Chapter 6Pathways of Photosynthesis
Photosynthesis produces food and        released oxygenPhotosynthesizers are autotrophs that produce  their own food• Phot...
In eukaryotes, chloroplasts carry         out photosynthesis• Materials for photosynthesis  – CO2     • Comes through stom...
Photosynthesis involves two sets ofreactions: the light reactions and the Calvin              cycle reactions• Oxidation  ...
• Light reactions  – Only occur in the presence of light  – Energized electrons from the breakdown of H2O are    taken up ...
• Calvin Cycle  – Light independent (can occur with or without light)  – CO2 reduces to CH2O, which can be used to form   ...
The light reactions capture solar                energySolar energy is absorbed by  pigments• Solar energy   – Radiant ene...
• Chlorophyll a, chlorophyll b, and carotenoids are  found in photosynthesizing cells and are capable  of absorbing variou...
During fall, enzymes that rebuild chorophyll work at a slower speed due to lower temperatures. Chlorophyll eventually disi...
Solar energy boosts electrons to a       higher energy levelAntenna molecule  – Takes in light energy  – Pass energy to th...
Electrons release their energy as             ATP forms• Chloroplasts use  electrons energized by  solar energy to generat...
The Calvin cycle reactions       synthesize carbohydratesATP and NADPH from the light dependent reactions are  needed to p...
http://media.pearsoncmg.com/bc/bc_0media_bio/bioflix/bioflix.htm?cc5photosynthesis
Tropical rain forests and global            climates change• Rain forest vegetation absorbs large amounts of  CO2• CO2 tra...
• Burning fossil fuels releases CO2, clearing  rainforests usually involves burning them (slash  and burn), releasing the ...
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Bio 100 Chapter 6

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Bio 100 Chapter 6

  1. 1. Chapter 6Pathways of Photosynthesis
  2. 2. Photosynthesis produces food and released oxygenPhotosynthesizers are autotrophs that produce their own food• Photosynthesis – Converts solar energy to chemical energy (glucose)• Autotrophs – Produce their own food• Heterotrophs – Consumers• Nearly all food chains start with plants or algae
  3. 3. In eukaryotes, chloroplasts carry out photosynthesis• Materials for photosynthesis – CO2 • Comes through stomata • Comes from organisms breathing out – H2O • Comes in through roots• The materials diffuse into chloroplasts, where photosynthesis occurs• Thylakoids are within chloroplasts and chlorophyll is found inside of them• Chlorophyll is within thylakoids and absorbs solar energy
  4. 4. Photosynthesis involves two sets ofreactions: the light reactions and the Calvin cycle reactions• Oxidation – Loss of hydrogen atoms – Loses electrons• Reduction – Gain of hydrogen atoms – Gains electrons• This type of reactions is called a redox reaction
  5. 5. • Light reactions – Only occur in the presence of light – Energized electrons from the breakdown of H2O are taken up by a coenzyme (NADP+) – NADP+ also combines with H+ (a reduction reaction) to form NADPH – ATP is also produced
  6. 6. • Calvin Cycle – Light independent (can occur with or without light) – CO2 reduces to CH2O, which can be used to form glucose – H+ comes from NADPH – Energy comes from ATP
  7. 7. The light reactions capture solar energySolar energy is absorbed by pigments• Solar energy – Radiant energy from the sun• Visible light – Type of radiation used for photosynthesis and vision – Shorter wavelength means more energy • Violet-shortest wavelength, most energy • Red-longest wavelength, least energy
  8. 8. • Chlorophyll a, chlorophyll b, and carotenoids are found in photosynthesizing cells and are capable of absorbing various portions of visible light• Green is reflected instead of absorbed, this is why plants appear green
  9. 9. During fall, enzymes that rebuild chorophyll work at a slower speed due to lower temperatures. Chlorophyll eventually disintegrates, leaving only carotenoids to absorb light. Carotenoids reflect yellow, orange, and red, which is why leaves appear to change colors.
  10. 10. Solar energy boosts electrons to a higher energy levelAntenna molecule – Takes in light energy – Pass energy to the reaction center
  11. 11. Electrons release their energy as ATP forms• Chloroplasts use electrons energized by solar energy to generate ATP by way of electron transport chain – High energy electrons enter – Low energy electrons leave – Energy is released each time the electron is transferred – Energy is ultimately used to make ATP
  12. 12. The Calvin cycle reactions synthesize carbohydratesATP and NADPH from the light dependent reactions are needed to produce a carbohydrate• CO2 comes in from the atmosphere and combines with RuBP (an enzyme that speeds the Calvin cycle)• CO2 is reduced to form CH2O – ATP and NADPH are needed for this to occur – ATP breaks down to ADP + P – NADPH breaks down to NADP+• G3P (glyceraldehyde-3-phosphate) (CH2O)is then produced, which is the building block for many carbohydrates (glucose, starch, and cellulose) and RuBP• The ADP + P and NADP+ can go back to the light reactions to form ATP and NADPH again
  13. 13. http://media.pearsoncmg.com/bc/bc_0media_bio/bioflix/bioflix.htm?cc5photosynthesis
  14. 14. Tropical rain forests and global climates change• Rain forest vegetation absorbs large amounts of CO2• CO2 traps radiant heat from the sun and warms the world, similar to a greenhouse, which is why it is called a greenhouse gas• Without greenhouse gasses, Earth would be about 33˚C cooler• With excess greenhouse gasses, climate patterns will be disrupted (more heatwaves, droughts, and storms) and more hurricanes and tornadoes will occur
  15. 15. • Burning fossil fuels releases CO2, clearing rainforests usually involves burning them (slash and burn), releasing the trapped CO2, and reducing the amount of vegetation that can absorb CO2• At warmer temperatures, photosynthesis rates have been seen to decrease• Cut down forests => more CO2 in the air => warmer temperatures => lower photosynthesis rates => less CO2 is absorbed• Protecting remaining forests and reestablishing deforested areas may help to slow climate change

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