Photosynthesis Introduction PDF

Energy needs of life  All life needs a constant input of energy Photosynthesis  Heterotrophs (Animals) Introduction...

Energy needs of life  All life needs a constant input of energy Photosynthesis  Heterotrophs (Animals) Introduction get their energy from “eating others” eat food = other organisms = organic molecules make energy through respiration  Autotrophs (Plants) get their energy from “self” self get their energy from sunlight Ch 10.1 build organic molecules (food) from CO2 make energy & synthesize sugars through photosynthesis How are they connected? Energy cycle sun Heterotrophs making energy & organic molecules from ingesting organic molecules glucose + oxygen carbon + water + energy Photosynthesis dioxide plants C6H12O6 + 6O2 6CO2 + 6H2O + ATP exergonic CO2 H2O glucose O2 Autotrophs making ki energy & organic i molecules l l fromf light li h energy animals, plants carbon + water + energy glucose + oxygen Cellular Respiration dioxide 6CO2 + 6H2O + light energy C6H12O6 + 6O2 ATP endergonic 1  Photosynthesis Photosynthesis  Using the sun to make useful forms of energy Photosynthesis is the conversion of light energy into  Sunlight S li ht plays l a much h llarger role l in i our sustenance t than th chemical energy by living organisms. organisms we may expect: all the food we eat and all the fossil fuel How can sunlight be the source of energy for virtually we use is a product of photosynthesis, which is the every living thing? process that converts energy in sunlight to chemical forms of energy that can be used by biological systems General Equation: chlorophyll 6 CO2 + 6H2O + light li ht energy C6H12O6 + 6O2 Photosynthetic Organisms Chlorophyll  Plants, algae, some protists, and cyanobacteria all contain chlorophyll Chlorophyll  Absorbs light energy and begins photosynthesis  Chlorophyll a: red and violet‐blue  Chlorophyll b: yellow‐red and blue  Composed of porphyrin ring and long hydrocarbon tail  All photosynthetic organism use chlorophyll a as the primary pigment 2  Chlorophyll Prokaryotic Autotrophs: Cyanobacteria Chlorophyll a contains –CH3 at R  Largest group of photosynthetic Chlorophyll b contains –COH at R prokaryotes R  Unicellular, but grow in colonies  Live in different environments: oceans, freshwater lakes, rivers, on rocks and soil Porphyrin ring Phytol Chain  Dense D blooms bl produce d toxins i that h Mg ion in centre, surrounded Hydrocarbon tail anchors the pose environmental hazard by hydrocarbon ring. This ring molecule to a membrane contains the electrons that absorb light energy Eukaryotic Autotrophs: Algae, Protists, Cyanobacteria Plants  First organisms to use sunlight in the production of  Contain chlorophyll within chloroplasts organic compounds from water and CO2  Chloroplasts Chl l t give i lleaves, stems t characteristic h t i ti green  Contain chlorophyll a to carry out photosynthesis colour and d : photosynthetic pigments called phycobilins  Leaves are the primary photosynthetic organs of most  Closely related to chloroplasts plants  endosymbiotic theory  To undergo photosynthesis, a plant cell must contain chlorophyll hl h ll and d obtain b i carbon b dioxide, di id water and d light li h energy from its environment 3  Leaves: The Photosynthetic Organs of Plants Transpiration & Photosynthesis Waxy and water resistant, protection  Transpiration is the evaporation Vascular of water from leaves bundle – Allows light to pass to mesophyll transport  creates a “transpiration pull” that water, Chloroplasts are abundant, helps to move water, minerals minerals, carbs location of most of and other substances upward photosynthesis  produces an evaporative cooling effect that prevents overheating  Conditions that promote Regulate exchange of transpiration cause guard cells to CO2 and O2, allow Create openings called stomata (sing. stoma) reduce size of stomata water to escape by transpiration Plants & Leaves Gas Exchange in Leaves  Plants are the only  Leaves are usually photosynthetic p covered with waterproof organisms to have covering (cuticle) leaves (and not all  On underside of leaves, plants have leaves). there are small A leaf may be structures called viewed as a solar stomata (singular: collector crammed stoma) for gas exchange full of  Each stoma has: photosynthetic  A pore enclosed by a pair cells. of guard cells 4  Structure and function of stomata Structure and function of stomata  Generally stomata open  Stomatal opening and closing during day and close during depends on changes in the the night. The guard cells on turgor of the guard cells. each side of the stoma pore  When water flows into the control the size of the pore guard cells by osmosis, their by changing their shape. turgor increases and they expand. expand  If the guard cells lose water the opposite happens and the pore closes. Stomata Opening/Closing  When K+ ions diffuse out of the guard cells, water also moves out by osmosis and the guard cells become flaccid and the stomata closes. Stomata are usually closed during the night.  When K+ ions diffuse into the guard cells, ll water also l moves iin bby osmosis i and the guard cells swell, opening the stomata. Stomata are usually open during the day. 5  Chloroplasts Review: Plant structure  Photosynthesis factories of plants and algae  Chloroplasts  double membrane  stroma Protein‐rich semiliquid material in fluid‐filled interior the interior of chloroplast  thylakoid sacs  grana stacks  Thylakoid membrane contains  chlorophyll molecules  electron transport chain Lamellae‐ unstacked thylakoids between grana  ATP synthase Membrane bound, flattened H+ gradient built up within + + H+ H + sacs that stack to form granum Chlorophyll embedded in thylakoid thylakoid sac H+ H+ H + H+ H+ HH+ H+ H (columns) membranes Photosynthesis The stages All photosynthesis reactions occur within the  Stage 1: Capturing light chloroplasts energy Partly within the stroma and partly within thylakoid  Stage 2: Using captured light membranes energy to make ATP and Chloroplasts contain their own DNA and ribosomes and reduce NADP+ to NADPH are able to replicate p byy fission  Stage 3: Using the free energy of ATP and the reducing power of NADPH to make glucose and oxygen 6  Stages cont’d Photosynthesis  Photosystems absorb particular wavelengths and  Light reactions transfer their energy to ADP ADP, Pi and NADP+ forming ATP  light‐dependent reactions and NADPH  energy production reactions  2 types of reactions occur in photosynthesis; the light convert solar energy to chemical energy reactions and carbon fixation ATP & NADPH  Light reactions: only take place when light available ,  Calvin cycle not affected by changes in temperature, temperature use light and  light light‐independent independent reactions water, produce NADPH and ATP  sugar production reactions uses chemical energy (ATP & NADPH) to reduce CO2 &  Carbon fixation: dependent on NADPH and ATP, synthesize C6H12O6 (therefore on light reactions too), varies with temperature not intensity of light Stage 1 & 2 = Light Reactions Stage 3: Calvin Cycle H2O + light energy ATP + NADPH + O2 CO2 + ATP + NADPH C6H12O6 + ADP + NADP sunlight H2 O  produces ATP CO2  builds sugars  produces NADPH  uses ATP & ADP  releases O2 as a NADPH waste product NADP Sugar  recycles ADP & Energy Building Building Reactions Reactions NADP back to NADPH NADPH make more ATP ATP ATP & NADPH sugars O2 C6H12O6 7  + H+ H+ H+ Putting it all together Light reactions H+ H+ H + + + H+ H H H H + + H+ H+ H+ H+ H+ H + + + H+ H H H H + light  Electron Transport Chain CO2 + H2O + energy C6H12O6 + O2 like in cellular respiration  membrane‐bound b b d proteins i ini organelle ll H2 O CO2 sunlight Plants make both:  electron acceptors  energy NADPH ADP ATP & NADPH  proton (H+) Energy NADP Sugar  sugars gradient across Buildingg Building inner membrane Reactions Reactions NADPH  ATP synthase enzyme ATP sugars O2 C6H12O6 How does this occur A Look at Light  The spectrum of color  Various forms of radiation surround us, from the sun and other sources. sources  Some are visible and some are invisible. V I B G Y O R 8   Frequencies of visible Highest frequency, Wave model of light radiation (light) are smallest wavelength = perceived as different violet colours.  Electromagnetic radiation travels at 300000000m/s  Frequencies of visible radiation (light) are perceived as p different colours We can remember the visible spectrum with ROY G BIV! Lowest frequency, All frequencies and largest wavelength = red wavelengths = white How Does a Plant Capture Light? Light Light can be  Electromagnetic radiation, travelling at 3x108  transmitted ((light g passes p through g an object. j m/s  Exhibits properties of waves and photons (particles)  Wavelength is inversely proportional to its Reflected (light bounces off energy object)  Visible Vi ibl light li h ranges from f 400 to 700 nm Absorbed (light goes into object) 9  How Does a Plant Capture Light? Absorption spectrum  Plants have chlorophyll PIGMENTS (molecules that can Graph that illustrates the wavelengths of light absorbed by a absorb specific wavelengths of light) pigment Plant leaves appear green. Therefore, what colours must the chlorophyll pigments absorb? reflect? Everything but GREEN Green http://www.johnkyrk.com/photosynthesis.html Chlorophyll and Accessory Pigments Accessory pigments cont’d  Chlorophyll a is the only pigment that can transfer light  Xantophylls – produce yellow color energy to the carbon fixation reactions of photosynthesis  Carotenoids C t id – produce d yellow‐orange ll colour l  Chlorophyll b and carotenoids acts as accessory  Interspersed within thylakoid membrane pigments, absorbing wavelengths that chlorophyll a cannot  Anthocyanins – produce red, violet, blue colour  Carotenoids: (ex β‐ carotene) possess 2 hydrocarbon  Located in p plant cell vacuoles rings connected by hydrocarbon chain – Photosynthetically active radiation (PAR) – wavelengths between 400 nm – 700nm support photosynthesis 10