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Chapter 8 photosynthesis rap 8-1 Autotrophs – make their own food Heterotrophs – consume their food Forms of energy: ◦ Light, heat, sound, electrical, chemical… The form of energy used by living things is chemical. The principal chemical compound that stores and releases energy in cells is ATP ◦ Adenosine triphosphate ATP Section 8-1 Adenine ATP Ribose 3 Phosphate groups ATP stores energy in the bonds between the phosphates. To store energy, ADP adds on a third phosphate to become ATP. To release energy, ATP gives up the third phosphate to become ADP ATP charging Figure 8-3 Comparison of ADP and ATP to a Battery Section 8-1 ADP ATP Energy Adenosine diphosphate (ADP) + Phosphate Partially charged battery Energy Adenosine triphosphate (ATP) Fully charged battery Active transport Charging nerve cells Movement Protein synthesis Cell division ALL chemical reactions! Everything! 8-2 1643 Jan van Helmont After careful measurements of a plant’s water intake and mass increase, van Helmont concluded that trees gain most of their mass from water. 1771 Joseph Priestley Using a bell jar, a candle and a plant, Priestley finds that a plant releases oxygen. Jan Ingenhousz Ingenhousz finds that aquatic plants produce oxygen bubbles in the light but not in the dark. He concludes that plants need sunlight to produce oxygen. Julius Robert Mayer Mayer proposes that plants convert light energy into chemical energy. Melvin Calvin Calvin traces the chemical path that carbon follows to form glucose. These reactions are known as the Calvin Cycle. Rudolph Marcus Marcus wins the Nobel prize in chemistry for describing the process by which electrons are transferred from one molecule to another in the electron transport chain. Are they made by a single scientist? Or are they the work of many scientists over many years? Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into highenergy sugars and oxygen. Carbon dioxide + water + light glucose + oxygen 6CO2 + 6H2O + light C6H12O6 + 6O2 Photosynthesis requires the presence of light- absorbing molecules called pigments. ◦ Chlorophyll is the principal pigment. ◦ This pigment is located in the chloroplasts. Photosynthesis: Reactants and Products Light Energy Chloroplast CO2 + H2O Sugars + O2 Chlorophyll a absorbs violet and red light the best. ◦ It does NOT absorb green or yellow well. Chlorophyll b absorbs mainly blue and red wavelengths of light. ◦ It does NOT absorb green or yellow either. There are two other photosynthetic pigments, carotene (orange) and xanthophyll (yellow). ◦ They absorb other wavelengths of light and transfer the energy to chlorophyll. Photosynthetic Pigments Absorption of Light by Chlorophyll a and Chlorophyll b Chlorophyll b Chlorophyll a V B G YO R 8-3 Photosynthesis overview Stacks of internal membranes called thylakoids contain photosystems. Photosystems carry out the reactions of photosynthesis involving light (“light reactions”). In between the thylakoids the stroma carries out more reactions that do not require light (“dark reactions”). Figure 8-7 Photosynthesis: An Overview Section 8-3 Light H20 Chloroplast CO2 NADP+ ADP + P LightDependent Reactions Calvin Cycle ATP NADPH O2 Sugars Chloroplast Takes place in the thylakoids. Chlorophyll absorbs light. Light energy is used to do two things: 1. Split water into hydrogen and oxygen gas. Oxygen is released to the environment. Hydrogen is carried to the stroma for the next set of reactions. 2. Produce high energy carriers ATP and NADPH Both are used in the dark reactions. http://vcell.ndsu.nodak.edu/animations/ http://www.youtube.com/watch?feature=playe r_embedded&v=BK_cjd6Evcw Figure 8-10 Light-Dependent Reactions Section 8-3 Photosystem II Hydrogen Ion Movement ATP synthase Inner Thylakoid Space Thylakoid Membrane Stroma Electron Transport Chain Photosystem I ATP Formation Chloroplast Take place in the stroma Don’t require light Carbon dioxide is combined with hydrogen to make glucose. Energy (ATP) from the light reactions runs the dark reactions. Also known as the “Calvin Cycle” and “carbon fixation”. Figure 8-11 Calvin Cycle Section 8-3 CO2 Enters the Cycle Energy Input ChloropIast 5-Carbon Molecules Regenerated 6-Carbon Sugar Produced Sugars and other compounds Availability of water Temperature Light intensity Availability of minerals Concentration of carbon dioxide How does water get to the leaves for photosynthesis? “Transpiration pull” brings water up to the leaves. ◦ Transpiration is the loss of water vapor out the leaves through openings called stomates. Section 23-5 A B Evaporation of water molecules out of leaves. Pull of water molecules upward from the roots. Section 23-5 A B Evaporation of water molecules out of leaves. Pull of water molecules upward from the roots. What regulates water loss from the leaves? ◦ Guard cells open and close the stomates to regulate water loss. In dry conditions guard cells close the stomates. In wet conditions guard cells open the stomates. Section 23-4 Cuticle Veins Epidermis Palisade mesophyll Xylem Phloem Vein Spongy mesophyll Epidermis Stoma Guard cells Section 23-4 Guard cells Guard cells Inner cell wall Inner cell wall Stoma Stoma Open Stoma Closed What else does a plant need from the soil besides water? Section 23-2 Nutrient Role in Plant Result of Deficiency Nitrogen Proper leaf growth and color; synthesis of amino acids, proteins, nucleic acids, and chlorophyll Stunted plant growth; pale yellow leaves Phosphorus Synthesis of DNA; development of roots, stems, flowers, and seeds Poor flowering; stunted growth Potassium Synthesis of proteins and carbohydrates; development of roots, stems, and flowers; resistance to cold and disease Weak stems and stunted roots; edges of leaves turn brown Magnesium Synthesis of chlorophyll Thin stems; mottled, pale leaves Calcium Cell growth and division; cell wall structure; cellular transport; enzyme action Stunted growth; curled leaves