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Chapter 8

Chapter 8. Wakefield 2010-2011. Photosynthesis - Energy & Life. Energy is the ability to do work Comes in many forms Light – heat – electrical – chemical Can be stored and released Can be changed from one form to another Light energy to chemical energy. Photosynthesis - Energy & Life.

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Chapter 8

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  1. Chapter 8 Wakefield 2010-2011

  2. Photosynthesis - Energy & Life • Energy is the ability to do work • Comes in many forms • Light – heat – electrical – chemical • Can be stored and released • Can be changed from one form to another • Light energy to chemical energy

  3. Photosynthesis - Energy & Life • Autotrophs – organisms that can use light energy from the sun to produce chemical energy in the form of food • Producers • Heterotrophs – organisms which cannot make their own food • Consumers

  4. Photosynthesis - Energy & Life • Energy comes in many forms • Light – heat – electrical – chemical • Energy can be changed from one form to another

  5. Photosynthesis - Energy & Life • Living things use chemical energy • Living things store energy in 2 ways • Short term as ATP • Adenosine triphosphate • Long term as glucose or glycogen

  6. Figure 8-3 Comparison of ADP and ATP to a Battery Section 8-1 ADP ATP Energy Energy Adenosine diphosphate (ADP) + Phosphate Adenosine triphosphate (ATP) Partially charged battery Fully charged battery

  7. Energy Transfer • Energy from ATP is powers: • Cellular processes • Active transport • Synthesis of proteins & nucleic acids • Aids in responses to chemical signals from the cell membrane • Produce light (fireflies)

  8. Energy Transfer • ATP stores only very small amounts of energy • ATP is great to for transferring energy over short terms • Not good for long term energy storage

  9. Energy Transfer • Single molecule of sugar (glucose) stores more than 90 times the chemical energy as one molecule of ATP • ATP can be generated from ADP as needed by using the energy in glucose / and other foods

  10. Breakdown of glucose in the cell to form ATP

  11. Photosynthesis • Jan van Helmont – 1643 • Stated that trees gain most of their mass from water

  12. Photosynthesis • Joseph Priestley – 1771 • Using a bell jar, a candle and a plant, he found that the plant releases oxygen

  13. Photosynthesis • Jan Ingenhousz– 1779 • Found that aquatic plants also produce tiny bubbles / Oxygen • Julius Robert Mayer – 1845 • Proposed that plants convert light energy into chemical energy

  14. Photosynthesis • Melvin Calvin – 1948 • Traced the chemical path that carbon follow to form glucose • Now known as the Calvin Cycle

  15. Photosynthesis • Rudolph Marcus – 1992 • Won the Nobel Prize for chemistry for describing the process by which electrons are transferred from one molecule to another in the electron transport chain

  16. Photosynthesis • The process in which autotrophs use energy from the sun (or chemicals) to convert water and carbon dioxide into high-energy carbohydrates (sugars & starches) and oxygen • Photosynthesis takes place in the chloroplast

  17. Photosynthesis • In addition to the sun’s energy, producers also need chlorophyll for photosynthesis • Chlorophyll is the light absorbing pigment in plants • Since chlorophyll absorbs light it is consequently absorbing energy which can be used in photosynthesis • Chlorophyll a and chlorophyll b • Absorb light in the red, blue and blue-violet parts of the spectrum • Does not absorb green light (reflects green light) so plants appear shades of green • Stored in chloroplast – where photosynthesis takes place

  18. Figure 8-5 Chlorophyll Light Absorption Section 8-2 Absorption of Light by Chlorophyll a and Chlorophyll b Chlorophyll b Chlorophyll a V B G Y O R

  19. Critical Thinking ? ? ? ? • How well would a plant grow under pure green or yellow light?

  20. Critical Thinking ? ? ? ? • How well would a plant grow under pure green or yellow light? It would not grow well because chlorophyll does not absorb much light in the green or yellow region of the visible spectrum

  21. Reactions of Photosynthesis • What happens when light is absorbed by chlorophyll in the chloroplast? • Light is a form of energy so . . . • Much of the energy from the light absorbed by the chlorophyll is transferred directly to electrons in the chlorophyll molecule • These high energy electrons make photosynthesis work Plant cells with chloroplasts

  22. Photosynthesis: Reactants and Products Section 8-2 Light Energy Chloroplast CO2 + H2O Sugars + O2

  23. Reactions of Photosynthesis • Electron Carriers • Sun has so much energy it needs special carries to move it from the chlorophyll to other molecules • These carriers are called NADP+ • Each NADP+ can “carry” 2 high energy electrons (e-)(energy) and 1 Hydrogen ion (H+) • Forms NADPH which traps and holds energy from the sun • NADPH then carries the energy from light absorption in the chlorophyll to chemical reactions elsewhere in the cell • This energy is then used for the cell’s needs; including the production of glucose

  24. Reactions of Photosynthesis • Two parts to photosynthesis - • Light Dependent Reactions – (requires light) • Produce O2 and convert light energy into ATP & NADPH • Occurs in the thylakoid of the cell (located in the chloroplast • aka the Photosystem II • Calvin Cycle ( needs no light ) • Takes Carbon from CO2 & hydrogen from light dependent reaction to create C6H12O6 and releases oxygen as a waste product • Occurs in the stroma of the cell – just outside the thylakoid (inside the chloroplast)

  25. Reactions of Photosynthesis • Light Dependent Reaction (requires light) – • The sun’s energy is uses ADP and NADP (energy carriers) • Splits water taken up in the roots of the plant from the soil to create O2 and 2 high energy compounds (ATP and NADPH) • This energy is used to create energy containing sugars (glucose) in the Calvin Cycle (Light Independent Cycle) • O2 is given off as a waste product into the atmosphere

  26. Reactions of Photosynthesis • Calvin Cycle – aka Light Independent Cycle – (does not require light) • Uses high energy compounds ATP & NADPH (created in the Light Dependent Cycle) • Removes CO2 from the atmosphere • Uses 6 molecules of CO2 to produce 1 molecule of C6H12O6 • Produces high energy sugars (glucose) • The plant uses this sugar to: • meet its energy needs • Growth & development • Consumers use this sugar for their energy needs when they eat the producer

  27. Light- dependent reactions Calvin cycle Energy from sunlight Thylakoid membranes ATP Stroma NADPH High-energy sugars ATP NADPH O2 Chloroplasts Concept Map 2 Parts to Photosynthesis Section 8-3 Photosynthesis includes takes place in uses use take place in to produce to produce of

  28. Factors Affecting Photosynthesis • Temperature • Best between 0oC and 35oC • At very low temperatures photosynthesis may stop completely • Light Intensity • Increasing the intensity of light increases the rate of photosynthesis . . . to a certain point – once photosynthesis has reached its maximum rate it cannot increase more • This maximum level varies from plant to plant

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