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Photosynthesis and Cellular Respiration

Photosynthesis and Cellular Respiration. Chapter 5. Energy and Living T hings. Section 5-1 . Directly or indirectly, all energy needed for metabolism comes from the SUN Energy enters living systems when plants, algae and bacteria absorb sunlight

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Photosynthesis and Cellular Respiration

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  1. Photosynthesis and Cellular Respiration Chapter 5

  2. Energy and Living Things Section 5-1

  3. Directly or indirectly, all energy needed for metabolism comes from the SUN • Energy enters living systems when plants, algae and bacteria absorb sunlight • Some energy from the sun is captured to make organic compounds which are then stored Where does energy in food come from?

  4. Metabolism either uses energy to build molecules or break down molecules that store energy Building molecules that store energy

  5. Photosynthesis is the process by which light energy is converted to chemical energy • Autotrophs are organisms that use energy from sunlight or inorganic substances to make organic compounds • Most autotrophs like plants are photosynthetic Building molecules that store energy

  6. Chemical energy in organic compounds can transfer to organisms that consume those compounds • Heterotrophs are organisms that must get energy from food instead of directly from sunlight or inorganic substances • Cellular respiration is a metabolic process where organisms harvest energy from food Breaking down food for energy

  7. Cells burn energy differently than wood burns • In cells, stored energy is released in a series of enzyme assisted reactions • When cells break down food molecules, some energy is released as heat, most is released as ATP Cells Transfer energy from food to ATP

  8. ATP (adenosine triphosphate) is a nucleotide with 2 energy storing phosphate groups • Phosphate groups store energy like a spring and releases it when the bonds holding the groups together break • ATP ADP + P + Energy ATP stores and Releases energy

  9. Photosynthesis Section 5-2

  10. Plants, algae and some bacteria capture 1% of the energy in the sunlight that reaches Earth Photosynthetic Organisms Use Sunlight’s Energy

  11. Stage 1: Energy is captured from sunlight • Stage 2: Light energy is converted to chemical energy; stored as ATP and the energy carrier molecule NADPH • Stage 3: Energy from ATP and NADPH powers the formation of organic compounds using carbon dioxide (CO2) • 6CO2 +6H2OC6H12O6+ 6O2 Light Photosynthesis Overview

  12. First and second stage of photosynthesis are light stages • Without light, these reactions would not occur • Light energy is used to make energy storing compounds Light Reactions

  13. Pigments are molecules that absorb certain wavelengths of light and reflect others • Chlorophyll is the primary pigment involved in photosynthesis and it absorbs red and blue and reflects green and yellow • Carotenoids are pigments that produce yellow and orange fall leaf colors • Using both carotenoids and chlorophyll absorbs more light energy, so plants use both Pigments absorb different wavelengths of light

  14. Pigments used in photosynthesis are found in the chloroplast • Clusters of pigments are embedded in disk-shaped structures calledthylakoids • When light strikes a thylakoid, energy is transferred to electrons in pigments and the electrons are excited Production of Oxygen

  15. Excited electrons jump from pigment molecules to others and power second stage of photosynthesis • The electrons must be replaced so water molecules split, taking electrons from hydrogen, leaving H+ and oxygen O which forms oxygen gas Production of Oxygen cont…

  16. Cellular Respiration Section 5-3

  17. Oxygen makes the production of ATP more efficient • Some ATP is made without oxygen • Metabolic processes that require oxygen are called aerobic • Metabolic processes that do not require oxygen are called anaerobic Cellular Respiration Produces ATP

  18. Cellular respiration harnesses the energy in organic compounds • C6H12O6 +602 6CO2 + 6H2O + energy • Primary fuel for cellular respiration is glucose • Glucose is formed when starch or sucrose are broken down Cellular Respiration

  19. Glucose (sugar) is broken down in the cytoplasm by the process glycolysis • Glycolysis is an enzyme assisted anaerobic process that breaks down one 6-carbon molecule of glucose to two 3-carbon pyruvates • Glycolysis uses 2 ATP molecules but produces 4 ATP molecules Stage 1: Glucose is broken down

  20. Step 1: Phosphate groups from 2 ATP molecules are transferred to glucose • Step 2: The 6-carbon compound is broken down into two 3-carbon compounds + 1 Phosphate • Step 3: Two NADH molecules are made 1 more phosphate group is added • Step 4: Each 3 carbon compound is converted to 3-carbon pyruvates, which produces 4 ATP Glycolysis

  21. When oxygen is present, pyruvate from glycolysis enters a mitochondria and is converted to a 2 carbon compound • This produces CO2, one NADH and a 2-carbon acetyl group • This attaches to an enzyme A (CoA) making acetyl-CoA • Acetyl-CoA enters a series of enzyme-assisted reactions called Krebs Cycle Stage 2: More ATP is made

  22. Step 1: Acetyl-CoA combines with a 4-C comp, making a 6-C comp and releasing CoA • Step 2: CO2 is released from the 6-C comp forming a 5-C comp. e- transfer making NADH • Step 3: CO2 is released from 5-C comp, making a 4-C, ATP and NADH • Step 4: 4-C comp is converted to another, and e- transfer to make electron carrier, FADH2 • Step 5: 4-C comp is converted to original 4-C comp, NADH is produced and cycle can start over Krebs Cycle

  23. In aerobic respiration, electrons donated by NADH and FADH2 pass through electron transport chains • The chain pumps H+ out of the mitochondria which combines with O2 to make H2O • ATP is produced as H+ diffuses back into the mitochondria Electron Transport Chain

  24. Without enough oxygen, Electron Transport Chain does not function the same • O2 receives electrons and when not present, NADH and NAD+ cannot be recycled • So NAD+ undergoes fermentation to recycle it Fermentation Follows Glycolysis in Absence of Oxygen

  25. Lactate is the ion of an organic acid called lactic acid • A 3-C pyruvate converts to a 3-C lactate in order to continue glycolysis to produce ATP Lactic Acid Fermentation

  26. 3-C pyruvate is broken down to ethanol, a 2-C compound during alcoholic fermentation • CO2is released • Electrons transfer from NADH to the 2-C compound producing ethanol • NAD+ is recycled to continue glycolysis Alcoholic Fermentation

  27. The total amount of ATP harvested from each glucose molecule depends on oxygen • Cells use energy more efficiently when oxygen is present • In stage 1: glucose is broken down by glycolysis (anaerobic) and gains 2 ATP • In Stage 2: pyruvate passes thru aerobic respiration or (anaerobic) fermentation • In fermentation, small amounts of ATP is produced • In respiration, up to 2 ATP are produced by Krebs cycle and 34 through electron transport chains Comparing Anaerobic with Aerobic

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