PHOTOSYNTHESIS

2 Autotrouphs

3 Photosynthesis Anabolic (small molecules combined)Anabolic (small molecules combined) Endergonic (stores energy)Endergonic (stores energy) Carbon dioxide (CO 2 ) requiring process that uses light energy (photons) and water (H 2 O) to produce organic macromolecules (glucose).Carbon dioxide (CO 2 ) requiring process that uses light energy (photons) and water (H 2 O) to produce organic macromolecules (glucose). 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 glucose SUN photons

4 Question: Where does photosynthesis take place?

5 Plants Autotrophs – produce their own food (glucose)Autotrophs – produce their own food (glucose) Process called photosynthesisProcess called photosynthesis Mainly occurs in the leaves:Mainly occurs in the leaves: a.stoma - pores b.mesophyll cells Stoma Mesophyll Cell Chloroplast

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7 Stomata (stoma) Pores in a plant’s cuticle through which water vapor and gases (CO 2 & O 2 ) are exchanged between the plant and the atmosphere. Guard Cell Carbon Dioxide (CO 2 ) Oxygen (O 2 ) Found on the underside of leaves Stoma

8 Question: Why are plants green?

9 Chlorophyll Molecules Located in the thylakoid membranesLocated in the thylakoid membranes Chlorophyll have Mg + in the centerChlorophyll have Mg + in the center Chlorophyll pigments harvest energy (photons) by absorbing certain wavelengths (blue-420 nm and red- 660 nm are most important)Chlorophyll pigments harvest energy (photons) by absorbing certain wavelengths (blue-420 nm and red- 660 nm are most important) Plants are green because the green wavelength is reflected, not absorbedPlants are green because the green wavelength is reflected, not absorbed.

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11 Wavelength of Light (nm) Short waveLong wave (more energy)(less energy)

12 Absorption of Light by Chlorophyll wavelength Absorption violet blue green yellow orange red Chlorophyll absorbs blue-violet & red light best

13 Question: During the fall, what causes the leaves to change colors?

14 Fall Colors In addition to the chlorophyll pigments, there are other pigments presentIn addition to the chlorophyll pigments, there are other pigments present During the fall, the green chlorophyll pigments are greatly reduced revealing the other pigmentsDuring the fall, the green chlorophyll pigments are greatly reduced revealing the other pigments Carotenoids are pigments that are either red, orange, or yellowCarotenoids are pigments that are either red, orange, or yellow

15 Redox Reaction The transfer of one or more electrons from one reactant to another Two types: 1.Oxidation is the loss of e - 2.Reduction is the gain of e -

16 Question: Why do cells use for energy?

17 Energy for Life on Earth Sunlight is the ULTIMATE energy for all life on Earth Plants store energy in the chemical bonds of sugars Chemical energy is released as ATP during cellular respiration

18 Structure of ATP ATP stands for adenosine triphosphate It is composed of the nitrogen base ADENINE, the pentose (5C) sugar RIBOSE, and three PHOSPHATE groups The LAST phosphate group is bonded with a HIGH ENERGY chemical bond This bond can be BROKEN to release ENERGY for CELLS to use

19 Removing a Phosphate from ATP Breaking the LAST PHOSPHATE bond from ATP, will --- –Release ENERGY for cells to use –Form ADP –Produce a FREE PHOSPHATE GROUP

20 High Energy Phosphate Bond

21 FREE PHOSPHATE can be re-attached to ADP reforming ATP Process called Phosphorylation

22 Phosphorylation

23 Parts of Photosynthesis

24 Two Parts of Photosynthesis Two reactions make up photosynthesis: 1.Light Reaction or Light Dependent Reaction - Produces energy from solar power (photons) in the form of ATP and NADPH. SUN

25 Two Parts of Photosynthesis 2. Calvin Cycle or Light Independent Reaction Also called Carbon Fixation or C 3 FixationAlso called Carbon Fixation or C 3 Fixation Uses energy (ATP and NADPH) from light reaction to make sugar (glucose).Uses energy (ATP and NADPH) from light reaction to make sugar (glucose).

26 Photosynthesis Overview

27 Light Reaction (Electron Flow) Occurs in the Thylakoid membranesOccurs in the Thylakoid membranes During the light reaction, there are two possible routes for electron flow:During the light reaction, there are two possible routes for electron flow: A.Cyclic Electron Flow B.Noncyclic Electron Flow

28 Energy Carriers Nicotinamide Adenine Dinucleotide Phosphate (NADP + )Nicotinamide Adenine Dinucleotide Phosphate (NADP + ) NADP + = Oxidized Form (Empty, needs e-)NADP + = Oxidized Form (Empty, needs e-) Picks Up 2 high-energy electrons and H + from the Light Reaction to form NADPH (Full)Picks Up 2 high-energy electrons and H + from the Light Reaction to form NADPH (Full) NADPH carries energy to be passed on to another moleculeNADPH carries energy to be passed on to another molecule

29 NADPH

30 Occurs across the thylakoid membranesOccurs across the thylakoid membranes Uses light energyUses light energy Produce Oxygen from waterProduce Oxygen from water Convert ADP to ATP (ATP Synthease)Convert ADP to ATP (ATP Synthease) Also convert NADP + into the energy carrier NADPH (NADP+ Reductase) Light Dependent Reactions

31 Light Reactions

32 Chemiosmosis Powers ATP synthesisPowers ATP synthesis Takes place across the thylakoid membraneTakes place across the thylakoid membrane Uses ETC and ATP synthase (enzyme)Uses ETC and ATP synthase (enzyme) H+ move down their concentration gradient through channels of ATP synthase forming ATP from ADPH+ move down their concentration gradient through channels of ATP synthase forming ATP from ADP

33 Chemiosmosis

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35 Calvin Cycle Carbon Fixation (light independent reaction)Carbon Fixation (light independent reaction) C 3 plants (80% of plants on earth)C 3 plants (80% of plants on earth) Occurs in the stroma Occurs in the stroma Uses ATP and NADPH from light reaction as energyUses ATP and NADPH from light reaction as energy Uses CO 2Uses CO 2 To produce glucose: it takes 6 turns and uses 18 ATP and 12 NADPH.To produce glucose: it takes 6 turns and uses 18 ATP and 12 NADPH.

36 Calvin Cycle (C 3 fixation) 6CO 2 6C-C-C-C-C-C 6C-C-C 6C-C-C-C-C 12PGA RuBP 12G 3 P (unstable) 6NADPH 6ATP C-C-C-C-C-C Glucose (6C) (36C) (30C) (6C) 6C-C-C C3C3 glucose

37 Photorespiration Occurs on hot, dry, bright daysOccurs on hot, dry, bright days Stomates closeStomates close Fixation of O 2 instead of CO 2Fixation of O 2 instead of CO 2 Produces 2-C molecules instead of 3-C sugar moleculesProduces 2-C molecules instead of 3-C sugar molecules Produces no sugar molecules or no ATPProduces no sugar molecules or no ATP

38 Photorespiration Because of photorespiration, plants have special adaptations to limit the effect of photorespiration: 1.C 4 plants 2.CAM plants

39 C 4 Plants Hot, moist environmentsHot, moist environments 15% of plants (grasses, corn, sugarcane)15% of plants (grasses, corn, sugarcane) Photosynthesis occurs in 2 placesPhotosynthesis occurs in 2 places Light reaction - mesophyll cellsLight reaction - mesophyll cells Calvin cycle - bundle sheath cellsCalvin cycle - bundle sheath cells

40 CAM Plants Hot, dry environmentsHot, dry environments 5% of plants (cactus and ice plants)5% of plants (cactus and ice plants) Stomates closed during dayStomates closed during day Stomates open during the nightStomates open during the night Light reaction - occurs during the dayLight reaction - occurs during the day Calvin Cycle - occurs when CO 2 is presentCalvin Cycle - occurs when CO 2 is present

41 Question: Why do CAM plants close their stomata during the day?

Cam plants close their stomata in the hottest part of the day to conserve water