PHOTOSYNTHESISPHOTOSYNTHESIS

I. Autotrophs and HeterotrophsA. Energy for living things comes from the SUNSUNB. Plants and other organisms use light energy

from the sun to produce foodC. Autotrophs- make their own food

» Ex: plants

D.Heterotrophs- cannot use sun energy to make their food and obtain it from the foods they

consume» Ex: leopards, mushrooms

II. Chemical Energy and II. Chemical Energy and ATPATP

A. To live, organisms must release A. To live, organisms must release energy in sugars and other energy in sugars and other compoundscompounds

B. ATPB. ATP»adenosine triphosphateadenosine triphosphate»chemical compound used to chemical compound used to

store energystore energy

C. Releasing energy from ATP-> Stored energy is released from

ATP when ATP is broken down into ADP + Phosphate

-> Add/subtract Phosphate and you can store/release ENERGY!

D. When is ATP used?»Active transport»Powers movement inside cell:

microtubules use energy

III. Light & PigmentsA. Photosynthesis requires LIGHT LIGHT and

CHLOROPHYLLCHLOROPHYLL, a molecule in chloroplasts, in addition to water & CO2

B. Sunlight is “white” but contains mixtures of visible wavelengths

C. Plants gather sun’s energy using light-absorbing molecules called PIGMENTSPIGMENTS

D. Leaves absorb blue-violet & red-orange light very well E. Green light is reflected- why plants look green!

Chlorophyll a - Absorbs all colors of light

except green

- Plays major role in light

reactions of photosynthesis

Chlorophyll b - Appears yellow-green

- Absorbs additional light

Xanthophyll - In carotenoid family

- Yellow

- Fat soluble

Carotene - Accessory pigments

- Red & orange pigments

Major Pigments-

use light energy directly

Accessory Pigments-

pass absorbed light energy to chlorophyll

IV. LOCATION OF PHOTOSYNTHESIS

V. Role of Pigments

A. When chlorophyll absorbs A. When chlorophyll absorbs light, much of the energy is light, much of the energy is transferred to raising the transferred to raising the ENERGY LEVELENERGY LEVEL in the in the CHLOROPLASTSCHLOROPLASTS

B. EQUATIONB. EQUATION

Inputs: Light, carbon dioxide, & waterInputs: Light, carbon dioxide, & water

Outputs: sugar and oxygenOutputs: sugar and oxygen

** Chloroplast has double membrane **** Chloroplast has double membrane **

ThylakoidsThylakoids: sac-like photosynthetic : sac-like photosynthetic

membranesmembranes– Arranged in stacks called GRANAArranged in stacks called GRANA– Have clusters of Have clusters of chlorophyllchlorophyll and other and other

pigments pigments

StromaStroma: Fluid area surrounding : Fluid area surrounding

thylakoidsthylakoids

CHLOROPLAST STRUCTURE

* Light-Dependent* Light-Dependent: :

takes place in takes place in

thylakoidsthylakoids

* Calvin Cycle:* Calvin Cycle:

takes place in takes place in

stromastroma

Light ReactionLight Reaction

1.1. Chlorophyll molecules in Chlorophyll molecules in thylakoid capture light thylakoid capture light energyenergy

2.2. This energy releases This energy releases electrons from Helectrons from H22OO

3.3. HH22O then splits into OO then splits into O22 and and H+ H+

4.4. Oxygen is a "waste Oxygen is a "waste product" & escapes to the product" & escapes to the atmosphereatmosphere

So what happens to the So what happens to the electrons and hydrogen ions?electrons and hydrogen ions?

• Chloroplasts use them to make an Chloroplasts use them to make an energy-rich molecule called NADPH energy-rich molecule called NADPH and ATPand ATP

• The overall result of the light reaction?The overall result of the light reaction?Light Oxygen + NADPH + ATPLight Oxygen + NADPH + ATP

• ATP and NADP are ATP and NADP are recycledrecycled back back into the systeminto the system

• Light reaction is charging up the Light reaction is charging up the ““batterybattery”” needed to synthesize needed to synthesize sugars in Calvin Cyclesugars in Calvin Cycle

Calvin CycleCalvin Cycle

• Does NOT use light at allDoes NOT use light at all• Process to store energy Process to store energy

that was made in light that was made in light cycle in the form of sugarcycle in the form of sugar

1.1. The enzymes for the Calvin cycle are located The enzymes for the Calvin cycle are located outside the thylakoids dissolved in the STROMA.outside the thylakoids dissolved in the STROMA.

2.2. Uses COUses CO22 and energy powered by ATP and and energy powered by ATP and NADPH to produce sugarNADPH to produce sugar

3.3. NAPDH and ATP are recycled back to the Light NAPDH and ATP are recycled back to the Light Cycle for Cycle for ““rechargingrecharging””

The Calvin Cycle

Reactants:Reactants:

Products:Products:

Two ProcessesTwo Processes

Light ReactionLight Reaction Calvin CycleCalvin Cycle

Factors Affecting Factors Affecting PhotosynthesisPhotosynthesis

• Shortage of raw materialsShortage of raw materials• TemperatureTemperature• Light intensityLight intensity