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Essential Questions • What are the two laws of thermodynamics? • What is the difference between an anabolic pathway and a catabolic pathway? • How does ATP work in a cell? Copyright © McGraw-Hill Education How Organisms Obtain Energy Vocabulary Review New • • • • • • • trophic level Copyright © McGraw-Hill Education energy thermodynamics metabolism photosynthesis cellular respiration adenosine triphosphate (ATP) How Organisms Obtain Energy Transformation of Energy • Cellular processes require energy – the ability to do work. • Thermodynamics is the study of the flow and transformation of energy in the universe. Copyright © McGraw-Hill Education How Organisms Obtain Energy Transformation of Energy Laws of thermodynamics • First law—the law of conservation of energy: energy can be converted from one form to another, but it cannot be created nor destroyed. • Second law: energy cannot be converted without the loss of usable energy, that is, entropy—disorder or unusable energy—increases. Copyright © McGraw-Hill Education How Organisms Obtain Energy Transformation of Energy Autotrophs and Heterotrophs • Directly or indirectly, nearly all the energy for life comes from the Sun. • Autotrophs make their own food, either with energy from the sun or from inorganic substances. • Heterotrophs ingest other organisms to obtain energy. Copyright © McGraw-Hill Education How Organisms Obtain Energy Metabolism • All of the chemical reactions in a cell are referred to as the cell’s metabolism. • A series of chemical reactions in which the product of one is the substrate for the next is called a metabolic pathway. • Catabolic pathways release energy by breaking down larger molecules. • Anabolic pathways use energy to build larger molecules. Copyright © McGraw-Hill Education How Organisms Obtain Energy Metabolism • Photosynthesis – anabolic pathway in which light energy from the Sun is converted to chemical energy for use by the cell • Cellular respiration – catabolic pathway in which organic molecules are broken down to release energy for use by the cell Copyright © McGraw-Hill Education How Organisms Obtain Energy ATP: The Unit of Cellular Energy • In living things, chemical energy is stored in biological molecules. • Adenosine triphosphate (ATP) is the most important biological molecule that provides chemical energy. Copyright © McGraw-Hill Education How Organisms Obtain Energy ATP: The Unit of Cellular Energy ATP structure • Most abundant energy-carrier in cells • Nucleotide made of an adenine base, a ribose sugar, and three phosphate groups Copyright © McGraw-Hill Education How Organisms Obtain Energy ATP: The Unit of Cellular Energy ATP function • Releases energy when the bond between the second and third phosphate groups is broken. • Transforms into a molecule called adenosine diphosphate (ADP) and a free phosphate group. Copyright © McGraw-Hill Education How Organisms Obtain Energy Movie Clip (take notes here) Copyright © McGraw-Hill Education How Organisms Obtain Energy Review Essential Questions • • • What are the two laws of thermodynamics? What is the difference between an anabolic pathway and a catabolic pathway? How does ATP work in a cell? Vocabulary • • • energy thermodynamics metabolism Copyright © McGraw-Hill Education • • photosynthesis cellular respiration • adenosine triphosphate (ATP) How Organisms Obtain Energy Essential Questions • What are the two phases of photosynthesis? • What is the function of a chloroplast during the light reactions? • How can electron transport be described and diagramed? Copyright © McGraw-Hill Education Photosynthesis Vocabulary Review New • • • • • • • • carbohydrate Copyright © McGraw-Hill Education thylakoid granum stroma pigment NADP+ Calvin cycle rubisco Photosynthesis Overview of Photosynthesis • Most autotrophs make organic compounds using photosynthesis. • Photosynthesis is the process of converting light energy into chemical energy. Copyright © McGraw-Hill Education Photosynthesis Overview of Photosynthesis • Photosynthesis occurs in two phases. • In the light-dependent phase, light energy is converted into chemical energy. • In the light-independent phase, chemical energy used to synthesize glucose. Copyright © McGraw-Hill Education Photosynthesis Phase One: Light Reactions • The absorption of light is the first step in photosynthesis. • Once light energy is captured, it can be stored as ATP or NADPH. Copyright © McGraw-Hill Education Photosynthesis Phase One: Light Reactions Chloroplasts • Organelles that capture light energy • Contain two main compartments: • Thylakoids: flattened saclike membranes • • Stacks of thylakoids are called grana. The fluid filled space outside the grana called the stroma. Can you identify them? Copyright © McGraw-Hill Education Photosynthesis Phase One: Light Reactions Pigments • Light-absorbing colored molecules called pigments are found in the thylakoid membranes. • Different pigments absorb specific wavelengths of light. • Most common pigment in plants is chlorophyll. • Plants also have accessory pigments. Can you read this Graph? Copyright © McGraw-Hill Education Photosynthesis Phase One: Light Reactions Electron transport • The thylakoid membrane has a large surface area, providing space for a large number of electron transporting molecules and two types of protein complexes called photosystems. • Photosystems house the light-capturing pigments. What does the light do? How come Hydrogen Crosses the membrane? Copyright © McGraw-Hill Education Photosynthesis Phase One: Light Reactions Electron transport • Light energy excites electrons in photosystem II. • This light energy causes a water molecule to split – releasing an electron into the electron transport system, a hydrogen ion (H+ or proton) into the thylakoid space, and oxygen as a waste product. What does the light do? How come Hydrogen Crosses the membrane? Copyright © McGraw-Hill Education Photosynthesis Phase One: Light Reactions Electron transport • The activated electrons move from photosystem II to an acceptor molecule in the thylakoid membrane. • The electron acceptor molecule transfers the electrons along a series of electron carriers to photosystem I. Copyright © McGraw-Hill Education Photosynthesis Phase One: Light Reactions Electron transport • In the presence of light, photosystem I transfers the electrons to a protein called ferrodoxin. • Ferrodoxin transfers the electrons to the carrier molecule NADP+, forming the energy storage molecule NADPH. Copyright © McGraw-Hill Education Photosynthesis Phase One: Light Reactions Electron transport • ATP is produced in conjunction with the electron transport system through chemiosmosis. • ATP is produced through the flow of electrons down a concentration gradient. • The breakdown of water provides the necessary protons for ATP synthesis. • Copyright © McGraw-Hill Education Photosynthesis Visualizing Electron Transport – Video (Take notes here) https://www.youtube.com/watch?v=YeD9idmcX0w Copyright © McGraw-Hill Education Photosynthesis Phase Two: The Calvin Cycle • In the second phase of photosynthesis, called the Calvin cycle, energy is stored in organic molecules such as glucose. Copyright © McGraw-Hill Education Photosynthesis Phase Two: The Calvin Cycle • The first step of the Calvin cycle is called carbon fixation. • CO2 molecules combine with 5-carbon molecules to form 3phosphoglycerate (3-PGA) Copyright © McGraw-Hill Education Photosynthesis Phase Two: The Calvin Cycle • In the second step, chemical energy stored in ATP and NADPH is transferred to the 3-PGA to form glyceraldehyde 3-phospate (G3P). Copyright © McGraw-Hill Education Photosynthesis Phase Two: The Calvin Cycle • In the third step, some G3P molecules leave the cycle to be used for the production of glucose and other organic compounds. Copyright © McGraw-Hill Education Photosynthesis Phase Two: The Calvin Cycle • In the fourth and final step, an enzyme called rubisco converts the remaining G3P molecules into 5-carbon molecules called ribulose 1,5-bisphospates (RuBP). • These molecules combine with new CO2 and continue the cycle. Copyright © McGraw-Hill Education Photosynthesis The Calvin Cycle Video- (Take notes here) https://www.youtube.com/watch?v=0UzMaoaXKaM Copyright © McGraw-Hill Education Photosynthesis Alternative Pathways C4 plants • The C4 pathway allows plants to maintain photosynthesis while reducing water loss. • Significant structural modification in the arrangement of cells within the leaves – separate CO2 uptake from location of Calvin cycle • https://www.youtube.com/watch?v=7ILTenU0Ofw Copyright © McGraw-Hill Education Photosynthesis Alternative Pathways CAM plants • Crassulacean acid metabolism (CAM) is found in desert plants. • Collect CO2 at night and store it in organic compounds • During the day, release CO2 from organic compounds for the light-dependent cycle of photosynthesis Copyright © McGraw-Hill Education Photosynthesis Review https://www.youtube.com/watch?v=uixA8ZXx0KU Essential Questions • • • What are the two phases of photosynthesis? What is the function of a chloroplast during the light reactions? How can electron transport be described and diagramed? Vocabulary • • • thylakoid granum stroma Copyright © McGraw-Hill Education • • pigment NADP+ • • Calvin cycle rubisco Photosynthesis Essential Questions • What are the stages of cellular respiration? • What is the role of electron carriers in each stage of cellular respiration? • What are the similarities between alcoholic fermentation and lactic acid fermentation? Copyright © McGraw-Hill Education Cellular Respiration Vocabulary Review New • • • • • • • cyanobacterium Copyright © McGraw-Hill Education anaerobic process aerobic respiration aerobic process glycolysis Krebs cycle fermentation Cellular Respiration Overview of Cellular Respiration • Organisms obtain energy in a process called cellular respiration. • Respiration harvests electrons from organic molecules and uses the energy to make ATP. • The equation for cellular respiration is the opposite of the equation for photosynthesis: Copyright © McGraw-Hill Education Cellular Respiration Overview of Cellular Respiration • Cellular respiration occurs in two main parts: glycolysis and aerobic respiration. • Glycolysis is an anaerobic process, meaning it does not require oxygen. • Aerobic respiration involves the Krebs cycle and electron transport. • Aerobic processes require oxygen. Copyright © McGraw-Hill Education Cellular Respiration Glycolysis • Glucose is broken down in the cytoplasm through the process of glycolysis. • Two molecules of ATP and two molecules of NADH are formed for each molecule of glucose that is broken down. Copyright © McGraw-Hill Education Cellular Respiration Krebs Cycle • Glycolysis has a net result of two ATP, 2 NADH, and two pyruvate. • Most of the energy from the glucose is still contained in the pyruvate. • In the presence of oxygen, pyruvate is transported into the mitochondrial matrix, where it is converted into carbon dioxide. • The series of reactions in which pyruvate is broken down into carbon dioxide is the Krebs cycle, also know as the tricarboxylic acid (TCA) cycle or the citric acid cycle. Copyright © McGraw-Hill Education Cellular Respiration Krebs Cycle Steps of the Krebs cycle • Prior to the Krebs cycle, pyruvate reacts with coenzyme A (CoA) to form acetyl CoA. • Acetyl CoA moves into the mitochondrial matrix. • Acetyl CoA combines with a 4carbon compound to form citric acid. Copyright © McGraw-Hill Education Cellular Respiration Krebs Cycle Steps of the Krebs cycle • Citric acid is broken down releasing two molecules of carbon dioxide and generating one ATP, three NADH, and one FADH2. • Finally, acetyl CoA and citric acid are generated and the cycle continues. Copyright © McGraw-Hill Education Cellular Respiration The Krebs Cycle- Take notes on video Song-https://www.youtube.com/watch?v=JPCs5pn7UNI Crash Course- https://www.youtube.com/watch?v=00jbG_cfGuQ Copyright © McGraw-Hill Education Cellular Respiration Electron Transport • In aerobic respiration, electron transport is the final step in the breakdown of glucose. • NADH and FADH2 from the Krebs cycle are used to convert ADP to ATP. • Electron transport and chemiosmosis in aerobic respiration are similar to the processes of photosynthesis. Copyright © McGraw-Hill Education Cellular Respiration Electron Transport Prokaryotic cellular respiration • Some prokaryotes undergo aerobic respiration. • They do not have mitochondria, so they use the cellular membrane as the location of electron transport. Copyright © McGraw-Hill Education Cellular Respiration Anaerobic Respiration • • • When oxygen is unavailable, cells cannot follow glycolysis with the aerobic respiration (Krebs cycle and electron transport). The anaerobic process that follows glycolysis is anaerobic respiration, or fermentation. Fermentation occurs in the cytoplasm of the cell, and produces NAD+ and ATP. Copyright © McGraw-Hill Education Cellular Respiration Anaerobic Respiration Lactic acid fermentation • Enzymes convert the pyruvate made during glycolysis into lactic acid. • Skeletal muscles produce lactic acid when the body cannot supply enough oxygen, such as during periods of strenuous exercise. Copyright © McGraw-Hill Education Cellular Respiration Anaerobic Respiration Alcohol fermentation • Occurs in yeast and some bacteria • Converts pyruvate into ethyl alcohol and carbon dioxide Copyright © McGraw-Hill Education Cellular Respiration Photosynthesis and Cellular Respiration Copyright © McGraw-Hill Education Cellular Respiration Energy in a Cell- Perform your online text Virtual Lab Copyright © McGraw-Hill Education Cellular Respiration Review Essential Questions • • • What are the stages of cellular respiration? What is the role of electron carriers in each stage of cellular respiration? What are the similarities between alcoholic fermentation and lactic acid fermentation? Vocabulary • • anaerobic process aerobic respiration Copyright © McGraw-Hill Education • • aerobic process glycolysis • • Krebs cycle fermentation Cellular Respiration
