Photosynthesis PDF

“Failure is an event, not a person.Yesterday ended last night” -Zig Ziglar “To improve is to change; to be perfect is to change often” -Winston Churchill The Green World’s Gift: Photosynthesis Wo rld : G lo b a l Wa rm...

“Failure is an event, not a person.Yesterday ended last night” -Zig Ziglar “To improve is to change; to be perfect is to change often” -Winston Churchill The Green World’s Gift: Photosynthesis Wo rld : G lo b a l Wa rm in g ! A n d M a n ’s G if t to t h e What is photosynthesis? Process by which plants use sunlight to synthesize foods from carbon dioxide and water. Photosynthesis in plants involves chlorophyll (green pigment) and generates oxygen as a byproduct. Cellular Respiration and Photosynthesis Cellular Respiration: aerobic harvesting of energy Aerobic = requires oxygen Photosynthesis: conversion of solar energy to chemical energy Photosynthesis Light energy 6H2O + 6CO2 C6H12O6 + 6O2 Water Carbon dioxide Glucose Oxygen Cellular Respiration C6H12O6 + 6O2 6H2O + 6CO2 + 36ATP + Heat Glucose Oxygen Water Carbon dioxide Cellular Respiration and Photosynthesis Cellular Respiration and Photosynthesis In photosynthesis, light energy is used to convert carbon dioxide to carbohydrates Cellular respiration converts energy stored in carbohydrates to ATP ATP powers chemical reactions  What organisms can photosynthesize? Phytoplankton Cyanobacteria Protists Kelp Flowering plants Conifers Ferns Mosses Role of Photosynthetic Organisms Photosynthetic organisms make up the base of all food webs.  Site of Photosynthesis Stomata: pores on leaf where gas exchange occurs Chloroplasts: organelles in plants and algae where photosynthesis occurs Thylakoids: membranes within the chloroplasts Location of photosynthetic pigments Stroma: fluid inside chloroplasts  Exergonic and Endergonic Reactions Cellular respiration: process by which all living things extract energy stored in the chemical bonds of molecules and use it to fuel cellular processes. Photosynthesis: conversion of solar energy to chemical energy  Light Energy Light energy: a type of kinetic energy made up of tiny packets of energy called photons Wavelength of photon determines energy level Shorter wavelength = more energy Longer wavelength = less energy  Photosynthetic Pigments Pigments: molecules that absorb and reflect certain wavelengths of light Photosynthetic pigments in plants: Chlorophyll a : absorbs red and blue-violet wavelengths Chlorophyll b : absorbs blue and red-orange wavelengths Carotenoids: absorbs blue-violet and blue-green wavelengths  Changing Seasons Changing Leaves Deciduous trees breakdown and conserve chlorophyll a and b during fall months. Carotenoids left in leaves reflect red yellow, and orange wavelengths of light  Role of Stomata H2O CO2 O2 Stomata Open Stomata Closed  Two Stages of Photosynthesis 1) Light Reactions Takes place in thylakoid membrane 2) Calvin Cycle Takes place in stroma  Light Reactions 1) In Photosystem II, energy from photons excite electrons in chlorophyll to higher energy level Chlorophyll replaces electrons by splitting water molecules 2) Falling electrons power the electron transport chain and ATP production 3) Energy from photons excite electrons again in Photosystem I NADP+ acts as final electron acceptor  Photosystems Antenna pigments: chlorophyll molecules that transfer light energy to reaction center Reaction center: specialized chlorophyll molecule that losses electron when it is excited to a higher energy level. Primary electron acceptor: molecule that initially accepts excited electron Light Reactions  Summary of Light Reactions Electrons excited in Photosystem II power membrane proteins, which pump hydrogen ions (H+) into thylakoid space Hydrogen ions (protons) move down their concentration gradient through ATP synthase which forms ATP Electrons excited in Photosystem I are captured by NADP+ and transported to Calvin Cycle Summary of Light Reactions  Calvin Cycle 1 Rubisco combines three molecules of atmospheric carbon with three molecules of the sugar RuBP. Three 6 carbon molecules broken down into six 3 carbon molecules (3-PGA) 2 ATP and NADPH from light reactions energize 3-PGA molecules forming six molecules the energy-rich sugar G3P 3 One molecule of G3P exits Calvin Cycle 4 ATP used to convert remaining G3P molecules into three molecules of RuBP Outputs of the Calvin Cycle Sugars used in mitochondria to produce ATP n tio ira sp Re lar th llu ow t gr Ce Plan Glucose linked together to form cellulose, creating more G3P plant tissue Stora ge Excess sugars can be stored as starch  Summary of Photosynthesis Light dependent reactions Water donates electrons to Photosystem II in the thylakoid membrane, which are then excited by light energy and used to make ATP. The electron gets excited again in Photosystem I before being passed to NADP+ to make NADPH. ATP and NADPH move to the Calvin Cycle Calvin Cycle In the stroma of the chloroplast, the enzyme Rubisco combines atmospheric CO2 with an existing carbon molecule, which is then transformed by the ATP and NADPH from the light reactions to make G3P. G3P goes on to make glucose, starch, and cellulose.  Check Your Understanding 1. True or False: Leaves are green because the green and yellow wavelengths of light are the only wavelengths absorbed by plants 2. True or False: The primary purpose of photosynthesis is to produce ATP 3. True or False: The Calvin Cycle takes place in the stomata  Check Your Understanding 4. Which of the following enter the plant through the stomata? a. Carbon dioxide b. Oxygen c. Water d. Light e. More than one of the above  Check Your Understanding 5. Which of the following best describes the role of water in photosynthesis? a. Water acts as the final electron acceptor b. Water diffuses through the thylakoid membrane through ATP synthase c. Water is a byproduct of photosynthesis d. Water donates electrons to Photosystem II e. Water transports electrons to the Calvin Cycle  Check Your Understanding 6. Which of the following best describes the role of the light reactions of photosynthesis? a. Energy from light used to convert glucose to ATP b. Energy from light is used to convert carbon dioxide to glucose c. Energy from light is used to create ATP and NADPH d. Rubisco is used to convert carbon dioxide to glucose e. Rubisco is used to convert water to oxygen  Photorespiration Under hot, arid conditions, Heat plants will close their stomata to conserve water. Photorespiration: process in which the enzyme rubisco binds with oxygen instead of H2 O carbon dioxide O2 Reduces carbohydrate production CO2 Closed stomata  Different Photosynthetic Pathways Gases Gases are exchanged at Gases are exchanged exchanged night through Carbon through slightly Carbon open stomata dioxide through open open stomata dioxide stomata Carbon uptake Carbon uptake by by PEP PEP carboxylase carboxylase Rubisco requires ATP Night requires ATP Day Rubisco Rubisco Stomata close during the day Sugar Sugar Sugar  C3, C4, and CAM Plants C3 C4 CAM Photorespiration High Low Low CO2 Fixation Rubisco Pep carboxylase Pep carboxylase Stomata (day/night) Open/close Open/close Close/open Advantage Efficient use of ATP Water conservation Water conservation Require more Disadvantage Photorespiration Requires more energy energy, Slow growth Pineapple, cacti, Examples Most plants Sugarcane, corn, grass succulents  Distribution of C3 and C4 Plants C4 plants outcompete C3 plants in hot, dry regions Global warming predicted to expand the ranges of C4 plants  Climate Change and Global Warming Greenhouse gases: gases that trap heat in the atmosphere Carbon dioxide Methane Nitrous oxide Fluorinated gases Greenhouses gases reflect infrared radiation back to earth’s surface  Sources of Greenhouse Gases Carbon dioxide: burning of fossil fuels, solid waste, trees and wood products. Methane: decomposition in landfills, production of coal, natural gas and oil, agriculture Nitrous oxide: agriculture and fertilizers, combustion of fossil fuels Fluorinated gases: refrigerants, aerosols Global Greenhouse Gas Emissions  Carbon Dioxide and Global Warming Atmospheric CO2 has increased above 300 ppm for first time in recorded history Reached 400 ppm in 2013! Correlation or Causation? Intergovernmental Panel on Climate Change (IPCC) “Scientific evidence for the warming of the climate system is unequivocal”  Evidence for Climate Change Sea level rise – global sea levels rose about 6.7 inches in the last century Global temperature rise – 10 of the warmest years on record have occurred in the last 15 years Warming oceans – Oceans have warmed by 0.3°F since 1969 1909 Shrinking ice sheets – Greenland and Antarctica ice sheets declined by more than 30 cubic miles between 2002-2005 2005 Ocean acidification – acidity of oceans surface has increased by 30% since industrial revolution *Information above from climate.nasa.gov  Sources of Carbon Dioxide Electricity: burning of fossil fuels to produce electricity Renewable energy Increased energy efficiency Transportation: combustion of fossil fuels Alternative fuels Increased fuel efficiency Reduced travel Industry: burning fuel for power of heat Alternative fuels From www.epa.gov Sources of Global Greenhouse Gas Emissions Transportation and generation of electricity are greatest contributors to CO2 emissions. Developed and developing nations require energy to fuel population and industrial growth  Carbon Dioxide Emissions by Region U.S., Europe and Asia account for 88% of total global emissions in 2012 Carbon dioxide emissions are increasing in developing nations (ex: China and India) Carbon Dioxide Emissions Per Capita  Carbon Dioxide Capture and Sequestration Carbon sequestration: the removal and storage of Power plant atmospheric carbon dioxide Refinery in oceans, terrestrial environments, or geologic s Coal bed formations Carbon dioxide Oil “Clean” coal injection recovery Oil and Gas Reservoir Saline Aquifer Salt Caver n Carbon Dioxide Capture and Sequestration Carbon Dioxide Capture and Sequestration Carbon sink: anything that absorbs more carbon dioxide than it releases  For the Skeptics Comparison of Atmospheric CO2 concentrations contained in ice cores