Energy can be transformed from one form to another FREE ENERGY (available for work) vs. HEAT (not available for work)
Where do we get our energy?• Plants- sun, carbon dioxide, water• Animals-plants, animals that have eaten plants
Light Energy Harvested by Plants & OtherPhotosynthetic Autotrophs 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
THE BASICS OF PHOTOSYNTHESIS • Almost all plants are photosynthetic autotrophs, as are some bacteria and protists – Autotrophs generate their own organic matter through photosynthesis (c) Euglena (d) Cyanobacteria (b) Kelp(a) Mosses, ferns, andflowering plants
NON-PHOTOSYNTHETIC PLANTSmyco-heterophytesA fungus, called a mycorrhizal fungus,connects the myco-heterophytes to the tree andtransfers the nutrients from the host plant to theparasitic plant.The host plant does all the photosynthesis workto make food, then "shares" some of it,unwillingly no doubt, with the parasitic plant.
WHY ARE PLANTS GREEN? Its not that easy bein green Having to spend each day the color of the leaves When I think it could be nicer being red or yellow or gold Or something much more colorful like that… Kermit the Frog
Why are plants green? h t d lig ecte Transmitted light Refl
THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED Reflected Light light Absorbed light Transmitted Chloroplast light
Electromagnetic Spectrum and Visible Light Gamma rays X-rays UV Infrared & Microwaves Radio waves Visible light Wavelength (nm)
WHY ARE PLANTS GREEN?Different wavelengths of visible light are seen by the human eye as different colors. Gamma Micro- Radio X-rays UV Infrared rays waves waves Visible light Wavelength (nm)
The feathers of male cardinalsare loaded with carotenoidpigments. These pigmentsabsorb some wavelengths oflight and reflect others. gh t ted l i Reflec Sunlight minus absorbed wavelengths or colors equals the apparent color of an object.
WHY ARE PLANTS GREEN? The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).
Chlorophyll a & b •Chl a has a methyl group •Chl b has a carbonyl group Porphyrin ring delocalized e- Phytol tail
AN OVERVIEW OF PHOTOSYNTHESIS• Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water Carbon Water Glucose Oxygen dioxide gas PHOTOSYNTHESIS
AN OVERVIEW OF PHOTOSYNTHESIS• The light Light reactions Chloroplast convert solar NADP+ energy to ADP chemical energy +P Calvin Light cycle –Produce ATP & reactions NADPH
AN OVERVIEW OF PHOTOSYNTHESIS• The Calvin cycle makes Light sugar from carbon Chloroplast dioxide NADP+ – ATP from the light ADP +P Calvin reactions provides Light reactions cycle the energy for sugar synthesis
AN OVERVIEW OF PHOTOSYNTHESIS• The Calvin cycle makes Light sugar from carbon Chloroplast dioxide NADP+ – The NADPH produced ADP +P Calvin by the light reactions Light reactions cycle provides the electrons for the reduction of carbon dioxide to glucose
Chloroplasts: Sites of Photosynthesis• Photosynthesis– Occurs in chloroplasts, organelles in certain plants– All green plant parts have chloroplasts and carry out photosynthesis • The leaves have the most chloroplasts • The green color comes from chlorophyll in the chloroplasts • The pigments absorb light energy
• The location and structure of chloroplasts Chloroplast LEAF CROSS SECTION MESOPHYLL CELL LEAF Mesophyll CHLOROPLAST Intermembrane space Outer membrane Granum Inner membrane Grana Stroma Thylakoid Stroma Thylakoid compartment
Chloroplast PigmentsChloroplasts contain several pigmentsa) Chlorophyll a - major pigment for PSII, 680nmb) Chlorophyll b - major pigment for PS1, 700nm)c) Carotenoids (xanthophylls, carotenes, retinoids) Figure 7.7
Light Reactions Dark reactions- During the day or Calvin Cycle- Thylakoid - Day or night membrane - Stroma- Coverts H2O to - use these O2 products- Products : to convert = ATP + NADPH CO2 to CH2O (sugars)
Importance of the Calvin Cycle–Glucose phosphate (simple sugar)–Fructose (glucose and sucrose)–Starch – storage form of glucose–Fatty acids & glycerol - make plant oils–Cellulose – structural component of CW–Amino acids (protein) – G3P
• A Photosynthesis Road Map Chloroplast Light StromaStack of NADP+thylakoids ADP +P Light Calvin reactions cycle Sugar used for • Cellular respiration • Cellulose • Starch • Other organic compounds
Photosystem I and II• Photosystems are arrangements of chlorophyll and other pigments packed into thylakoids. Photosystem I uses chlorophyll a, in the form referred to as P700. Photosystem II uses a form of chlorophyll a known as P680.
Photosystem I and II• Photosystem I - boost electrons to a higher energy state by absorbing light with a wavelength of 700nm, chlorophyll a.• Photosystem II - do the same thing except with light that has a wavelength of 680 nm
Cyclic Photophosphorylation• Process for ATP generation associated with some Photosynthetic Bacteria• Reaction Center => 700 nm
• Two types of photosystems cooperate in the light reactions Photon ATP mill Photon Water-splitting NADPH-producing photosystem photosystem
Noncyclic Photophosphorylation• Photosystem II regains electrons by splitting water, leaving O2 gas as a by-product E l ec Primary tro n electron acceptor tra ns po rt Primary El electron acceptor ec tro n tra ns p or t ch ai n Photons Energy for synthesis of PHOTOSYSTEM I PHOTOSYSTEM II by chemiosmosis
Plants produce O2 gas by splitting H2O• The O2 liberated by photosynthesis is made from the oxygen in water (H+ and e-)
In the light reactions, electron transport chains generate ATP, NADPH, & O2• Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons• The excited electrons are passed from the primary electron acceptor to electron transport chains – Their energy ends up in ATP and NADPH
Chemiosmosis powers ATP synthesis in the light reactions• The electron transport chains are arranged with the photosystems in the thylakoid membranes and pump H+ through that membrane – The flow of H+ back through the membrane is harnessed by ATP synthase to make ATP – In the stroma, the H+ ions combine with NADP+ to form NADPH
• The production of ATP by chemiosmosis in photosynthesisThylakoidcompartment(high H+) Light LightThylakoidmembrane Antenna moleculesStroma ELECTRON TRANSPORT(low H+) CHAIN PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE
CO2 Dark Reactions ATP NADPHH2O + Light Reactions SugarsCO2 O2
Video Guide Questions1. Joseph Priestly’s Plant Experimenta. What happened to the mouse (w/ plant) inside a jar?b. What happened to the mouse (w/o plant) inside a jar?
Video Guide Questions2. Elodea (Aquarium) Experimenta.Why does the water level in the U- shaped tube changed?b.Is the rate of change greater or less when the light is moved closer? Further away?c.Is the rate of change greater or less when the water is warmed? Chilled?
Video Guide Questions3. Geranium Plant Experimenta.Which leaves, or part of leaves, show the presence of starch?b.What conclusions can be drawn from these results?
Video Guide Questions4. Importance of green pigments in leavesa.In which leaf is the starch produced?b.What does this suggest about wavelengths of light that are important in photosynthesis?
Video Guide Questions5. Spectrum Experimenta. What happens to the spectrum when pigment solution is placed in the light beam?b. What does this result suggests about wavelengths?