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“LIFE from LIGHT and AIR”PRODUCERS/AUTOTROPHS – CONVERT LIGHT ENERGY TO CHEMICAL ENERGY; SYNTHESIZE ORGANIC MOLECULES
CONSUMERS/HETEROTROPHS – CONSUME OTHERS FOR ORGANIC MOLECULES AND ENERGY
glucose + oxygen carbon dioxide + water + energy
carbon dioxide + water + energy glucose + oxygen
What’s the connection?
PHOTOSYNTHEIS:REDUCTION = ENDERGONIC
CELLULAR RESPIRATION:OXIDATION = EXERGONIC
OVERVIEW
6 CO2 + 6 H20 C6H1206 + 6O2
carbon dioxide water glucose oxygen
6 CO2 + 12 H20 C6H1206 + 6O2 + 6H20
HOW DO PLANTS ACQUIRE ENERGY AND RAW MATERIALS?
H2O enters roots
Leaves are “solar collectors”Organ of photosynthesis
CO2 enters through stomates
Roots take up needed nutrients: N, P, K, S, Fe, Mg………………….
HOW IS A LEAF ORGANIZED TO BE A “SOLAR COLLECTOR”?
stomate – opening for gas exchange
air space – gas exchange
vascular bundle – transport tissues of plant/ xylem & phloem; visible as leaf “vein”
mesophyll –photosynthesis
LIGHTLIGHT a form of energy called electromagnetic a form of energy called electromagnetic
radiationradiation Kinetic energyKinetic energy It has a dual nature: behaves like a wave It has a dual nature: behaves like a wave
and behaves like a discrete particleand behaves like a discrete particle
Light - wavesLight - waves
Light causes disturbance in electric and Light causes disturbance in electric and magnetic fields – like a pebble thrown magnetic fields – like a pebble thrown into waterinto water
Each form of electromagnetic radiation Each form of electromagnetic radiation has a specific wavelength and frequencyhas a specific wavelength and frequency
Light - particlesLight - particles
Photon – particles of lightPhoton – particles of light NOT A TANGIBLE PARTICLE RATHER NOT A TANGIBLE PARTICLE RATHER
A DISCRETE BUNDLE OF ENERGY A DISCRETE BUNDLE OF ENERGY THAT BEHAVES LIKE A PARTICLETHAT BEHAVES LIKE A PARTICLE
Amount of energy is INVERSELY related Amount of energy is INVERSELY related to wavelength – the shorter the to wavelength – the shorter the wavelength the greater the energy of the wavelength the greater the energy of the photonphoton
WHEN LIGHT MEETS WHEN LIGHT MEETS MATTER . . . MATTER . . . Light is reflected – We see the wavelengths of Light is reflected – We see the wavelengths of
light that are reflectedlight that are reflected Light is transmitted – Passes through the objectLight is transmitted – Passes through the object Light is absorbed – WORK MAY BE DONELight is absorbed – WORK MAY BE DONE PIGMENT – substance that absorbs lightPIGMENT – substance that absorbs light
Chlorophyll is green because it reflects green Chlorophyll is green because it reflects green wavelengths and absorbs or transmits other wavelengths and absorbs or transmits other wavelengthswavelengths
THINK ABOUT ITTHINK ABOUT IT
Why do some objects appear white?Why do some objects appear white? Why do some objects appear black?Why do some objects appear black?
Which car remains cooler in summer – Which car remains cooler in summer – one with white paint or one with black one with white paint or one with black paint?paint?
SPECTROPHOTOMETERSSPECTROPHOTOMETERS Device for measuring amount of light absorbed or Device for measuring amount of light absorbed or
transmitted by a pigmenttransmitted by a pigment
ABSORPTION SPECTRUMABSORPTION SPECTRUM
Chlorophyll a absorbs red and blue light Chlorophyll a absorbs red and blue light best; very little green light is absorbedbest; very little green light is absorbed
Other plant pigments have different Other plant pigments have different molecular structures – absorb different molecular structures – absorb different wavelengthswavelengths
BUT HOW DO WE KNOW WHICH BUT HOW DO WE KNOW WHICH WAVELENGTHS ARE IMPORTANT WAVELENGTHS ARE IMPORTANT IN PHOTOSYNTHESIS?IN PHOTOSYNTHESIS?
Grow plants under different colors of light Grow plants under different colors of light and see which ones stimulate greatest and see which ones stimulate greatest amount of oxygen – ACTION amount of oxygen – ACTION SPECTRUMSPECTRUM
How could you measure rate of How could you measure rate of photosynthesis?photosynthesis?
Measure disappearance of reactants - Measure disappearance of reactants - carbon dioxide or watercarbon dioxide or water
Measure appearance of products – oxygen Measure appearance of products – oxygen or glucoseor glucose
Measure change in energy of the systemMeasure change in energy of the system
Oxygen is easiest to measure – use a Oxygen is easiest to measure – use a water plant and count the bubbles that rise water plant and count the bubbles that rise to the surfaceto the surface
ENGLEMANN - 1883ENGLEMANN - 1883
Grew filamentous algae under light that Grew filamentous algae under light that had been passed through a prismhad been passed through a prism
Aerobic bacteria grew in greatest Aerobic bacteria grew in greatest numbers on part of filament exposed to numbers on part of filament exposed to red light and blue light – very little on part red light and blue light – very little on part exposed to green lightexposed to green light
ConclusionConclusion
Chlorophyll’s action spectrum overlaps its Chlorophyll’s action spectrum overlaps its absorption spectrumabsorption spectrum
These are the wavelengths of light that These are the wavelengths of light that power photosynthesispower photosynthesis
CHLOROPHYLL CHLOROPHYLL aa
Only chlorophyll Only chlorophyll aa can participate directly can participate directly in the light reactions – no chlorophyll a in the light reactions – no chlorophyll a means no photosynthesismeans no photosynthesis
Color – blue-greenColor – blue-green
Chlorophyll Chlorophyll bb
An ACCESSORY PIGMENTAn ACCESSORY PIGMENT Its absorption spectrum is not identical to Its absorption spectrum is not identical to
chlorophyll a; increases the amount of chlorophyll a; increases the amount of visible light that can be used for visible light that can be used for photosynthesisphotosynthesis
Transfers the energy it absorbs to Transfers the energy it absorbs to chlorophyll achlorophyll a
Color – yellow-green Color – yellow-green
CarotenoidsCarotenoids An ACCESSORY PIGMENTAn ACCESSORY PIGMENT Its absorption spectrum is not identical to Its absorption spectrum is not identical to
chlorophyll a or b; increases the amount of chlorophyll a or b; increases the amount of visible light that can be used for visible light that can be used for photosynthesisphotosynthesis
Transfers the energy it absorbs to chlorophyll Transfers the energy it absorbs to chlorophyll aa
Color – yellow to orangeColor – yellow to orange Also “sun screen” to protect plant DNA from Also “sun screen” to protect plant DNA from
UV radiationUV radiation