Photosynthesis: Life from Light and Air 2006-2007

Trapping Energy from Sunlight The process that uses the sun’s energy to make simple sugars is called photosynthesis.

AN OVERVIEW OF PHOTOSYNTHESIS Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water PHOTOSYNTHESIS

Plants are energy producers Like animals, plants need energy to live unlike animals, plants don’t need to eat food to make that energy Plants make both FOOD & ENERGY animals are heterotrophs(consumers) plants are autotrophs (producers)

What do plants need to grow? The “factory” for trapping energy & making sugars chloroplast Fuels sunlight carbon dioxide water The Products - Oxygen & Glucose The Helpers Enzymes sun CO2 O2 enzymes sugars H2O

Bring In Let Out Move Around leaves shoot roots  light CO2 H2O O2 sugars leaves shoot roots 6CO2 6H2O C6H12O6 6O2 light energy  +

Chloroplasts absorb sunlight & CO2 Leaf Leaves CO2 Chloroplasts in cell Chloroplast Chloroplast Chloroplasts contain Chlorophyll make ENERGY & SUGAR

Stomates & Guard Cells in the leaf Function of stomates CO2 in O2 out H2O out gets to leaves for photosynthesis Function of guard cells open & close stomates guard cell stomate

THE LIGHT REACTIONS: CONVERTING SOLAR ENERGY TO CHEMICAL ENERGY Visible radiation drives the light reactions Certain wavelengths of visible light drive the light reactions of photosynthesis X-rays Micro- waves Radio waves Gamma rays UV Infrared Visible light Wavelength (nm)

pigments in the chloroplast To trap the energy in the sun’s light, the thylakoid membranes contain pigments, molecules that absorb specific wavelengths of sunlight. Wavelengths that are NOT absorbed are reflected (bounce off) or transmitted (pass through) So the material in which the pigment is found appears to be the color of the wavelengths that are NOT absorbed Photosynthetic pigments: can absorb light energy & make it available for conversion to chemical energy . Light Reflected light Chloroplast Absorbed light

pigments in the chloroplast Chlorophyll a: most common pigment in chloroplast (absorbs blue &red light and reflects green light thus giving the chloroplast a green color)(chloro = green phylla + leaf) Accessory pigments: additional pigments that absorb different wavelengths (carotene, chlorophyll b, & xanthophyll)

Factors Affecting Rate of Photosynthesis Temperature: increases rate up to a certain point Light Intensity: increases rate up to a certain point CO2 level: Increases rate up to a certain point Water: decrease water, decrease photosynthesis Minerals; Ex. Magnesium, Nitrogen