PHOTOSYNTHESIS: THE LIGHT REACTIONS ECOSYSTEM Photosynthesis CO 2 +H 2 O Organic + O molecules 2 Cellular respiration in mitochondria 1
PHOTOAUTOTROPHS The producers of the biosphere AUTOTROPH means self feeder 20% of the world s oxygen is produced in rain forests PHOTOAUTOTROPHS Not just plants! Giant kelp (a eukaryote) can grow up to 2ft each day Marine alga produce 70 80% of the world s oxygen 2
PHOTOAUTOTROPHS Not just plants and protists Cyanobacteria are single celled prokaryotes that are also photoautotrophs CHLOROPLASTS Use sunlight to convert water and CO 2 to glucose Collection of enzymes and pigments Prokaryotes (like cyanobacteria) have similar parts that are NOT bound by membranes. 3
CO 2 O 2 9/13/2015 LEAVES Are made of millions of plant cells filled with chloroplasts Leaves have many stoma (stomata = singlular) which means mouth Stoma allow CO 2 to enter the leaf and O 2 to exit MESOPHYLL CELLS Each contain 30 40 chloroplasts. Important for photosynthesis! Leaf Cross Section Leaf Vein transports materials through plant Mesophyll Cell Stoma Chloroplast 4
MESOPHYLL CELLS Plant cells that contain 30 40 chloroplasts CHLOROPLASTS Photosynthetic machinery covered by an inner and outer membrane Mesophyll Cell Chloroplast Inner and outer membranes Note: prokaryotes can have similar structures but they are NOT bound by membranes 5
CHLOROPLASTS Photosynthetic machinery covered by an inner and outer membrane THYLAKOIDS: membrane that forms interconnected sacs where light energy is converted to chemical energy Chloroplast THYLAKOID SPACE: Space on the inside of the thylakoid membranes where ions are pumped to create a gradient Stroma Thylakoid Thylakoid space Granum PHOTOSYNTHESIS Use light energy to convert CO 2 and water to sugar and O 2 Another REDOX process! Yay! Our FAVORITE! 6 CO 2 6 H 2 O Carbon dioxide Water energy Photosynthesis Sugar 6 O 2 Thylakoid Thylakoid space 6
SOLAR ENERGY Solar energy is a type of electromagnetic energy (radiation) from the sun PIGMENTS HARVEST SOLAR ENERGY Pigments are molecules that absorb light 7
PIGMENTS IN CHLOROPHLASTS Chlorophyll a, chlorophyll b, carotenoids PIGMENTS ABSORB LIGHT ENERGY Energy from the sun excites electrons in pigments and increases their potential energy Excited state Photon of light Heat Photon (fluorescence) Ground state Chlorophyll molecule 8
PHOTOSYSTEM II STROMA Primary electron acceptor Pigments are organized into photosystems that capture and convert solar energy Thylakoid membrane THYLAKOID SPACE Transfer of energy Pair of chlorophyll a molecules Pigment molecules PHOTOSYSTEM II In the thylakoid membrane of a chloroplast of a mesophyll plant cell and we are passing energy from pigment to pigment Thylakoid membrane THYLAKOID SPACE An electron is transferred at the end of the energy chain 9
PHOTOSYSTEM II Use light energy to transport electrons from water molecules Photosystem II Electron transport chain H 2 O ½ o2 + 2 PHOTOSYSTEM I Excite electrons further, reduce NADP+ to NADPH NADP+ NADPH Electron transport chain 10
Photosystem II Electron transport chain Photosystem I NADP + NADPH H 2 O 1 O 2 + 2 2 THYLAKOID SPACE To Calvin Cycle Thylakoid membrane ATP synthase STROMA ADP + P ATP THE LIGHT REACTIONS Tale place on the membrane of the thylakoid PHOTOSYSTEM II Electrons are excited and transferred to transport chain using light energy Enzymes split water, replenish electrons and build a gradient Oxygen is formed and released PHOTOSYSTEM II Electrons are excited and transferred to NADP+ using light energy NADP+ is reduced to NADPH for use in the Calvin Cycle ATP synthase converts ADP + P used in the Calvin Cycle to ATP to be used again by the Calvin Cycle 11
Photosystem II Electron transport chain Photosystem I NADP + NADPH H 2 O 1 O 2 + 2 2 THYLAKOID SPACE To Calvin Cycle Thylakoid membrane ATP synthase STROMA ADP + P ATP REQUIRED VIDEOS This core concepts of this material is fair game for our next check in The simple story of photosynthesis and food See link on the course website 12