Did You Know? How Plants Make Food That most of the Oxygen in the air is thought to be from PHOTOSYNTHESIS Nutrition Autotrophs (make their own food) Ex) Green plants, protists, algae, phytoplankton Nutrition Heterotrophs (can t make their own food so they depend on other plants & animals as their source of food) Ex) Humans and animals Basic Needs For Plant Growth Carbon dioxide (CO2) Water (H2O) Light energy (sunlight) Light Energy: Sunlight Sunlight is a form of ENERGY Sunlight is a mixture of all wavelengths. Sunlight is called white light. 1
Visible Light Spectrum ROY ROY G BIV BV White Light Plants grow better in red & blue light. Plants don t grow well in green light so this is why green is the color that is reflected & not absorbed. So the reflected color is what we see, which is the color green in plants. Is autotrophic nutrition Chemical reactions controlled by enzymes that convert Solar Energy (sunlight) into Chemical Energy = GLUCOSE Inorganic molecules CO 2 and H 2 O are changed into Organic molecules C 6 H 12 O 6 Glucose is stored as starch How can we summarize? carbon dioxide+ water + energy glucose + oxygen + water CO 2 + H 2 O + light energy ---> C 6 H 12 O 6 + O 2 + H 2 O Reactants (Chlorophyll In leaf) Products CarbonDioxide + Water + Light Energy (Materials needed) (End Products) Glucose + Oxygen http://www.rwynn.com/bio20ap/ 2
Time Frame (when): During Daylight Location: Chloroplasts 2 Types of Chlorophylls A substance that absorbs light is called a pigment. Chlorophyll is a pigment found inside the chloroplast of plants & is used for photosynthesis. Chlorophyll A Chlorophyll B Chlorophyll is the chemical in chloroplast. Both absorb red and blue light. Both reflect green light. 2 Types of Chlorophylls 2 Types of Chlorophylls Chlorophyll A Chlorophyll B The main pigment involved in photosynthesis. Directly converts light energy into chemical energy. Known as Carotene (orange) & Xanthophylls (yellow). Absorbs light & transfers the energy to chlorophyll a. 3
Have You Ever Wondered Why Leaves in Autumn Change Color? Cholorplasts The site where photosynthesis takes place. Inside A Chloroplast Structures Inside The Chloroplast Thylakoids - Sac-like structures where photosynthesis occurs Grana - Stacks of thylakoids Stroma - The region or space between the grana. A Chloroplast Stroma Granum Thylakoid 4
2 Types of Reactions For Light Reaction light dependent reaction Reaction takes place ONLY in presence of light. Dark Reaction light independent reaction Reaction takes place Without light. Needs chemical energy products made during light energy reaction. Two reactions (steps) inside the Chloroplast 1)The light dependent reactions occur in GRANA 2)The light independent reaction (dark reaction) in STROMA I. Light Dependent Reaction Occurs in the grana Light energizes the Chlorophyll makes ATP Water enters the grana and is split into Hydrogen and Oxygen (Photolysis) Oxygen is released from the plant. Hydrogen is carried by NADPH over to the Calvin Cycle along with ATP. Plants produce O 2 gas by splitting H 2 O The O 2 released by photosynthesis comes from the water II The Calvin Cycle= Light Independent Reaction Occurs in the stroma (liquid part of chloroplast) CO 2 enters the Calvin Cycle and joins with the Hydrogen from NADP forming glucose. NADP + returns to the grana to pick up more Hydrogen from split H2O. 5
Light Reaction Materials that enter the chloroplasts are light energy (from sunlight) & water (from soil). Dark Reaction (Light Dependent Reaction) Oxygen is released into the air because water molecules (H2O) were split. The end products for the light reaction: ATP NADPH ATP, NADPH, & CO2 enters the Calvin Cycle. ATP provides energy & the NADPH helps to break down the CO2 to form GLUCOSE (C6H12O6). AN OVERVIEW OF PHOTOSYNTHESIS The light reaction convert solar energy to chemical energy Produce ATP & NADPH The Calvin cycle makes sugar from carbon dioxide ATP generated by the light reaction provides the energy for glucose synthesis The NADPH produced by the light reactions provides the hydrogen for carbon dioxide to make glucose Light Light reactions Chloroplast NADP + ADP + P Calvin cycle Chloroplasts & Stomates From A Leaf Stomates (Stomata) Stomata (opening) Guard cell OPENED STOMATA CO2 enters leaf O2 leaves leaf H2O leaves stomata in the form of water vapor Rapid cooling of the leaf CLOSED STOMATA CO2 level drops within leaf Dark reaction stops working & this stops Stomata are small pores or openings on the surface of leaves. Guard Cells a specialized cell under the surface of the leaves for controlling gas exchange & water loss. 6
Stomata (Stoma) & Guard Cell PHOTOSYNTHESIS The equation for changing light energy into chemical energy: 6CO2 + 12H2O C6H12O6 + 6O2 Carbon Dioxide + Water light Glucose + Oxygen : An Overview : An Overview AN Alternative Diagram Understanding the Light & Dark Reaction of Factors Affecting Light intensity Temperature Water Mineral Availability 7
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