AP Bio Photosynthesis

2Photosynthesis Uses light energy as energy source Uses light energy as energy source Uses CO 2 as a carbon source Uses CO 2 as a carbon source Synthesizes energy rich organic molecules (sugar and others) Synthesizes energy rich organic molecules (sugar and others) Supplies energy, stored in sugars, to most living organisms Supplies energy, stored in sugars, to most living organisms Occurs in the chloroplasts of autotrophs (green plants) Occurs in the chloroplasts of autotrophs (green plants)

3 Photosynthesis Phacts On a global scale, photosynthesis makes about 160 billion metric tons of carbohydrates a year. On a global scale, photosynthesis makes about 160 billion metric tons of carbohydrates a year. Sucrose is the transport form of carbohydrates in most plants. Sucrose is the transport form of carbohydrates in most plants. Plants consume about 50% of the photosynthate as fuel for cellular respiration. Plants consume about 50% of the photosynthate as fuel for cellular respiration. Extra sugars are synthesized into starch and stored in cells of roots, tubers, seeds, and fruits. Extra sugars are synthesized into starch and stored in cells of roots, tubers, seeds, and fruits.

4 Summary Equation One Overall Equation: 6 CO H 2 O + light energy  C 6 H 12 O O H 2 O In Two Stages: a) Light Dependent Reactions b) Light Independent Reactions

5 Chloroplast Structure Inner & Outer Membranes Thylakoids Granum Stroma

6 Organization of Photosynthesis

7 Leaf Structure Mesophyll Cells Upper Epidermis Lower Epidermis VeinVein StomaStoma

8 The Light-Dependent Reactions 1.Occur in thylakoid membranes 2.O 2 released by splitting water 3.Light energy boosts P.E. of electrons

9 Photosynthetic Pigments Chlorophyll a - main photosynthetic pigment in all organisms except bacteriaChlorophyll a - main photosynthetic pigment in all organisms except bacteria Accessory pigments absorb slightly different wavelengths of lightAccessory pigments absorb slightly different wavelengths of light Chlorophyll b Chlorophyll b Carotenoids Carotenoids

10 Absorption Spectra The combination of all of the pigments increases the range of colors that plants can use in photosynthe sis.

11 The Photosystems

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13 Photosystem II

14 The Light-Dependent Reactions 1.Occur in thylakoid membranes Photosystems Photosystems 2.O 2 released by splitting water Photolysis Photolysis 3.Light energy boosts P.E. of electrons Photoexcitation Photoexcitation 4.ATP is generated Photophosphorylation Photophosphorylation

15 Chemiosmosis 1

16 Chemiosmosis 2

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18 animat/metabolism/photosynthesis.swf animat/metabolism/photosynthesis.swf

19 Light-Dependent Reactions

20Glucose O2O2O2O2 Overview of Photosynthesis Light-Dependent Reactions (in thylakoids) Light-Independent Reactions (in stroma) Depleted Carriers (ADP, NADP + ) Energized Carriers (ATP, NADPH) H2OH2OH2OH2O CO 2 +H 2 O

21 Rubisco (RuBP carboxylase)

22 The Light-Independent Reactions 1.Occur in the stroma 2.Does not require light, but does require the products of the light reactions (ATP and NADPH) 3.Calvin Cycle (Melvin Calvin) 3 Phases 3 Phases Assimilation of atmospheric carbon dioxide into carbohydrates.

23 The C 3 Cycle of Carbon Fixation

24 A Summary of Photosynthesis Light-dependent reactions occur in thylakoids Light- independent reactions (c 3 cycle) occur in stroma

25 C 3 Plants & the Pathway C 3 plants use the C 3 pathway In a C 3 plant, most chloroplasts are in mesophyll cells.

26 C 3 Plants Much photorespiration occurs under hot, dry conditions

27 C 4 Plants & the C 4 Pathway C 4 plants use the C 4 pathway In a C 4 plant, both mesophyll & bundle- sheath cells contain chloroplasts.

28 C 4 Plants & the C 4 Pathway Almost no photorespiration occurs under hot, dry conditions. CO 2 is captured with a highly specific enzyme. Much glucose synthesis occurs. Mesophyll cell in a C 4 plant Bundle-sheath cell in a C 4 plant

29 Relationship of Photosynthesis & Respiration

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