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PHOTOSYNTHESIS AND CELLULAR RESPIRATION

PHOTOSYNTHESIS AND CELLULAR RESPIRATION. Chap 5 Section 1. ENERGY AND LIVING THINGS. Metabolism involves either using energy to build molecules or breaking down molecules in which energy is stored

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PHOTOSYNTHESIS AND CELLULAR RESPIRATION

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  1. PHOTOSYNTHESIS AND CELLULAR RESPIRATION Chap 5 Section 1

  2. ENERGY AND LIVING THINGS • Metabolism involves either using energy to build molecules or breaking down molecules in which energy is stored • PHOTOSYNTHESIS - the process by which light energy is converted to chemical energy of carbohydrates • - sugar and starches

  3. AUTOTROPHS – organisms that use energy from sunlight or from chemical bonds inorganic substances to make organic compounds (food)

  4. Some prokaryotes use chemosynthesis to produce organic compounds

  5. HETEROTROPHS – organisms that must get energy from food instead of directly from sunlight or inorganic substances

  6. CELLULAR RESPIRATION – a metabolic process similar to burning fuel, but it converts food energy to ATP • ATP provides cells with the energy needed to carry out the activities of life

  7. Chemical energy stored in food is released gradually • The product of one chemical reaction becomes a reactant in the next reaction • Some of the energy is released as heat, but the remaining energy is stored as ATP – portable form of energy • Adenosine triphosphate

  8. Flow of Energy • Energy flows from sunlight or inorganic substances to autotrophs, such as grasses, and then to heterotrophs, such as rabbits and foxes

  9. Energy Storage in Organisms • Plants store energy in the form of starch • Animals store energy in the form of glycogen

  10. Complete sentences • P.96 section review 1-6 • P. 112 5a,6,12

  11. PHOTOSYNTHESISsection 2 Using the Energy in Sunlight

  12. Requirements for Photosynthesis • Sunlight – nearly all organisms on Earth depend on sun for energy • Pigments – colored substance that absorb or reflect light

  13. Energy-Storing Compounds – stored in the bonds of compounds • Most important compound – one used by every living cell – ATP • Adenosine triphosphate • Inorganic substances – Water and Carbon Dioxide

  14. White Light – perceived as ”colorless” • Actually a mixture of different wavelengths of light • Visible spectrum – wavelengths visible to our eyes • Infrared and ultraviolet – not visible to our eyes

  15. About 1 % of the energy in the sunlight is converted to chemical energy • Three stages of Photosynthesis • Stage 1: Energy is captured from sunlight. • Stage 2: Conversion of Light Energy • Stage 3: Storage of Energy

  16. Stage 1Absorption of Light Energy • First & second stages are sometimes called “light reactions” • Light is a form of radiation – energy in the form of waves • Pigments absorb only certain wavelengths and reflect all the others • Chlorophyll absorbs mostly blue & red lights

  17. Plants contain two types of chlorophyll, a and b, a being the most important • Carotenoids – pigments that produce yellow & orange colors – absorb wavelengths of light different from chlorophyll • Most of the pigments reflect the color green, making the leaves appear green

  18. Production of Oxygen • Thylakoids-located in the chloroplasts & contain the pigments necessary for photosynthesis • Light energy is transferred to electrons causing them to be “excited”

  19. Electrons jump to other molecules where they are used to power the second stage • Replacement electrons come from water molecules • Water molecules are split by enzymes, leaving H+ ions, and O atoms, forming Oxygen gas,

  20. Stage Two: Conversion of Light Energy • Electron Transport Chains (2)- series of molecules through which excited electrons are passed along a thylakoid membrane • First, provides the energy needed to change ADP to ATP – needed by dark reaction

  21. A second electron transport chain provides energy used to make NADPH- which is needed by the dark reaction • NADPH – electron carrier that provides the high-energy electrons needed to make carbon-hydrogen bonds in the third stage • Excited electrons combine with hydrogen ions & NADP+ to form NADPH

  22. Animated Light Reaction • http://www.uic.edu/classes/bios/bios100/lectures/light_reaction.htm

  23. Photosynthesis Problem http://www.uic.edu/classes/bios/bios100/lectures/photorespiration.htm

  24. Dark Reaction(Light Independent Reaction) • Dark reactions generally take place in sunlight; light does not play a role in the dark reactions • The simple inorganic molecule carbon dioxide is used to make a complex organic molecule • Melvin Calvin, American, worked out cycle

  25. Stage Three: Storage of Energy • CARBON DIOXIDE FIXATION – transfer of carbon dioxide to organic compounds • Considered light-independent “dark reactions” • Most common method is the Calvin cycle • Calvin cycle- a series of enzyme-assisted chemical reactions that produces a 3-C sugar

  26. The reactions are cyclic – they recycle the five-carbon compound needed to begin the cycle again • The energy used in the Calvin cycle is supplied by ATP and NADPH made during the second stage of photosynthesis

  27. Calvin Cycle Animated http://www.uic.edu/classes/bios/bios100/lectures/calvin.htm

  28. Light and Dark Reactions • http://leavingbio.net/PHOTOSYNTHESIS.htm

  29. Factors that Affect Photosynthesis • Light – photosynthesis increases as light intensity increases until all the pigments are being used –limited by Calvin reaction which is the slowest step • Carbon dioxide concentration – once a certain concentration is reached photosynthesis is limited • Temperature- certain range is more efficient

  30. Water – the availability of water and the amount of rainfall • Nutrients – how much organic matter that soil contains

  31. P. 103 • Section 2 review 1-6 • P. 112 1,2, 5c,8,9, 11 • Standardized Test Prep 1-3

  32. Cellular Respiration • Food contains usable energy in the form of protein, fat, & carbs (considered organic) • Energy has to be transferred to ATP, which is done through cellular respiration • AEROBIC respiration- metabolic processes that require oxygen, more efficient in making ATP • ANAEROBIC-metabolic processes that do not require O2

  33. Stages of Cellular Respiration • Stage I: Breakdown of Glucose • Stage II: Production of ATP

  34. Stage I: Breakdown of Glucose • Glycolysis: takes place in the cytoplasm- an enzyme-assisted anaerobic process that breaks down one 6-C molecule of glucose to 2 3-C pyruvic ions • 4 Steps in the series on page 105 – you can copy them from the book

  35. Glycolysis uses two ATP but produces four ATP

  36. Stage 2: Production of ATP • Krebs Cycle enzyme-assisted reactions named for Hans Krebs, 1937 • 5 steps on p. 106 & 107 • Much of the energy that was stored in glucose & pyruvate is now stored in NADH and FADH2

  37. Krebs Cycle • http://www.1lecture.com/Biochemistry/How%20the%20Krebs%20Cycle%20Works/index.html

  38. Electron Transport Chain • The electron transport chain pumps hydrogen ions, H+, out of the inner compartment. • At the end of the chain, electrons & hydrogen ions combine with oxygen, forming water. • ATP is produced as hydrogen ions diffuse into the inner compartment through a channel protein.

  39. Respiration in the Absence of Oxygen • Electron transport chain does not function if oxygen is not available as final electron acceptor. • Electrons in NADH are transferred to pyruvate; enables the recycling of NAD+ which is needed to make ATP • Fermentation- recycling of NAD+ using an organic hydrogen acceptor

  40. Lactic Acid Fermentation • Pyruvate is converted to lactate • Lactate is the ion of lactic acid • Vigorous exercise –muscles must operate without enough O2 – • ATP produces only while glucose supply lasts • Blood removes excess lactate, but if not quickly-can cause muscle soreness

  41. Alcoholic Fermentation • Two step process • Pyruvate is converted to 2-C compound, releasing CO2 • Electrons are transferred from NADH to the two-C compound, producing ethanol Yeast, a fungus, uses alcoholic fermentation. Yeast is used in bread industry and alcoholic beverages Ethanol (12%) kills yeast

  42. Production of ATP • Total of ATP produced from glucose depends on the absence or presence of O2 • 2 ATP molecules are made during the Krebs cycle • 34 ATP are produced by the electron transport chain

  43. Types of chemical reactions • An exothermic reaction is a chemical reaction that releases energy in the form of heat..

  44. An endothermic reaction is any chemical reaction that absorbs heat from its environment. • These examples could be written as chemical reactions, but are more generally considered to be endothermic or heat-absorbing processes: • melting ice cubes • melting solid salts • evaporating liquid water

  45. converting frost to water vapor (melting, boiling, and evaporation in general are endothermic processes) • splitting a gas molecule • cooking an egg

  46. Homework • Page 110 - section review 1-6 • Page 112 – 3,4, 5b, 5d,7,10,13,14,19 • Test Part 2 over section 3 Monday 8th • 10 true false 14 multiple choice and discussion

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