ANNOUNCEMENTS Test 4 will be on Friday May 23 over photosynthesis, cellular

respiration, and biogeochemical cycles These information is not in your textbook, so notes will be

provided, it is critical you attend class to get the notes Posters Due Wednesday, May 28 Final Exam Schedule

PHOTOSYNTHESISSC.912.L.18.7 Identify the reactants, products, and basic functions of

photosynthesis.

PHOTOSYNTHESIS MEANING “LIGHT” “BUILDING”

Biological process by which energy from the sun (radiant energy) is transformed into chemical energy of sugar molecules

6 CO2 + 12 H2O + radiant energy

C6H12O6 + 6 H2O + 6 O2

PHOTOSYNTHESIS EQUATIONPhotosynthesis: “Synthesis from

light”The broad outline: Plants take in CO2,

produce carbohydrates, and release water and O2

Light is required

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PHOTOSYNTHESIS OVERVIEW

Energy for all life on Earth ultimately comes from photosynthesis.

Oxygenic photosynthesis is carried out by:cyanobacteria, 7 groups of algae, all land plants

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PHOTOSYNTHESIS IS DIVIDED INTO TWO MAIN PARTS

1.light-dependent reactionscapture energy from sunlightmake ATP and reduce NADP+ to NADPHOccurs in thylakoid membrane

2.carbon fixation reactionsuse ATP and NADPH to synthesize organic molecules from CO2

Occurs in stroma

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PHOTOSYNTHESIS STRUCTURE

Photosynthesis takes place in chloroplasts.Chloroplasts are found in the leaves of plants•thylakoid membrane – internal membrane arranged in flattened sacs that contain chlorophyll and other pigments•grana – stacks of thylakoid membranes•stroma – semiliquid substance surrounding thylakoid membranes

PHOTOSYNTHESISTwo pathways:1. Light reactions: Convert light energy

to chemical energy as ATP and NADPH2. Light-independent reactions: Use

ATP and NADPH (from the light reactions) plus CO2 to produce carbohydrates; sometimes called Calvin Cycle

PHOTOSYNTHESIS

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HOW SUNLIGHT IS CAPTURED

1. photon: a particle of lightacts as a discrete bundle of energyenergy content of a photon is inversely proportional to the wavelength of the light

2. photoelectric effect: removal of an electron from a molecule by light

occurs when photons transfer energy to electrons

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ELECTROMAGNETIC SPECTRUM

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PIGMENTS

Pigments: molecules that absorb visible lightEach pigment has a characteristic absorption spectrum, the range and efficiency of photons it is capable of absorbing.

1. Chlorophyll a – primary pigment in plants and cyanobacteria; absorbs violet-blue and red light

2. Chlorophyll b – secondary pigment absorbing light wavelengths that chlorophyll a does not absorb

3. Carotenoids- secondary pigment absorbs different light wavelengths, orange-red pigment; contains the antioxidant beta-carotene

4. Xanthophylls- secondary pigment; yellowish pigment

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ABSORPTION SPECTRUM OF 3 PIGMENTS

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STOMATA=PORES IN THE LEAF OF PLANTS Gas Exchange• CO2 in and O2 out•Water evaporates

3 DIFFERENT TYPES OF PHOTOSYNTHESIS1. C3 Plants- use the normal Calvin cycle to fix CO2 to glucose;

called C3 b/c CO2 is first incorporated into 3 carbon compound; stomata are open during day; most plants fall into this group

2. C4 Plants- use a different enzyme and have a special anatomy; called C4 b/c CO2 is incorporated into 4 carbon compound; stomata are open during day; examples include corn, Bermuda grass

3. CAM plants- CAM stands for Crassulacean Acid Metabolism; stomata are closed during the day; CO2 is converted to an acid at night; examples include pineapple plant, cacti, agaves

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CAM PHOTOSYNTHESIS

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CLIMATIC ADAPTATION Each method of photosynthesis has advantages and disadvantages Depends on the climateC4 plants most adapted to:

high light intensities high temperatures Limited rainfall

C3 plants better adapted to Cold (below 25C) High moisture

CAM plants better adapted to extreme aridity CAM occurs in 23 families of flowering plants