Review trophic level New energy thermodynamics metabolism photosynthesis cellular respiration adenosine triphosphate (ATP) Vocabulary 1

Photosynthesis Chapter 8 2

Chapter 8.1 Overview of Photosynthesis 3

Autotrophs Plants and some other types of organisms that contain chlorophyll are able to use light energy from the sun to produce food. 4

Autotrophs Autotrophs include organisms that make their own food Autotrophs can use the sun’s energy directly 5 Euglena

Heterotrophs Heterotrophs are organisms that can NOT make their own food Heterotrophs can NOT directly use the sun’s energy 6

Energy Laws of thermodynamics First law—the law of conservation of energy: energy can be converted from one form to another, but it cannot be created nor destroyed. Second law: energy cannot be converted without the loss of usable energy, that is, entropy—disorder or unusable energy--increases. 7

8

ATP – Cellular Energy Adenosine Triphosphate 2 high-energy phosphate bonds nitrogen base adenine & a ribose sugar 9

ADP Adenosine Diphosphate ATP releases energy, a free phosphate, & ADP when cells take energy from ATP 10 One phosphate bond has been removed

Sugar in ADP & ATP Called ribose Pentose sugar Also found on RNA 11

Releasing Energy From ATP ATP is constantly being used and remade by cells ATP provides all of the energy for cell activities high energy phosphate bonds can be BROKEN to release energy The process of releasing ATP’s energy & reforming the molecule is called phosphorylation 12

Releasing Energy From ATP Adding Phosphate Group To ADP stores Energy in ATP Removing Phosphate Group From ATP Releases Energy & forms ADP 13 Loose Gain

More on ATP Cells Have Enough ATP To Last For A Few Seconds ATP must constantly be made ATP Transfers Energy Very Well ATP Is NOT Good At Energy Storage 14

Glucose Glucose is a monosaccharide C 6 H 12 O 6 15

History of Photosynthesis & Plant Pigments 16

17

Photosynthesis Involves the Use Of light Energy to convert Water (H 2 0) and Carbon Dioxide (CO 2 ) into Oxygen (O 2 ) and High Energy Carbohydrates (sugars, e.g. Glucose) & Starches 18

Early Questions on Plants Several Centuries Ago, The Question Was: Does the increase in mass of a plant come from the air? The soil? The Water? 19

Priestley’s Experiment 1771 Burned Candle In Bell Jar Until It Went Out. Placed Sprig Of Mint In Bell Jar For A Few Days. Candle Could Be Relit And Burn. Concluded Plants Released Substance (O 2 ) Necessary For burning. 20

Ingenhousz’s Experiment Repeated Priestly experiment with & without sunlight

The Photosynthesis Equation 22

Pigments In addition to water, carbon dioxide, and light energy, photosynthesis requires Pigments Chlorophyll is the primary light-absorbing pigment in autotrophs Chlorophyll is found inside chloroplasts 23

Light and Pigments Energy From The Sun Enters Earth’s Biosphere As Photons Photon = Light Energy Unit Light Contains A Mixture Of Wavelengths Different Wavelengths Have Different Colors 24

Light & Pigments Different pigments absorb different wavelengths of light Photons of light “excite” electrons in the plant’s pigments Excited electrons carry the absorbed energy Excited electrons move to HIGHER energy levels 25

Chlorophyll 2 main types of chlorophyll molecules: Chlorophyll a Chlorophyll b 26 Magnesium atom at the center of chlorophyll

Chlorophyll a Found in all plants, algae, & cyanobacteria Makes photosynthesis possible Participates directly in the Light Reactions Can accept energy from chlorophyll b 27

Chlorophyll b Chlorophyll b is an accessory pigment Like chlorophyll a, it absorbs red & blue light and REFLECTS GREEN 28

The Biochemical Reactions chapter

It Begins with Sunlight! 30

Photoautotrophs Absorb Light Energy 31

Inside A Chloroplast 32

Structure of the Chloroplast Double membrane organelle Outer membrane smooth Inner membrane forms stacks of connected sacs called thylakoids Thylakoid stack is called the granun (grana- plural) Gel-like material around grana called stroma 33

Function of the Stroma Light Independent reactions occur here ATP used to make carbohydrates like glucose Location of the Calvin Cycle 34

35

Thylakoid membranes Light Dependent reactions occur here Photosystems are made up of clusters of chlorophyll molecules Photosystems are embedded in the thylakoid membranes 2 photosystems are: Photosytem I Photosystem II 36

Photosynthesis Overview 37

Energy Carriers Nicotinamide Adenine Dinucleotide Phosphate (NADP + ) NADP + = Reduced Form Picks Up 2 high-energy electrons and H + from the Light Reaction to form NADPH NADPH carries energy to be passed on to another molecule 38

Light Dependent Reactions Occurs across the thylakoid membranes Uses light energy Produce Oxygen from water Convert ADP to ATP Also convert NADP + into the energy carrier NADPH 39

Light Dependent Reaction 40

Light Dependent Reaction 41

42 Photosystem I Discovered First Active in the final stage of the Light Dependent Reaction Almost completely chlorophyll a

43 Photosystem II Discovered Second Active in the beginning stage of the Light Dependent Reaction Contains about equal amounts of chlorophyll a and chlorophyll b

44 Photosynthesis Begins Photosystem II absorbs light energy Electrons are energized and passed to the Electron Transport Chain Lost electrons are replaced from the splitting of water into 2H +, free electrons, and Oxygen 2H + pumped across thylakoid membrane

45 Photosystem I High-energy electrons are moved to Photosystem I through the Electron Transport Chain Energy is used to transport H + from stroma to inner thylakoid membrane NADP+ converted to NADPH when it picks up 2 electrons & H+

46 Phosphorylation Enzyme in thylakoid membrane called ATP Synthase As H+ ions passed through thylakoid membrane, enzyme binds them to ADP Forms ATP for cellular

47 Light Reaction Summary Reactants: H 2 O Light Energy Energy Products: ATP NADPH

48 Light Independent Reaction ATP & NADPH from light reactions used as energy Atmospheric C0 2 is used to make sugars like glucose and fructose Six-carbon Sugars made during the Calvin Cycle Occurs in the stroma

49 The Calvin Cycle Two turns of the Calvin Cycle are required to make one molecule of glucose 3-CO 2 molecules enter the cycle to form several intermediate compounds (PGA) A 3-carbon molecule called Ribulose Biphosphate (RuBP) is used to regenerate the Calvin cycle

50 Calvin Cycle Carbon Fixation (light independent reaction) C 3 plants (80% of plants on earth) Occurs in the stroma Uses ATP and NADPH from light reaction as energy Uses CO 2 To produce glucose: takes 6 turns and uses 18 ATP and 12 NADPH. Granum Thylakoid STROMA– where Calvin Cycle occurs Outer Membrane Inner Membrane

51 Calvin Cycle Remember: C 3 = Calvin Cycle C3C3 Glucose

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

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

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

55 C 4 Plants Mesophyll Cell CO 2 C-C-C PEP C-C-C-C Malate-4C sugar ATP Bundle Sheath Cell C-C-C Pyruvic Acid C-C-C-C CO 2 C3C3 Malate Transported glucose Vascular Tissue

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

57 CAM Plants Night (Stomates Open)Day (Stomates Closed) Vacuole C-C-C-C Malate C-C-C-C Malate C-C-C-C CO 2 C3C3 C-C-C Pyruvic acid ATP C-C-C PEP glucose