Photosynthesis Chapter 5 PDF

Photosynthesis Chapter 5  Where do we acquire energy from? ▪ Extracting energy stored in the organic products of photosynthesis T.E. Adams Autotrophs Carolina Biological Autotrophs Tom Uhlman Heterotrophs Adam Jones Heterotrophs John and Barbara Gerlach  So...

Photosynthesis Chapter 5  Where do we acquire energy from? ▪ Extracting energy stored in the organic products of photosynthesis T.E. Adams Autotrophs Carolina Biological Autotrophs Tom Uhlman Heterotrophs Adam Jones Heterotrophs John and Barbara Gerlach  Solar-Powered Sea Slug ▪ As the Emerald green sea slug (Elysia chlorotica) feeds on algae (Vaucheria littorea), it takes their chloroplasts into the cells of its own digestive system, where they provide it with energy and sugars. “Solamander”: Photosybnthetic Spotted Salamander ▪ In 1888, Henry Orr was collecting spotted salamander eggs from a small, swampy pool when he noticed that some of them were green ▪ More than 120 years later, Ryan Kerney from Dalhousie University found that the algae actually invade the cells of the growing embryo, becoming part of its body. ▪ There were algal symbionts located inside the salamander cells. ▪ algae is present in the oviducts of adult female spotted salamanders, where the embryos form in their sacs. This means that it's possible symbiotic algae are passed from mother to offspring during reproduction.  Photosynthesis and Aerobic Respiration: A Global Connection ▪ Earth’s early atmosphere – no O2 permanently ▪ Evolution of photosynthesis ▪ Ancient organisms extracted energy and carbon from molecules such as methane and hydrogen sulfide  Light - form of electromagnetic energy, radiating from the sun traveling through space, in waves Visible light: wavelengths 380-750 nm (25 million nanometers =1 inch) shortest wavelengths range of most radiation longest wavelengths (highest energy) reaching Earth’s surface (lowest energy) visible light gamma ultraviolet near-infrared infrared x-rays microwaves radio waves rays radiation radiation radiation 400 nm 500 nm 600 nm 700 nm We see the combined wavelengths as white light ▪ Wavelength - Distance between the crests of two successive waves of light The shorter the wavelength, the greater the energy Humans perceive different wavelengths of visible light as different colors Photosynthetic Pigments: Organic molecules that absorb light at specific wavelengths Chlorophyll a - Main photosynthetic pigment in plants Some Photosynthetic Pigments ▪ Chloroplast Thylakoid membrane two outer membranes Stroma of chloroplast Semifluid substance stroma between the thylakoid membrane and the membranes of a chloroplast  Two Stages of Photosynthesis 6CO2 + 6H2O → (light energy) → C 6 H12O6 + 6O2 Occurs in thylakoid Occurs in membrane stroma Two Stages of Photosynthesis ADP ATP NADP+ A) Light-dependent reactions NADPH H2O energy O2 ATP ADP B) Light-independent NADPH NADP + reactions (Calvin–Benson CO2 glucose cycle)  Light-Dependent Reactions: in Thylakoid Membranes light energy electron electron transfer transfer chain chain ATP 8 1 light energy 5 synthase 4 6 ADP, 3 phosphat photosystem e thylakoid compartment 2 stroma H2O O2 7 ▪ 1. Light energy ejects electrons from a photosystem. ▪ 2. The photosystem pulls replacement electrons from water molecules, which break apart into oxygen and hydrogen ions. The oxygen leaves the cell as O2. ▪ 3. The electrons enter an electron transfer chain in the thylakoid membrane. ▪ 4. Energy lost by the electrons as they move through the chain is used to actively transport hydrogen ions from the stroma into the thylakoid compartment. A hydrogen ion gradient forms across the thylakoid membrane.  Light-Dependent Reactions: in Thylakoid Membranes light energy electron electron transfer transfer chain chain ATP 8 1 light energy 5 synthase 4 6 3 ADP, photosystem phosphate thylakoid compartment 2 stroma H2O O2 7 ▪ 5. Light energy ejects electrons out of another photosystem. Replacement electrons come from an electron transfer chain. ▪ 6. The ejected electrons move through a second electron transfer chain, then combine with NADP+ and H+, so NADPH forms. ▪ 7. Hydrogen ions in the thylakoid compartment are propelled through the interior of ATP synthases by their gradient across the thylakoid membrane.  Carbon Fixation ▪ Process by which CO2 (inorganic) is incorporated into an organic molecule (sugar) ▪ In the stroma, enzyme Rubisco (ribulose-1, 5-biphosphate carboxylase) adds CO2 to RuBP (ribulose biphosphate) in the Calvin-Benson cycle ▪ Glucose is produced after 6 cycles. Adaptations to Hot and Dry Climates ▪ Waterproof cuticle - allows plants to live where water is scarce ▪ Stomata Closable gaps on plant surfaces; allow gas exchange ▪ C3 plants Close stomata on dry days to conserve water But oxygen builds up and thus, problem  Photorespiration ▪ Problem: O2 binds to the active site of Rubisco enzyme instead of CO2 (photorespiration) ▪ Slows glucose production ▪ Compensate by making more Rubisco Photosynthesis and Aerobic Respiration 1. The O2 molecules released during photosynthesis come from … ▪ A. Glucose ▪ B. O2 ▪ C. atmosphere ▪ D. water 2. What is/are the product/products of the light- independent reactions? ▪ A. ATP ▪ B. NADPH ▪ C. Sugar ▪ D. O2 3. Which of the following are the product/products of the light-dependent reaction? ▪ A. ATP ▪ B. NADPH ▪ C. Sugar ▪ D. a & b