Adapted from Mader by D Herder Photosynthesis Biology Sylvia S. Mader Michael Windelspecht Chapter 7 Photosynthesis Lecture Outline Adapted from Mader by D Herder

Photosynthetic Organisms Biology, 9th ed,Sylvia Mader Chapter 07 Photosynthetic Organisms Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. mosses trees garden plants kelp Euglena cyanobacteria diatoms (Moss): © Steven P. Lynch; (Trees): © Digital Vision/PunchStock; (Kelp): © Chuck Davis/Stone/Getty Images; (Cyanobacteria): © Sherman Thomas/Visuals Unlimited; (Diatoms): © Ed Reschke/Peter Arnold; (Euglena): © T.E. Adams/Visuals Unlimited; (Sunflower): © Royalty-Free/Corbis

Biology, 9th ed,Sylvia Mader Chapter 08 Photosynthesis Cellular Respiration Oxidation Solar Energy glucose 6H2O + 6CO2 6O2 + C6H12O6 Reduction LEOxidized and GEReduced H+ + e- -Therefore H atoms are removed electrons are also removed.

Biology, 9th ed,Sylvia Mader Chapter 08 NADP+ Cellular Respiration Coenzyme of oxidation-reduction Electron Carrier

Photosynthesis Light Reaction Calvin Cycle

Leaves and Photosynthesis Biology, 9th ed,Sylvia Mader Chapter 07 Leaves and Photosynthesis Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. cuticle upper epidermis Leaf cross section mesophyll lower epidermis CO2 O2 leaf vein stoma outer membrane inner membrane stroma stroma granum Chloroplast 37,000 thylakoid space thylakoid membrane Grana independent thylakoid in a granum overlapping thylakoid in a granum © Dr. George Chapman/Visuals Unlimited

Biology, 9th ed,Sylvia Mader Chapter 07 Light Reactions Photosynthesis Take place in the presence of light Energy‑capturing reactions Chlorophyll absorbs solar energy This energizes electrons Electrons move down an electron transport chain Pumps H+ into thylakoids Used to make ATP out of ADP and NADPH out of NADP

Overview of Photosynthesis Biology, 9th ed,Sylvia Mader Overview of Photosynthesis Chapter 07 Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. thylakoid membrane

Overview of Photosynthesis Biology, 9th ed,Sylvia Mader Overview of Photosynthesis Chapter 07 Slide #9 Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. solar energy thylakoid membrane

Overview of Photosynthesis Biology, 9th ed,Sylvia Mader Overview of Photosynthesis Chapter 07 Slide #10 Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H2O solar energy ADP + NADP+ Light reactions thylakoid membrane

Overview of Photosynthesis Biology, 9th ed,Sylvia Mader Overview of Photosynthesis Chapter 07 Slide #11 Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H2O solar energy ADP + NADP+ Light reactions NADPH ATP thylakoid membrane O2

Photosynthesis Releases Oxygen Biology, 9th ed,Sylvia Mader Chapter 07 Photosynthesis Releases Oxygen Photosynthesis

Solar Energy Converters Biology, 9th ed,Sylvia Mader Chapter 07 Solar Energy Converters Photosynthesis Pigments: Chemicals that absorb certain wavelengths of light Wavelengths that are not absorbed are reflected/transmitted Absorption Spectrum Pigments found in chlorophyll absorb various portions of visible light Chlorophyll is green because it absorbs much of the reds and blues of white light

Photosynthetic Pigments Biology, 9th ed,Sylvia Mader Chapter 07 Photosynthetic Pigments Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Increasing wavelength chlorophyll a chlorophyll b carotenoids Increasing energy Gamma rays Micro- waves Radio waves X rays UV Infrared Relative Absorption visible light 500 600 750 380 500 600 750 Wavelengths (nm) Wavelengths (nm) a. The electromagnetic spectrum includes visible light. b. Absorption spectrum of photosynthetic pigments.

Organization of a Thylakoid Biology, 9th ed,Sylvia Mader Organization of a Thylakoid Chapter 07 Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H2O CO2 solar energy ADP + P NADP + Calvin cycle reactions Light reactions NADPH ATP thylakoid membrane thylakoid membrane thylakoid thylakoid space O2 CH2O granum photosystem II electron transport chain H+ stroma photosystem I NADP reductase H+ Pq e- e- e- NADP+ NADPH e- e- H+ H+ H2O 2 1 H+ + O2 2 H+ H+ H+ H+ H+ ATP synthase H+ H+ H+ H+ H+ H+ ATP Thylakoid space H+ H+ H+ chemiosmosis P + ADP Stroma

Plants as Solar Energy Converters Biology, 9th ed,Sylvia Mader Chapter 07 Plants as Solar Energy Converters Photosynthesis Noncyclic pathway Thylakoid membrane Uses two photosystems, PS I and PS II PS II captures light energy Causes an electron to be ejected from the reaction center (chlorophyll a) Electron travels down electron transport chain to PS I Replaced with an electron from water, which is split to form O2 and H+ This causes H+ to accumulate in thylakoid chambers The H+ gradient is used to produce ATP PS I captures light energy and ejects an electron The electron is transferred permanently to a molecule of NADP+ Causes NADPH production

Noncyclic Electron Pathway Biology, 9th ed,Sylvia Mader Chapter 07 Slide #17 Noncyclic Electron Pathway Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H2O CO2 solar energy ADP+ P NADP+ Calvin cycle sun Light reactions sun NADPH ATP electron acceptor thylakoid membrane electron acceptor O CH2O energy level e– e– e– electron transport chain (ETC) e– NADP+ H + ATP e– e– NADPH reaction center reaction center pigment complex pigment complex Photosystem I Photosystem II e– CO2 CH2O H2O Calvin cycle reactions 2H+ 1 – O2 2

Calvin Cycle Reactions Take place in the stroma CO2 is reduced to a carbohydrate Use ATP and NADPH to produce carbohydrate

Overview of Photosynthesis Biology, 9th ed,Sylvia Mader Overview of Photosynthesis Chapter 07 Slide #19 Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H2O CO2 solar energy ADP + P NADP+ Calvin cycle reactions Light reactions NADPH ATP stroma thylakoid membrane CH2O O2

Biology, 9th ed,Sylvia Mader Chapter 07 Carbon Dioxide Fixers Photosynthesis Series of reactions that use atmospheric carbon dioxide to produce carbohydrates Known as C3 photosynthesis Involves three stages: Carbon dioxide fixation Carbon dioxide reduction RuBP regeneration CO2 is “fixed” into a carbohydrate

The Calvin Cycle Reactions Biology, 9th ed,Sylvia Mader The Calvin Cycle Reactions Chapter 07 Slide #21 Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H2O CO2 solar energy ADP + P NADP + Calvin cycle Light reactions NADPH ATP Metabolites of the Calvin Cycle stroma RuBP ribulose-1,5-bisphosphate O2 CH2O 3PG 3-phosphoglycerate 3CO2 intermediate BPG 1,3-bisphosphoglycerate G3P glyceraldehyde-3-phosphate 3 C6 6 3PG C3 3 RuBP C5 CO2 fixation 6 ATP CO2 reduction These ATP and NADPH molecules were produced by the light reactions. Calvin cycle 3 ADP + 3 P 6 ADP + 6 P regeneration of RuBP 6 BPG C3 These ATP molecules were produced by the light reactions. 3 ATP 5 G3P C3 6 NADPH 6 G3P C3 6 NADP+ net gain of one G3P Other organic molecules Glucose

Plants as Carbon Dioxide Fixers Biology, 9th ed,Sylvia Mader Chapter 07 Plants as Carbon Dioxide Fixers Photosynthesis Importance of the Calvin Cycle: G3P (glyceraldehyde-3-phosphate) can be converted to many other molecules The hydrocarbon skeleton of G3P can form Fatty acids and glycerol to make plant oils Glucose phosphate (simple sugar) Fructose (which with glucose = sucrose) Starch and cellulose Amino acids

© Herman Eisenbeiss/Photo Researchers, Inc. Biology, 9th ed,Sylvia Mader Fate of G3P Chapter 07 Slide #23 Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. G3P fatty acid synthesis amino acid synthesis glucose phosphate + fructose phosphate Sucrose (in leaves, fruits, and seeds) Starch (in roots and seeds) Cellulose (in trunks, roots, and branches) © Herman Eisenbeiss/Photo Researchers, Inc.

Other Types of Photosynthesis Biology, 9th ed,Sylvia Mader Chapter 07 Other Types of Photosynthesis Photosynthesis In hot, dry climates Stomata must close to avoid wilting CO2 decreases and O2 increases O2 starts combining with RuBP, leading to the production of CO2 This is called photorespiration C4 plants solve the problem of photorespiration Fix CO2 to PEP (a C3 molecule) The result is oxaloacetate, a C4 molecule In hot & dry climates C4 plants avoid photorespiration Net productivity is about 2-3 times greater than C3 plants In cool, moist environments, C4 plants can’t compete with C3 plants

Chloroplast Distribution in C4 vs. C3 Plants Biology, 9th ed,Sylvia Mader Chapter 07 Chloroplast Distribution in C4 vs. C3 Plants Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. C3 Plant C4 Plant mesophyll cells bundle sheath cell vein vein bundle sheath cell stoma stoma

CO2 Fixation in C3 and C4 Plants Biology, 9th ed,Sylvia Mader CO2 Fixation in C3 and C4 Plants Chapter 07 Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CO2 RuBP Calvin cycle 3PG G3P mesophyll cell a. CO2 fixation in a C3 plant, wildflowers CO2 mesophyll cell C4 bundle sheath cell CO2 Calvin cycle G3P b. CO2 fixation in a C4 plant, corn, Zea mays a: © Brand X Pictures/PunchStock RF; b: Courtesy USDA/Doug Wilson, photographer

CO2 Fixation in a CAM Plant Biology, 9th ed,Sylvia Mader Chapter 07 CO2 Fixation in a CAM Plant Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. night CO2 C4 day CO2 Calvin cycle G3P CO2 fixation in a CAM plant, pineapple, Ananas comosus © S. Alden/PhotoLink/Getty Images.

Other Types of Photosynthesis Biology, 9th ed,Sylvia Mader Chapter 07 Other Types of Photosynthesis Photosynthesis Each method of photosynthesis has advantages and disadvantages Depends on the climate C4 plants most adapted to: High light intensities High temperatures Limited rainfall C3 plants better adapted to Cold (below 25°C) High moisture CAM plants are better adapted to extreme aridity CAM occurs in 23 families of flowering plants Also found among nonflowering plants