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Chapter 8

Chapter 8. Cellular Energy. Section 1. How Organisms Obtain Energy. Section 1: How Organisms Obtain Energy. All living organisms use energy to carry out all biological processes. Transformation of Energy Cellular processes require energy – the ability to do work.

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Chapter 8

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  1. Chapter 8 Cellular Energy

  2. Section 1 How Organisms Obtain Energy

  3. Section 1: How Organisms Obtain Energy All living organisms use energy to carry out all biological processes.

  4. 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. How Organisms Obtain Energy

  5. 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. How Organisms Obtain Energy

  6. 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. How Organisms Obtain Energy

  7. 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. How Organisms Obtain Energy

  8. 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 How Organisms Obtain Energy

  9. 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. How Organisms Obtain Energy

  10. ATP Crash Course https://www.youtube.com/watch?v=00jbG_cfGuQ

  11. 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 How Organisms Obtain Energy

  12. 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. How Organisms Obtain Energy

  13. ATP • When chlorophyll absorbs light, it is absorbing energy • It stores it in the __________ of Adenosine Triphosphate (ATP) bonds

  14. ATP, continued. • Carbs are most commonly broken down to make ATP. • Breakdown of glucose yields 36 ATP. • ATP = Energy currency of the cell. • Cells use ATP for functions such as building molecules & moving materials by Active Transport. • ATP releases energy when phosphate group released. • Becomes Adenosine DiPhosphate (ADP). • Can be converted back to ATP by adding phosphate.

  15. ATP vs. ADP

  16. ATP ADP Cycle

  17. Video • ATP

  18. 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? How Organisms Obtain Energy

  19. Section 2 Photosynthesis

  20. Section 2: Photosynthesis Light energy is trapped and converted into chemical energy during photosynthesis.

  21. Crash Course: Photosynthesis https://www.youtube.com/watch?v=sQK3Yr4Sc_k

  22. Overview of Photosynthesis • Most autotrophs make organic compounds using photosynthesis. • Photosynthesis is the process of converting light energy into chemical energy. Photosynthesis

  23. THE FORMULA, continued.

  24. 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. Photosynthesis

  25. Bill Nye: Photosynthesis https://www.youtube.com/watch?v=pdgkuT12e14

  26. 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 NAPDH. Photosynthesis

  27. Phase One: Light Reactions Chloroplasts • Are 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 Photosynthesis

  28. Chloroplast structure

  29. 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. Photosynthesis

  30. Video • Chlorophyll Borophyll

  31. 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. Photosynthesis

  32. 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. Photosynthesis

  33. 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. Photosynthesis

  34. Phase One: Light Reactions Electron transport • In the presence of light, photosystem I transfers the electrons to a protein. • The protein transfers the electrons to the carrier molecule NADP+, forming the energy storage molecule NADPH. Photosynthesis

  35. 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 Photosynthesis

  36. Phase Two: The Calvin Cycle (light independent reactions) • In the second phase of photosynthesis, called the Calvin cycle, energy is stored in organic molecules such as glucose. Photosynthesis

  37. 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 3-phosphoglycerate (3-PGA) Photosynthesis

  38. 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). Photosynthesis

  39. 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. Photosynthesis

  40. 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. Photosynthesis

  41. 2 Main steps of PS - Summary • Light reactions—occurs only in the presence of ___________ • Occurs in the grana (thylakoids) of the chloroplasts • Also known as Photolysisbecause light is used to __________ _________ molecules into hydrogen and oxygen light split water

  42. 2 Main steps of PS - Summary 2. Dark Reactions—can occur in light ____ darkness. Follows light reactions • Occurs in the stroma of the chloroplasts • Also known as Carbon fixationbecause CO2 will get “fixed up” with the hydrogens and energy from the light reaction or

  43. Light Reactions Take place within the membrane of the thylakoid. • Chlorophyll absorbs energy from sunlight. • Water is __________ _________ • Oxygen is ______________ • Oxygen leaves the plant and goes into the air broken down released

  44. The Dark Reactions Occur in stroma of chloroplasts. • _________ is added to a cycle of reactions to build larger molecules • A molecule of simple sugar is formed • _____________ CO2 glucose

  45. Video • Summary of Photosynthesis

  46. 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 Photosynthesis

  47. 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 Photosynthesis

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