1 Photosynthesis Energy & Life Created by C. Massengale

2 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 foodAutotrophs include organisms that make their own food Autotrophs can use the sun’s energy directlyAutotrophs can use the sun’s energy directly Microscopic protists called Euglena

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

6 Energy Energy Takes Many Forms such as light, heat, electrical, chemical, mechanicalEnergy Takes Many Forms such as light, heat, electrical, chemical, mechanical Energy can be changed from one form to anotherEnergy can be changed from one form to another Energy can be stored in chemical bonds & then released laterEnergy can be stored in chemical bonds & then released later Candles release energy as HEAT & LIGHT

7 ATP – Cellular Energy ATP = Adenosine TriphosphateATP = Adenosine Triphosphate Contains two, high-energy phosphate bondsContains two, high-energy phosphate bonds Also contains the nitrogen base adenine & a ribose sugarAlso contains the nitrogen base adenine & a ribose sugar

8 ADP – Other Cellular Energy ADP = Adenosine DiphosphateADP = Adenosine Diphosphate When cells need energy, ATP releases energy by breaking bonds with a phosphate.When cells need energy, ATP releases energy by breaking bonds with a phosphate. ADP is what’s leftover ADP is what’s leftover One phospha te bond has been removed

9 Sugar in ADP & ATP Called ribose Pentose (5-carbon) sugar Also found on RNA RIBOSE

10 Importance of ATP Primary compound used to store energy in living organisms

11 Releasing Energy From ATP ATP is constantly being used and remade by cellsATP is constantly being used and remade by cells ATP provides all of the energy for cell activitiesATP provides all of the energy for cell activities The high energy phosphate bonds can be BROKEN to release energyThe high energy phosphate bonds can be BROKEN to release energy

12 Releasing Energy From ATP Adding A Phosphate Group To ADP stores Energy in ATPAdding A Phosphate Group To ADP stores Energy in ATP Removing A Phosphate Group From ATP Releases Energy & forms ADPRemoving A Phosphate Group From ATP Releases Energy & forms ADP Lose Gain

13 Cells Using Biochemical Energy Cells Use ATP For: Movement Photosynthesis Cellular respiration Protein Synthesis Actively transporting large molecules across membrane

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

15 The Glucose Molecule Glucose is aGlucose is amonosaccharide (simple sugar) (simple sugar) Formula is C 6 H 12 O 6Formula is C 6 H 12 O 6 One molecule of glucose stores 90 TIMES more chemical energy than one molecule of ATPOne molecule of glucose stores 90 TIMES more chemical energy than one molecule of ATP

16 History of Photosynthesis & Plant Pigments

17 Photosynthesis Involves the use of light energy to convert Water (H 2 0) and Carbon Dioxide (CO 2 ) into into Oxygen (O 2 ) and Carbohydrates (sugars, e.g. Glucose, & Starches)

18 Investigating Photosynthesis Many Scientists Have Contributed To Understanding PhotosynthesisMany Scientists Have Contributed To Understanding Photosynthesis Early Research Focused On The Overall ProcessEarly Research Focused On The Overall Process Later Researchers Investigated The Detailed Chemical PathwaysLater Researchers Investigated The Detailed Chemical Pathways

19 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? WHAT DO YOU THINK?

20 Van Helmont’s Experiment 1643 Planted a seed into a pre- measured amount of soil and watered it for 5 yearsPlanted a seed into a pre- measured amount of soil and watered it for 5 years Weighed plant & soil. Plant was 75 kg; soil mass didn’t change.Weighed plant & soil. Plant was 75 kg; soil mass didn’t change. Concluded mass came from waterConcluded mass came from water WHAT DO YOU THINK?

21 Priestley’s Experiment 1771 Burned candle in bell jar & timed until it went out. Placed sprig of mint in bell jar for a few days. Relit candle. Burned longer with mint plant in jar. Concluded plants must release a gaseous substance necessary for burning.

22 Ingenhousz’s Experiment 1779 Repeated Priestly experiment with & without sunlight, and with & without green plant

23 Results of Ingenhousz’s Experiment Showed that Priestley’s results only occurred in the presence of sunlight and a green plant.Showed that Priestley’s results only occurred in the presence of sunlight and a green plant. Light was necessary for plants to produce the “burning gas”Light was necessary for plants to produce the “burning gas”

24 Julius Robert Mayer 1845 Proposed that plants can convert Light Energy Light Energyinto Chemical Energy

25 Samuel Ruben & Martin Kamen 1941 Used radioactive isotopes to determine that the oxygen liberated in photosynthesis comes from the water molecule KAMEN RUBIN

26 Melvin Calvin 1948 First to trace the path that carbon (CO 2 ) takes in forming GlucoseFirst to trace the path that carbon (CO 2 ) takes in forming Glucose Pathway does NOT require sunlightPathway does NOT require sunlight Called the Calvin Cycle or Light Independent ReactionCalled the Calvin Cycle or Light Independent Reaction Also known as the Dark ReactionAlso known as the Dark Reaction

27 Rudolph Marcus 1992 Studied the Calvin Cycle (Light Independent Reactions)Studied the Calvin Cycle (Light Independent Reactions) First to describe the Electron Transport Chain as source of energyFirst to describe the Electron Transport Chain as source of energy

28 The Photosynthesis Equation

29 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

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

31 Light & Pigments Different pigments absorb different wavelengths of lightDifferent pigments absorb different wavelengths of light Photons of light “excite” electrons in the plant’s pigmentsPhotons of light “excite” electrons in the plant’s pigments Excited electrons carryExcited electrons carry the absorbed energy Excited electrons leap toExcited electrons leap to HIGHER energy levels (1 level = 1 quantum leap)(1 level = 1 quantum leap)

32 Chlorophyll There are 2 main types of chlorophyll molecules: Chlorophyll a Chlorophyll b A third type, chlorophyll c, is found in microscopic dinoflagellates

33 Chlorophyll a and b Not much diff eren ce. Can you find it??

34 Chlorophyll a Found in all plants, algae, & cyanobacteriaFound in all plants, algae, & cyanobacteria Makes photosynthesis possibleMakes photosynthesis possible Absorbs red & blue light and REFLECTS GREENAbsorbs red & blue light and REFLECTS GREEN Participates directly in the Light ReactionsParticipates directly in the Light Reactions

35 Chlorophyll b Chlorophyll b is an accessory (helper) pigmentChlorophyll b is an accessory (helper) pigment Chlorophyll b acts indirectly in photosynthesis by transferring the light energy it absorbs to chlorophyll aChlorophyll b acts indirectly in photosynthesis by transferring the light energy it absorbs to chlorophyll a Like chlorophyll a, it absorbs red & blue light and REFLECTS GREENLike chlorophyll a, it absorbs red & blue light and REFLECTS GREEN

36 The Biochemical Reactions

37 It Begins with Sunlight!

38 Photoautotrophs Absorb Light Energy

39 Inside A Chloroplast

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

41 Function of the Stroma Light Independent reactions occur hereLight Independent reactions occur here ATP used to make carbohydrates like glucoseATP used to make carbohydrates like glucose Location of the Calvin CycleLocation of the Calvin Cycle

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43 Thylakoid membranes Light Dependent reactions occur hereLight Dependent reactions occur here Contain clusters of chlorophyll molecules embedded in the thylakoid membranesContain clusters of chlorophyll molecules embedded in the thylakoid membranes

44 Photosynthesis Overview

45 Energy Carriers NADP + =Nicotinamide Adenine Dinucleotide PhosphateNADP + =Nicotinamide Adenine Dinucleotide Phosphate Picks Up 2 high-energy electrons and H + from the Light Reaction to form NADPHPicks Up 2 high-energy electrons and H + from the Light Reaction to form NADPH NADPH carries energy to be passed on to another moleculeNADPH carries energy to be passed on to another molecule

46 NADPH Amazing that a simple plant knows what to do with all of this!

47 Occurs across the thylakoid membranesOccurs across the thylakoid membranes Uses light energyUses light energy Produce Oxygen from waterProduce Oxygen from water Convert ADP to ATPConvert ADP to ATP Also convert NADP + into the energy carrier NADPHAlso convert NADP + into the energy carrier NADPH Light Dependent Reactions

48 Light Dependent Reaction

49 Light Dependent Reaction

50 Photosynthesis Begins Chlorophyll a & b absorb 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

51 Photosynthesis continues High-energy electrons are moved into chemical reactions 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+

52 Photosynthesis continues Enzyme in thylakoid membrane called ATP Synthase As H+ ions passed through thylakoid membrane, enzyme binds them to ADP This forms ATP used for cellular respiration

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54 Light Reaction Summary Reactants: H 2 OH 2 O Light EnergyLight Energy Energy Products: ATP ATP NADPH NADPH “Dark Reaction” coming up in next slides

55 Light Independent Reaction ATP & NADPH from light reactions used as ‘batteries’ to supply energy for “dark” reactionsATP & NADPH from light reactions used as ‘batteries’ to supply energy for “dark” reactions Atmospheric C0 2 is used to make sugars like glucose and fructoseAtmospheric C0 2 is used to make sugars like glucose and fructose Six-carbon Sugars made during the Calvin CycleSix-carbon Sugars made during the Calvin Cycle Occurs in the stromaOccurs in the stroma

56 The Calvin Cycle Turns simple carbon into carbohydrates

57 The Calvin Cycle Two turns of the Calvin Cycle are required to make one molecule of glucoseTwo turns of the Calvin Cycle are required to make one molecule of glucose 3 CO 2 molecules enter the cycle each time to eventually form the 6-carbon glucose 3 CO 2 molecules enter the cycle each time to eventually form the 6-carbon glucose

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59 Factors Affecting the Rate of Photosynthesis Amount of available waterAmount of available water TemperatureTemperature Amount of available light energyAmount of available light energy

Water affects Photosynthesis Aqueous solutions are needed for many chemical reactions to occur 60 Water molecules are split to release H + and energy. This recharges the ATP/NADPH batteries Oxygen is released as ‘waste’ from splitting water

Enzymes in Photosynthesis Temperature effects photosynthesis for several reasons. Water cannot be used in photosynthesis reactions if it is frozen Enzymes do not function well at extreme temperatures 61 Enzyme - assisted action in photosyn thesis

Light and Photosynthesis Energy to power Photosynthesis reactions depends on… Hours of light energy Wavelength of light 62 Chlorophyll a & b work best in these light waves Chlorophyll a & b reflect GREEN light (that’s why leaves appear green)

Self-Check Quiz What two molecules are formed by plants when carbon dioxide & water are combined using sunlight as the energy? 63

64 glucose and oxygen Self-Check Quiz

65 Plants cells use light energy to make what two energy carrying molecules? Self-Check Quiz

66 ATP and NADPH Self-Check Quiz

67 Complex carbohydrates are made during what cycle of photosynthesis? Self-Check Quiz

68 Calvin Cycle AKA Light - Independent Cycle AKA The Dark Reaction Self-Check Quiz

69 Which macromolecule stores 90 times the energy of an ATP molecule? Self-Check Quiz

70 Glucose Self-Check Quiz

71 What term applies to the tiny packets of radiant energy that travel from a light source to chlorophyll? Self-Check Quiz

72 Self-Check Quiz Photons