2007-2008
Photosynthesis: Life from Light and Air
Energy needs of life All life needs a constant input of energy Heterotrophs (Animals) get their energy from “eating others” eat food = other organisms = organic molecules make energy through respiration Autotrophs (Plants) produce their own energy (from “self”) convert energy of sunlight build organic molecules (CHO) from CO2 make energy & synthesize sugars through photosynthesis consumers producers
Important Vocabulary ATP: Adenosine triphosphate Three phosphates attached, energy is stored between the carbon bonds ADP: Adenosine diphosphate Two phosphates attached
How are they connected? glucose + oxygen carbon + water + energy Heterotrophs (Do cellular respiration to produce energy) making energy & organic molecules from ingesting organic molecules glucose + oxygen carbon + water + energy dioxide C6H12O6 6O2 6CO2 6H2O ATP + Autotrophs (Do photosynthesis to store sunlight energy into glucose, then do cellular respiration Label the products and reactants making energy & organic molecules from light energy So, in effect, photosynthesis is respiration run backwards powered by light. Cellular Respiration oxidize C6H12O6 CO2 & produce H2O fall of electrons downhill to O2 exergonic Photosynthesis reduce CO2 C6H12O6 & produce O2 boost electrons uphill by splitting H2O endergonic + water + energy glucose + oxygen carbon dioxide 6CO2 6H2O C6H12O6 6O2 light energy +
Simple Song http://youtu.be/C1_uez5WX1o
What does it mean to be a plant Need to… collect light energy transform it into chemical energy store light energy in a stable form to be moved around the plant or stored need to get building block atoms from the environment C,H,O,N,P,K,S,Mg produce all organic molecules needed for growth carbohydrates, proteins, lipids, nucleic acids ATP glucose CO2 H2O N P K …
http://youtu.be/0PEYAOKTqEU
Plant structure Obtaining raw materials sunlight CO2 H2O nutrients leaves = solar collectors CO2 stomates = gas exchange H2O uptake from roots nutrients N, P, K, S, Mg, Fe…
stomate transpiration gas exchange
Let’s take a quick break and do a stomata peeling to see what they look like!
Pigment Molecules Pigment molecules give organisms their color because of selective absorption The color they DON’T absorb is the color they appear Plants have pigment molecules called chlorophyll in them Examples of pigment molecules that animals have are retinal in human eyes and melanin in human skin
A Look at Light The spectrum of color V I B G Y O R
Light: absorption spectra Photosynthesis gets energy by absorbing wavelengths of light chlorophyll a absorbs best in red & blue wavelengths & least in green accessory pigments with different structures absorb light of different wavelengths chlorophyll b, carotenoids, xanthophylls Why are plants green?
chloroplasts in plant cell chloroplasts contain chlorophyll absorb sunlight & CO2 cross section of leaf leaves CO2 chloroplasts in plant cell chloroplasts contain chlorophyll chloroplast make energy & sugar
Plant structure Chloroplasts Thylakoid membrane contains ATP thylakoid Chloroplasts double membrane stroma fluid-filled interior thylakoid sacs grana stacks Thylakoid membrane contains chlorophyll molecules electron transport chain ATP synthase H+ gradient built up within thylakoid sac outer membrane inner membrane granum stroma thylakoid A typical mesophyll cell has 30-40 chloroplasts, each about 2-4 microns by 4-7 microns long. Each chloroplast has two membranes around a central aqueous space, the stroma. In the stroma are membranous sacs, the thylakoids. These have an internal aqueous space, the thylakoid lumen or thylakoid space. Thylakoids may be stacked into columns called grana.
Photosynthesis – 2 parts 1. Light reactions light-dependent reactions energy conversion reactions convert solar energy to chemical energy ATP & NADPH 2. Calvin cycle “dark reactions” light-independent reactions sugar building reactions uses chemical energy (ATP & NADPH) to turn CO2 & C6H12O6 (glucose) It’s not the Dark Reactions!
Light Reactions Electron Transport Chain Pigments (proteins) in the chloroplast membrane called chlorophyll absorb light waves Not all wavelengths of light are absorbed
Light Reactions Chlorophyll molecules absorb photons of light This photon of light splits a water molecule inside the membrane into oxygen gas and strips off electrons from the hydrogen to be passed on 1 photosystem is not enough. Have to lift electron in 2 stages to a higher energy level. Does work as it falls. First, produce ATP -- but producing ATP is not enough. Second, need to produce organic molecules for other uses & also need to produce a stable storage molecule for a rainy day (sugars). This is done in Calvin Cycle! generates O2
Light Reactions The electrons get excited within the chlorophyll and passed on to the next protein The proteins in the electron transport chain raise the electrons to a higher energy level As the electron gets passed along one of the proteins it passes through generates ATP Eventually it gets passed on through all the proteins and the energy filled electron gets stores as NADPH (money in the bank… aka we will be using later) 1 photosystem is not enough. Have to lift electron in 2 stages to a higher energy level. Does work as it falls. First, produce ATP -- but producing ATP is not enough. Second, need to produce organic molecules for other uses & also need to produce a stable storage molecule for a rainy day (sugars). This is done in Calvin Cycle! ATP Chlorophyll Chlorophyll
ETC of Photosynthesis e e O split H2O H+ sun sun to Calvin Cycle ATP Two places where light comes in. Remember photosynthesis is endergonic -- the electron transport chain is driven by light energy. Need to look at that in more detail on next slide O to Calvin Cycle split H2O ATP
A little more complicated than you need to know it but a good animation… http://youtu.be/v590JJV96lc http://www.youtube.com/watch?v=BK_cjd6Evcw
Photosynthesis – Part 1 summary Why do plants appear green? (use wavelengths in your answer) What are the light absorbing pigments in plants called? Where does the oxygen that plants give off come from? Why are light reactions called light reactions? (Hint: what do they require?) Where do the light reactions occur? What do chlorophyll molecules do to electrons? Where did the energy come from? The Sun Where did the electrons come from? Chlorophyll Where did the H2O come from? The ground through the roots/xylem Where did the O2 come from? The splitting of water Where did the O2 go? Out stomates to air Where did the H+ come from? The slitting of water Where did the ATP come from? Photosystem 2: Chemiosmosis (H+ gradient) What will the ATP be used for? The work of plant life! Building sugars Where did the NADPH come from? Reduction of NADP (Photosystem 1) What will the NADPH be used for? Calvin cycle / Carbon fixation …stay tuned for the Calvin cycle
Photosynthesis: The Calvin Cycle Life from Air 2007-2008
http://www.youtube.com/watch?v=aupr9qT2qgc
Remember what it means to be a plant… Need to produce all organic molecules necessary for growth carbohydrates, lipids, proteins, nucleic acids Need to store chemical energy (ATP) produced from light reactions in a more stable form that can be moved around plant saved for a rainy day + water + energy glucose + oxygen carbon dioxide 6CO2 6H2O C6H12O6 6O2 light energy +
build stuff !! photosynthesis Light reactions Convert solar energy to chemical energy ATP NADPH What can we do now? ATP energy Stored power build stuff !! photosynthesis
CO2 C6H12O6 What is the goal? Want to make C6H12O6 synthesis How? From what? What raw materials are available? CO2 CO2 contains little energy because it is fully oxidized Reduce CO2 in a series of steps to synthesize a stable energy storage molecule NADPH reduces CO2 carbon fixation NADP NADP C6H12O6
Calvin Cycle = “Dark Reactions” CO2 is going to be converted into glucose during the Calvin Cycle This is often referred to as the “Dark Reactions” Calling it the “Dark Reactions” is misleading It doesn’t only happen in the dark, but rather in the light AND dark! Remember light reactions can only happen in the light!
From Light reactions to Calvin cycle Takes place in the chloroplast stroma (which is like the cytoplasm of the chloroplast) Need products of light reactions to drive the Calvin cycle ATP NADPH stroma ATP thylakoid
Calvin Cycle summary Calvin cycle Consumed (used) CO2 Produced (made) glucose Regenerated (recycled) ADP Regenerated NADP ADP NADP
http://youtu.be/ixpNw6mx3lk
Putting it all together CO2 H2O C6H12O6 O2 light energy + H2O CO2 Plants make both: energy ATP & NADPH sugars sunlight ADP NADP Energy Building Reactions Sugar Building Reactions NADPH ATP O2 sugars
The Great Circle of Life,Mufasa! sun Energy cycle Photosynthesis CO2 H2O C6H12O6 O2 light energy + H2O plants CO2 glucose O2 animals, plants CO2 H2O C6H12O6 O2 ATP energy + Cellular Respiration ATP The Great Circle of Life,Mufasa!
If plants can do it… You can learn it! Ask Questions!! 2007-2008