PHOTOSYNTHESISPHOTOSYNTHESIS

I. Autotrophs and HeterotrophsEnergy for living things comes from the SUNSUNPlants and other organisms use light energy from the sun to produce food

A. Autotrophs- make their own food• Ex: plants, some bacteria, protists

• Heterotrophs- obtain it from the foods they consume

» Ex: animals, some bacteria, protozoans (and even fungi!)

• Sooo… food as energy is either MADE through photosynthesis or OBTAINED through consumption

II. Light & PigmentsA. In addition to water & CO2,

photosynthesis requires LIGHT LIGHT and

CHLOROPHYLLCHLOROPHYLL, a molecule in chloroplasts

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

C. Visible energy spans wavelengths of approx. 400-700 nm

D. It is part of the electromagnetic spectrum

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

F. Leaves blue-violet & red-orange light very well G. Green light is REFLECTED why plants look green!

ABSORB

Plant pigments absorb different wavelengths of energy- which wavelength is the LEAST absorbed?

Green is NOT absorbed!

H. Plant Pigments

Chlorophyll a - Absorbs all colors of light

except green - Plays major role in light

reactions of photosynthesis

Chlorophyll b - Yellow-green

Xanthophyll - In carotenoid family- Yellow

Carotene - Red & orange pigments

III. Role of Pigments

A.A. When chlorophyll absorbs light, much When chlorophyll absorbs light, much

of the energy is transferred to raising of the energy is transferred to raising

the energy level of the energy level of ELECTRONSELECTRONS in in

the the CHLOROPLASTSCHLOROPLASTS

B. These electrons power photosynthesisB. These electrons power photosynthesis

Think about the Location of Photosynthesis…

Location of PhotosynthesisWhich tissues contain chloroplasts?

Other Important Parts

Xylem: transports H2O

Stoma: pore that allows gases to enter and exit

A.A. Double-membrane Double-membrane structurestructure

1outer membrane

2 inner membrane

3 granum (stack)

4 Thylakoid (individual)

5 Stroma (fluid)

I. CHLOROPLAST STRUCTURE

ThylakoidsThylakoids: : photosynthetic membranes that have clusters of photosynthetic membranes that have clusters of chlorophyll II and other pigmentschlorophyll II and other pigments

GranaGrana are stacks of thylakoids are stacks of thylakoids

StromaStroma: Fluid surrounding thylakoids: Fluid surrounding thylakoids

Photosynthesis Has Two Parts:

D. PHOTOSYNTHESISD. PHOTOSYNTHESIS

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

Outputs: sugar and oxygenOutputs: sugar and oxygen

II. Chemical Energy & ATPII. Chemical Energy & ATP

A. ATP (adenosine triphosphate) is an organic molecule that is a source of potential energy for all cells.

Using Biochemical energy• ATP is useful to all types of cells as their

basic energy source

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

microtubules use energy

Releasing energy from ATP Stored energy is released from ATP when ATP is broken down into ADP + Phosphate

B. Add/subtract Phosphate and you can store/release ENERGY!

III. Light ReactionIII. Light Reaction

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

1.1. Chloroplasts use them to make energy-Chloroplasts use them to make energy- rich molecules called rich molecules called NADPHNADPH and and ATPATP

2.2. The overall result of the The overall result of the LIGHTLIGHT reaction only? reaction only?

Light + Chlorophyll + HLight + Chlorophyll + H22O Oxygen + NADPH + ATPO Oxygen + NADPH + ATP

3.3. ADP and NADP+ are ADP and NADP+ are recycledrecycled back back into the systeminto the system

4.4. Light reaction is charging up the Light reaction is charging up the ““batterybattery””

needed to synthesize sugars in Calvin needed to synthesize sugars in Calvin CycleCycle

IV. Calvin CycleIV. Calvin Cycle

A.A. Does NOT use light at allDoes NOT use light at all

B.B. This is the process to use This is the process to use energy from Light Cycle to energy from Light Cycle to convert COconvert CO22 into glucose into glucose

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

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

3.3. NADP+ and ADP are recycled back to NADP+ and ADP are recycled back to the Light Cycle for the Light Cycle for ““rechargingrecharging””

C. The Process

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