PhotosynthesisPhotosynthesisChapter 6Chapter 6Miss ColabelliMiss ColabelliBiology CPABiology CPA

Obtaining EnergyObtaining Energy

Autotroph: energy (Autotroph: energy (glucoseglucose) from ) from sunlightsunlight..6CO6CO22 + 6H + 6H22O + sunlight O + sunlight C C66HH1212OO66 + 6O + 6O22

Heterotroph: energy from Heterotroph: energy from food food

Why is Photosynthesis Why is Photosynthesis important?important?

Makes Makes organicorganic molecules molecules out of out of inorganicinorganic materials materials

It begins all food chains & It begins all food chains & webswebs

All life is supported by this All life is supported by this processprocess

It also makes It also makes oxygen gas!oxygen gas!

Photosynthesis-starts ecological food webs!

Plants use Plants use sunlightsunlight to to turn water and turn water and carboncarbon dioxidedioxide into into glucose.glucose.

Plants use Plants use glucoseglucose as as food food

AutotrophsAutotrophs make make glucose and glucose and heterotrophsheterotrophs are are consumersconsumers of it. of it.

Photo-synthesisPhoto-synthesis == "putting together with light.""putting together with light."

Overview of PhotosynthesisOverview of Photosynthesis

Light ReactionsLight ReactionsSunlightSunlight is absorbed and converted to is absorbed and converted to

chemical energychemical energyChemical energy is temporarily stored in Chemical energy is temporarily stored in

plants as plants as ATPATP and and NADPHNADPH

Calvin CycleCalvin CycleCOCO22, , ATPATP, and , and NADPHNADPH make organic make organic

compounds compounds

6CO2 + 6H2O C6H12O6 + 6O2

PhotosynthesisPhotosynthesis

Carbon dioxide + water glucose + oxygenCarbon dioxide + water glucose + oxygensunlightsunlight

absorbed by chlorophyllabsorbed by chlorophyll

66COCO22 + + 66HH22O + energy O + energy C C66HH1212OO66 + + 66OO22

Plants Plants in in

ActionAction

Capturing Light EnergyCapturing Light Energy

During light reactions, the plant’s During light reactions, the plant’s chloroplastschloroplasts absorb the sunlightabsorb the sunlight

ElodeaElodeaSame plant that we used for transport. The green circular

organelles are the chloroplasts!

Elodea using Elodea using photosynthesphotosynthes

isis

What gas do What gas do you think is you think is

in the in the bubbles that bubbles that

the plant the plant made?made?

Why are plants green?Why are plants green?

The light we see from the sun is The light we see from the sun is whitewhite light, but its light, but its way more than white!way more than white!

Colors that we see are Colors that we see are reflected reflected from the object. from the object.

Pigment in PlantsPigment in Plants

Why do we see green? Why do we see green? Green color from white light Green color from white light reflectedreflected NOT NOT

absorbed by the chlorophyll in the chloroplastabsorbed by the chlorophyll in the chloroplast

Visible light is only a small part of the electromagnetic

spectrum (all forms of light).

Converting Light Energy Converting Light Energy to Chemical Energyto Chemical Energy

Absorbing light energy to make Absorbing light energy to make chemicalchemical energyenergy

Pigments: Absorb different colors of white Pigments: Absorb different colors of white light (ROY G BIV)light (ROY G BIV)

Main pigment: Main pigment: Chlorophyll aChlorophyll a Accessory pigments: Accessory pigments: Chlorophyll bChlorophyll b and and

CarotenoidsCarotenoids These pigments absorb These pigments absorb allall wavelengths (light) wavelengths (light)

EXCEPT green!EXCEPT green!http://www.youtube.com/watch?v=ljPU1nDVq-0

Absorption Spectra for Photosynthetic Pigment

Photosystem IIPhotosystem II

Light Light Energy Energy ReactionsReactions

PhotosystemsPhotosystems

Each photosystem is light Each photosystem is light dependentdependent Photosystem II is occurs first Occurs on the membrane of the Occurs on the membrane of the thylakoidthylakoid sacs in sacs in

the chloroplaststhe chloroplasts 1. Water is split and electrons are passed to a

protein 2. Once light is absorbed the electrons are

excited and move to the following protein in the membrane

3. The primary electron acceptor donates the electron to the electron transport chain

Light Light Energy Energy ReactionsReactions

Photosystem I occurs next4. The electrons from the electron transport

chain are transferred to the primary acceptor protein once light is absorbed

5. Primary electron acceptor donates to another electron transport chain (towards the stroma)

6. The electrons are donated once last time to a molecule NADP+ (low energy) and this become NADPH (higher energy)

http://www.dnatube.com/video/2899/Photosynthesis-101-presented-by-Dr-Undergrad

How do you get an e- How do you get an e- from water?from water?

There is an There is an enzymeenzyme that can break water that can break water molecules into 3 productsmolecules into 3 products

One of the final products is electronsOne of the final products is electrons

2H2H22O O 4H4H++ + 4e + 4e-- + O + O22For every 2 molecules of For every 2 molecules of waterwater, you get 4 electrons , you get 4 electrons

and and oxygen gasoxygen gasThis is the oxygen we breathe!This is the oxygen we breathe!

Making ATP!Making ATP!

The The thylakoidthylakoid has its membrane has its membrane and proteins throughout and proteins throughout

HH++ ions are ions are higherhigher concentration concentration inin the cell the cell

ATP ATP synthasesynthase: protein in membrane that : protein in membrane that transferstransfers H H++ ions via ions via facilitatedfacilitated diffusion diffusion

This process give the needed This process give the needed energyenergy to to combine ADP + extra P in the cell to make combine ADP + extra P in the cell to make ATPATP

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

http://www.youtube.com/watch?v=AUPugYBkNJQ&list=PLB3AF0B8D290D071D

CalvinCalvin

Named after American Named after American biochemist biochemist Melvin CalvinMelvin Calvin

Most commonly used pathway by most Most commonly used pathway by most plantsplants

Calvin cycle is used by plants that are Calvin cycle is used by plants that are called C3 because of the called C3 because of the 3-Carbon 3-Carbon molecules molecules that are madethat are made

Calvin CycleCalvin Cycle

Light-independent reaction Light-independent reaction ((Dark ReactionDark Reaction))Does Does notnot require light require light

Calvin CycleCalvin CycleOccurs in Occurs in stromastroma of chloroplast of chloroplastRequires Requires COCO22

Uses Uses ATPATP and and NADPHNADPH as fuel to run as fuel to runMakes Makes glucoseglucose sugar from CO sugar from CO22 and and

HydrogenHydrogen

Uses Uses productsproducts from the light reactions from the light reactions + CO+ CO22 to make to make sugarssugars and other and other compoundscompounds

What are the products of the light What are the products of the light reactions?reactions?

Where does the COWhere does the CO22 come from? come from?

Calvin CycleCalvin Cycle

Step 1Step 1COCO22 is diffused into the is diffused into the stromastroma of the of the

chloroplast chloroplast

A 5-Carbon molecule named A 5-Carbon molecule named RuBPRuBP combines to combines to the COthe CO22

The Enzyme that catalyzes this reaction is The Enzyme that catalyzes this reaction is rubiscorubiscoThis becomes a 6-Carbon molecule that is very This becomes a 6-Carbon molecule that is very

unstableunstableSplit to become Split to become twotwo 3-Carbon molecules called 3- 3-Carbon molecules called 3-

phosphoglycerate (phosphoglycerate (3-PGA3-PGA))

6-Carbon Sugar 6-Carbon Sugar 3-PGA + 3-PGA 3-PGA + 3-PGA

Step 2Step 2

3-PGA is still 3-PGA is still unstableunstable 3-PGA 3-PGA glyceraldehyde 3-phosphate ( glyceraldehyde 3-phosphate (G3PG3P))

For this to occur, each 3-PGA molecule For this to occur, each 3-PGA molecule gets a gets a phosphatephosphate from ATP and a from ATP and a protonproton from NADPH from NADPH

Once the molecule receives the P and Once the molecule receives the P and proton it converts into proton it converts into G3PG3P

3-PGA + P + H 3-PGA + P + H G3PG3P

Where did the P and H come Where did the P and H come from?from?

*ATP*ATP ADP + P ADP + P

*NADPH *NADPH NADP NADP++ + H + H

Step 3Step 3One G3P molecule leaves the Calvin One G3P molecule leaves the Calvin

cycle cycle This will be used to make a This will be used to make a carbohydratecarbohydrate

laterlater

Step 4Step 4

The other G3P molecule gets converted The other G3P molecule gets converted BACKBACK to to RuBPRuBP due to an addition of another due to an addition of another phosphatephosphate from ATP from ATP G3P + P G3P + P RuBP RuBP

This RuBP goes back to the Calvin cycle to be This RuBP goes back to the Calvin cycle to be fixed againfixed again

StomaStomaThis opening how plants exchange This opening how plants exchange

gases!gases!

Why are the Why are the stomata located stomata located on the bottom of on the bottom of leaves?leaves?

StomaStomaStoma OpenStoma Open

COCO22 can can increaseincrease

OO22 will will decreasedecrease and and leave cellsleave cells

Stoma Stoma ClosedClosedCOCO22

decreasedecreaseOO22

increasesincreases

CC44 Pathway Pathway

Plants that use this are called Plants that use this are called CC44 plants plants and have stomata and have stomata closedclosed during hot part during hot part of of dayday

Enzyme fixes COEnzyme fixes CO22 to a to a 4-carbon 4-carbon compound when COcompound when CO2 2 is low and Ois low and O22 is is highhigh

Corn, sugar cane, & crab grassCorn, sugar cane, & crab grass

Usually Usually tropicaltropical climates climates

CAM PathwayCAM Pathway

Water Water conservingconserving pathway pathway

Hot dry Hot dry climatesclimates

Stoma Stoma closedclosed during day & during day & openopen at at nightnightOpposite of ordinary plantsOpposite of ordinary plants

Pineapples & cactusesPineapples & cactuses

CAM PathwayCAM Pathway

During the dayDuring the dayStoma are Stoma are closedclosedCOCO22 is is releasedreleased from compounds and from compounds and

enters Calvin cycleenters Calvin cycle

During the nightDuring the nightStoma are Stoma are openopenTake in COTake in CO2 2 and and fixfix into carbon into carbon

compoundscompounds

PHOTOSYNTHESISPHOTOSYNTHESIS

What affects photosynthesis?What affects photosynthesis? Light intensity: as Light intensity: as lightlight increases, rate of photosynthesis increases, rate of photosynthesis

increasesincreases until it reaches a certain point until it reaches a certain point

PHOTOSYNTHESISPHOTOSYNTHESIS

What affects photosynthesis?What affects photosynthesis? Carbon Dioxide: As Carbon Dioxide: As COCO22 increases, rate of increases, rate of

photosynthesis photosynthesis increasesincreases until it reaches a certain point until it reaches a certain point

PHOTOSYNTHESISPHOTOSYNTHESIS

What affects photosynthesis?What affects photosynthesis? Temperature: Temperature:

Temperature Temperature LowLow = Rate of photosynthesis = Rate of photosynthesis lowlow Temperature Temperature IncreasesIncreases = Rate of photosynthesis = Rate of photosynthesis

increasesincreases If temperature is If temperature is too hottoo hot, rate , rate dropsdrops