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Photosynthesis Chapter 8

Photosynthesis Chapter 8. 8–2 PHOTOSYNTHESIS: AN OVERVIEW. Joseph Priestley - English minister- experimented to learn more about photosynthesis Took a candle & put it under a glass – went out because of the lack of oxygen.

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Photosynthesis Chapter 8

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  1. PhotosynthesisChapter 8

  2. 8–2 PHOTOSYNTHESIS: AN OVERVIEW • Joseph Priestley - English minister- experimented to learn more about photosynthesis • Took a candle & put it under a glass – went out because of the lack of oxygen. • Placed mint sprig in the glass with the candle - Stayed lit because mint sprig produced oxygen. • Experiments showed that in the presence of light, plants turn carbon dioxide (CO2) and water into carbohydrates (C6H12O6) and release oxygen (O2).

  3. The Photosynthesis Equation • The chemical equation for photosynthesis is: 6CO2 + 6H2O C6H12O6 + 6O2 • In words: 6 carbon dioxide molecules + 6 water molecules yields (in the presence of sunlight) 1 glucose molecule + 6 oxygen molecules • Plants use the carbohydrates to make starches. • See Fig. 8-4, pg. 206

  4. PHOTOSYNTHESIS: REACTANTS AND PRODUCTS Light Energy Product Reactant C6H12O6 + O2 CO2 + H2O

  5. Light CO2 Sugars O2 PHOTOSYNTHESIS: AN OVERVEIW Chloroplast Chloroplast Calvin Cycle Light- Dependent Reactions Fig 8-7 - page 209

  6. LIGHT AND PIGMENTS • Plants also need certain pigments to perform photosynthesis. • Chlorophyll is the pigment in the chloroplast necessary for green plants to perform photosynthesis. • Two types of chlorophyll: chlorophyll a and chlorophyll b • Each type absorbs a different wavelength of light. • Chlorophyll absorbs all colors of light, EXCEPT green. This is why plants appear green because green is reflected and not absorbed.

  7. Absorption of Light by Chlorophyll a and Chlorophyll b Chlorophyll b Chlorophyll a Fig. 8-5 – Page 207 – Potosynthesis requires light and cholorphyll. In the graph above, notice how cholorphyll a absorbs light mostly in the blue-violet and red regions, whereas chlorophyll b absorbs light in the blue and red regions of the visible spectrum.

  8. 8–1 ENERGY AND LIFE Chemical Energy and ATP • ATP – adenosine triphosphate – basic source of energy for all types of cells. • Energy is stored in the bonds of this molecule • ATP – 1 molecule of adenine (a nitrogen compound), 3 phosphates and a ribose sugar • ADP – adenosine diphosphate – What ATP becomes when energy is released. • ADP - 1 molecule of adenine, 2 phosphates and a ribose sugar.

  9. ATP MOLECULE Adenine Ribose 3 Phosphates Fig. 8-2 pg. 202 – ATP is used by all types of cells as their basic energy source.

  10. STORING & RELEASING ENERGY Storing Energy • Energy is stored in the bonds of ATP - between the 2nd and third phosphates Releasing Energy • Energy is released when the bond between the 2nd and 3rd phosphate on an ATP molecule is broken. • Produces ADP + Energy. • ATP is used by all types of cells as their basic energy source.

  11. ADP ATP Adenosine diphosphate (ADP) + Phosphate Adenosine triphosphate (ATP) Partially charged battery Fully charged battery Fig. 8-3, page 203 – ATP can be compared to a fully charged battery because both contain sotred energy, whereas ADP resembles a partially charged battery

  12. USING ATP – ACTIVE TRANSPORT ACTIVE TRANSPORT • Sodium –Potassium pump – cells need to move sodium (Na+) ions out of the cell and potassium (K+) ions into the cell. • This goes against the concentration gradient and requires energy. • 1 ATP molecule provides enough energy to move 3 Na+ ions and 2 K+ ions.

  13. USING ATP - GLUCOSE • ATP is available to a cell in very small amounts. • ATP is good for transferring energy, but cannot store a lot of energy. • Glucose can store 90 times the energy of one molecule of ATP. • Cells only keep a small amount of ATP on hand. • Cells can make ATP from ADP very quickly when it is needed.

  14. Light- dependent reactions Calvin cycle Energy from sunlight Thylakoid membranes ATP Stroma NADPH High-energy sugars ATP NADPH O2 Chloroplasts Photosynthesis includes takes place in uses use take place in to produce to produce of

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