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Unit 4 Notes Photosynthesis. Converts light energy into food energy 6CO 2 + 12H 2 O light, enzymes, chlorophyll C 6 H 12 O 6 + 6O 2 + 6H 2 O.

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Presentation on theme: "Unit 4 Notes Photosynthesis. Converts light energy into food energy 6CO 2 + 12H 2 O light, enzymes, chlorophyll C 6 H 12 O 6 + 6O 2 + 6H 2 O."— Presentation transcript:

1 Unit 4 Notes Photosynthesis

2 Converts light energy into food energy 6CO H 2 O light, enzymes, chlorophyll C 6 H 12 O 6 + 6O 2 + 6H 2 O

3 Photosynthesis  Two types of autotrophic organisms  Photosynthetic—make food from sun’s energy  Chemosynthetic—make food from other inorganic molecules  2 Steps to Photosynthesis  Light dependent reactions—need light and chlorophyll to make ATP and NADPH  Light independent reactions—take ATP and NADPH + CO 2 to make glucose (or other sugars)

4 Plant Structure Leaf Structure

5 Plant Structure  Leaf Parts  Cuticle—waxy—provides protection from insects, environmental damage, etc., and keeps water from getting out  Epidermis—defense/barrier—reduces water loss  Palisade Mesophyll—structure (lots of chloroplasts)  Spongy Mesophyll—air flow (lots of chloroplasts)  Xylem—vascular tissue that moves water  Phloem—vascular tissue that moves sugars  Stomata—openings on bottom of leaf—lets CO 2 in and O 2 and H 2 O out

6 Plant Structure  Leaf Parts (continued)  Guard Cells—cells around the opening of the stomata—open when water flows in by osmosis  Open  Triggers = Light / Decrease CO 2 / Internal Clock  K + enters cell  water potential decreases  osmosis in  cells become turgid  stomata opens  Close  Triggers = No Light / Increased Temperature / Lose H 2 O / Increase CO 2  K + leaves  osmosis out  cells become flaccid  stomata close

7 Plant Structure

8  Chloroplasts  Site of Photosynthesis  The membranes (thylakoids) within the chloroplast give it the ability to build up concentration gradients for “whooshing”— chemiosmosis

9 Light Dependent Reactions Light energy (photons) is absorbed by pigments in the thylakoid membranes PigmentAbsorbsReflects Chlorophyll aRed/BlueGreen Chlorophyll bRed/BlueGreen CarotenoidsBlue/GreenOrange/Yellow

10 Light Dependent Reactions  Photosystems—Light Harvesting Units  Photosystem I—has chlorophyll p700 (longer wavelength)  Photosystem II—has chlorophyll p680 (shorter wavelength)  Pigments absorb light energy and transfer the energy to other pigments until it is absorbed by a photosystem  The photosystem gathers enough energy to raise 1e - to a higher energy level (can be used for ETS!)

11 Light Dependent Reactions  Cyclic Photophosphorylation—Electron transfer with PS I  Electrons from PSI go through an ETS and create ATP--electrons then goes back to PSI  Electrons are cycling!  Not enough energy for most plants

12 Light Dependent Reactions  Non-cyclic Photophosphorylation—Electron transfer with PS I & PS II  PS II gathers light energy which raises electron to ETS—ATP is made by chemiosmosis  Electron goes to PS I and then is raised to a 2 nd ETS—NADP is reduced to NADPH  Electrons in PS II are replaced by photolysis of H 2 O

13 Light Dependent Reactions

14 Light Independent Reactions  Reactions occur on the stromal surface of the thylakoid  Need:  Enzymes  Ribulose Biphosphate (RuBP)—a 5-Carbon sugar  CO 2 (From Air)  NADPH  ATP Plant Makes From Non-Cyclic Photophosphorylation

15 Light Independent Reactions— Calvin Cycle  Carbon Dioxide Fixation:  6CO 2 + 6RuBP  6-6C molecules (unstable); so they split into 12-3C molecules called PGA (phosphoglyceric acid)  Reduction  Each PGA is phosphorylated by ATP and reduced by NADPH into 12 molecules of PGAL (phosphoglyceraldehyde)  Regeneration of RuBP  10 of 12 PGAL remake RuBP—need ATP to do it!  2 of 12 PGAL make 6C sugar (glucose)

16 Light Independent Reactions— Calvin Cycle


18 Cellular Respiration & Photosynthesis CategoryCellular RespirationPhotosynthesis PurposeConvert stored chemical energy (glucose) to usable energy (ATP Convert solar energy to stored chemical energy (glucose) WhoALL CELLSPhotosynthetic Autotrophs WhereCytoplasm & Mitochondria Chloroplast Steps1.Glycolysis 2.Intermediate Step 3.Kreb’s Cycle 4.ETS 1.Light Dependent 2.Light Independent

19 Cellular Respiration & Photosynthesis Sun Photosynthesis Glucose + Oxygen Gas Cellular Respiration Carbon Dioxide ATPWork

20 Photosynthesis in Dry Environments  C 3 Plants—Plants that fix CO 2 with Rubisco & make 3-C PGA  In hot / dry environment, must close stoma to conserve water  Closing of stoma reduces access to CO 2  Rubisco fixes O 2 instead of CO 2 —leading to photorespiration—consumes oxygen gas and makes carbon dioxide without making ATP (actually uses ATP)

21 Photosynthesis in Dry Environments  C 4 Plants—Plants have an alternative mode of fixing CO 2 that is more efficient  Leaf structure is slightly different  Bundle sheath cells packed around veins  Mesophyll cells loosely packed around  Calvin Cycle limited to Bundle Sheath Cells  Process  PEP carboxylase fixes CO 2 making a 4C product  4C product is sent to bundle sheath cells and releases CO 2 for Calvin Cycle  Process requires ATP but is more efficient than CR

22 Photosynthesis in Dry Environments

23  CAM Plants—crassulacean acid metabolism  Plants open stomata at night & close during the day—helps conserve water  CO 2 enters stomata at night & is incorporated into organic acids stored in central vacuoles  CO 2 is released from acids in the morning to enter Calvin Cycle

24 Photosynthesis in Dry Environments

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