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Photosynthesis

Photosynthesis. Plant – multicellular eukaryotes that have cell walls made of cellulose and photosynthesize. “stationary animals that eat sunlight”. Adenosine Triphosphate (ATP). One of the most important compounds that cells use. Stores and releases energy - adenosine triphosphate (ATP).

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Photosynthesis

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  1. Photosynthesis Plant – multicellular eukaryotes that have cell walls made of cellulose and photosynthesize. “stationary animals that eat sunlight”

  2. Adenosine Triphosphate (ATP) • One of the most important compounds that cells use. Stores and releases energy - adenosine triphosphate (ATP). • ATP consists of adenine, a 5-carbon sugar called ribose, and three phosphate groups.

  3. Adenosine Triphosphate (ATP) • Adenosine diphosphate (ADP) has two phosphate groups instead of three. ADP does not contain as much energy as ATP. Another P is added to ADP to form ATP. • Cells release the energy stored in ATP by breaking the bonds between the second and third phosphate groups.

  4. Uses of ATP • Powers protein pumps in the cell membrane • Powers cilia and flagella • Power for synthesis of proteins • Powers motor proteins that contract muscles • Provides cell energy

  5. Heterotroph – obtains energy from food it consumes How could a small seed become a giant tree? Autotroph – uses energy from the sun to produce food • Photosynthesis - the process by which autotrophs use the energy of sunlight to produce high-energy carbohydrates that can be used for food.

  6. Autotroph or Heterotroph

  7. Photosynthesis LIGHT 6CO2 + 6H2O C6H12O6 + 6O2 Carbon Dioxide Glucose Water Oxygen

  8. What is Light? Which type of light carries more energy, blue or red? Light Speed, c = 2.9979 x 108 m/s Or 670.6 million mph

  9. Electromagnetic Spectrum • Wave length and energy are inversely proportional • The smaller the wave length, the more energy • Blue light is high energy • Red light is low energy Why are plants usually green? They reflect green light

  10. Plant Pigments • Pigments – light absorbing molecules • Chlorophyll – the most abundant pigment in plants, that absorbs blue and red light. • Chlorophyll a - a blue-green pigment • Chlorophyll b - a yellow-green pigment

  11. Accessory Pigments • Carotene - an orange pigment • Xanthophyll - a yellow pigment • Anthocyanin – a red pigment

  12. Accessory Pigments • Why do plants need accessory pigments? • They absorb light in other regions of the spectrum • The accessory pigments are always present in most plants but masked by the chlorophyll.

  13. Pigments • Why do leaves change color in the fall? Answer: Shorter day lengths stop chlorophyll production, and expose accessory pigments

  14. Photosynthesis • Takes place in the chloroplast • Thylakoids – saclike photosynthetic membrane in the chloroplast • Grana – stacks of thylakoids • Stroma - the region outside of the thylakoid membranes

  15. H2O CO2 Chloroplast Light NADP+ ADP + P CALVIN CYCLE (in stroma) LIGHT REACTIONS (in thylakoids) ATP Electrons NADPH O Sugar Photosynthesis (Overall) Dark Light

  16. Connection between light and dark reactions • The electron acceptor NADP+ and ADP enter the light reaction • NADP+ accepts 2 high energy electrons and a hydrogen ion making NADPH. • ADP is converted to ATP • Without these products from the light reaction the dark reaction could not proceed.

  17. Light-Dependent Reaction • Inputs = Light, Water, NADP+, ADP • Occurs in the thylakoid membranes • Conversion of light energy to ATP and NADPH • Oxygen is released through the stoma.

  18. Light Reaction

  19. Light Reaction Steps • Photosystem II – light energy is absorbed and sends electrons through electron transport chain (ETC). Note: H2O is the source of electrons, hydrogen and oxygen • Electrons move along ETC and pump H+ into the thylakoid space • Photosystem I – electrons are re-energized and NADP+ picks up electrons and H+ (NADPH formed) • H+ builds up in thylakoid space, exits from high to low to stroma THROUGH ATP SYNTHASE (a turbine that adds P to ADP = ATP)

  20. THE DARK SIDE

  21. Dark Reaction (Calvin Cycle) • Takes place in the stroma • Use ATP and NADPH to make carbohydrates • Glucose • Starch – long chain of stored glucose. • Cellulose – tough fibers that give plants strength and rigidity

  22. Dark Reaction (Calvin Cycle) (PGAL) (PGAL)

  23. Dark Reaction (Calvin Cycle) Steps CO2 enters the Calvin Cycle from the atmosphere.The enzyme rubisco combines CO2 with a 5 carbon compound called Ribulose biphosphate (RuBP). The result are six 3 carbon compoundsthat are reduced and combine with ATP and NADPH to make Glyceraldehyde 3-phosphate (PGAL), a sugar. One PGAL leaves the cycle at midpoint and becomes the building block for glucose The remaining five 3 carbon compounds continue through the cycle to reform the 5 carbon compound RuBP

  24. H2O CO2 Chloroplast Light NADP+ ADP + P CALVIN CYCLE (in stroma) LIGHT REACTIONS (in thylakoids) ATP Electrons NADPH O Sugar Photosynthesis The products of the light reaction fuel the Calvin cycle. The products of the Calvin cycle fuel the light reaction.

  25. Factors Affecting Photosynthesis • Shortage of water • H2O acts as the electron donor in the light dependent reaction • Temperature • Photosynthesis is controlled by enzymes that work best between 0 C and 35 C. • Light Intensity • More light increases rate of photosynthesis

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