Bellwork:What do you know

about photosynthesis?Photo-synthesisPhoto-synthesis

means means "putting together with light.""putting together with light."

6CO2 + 6H2O (+ light energy) -----> C6H12O6 + 6O2

Respiration Respiration

C6H12O6 + 6O2 -----> 6CO2 + 6H2O + Energy (ATP)

Photosynthesis-starts the ecological food webs!

What is photosynthesis?

A chemical reaction in which light energy is converted to chemical energy in the form

of glucose.  It is how the energy in

sunlight becomes usable to living things. 

Why is it so important?

Two big reasons:1. One product is glucose (sugar),

which provides the basis for most food chains. 

2. The second product is oxygen which is needed by aerobic organisms (require oxygen) for survival.

Photosynthesis

Carbon dioxide + water glucose + oxygen

sunlightsunlight

absorbed by chlorophyllabsorbed by chlorophyll

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

As can be seen from the equation for photosynthesis, the wood, bark, and root came from water and carbon dioxide.

Where does photosynthesis

occur?Most photosynthesis occurs in the oceans, the oceans occupy (70%) of the earth's surface!

In terms of organisms, photosynthesis occurs in autotrophs that contain the green pigment chlorophyll.

Review: What is an autotroph? 

Multicellular level: photosynthesis occurs in the leaves of plants. 

Cellular level: the reactions for photosynthesis occur in the chloroplasts of eukaryotes and in the cytoplasm of prokaryotes.

Plant leaves have many types of cells!

Chloroplasts make the sugars!

PlantsLeaves are green

because they contain

the pigment:

chlorophyllchlorophyll

Why do leaves Why do leaves have a broad have a broad surface area?surface area? "Thanks for the Glucose!""Thanks for the Glucose!"

PHOTOSYNTHESIS

• Why do we see green? • Green color from white light

reflected NOT absorbed• Chloroplast: organelle

responsible for photosynthesis• Chlorophyll: located within

Chloroplast• Green pigment

Plant Cells

The photograph below is an elodea leaf X 400. Individual cells are clearly visible. The tiny green structures within the cells are chloroplaststhis is where photosynthesis

happens.                                    

What raw materials are needed?

Chlorophyll   Sunlight Water Carbon dioxide

Biochemical Pathway

Photosynthesis is a series of two reactions

The products from the 1st rxn are used in the 2nd

PHOTOSYNTHESIS• 2 Phases

• Light-dependent reaction• Light-independent reaction

• Light-dependent: converts light energy into chemical energy; produces ATP molecules to be used to fuel light-independent reaction

• Light-independent: uses ATP produced to make simple sugars.

Summary of Photosynthesis

carbon dioxide + water + light energy ---> glucose + oxygen + water

As a chemical formula: CO2 + H2O + light energy

---> C6H12O6 + O2 + H2O

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Extra Tidbits Important part of Oxygen-

Carbon Dioxide Cycle.  –pumps out oxygen

–Removes CO2 from atmosphere

↑levels of CO2 linked with ↑ global temp (think "Global Warming"). 

Chloroplasts

½ of the chemistry occurs in a liquid inside the chloroplasts called STROMA

½ of photosynthesis occurs in stacks of membranes inside the chloroplast called GRANA.

ChlorophyllGreen pigment, which absorbs sunlight.

2 types of chlorophyll–chlorophyll a –chlorophyll b

Chlorophyll a is the main, b is an accessory 

Chemical ReactionOccurs in two phases.

Capture Energy #1 is called the "light reactions".  It

requires light!

Convert Energy to Food #2 is called "carbon fixation" or the

"dark reactions". Aka Calvin Cycle

It does not require light.Start with CO2 End with Glucose

Photosynthesis

EQUATION FOR PHOTOSYNTHESIS

6CO6CO22 + + 6H6H22OO + +ENERGYENERGY CC66HH1212OO66 + + 6O6O22

CARBON CARBON DIOXIDEDIOXIDE

WATERWATER

GLUCOSEGLUCOSE

OXYGENOXYGEN

Back to the Chloroplast

The light reactions occur in the grana, which contain the chlorophyll for absorbing light. 

The dark reactions occur in the stroma.

Detailed Light Reactions

The light reactions use light & water, & produce the oxygen "waste product". 

The light energy is used to split the water molecule (photolysis), which produces e-’s. H+ & O- ions.  The oxygen is released from the plant into the air.

ATP & NADPH2 are energy molecules. 

They will be used up during the dark reactions, as will the H+ ions.

                                                                      

           

Electron Transport

CONVERTS to useable Energy

1. Light excites the electrons2. E-’s leave chlorophyll a and

go to the primary electron acceptor (PEA) (in thylakoid membrane)

Sun

Chlorophyll passes energy down through the electron transport chain.

for the use in light-independent reactions

bonds Pto ADP

forming ATP

oxygenreleased

splitsH2O

H+

NADP+

NADPH

Light energy transfers to chlorophyll.

Energized electrons provide energy that

• At each step along the transport chain, the electrons lose energy.

3. PEA then donates the e’s to other molecules which pass them on over and over. (electron transport chain)

4. E’s join with a proton and NADP+ which forms NADPH

Replacing the Electrons

E-’s are taken from the chlorophyll to pass down the ETC.

They must be replaced to be passed down again.

E-’s accumulated during photolysis are given to the chlorophyll.

Check it!

Photosynthesis Rap

EQUATION FOR PHOTOSYNTHESIS

6CO6CO22 + + 6H6H22OO + +ENERGYENERGY CC66HH1212OO66 + + 6O6O22

CARBON CARBON DIOXIDEDIOXIDE

WATERWATER

GLUCOSEGLUCOSE

OXYGENOXYGEN

PHOTOSYNTHESIS

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

photosynthesis _____________________

PHOTOSYNTHESIS

• What affects photosynthesis?• Carbon Dioxide: As CO2 increases, rate of

photosynthesis _________________

PHOTOSYNTHESIS

• What affects photosynthesis?• Temperature:

• Temperature Low = Rate of photosynthesis low

• Temperature Increases = Rate of photosynthesis increases

• If temperature too hot, rate drops

Chlorophyll: A Light Absorbing PigmentChlorophyll: A Light Absorbing PigmentThe Solar Panel Chemical!The Solar Panel Chemical!

Photosynthesis

Glucose provides the energy and carbon needed to make other plant materials like wax and proteins.

Oxygen and Sugar!

• In plants and simple animals, waste products are removed by diffusion. Plants, for example, excrete O2, a product of

photosynthesis.

PHOTOSYNTHESIS

• How did we get O2 as a byproduct?!

• Photolysis: replaces lost electrons by splitting water

Check it!

1. The process that uses the sun’s energy to make simple sugars is _____________.

A. Cellular respiration

B. Glycolysis

C. Photosynthesis

D. Photolysis

Check it!

2. The function accomplished by the light-dependent reactions is ______________.

A. Energy storage

B. Sugar production

C. Carbon fixation

D. Conversion of sugar