1. Chapter 10 Photosynthesis

2. Modes of Nutrition Heterotrophs – obtain organic compounds by consuming other organisms (animals) Photoautotrophs – build organic compounds with light energy (plants) Chemoautotrophs – use inorganic substances (sulfur, ammonia) as an energy source to make organic compounds (some bacteria)

3. Photosynthesis NET: But really.. Opposite of Cellular Respiration!

4. Photosynthetic prokaryotes do not have chloroplasts. Chlorophyll is in their plasma membrane. Contains chlorophyll

6. Light Dependent: Closer Look Sunlight is electromagnetic energy – Wave-like properties and Particle-like properties – Waves  Wavelengths – Visible wavelengths = 380nm-750nm Pigments: Substances that absorb visible light Chlorophyll a is main pigment Accessory Pigments: -Chlorophyll b (yellow-green -Carotenoids (oranges, yellows) So, why do leaves look green?

7. Lab #4 – Plant Pigments

8.  What wavelengths are absorbed  Effectiveness of wavelengths = activity Doesn’t exactly match due to accessory pigments (transfer energy to Chlor. a)

9. Light Dependent: Photosystems  Light harvesting units of the thylakoid membrane  Composed mainly of protein and pigment antenna complexes  Antenna pigment molecules are struck by photons  Energy is passed to reaction centers  Excited e- from chlorophyll is trapped by a primary e- acceptor

10. Light Dependent: Photosystems 2 photosystems in thylakoid membrane – Photosystem II chlorophyll a P 680 = absorbs 680nm ~ red light – Photosystem I chlorophyll b P 700 = absorbs 700nm ~ red light

11. Light Dependent = The ETC ETC uses light energy to produce – ATP & NADPH go to Calvin cycle PS II absorbs light – excited electron passes from chlorophyll to “primary electron acceptor” – need to replace electron in chlorophyll – enzyme extracts electrons from H 2 O & supplies them to chlorophyll splits H 2 O O combines with another O to form O 2 O 2 released to atmosphere and we breathe easier!

12. Fill in Stroma (fluid) Thylakoid (disk)

13. Lab #4 - Photosynthesis DPIP was used to replace NADP+ DPIP accepted e- (reduced = RIG) Turned from Blue  Clear More light could pass through cuvette Transmittance % increased

14. Light Dependent: Photophosphorylation Using light energy to add a P to ADP Two types: – Non-Cyclic – Cyclic

15. Non-Cyclic Photophosphorylation Light reactions elevate electrons in 2 steps (PS II & PS I) – PS II generates energy as ATP – PS I generates reducing power as NADPH – NADPH used in Calvin Cycle (light independent)

16. Cyclic Photophosphorylation Involves only PS1 Generates ATP but no NADPH or O 2 Supplements the ATP supply required for the Calvin Cycle

17. Light Independent: A Closer Look AKA The Calvin Cycle In stroma Uses ATP and NADPH to convert CO 2 to sugar Makes a 3-C sugar Needs 3 CO 2 to make 1 Glucose (C 6 H 12 O 6 ) Uses 18 ATP (endergonic) and 12 NADPH to make 1 Glucose

20. G3P Glyceraldehyde-3-P – end product of Calvin cycle – energy rich 3 carbon sugar “C3 photosynthesis” G3P is an important intermediate G3P   glucose   carbohydrates   lipids   phospholipids, fats, waxes   amino acids   proteins   nucleic acids   DNA, RNA

21. RuBisCo Enzyme which fixes carbon from air – ribulose bisphosphate carboxylase – CO 2 + 5-C sugar (RuBP) is broken down by RuBisCo into 3-C sugars – most abundant enzyme

22. Types of Plants C3 - most plants, produce G3P – Ex: rice, wheat, soybeans – Occurs in a single chloroplast – CO 2 + RuBp (5-C) = 6-C  split into G3Ps  Glucose

23. Ruh-Roh… Hot, dry days – Stomata close to conserve water – CO 2 is depleted  – O 2 builds up from light reactions RuBisCo – when O 2 concentration is high RuBisCo bonds O to RuBP O 2 is a competitive substrate oxidation of RuBP breakdown sugars CALLED PHOTORESPIRATION !

24. Photorespiration Consumes oxygen Makes carbon dioxide Produces no ATP Decreases photosynthetic output (decreases organic molecules used in Calvin Cycle)

25. SOLUTIONS! Plants living in hot, arid climates have evolved different modes of carbon fixation – C4 and CAM plants

26. C4 – turn CO 2 into a 4-C compound – Ex: corn, sugarcane – Favored in hot, arid environments – 2 chloroplasts – Mesophyll = CO 2 is fixed into a 4-C – Bundle Sheath Cells (cells surrounding veins) = Calvin Cycle – Facilitates production of CO 2 to combat photorespiration FYI: the PEP Carboxylase has a much greater affinity for CO 2 than RuBisCo at higher temps

27. CAM Plants – Ex: Cacti, Pineapple – Very arid environments – At night: Stomata open, take in CO 2 – Store a 4-C compound in vacuole – During Day: Light Rxns supply ATP and NADPH, Uses stored CO 2 to complete Calvin Cycle

28. Photosynthesis Summary Light reactions – produced ATP – produced NADPH – consumed H 2 O – produced O 2 as byproduct Calvin cycle – consumed CO 2 – produced G3P (sugar) – regenerated ADP – regenerated NADP

29. Interdependence in Nature

30. REDOX rxns Cell Respiration Exergonic – Energy is RELEASED from the oxidation of sugar Electrons are transported to OXYGEN = Water – Oxygen pulls e - s down to produce concentration gradient of H + – H + is pumped through ATP Synthase  ADP + Pi = ATP Photosynthesis Endergonic – Energy is REQUIRED – Light is the energy source that moves e - Water is split, electrons are moved from water to carbon dioxide – CO 2 is reduced – Makes sugar (glucose)

31. Photosynthesis Animation http://dendro.cnre.vt.edu/forestbiology /photosynthesis.swf