Photosynthesis Energy Life 1 Autotrophs Plants and some

Photosynthesis Energy & Life 1

Autotrophs Plants and some other types of organisms that contain chlorophyll are able to use light energy from the sun to produce food. 2

Autotrophs • Autotrophs include organisms that make their own food • Autotrophs can use the sun’s energy directly Euglena 3

Heterotrophs • Heterotrophs are organisms that can NOT make their own food • Heterotrophs can NOT directly use the sun’s energy 4

Energy • Energy Takes Many Forms such as light, heat, electrical, chemical, mechanical • Energy can be changed from one form to another • Energy can be stored in chemical bonds & then released later Candles release energy as HEAT & LIGHT 5

ATP – Cellular Energy • Adenosine Triphosphate • Contains two, high-energy phosphate bonds • Also contains the nitrogen base adenine & a ribose sugar 6

ADP • Adenosine Diphosphate • ATP releases energy, a free phosphate, & ADP when cells take energy from ATP One phosphate bond has been removed 7

Sugar in ADP & ATP • Called ribose • Pentose sugar • Also found on RNA 8

Importance of ATP Principal Compound Used To Store Energy In Living Organisms 9

Releasing Energy From ATP • ATP is constantly being used and remade by cells • ATP provides all of the energy for cell activities • The high energy phosphate bonds can be BROKEN to release energy • The process of releasing ATP’s energy & reforming the molecule is called phosphorylation 10

Releasing Energy From ATP • Adding A Phosphate Group To ADP stores Energy in ATP • Removing A Phosphate Group From ATP Releases Energy & forms ADP Loose Gain 11

Cells Using Biochemical Energy Cells Use ATP For: • Active transport • Movement • Photosynthesis • Protein Synthesis • Cellular respiration • All other cellular reactions 12

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 13

Glucose • Glucose is a monosaccharide • C 6 H 12 O 6 • One Molecule of glucose Stores 90 Times More Chemical Energy Than One Molecule of ATP 14

Photosynthesis • Involves the Use Of light Energy to convert Water (H 20) and Carbon Dioxide (CO 2) into Oxygen (O 2) and High Energy Carbohydrates (sugars, e. g. Glucose) & Starches 15

Investigating Photosynthesis • Many Scientists Have Contributed To Understanding Photosynthesis • Early Research Focused On The Overall Process • Later Researchers Investigated The Detailed Chemical Pathways 16

The Photosynthesis Equation 17

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 18

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 19

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 20

Chlorophyll There are 2 main types of chlorophyll molecules: Chlorophyll a Chlorophyll b A third type, chlorophyll c, is found in dinoflagellates Magnesium atom at the center of chlorophyll 21

Chlorophyll a • Found in all plants, algae, & cyanobacteria • Makes photosynthesis possible • Participates directly in the Light Reactions • Can accept energy from chlorophyll b 22

Chlorophyll b • Chlorophyll b is an accessory pigment • Chlorophyll b acts indirectly in photosynthesis by transferring the light it absorbs to chlorophyll a • Like chlorophyll a, it absorbs red & blue light and REFLECTS GREEN 23

The Biochemical Reactions 24

Inside A Chloroplast 25

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 26

Function of the Stroma • Light Independent reactions occur here • ATP used to make carbohydrates like glucose • Location of the Calvin Cycle 27

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Thylakoid membranes • Light Dependent reactions occur here • Photosystems are made up of clusters of chlorophyll molecules • Photosystems are embedded in the thylakoid membranes • The two photosystems are: Photosytem I Photosystem II 29

Photosynthesis Overview 30

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 31

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 32

Light Dependent Reaction 33

Photosystem I • Discovered First • Active in the final stage of the Light Dependent Reaction • Made of 300 molecules of Chlorophyll • Almost completely chlorophyll a 34

Photosystem II • Discovered Second • Active in the beginning stage Of the Light Dependent Reaction • Contains about equal amounts of chlorophyll a and chlorophyll b 35

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 2 H+, free electrons, and Oxygen 2 H+ pumped across thylakoid membrane 36

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+ 37

Phosphorylation Enzyme in thylakoid membrane called ATP Synthetase As H+ ions passed through thylakoid membrane, enzyme binds them to ADP Forms ATP for cell 38

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Light Reaction Summary Reactants: • H 2 O • Light Energy Products: • ATP • NADPH 40

Light Independent Reaction • ATP & NADPH from light reactions used as energy • Atmospheric C 02 is used to make sugars like glucose and fructose • Six-carbon Sugars made during the Calvin Cycle • Occurs in the stroma 41

The Calvin Cycle 42

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 (Ru. BP) is used to regenerate the Calvin cycle 43

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Factors Affecting the Rate of Photosynthesis • Amount of available water • Temperature • Amount of available light energy 45