Day= CO2 falls and O2 risesfalls and O2 rises We don’t want photorespiration.We don’t want photorespiration.

In the Mesophyll In the Mesophyll PEP carboxylasePEP carboxylase grabs CO2 grabs CO2 not O2.not O2.

Sends CO2 to the Calvin cycleSends CO2 to the Calvin cycle

The C4 Pathway FIXES CO2 INTO A FOUR CARBON

COMPOUND OXALOACETATE. HENSE THE NAME: C4

Oxaloacetate in the mesophyll turns into Malate, an acid.

Malate is shipped through plasmodesmata into bundle sheath cells and release CO2

Calvin Cycle Starts

The CAM PlantsThe CAM Plants

Adaptation to Adaptation to Dry ConditionsConditions Stomata Closed during Day Open at NightStomata Closed during Day Open at Night Mesophyll stores CO2 at nightMesophyll stores CO2 at night Makes Sugar during Day Makes Sugar during Day All 3 (C3, C-4, and CAM) use the Calvin All 3 (C3, C-4, and CAM) use the Calvin

CycleCycle

Crassulacean Acid Metabolism

The CAM Pathway Plants that use the CAM pathway open their stomata at night and close them during the day—just the opposite of what other plants do.

RATE OF PHOTOSYNTHESIS

Review