Then what? • Plants convert the SOLAR ENERGY into CHEMICAL ENERGY (glucose and other high-energy carbs) • Julius Mayer discovered this conversion in 1845
Energy flow through ecosystems • Autotrophs (Producers) – organisms that can make their own food (glucose) • Ex. Plants, algae
Heterotrophs (Consumers) – Organisms that obtain energy from the food they eat • Ex. Fungi, Animals… anything that has to EAT to get ENERGY
Why do plants and animals need energy? • Mechanical functions (muscle contractions – animals, turning toward the sun – plants) • Protein synthesis • Active transport
PS and CR: Chloroplasts and Mitochondria Can PRODUCERS do both? Can CONSUMERS do both?
ATP = Energy Currency of the Cell • Adenosine TriPhosphate – most important energy storing compound used by every cell • Even used during PS to make glucose… which is used to make ATP!
Question Why are eukaryotes able to be larger and more complex than prokaryotes? Efficient energy conversion
Theory of Endosymbiosis • Lynn Margulies and many other scientists • The theory ofEndosymbiosis explains the origin of chloroplasts and mitochondria and their double membranes. • This concept postulates that chloroplasts and mitochondria are the result of years of evolution initiated by the endocytosis of bacteria and blue-green algae. • According to this theory, blue green algae and bacteria were not digested; they became symbiotic instead.
Support for Endosymbiotic Theory Mitochondria and chloroplasts… • reproduce like bacteria do (binary fission) • have their own ribosomes that resemble bacterial ribosomes (70S) • are double membrane-bound • have their own DNA which is different than the DNA in the nucleus, but similar to bacterial DNA • …
Photosynthesis • Involves the Use Of light Energy to convert Water (6H20) and Carbon Dioxide (6CO2) into Oxygen (6O2) and High Energy Carbohydrates (sugars, e.g. Glucose) & Starches
Investigating Photosynthesis • Many Scientists Have Contributed To Understanding Photosynthesis • Early Research: Overall Process • Later Researchers:Detailed Chemical Pathways
Early Questions on Plants Several Centuries Ago, The Question Was:Plants tend to grow… WHY? Does the increase in mass of a plant come from the air? The soil? The Water?
Van Helmont’sExperiment 1643 • Planted a seed into A pre-measured amount of soil and watered for 5 years • Weighed Plant & Soil. • Van Helmont dried and weighed the soil. • The plant gained approx. 74 kg of mass… but the dried soil weighed almost the same (lost ~2 ounces) • Concluded Mass Came From Water
Priestley’s Experiment 1771 • Burned Candle In Bell Jar Until It Went Out. • Placed Sprig Of Mint In Bell Jar For A Few Days. • Candle Could Be Relit And Burn. • Concluded Plants Released Substance (O2) Necessary For burning.
Priestley = O2 is the burning gas and plants release it • Thinking questions: • Do all types of plants release the same amount of oxygen gas? How could you test that? • What factors, if any, might have an effect on the production of oxygen?
Ingenhousz’s Experiment 1779 Repeated Priestly experiment with & without sunlight
Results of Ingenhousz’sExperiment • Showed That Priestley’s Results Only Occurred In The Presence Of Sunlight. • Light Was Necessary For Plants To Produce The “Burning Gas” or oxygen
Julius Robert Mayer 1845 Proposed That Plants can Convert Light Energy Into Chemical Energy
Samuel Ruben & Martin Kamen1941 Used Isotopes To Determine That The Oxygen Liberated In Photosynthesis Comes From Water RUBIN KAMEN
Melvin Calvin 1948 • First to trace the path that carbon (CO2) takes in forming Glucose • Used radioactive isotope Carbon-14 • Does NOT require sunlight • Called the Calvin Cycle or Light Independent Reaction or Dark Reaction
Rudolph Marcus 1992 • Studied the Light Independent Reactions • First to describe the Electron Transport Chain
Recap • Van Helmont = mass of a plant comes from water • Preistley = plants produce oxygen (the gas necessary for combustion) • Ingenhousz = plants only produce oxygen in the LIGHT (is a product of the light rnxs, NOT the calvin cycle) • Mayer = plants convert light into chemical energy
Ruben and Kamen = the O’s in oxygen gas comes from the O’s in water (breaking water molecules during light rxns). Used isotope of oxygen to trace its path. • Calvin = the C’s in glucose/ sugars comes from the C’s in carbon dioxide. Glucose/ sugars can be made in the absence of light. Used isotope of carbon. • Marcus = first to describe the ETC
SUN photons glucose Photosynthesis • Anabolic (small molecules combined) • Light energy is converted into chemical energy. • Endergonic (stores energy) • Carbon dioxide (CO2) requiring process that uses light energy (photons-particles of light) and water (H2O) to produce organic macromolecules (glucose). 6CO2 + 6H2O C6H12O6 + 6O2
Question: Where does photosynthesis take place?
Chloroplast Mesophyll Cell Stoma Plants • Autotrophs – produce their own food (glucose)-Known as Producers. Examples plants, algae, and some bacteria. • Process called photosynthesis • Mainly occurs in the leaves: a. stoma - pores b. mesophyll cells
Oxygen (O2) Carbon Dioxide (CO2) Stomata (stoma) Pores in a plant’s leaves through which water and gases are exchanged between the plant and the atmosphere. Found on the underside of leaves
Adaptations • Why are stomata usually located on the bottom/ underside of a leaf? • Where would a water lily’s stomata probably be located? • How would desert plants adapt? They need to avoid losing water from stomata BUT need to open the stomata to allow CO2 in and O2 out…
Nucleus Cell Wall Chloroplast Central Vacuole Mesophyll Cell of Leaf Photosynthesis occurs in these cells!!!
Stroma Outer Membrane Thylakoid Granum Inner Membrane Chloroplast Organelle where photosynthesistakes place. Thylakoid stacks are connected together Stroma is a solution surrounding thylakoids
Question: Why are plants green?
Chlorophyll Molecules Pigment-Light absorbing molecule Often stored in vacuoles • Plants are green because the green wavelength is reflected, not absorbed. • CHLOROPHYLL – reflects green light, absorbs light of other wavelengths. Found in chloroplasts • Carotenoids, Anthocyanins, Xanthophylls accessory pigments. Absorbs different wavelengths of light than chlorophyll
Short wave Long wave (more energy) (less energy) Wavelength of Light (nm)
Absorption of Light by Chlorophyll Absorption wavelength
Question: During the fall, what causes the leaves to change colors?
Fall Colors • In addition to the chlorophyll pigments, there are other pigments present • During the fall, the green chlorophyll pigments are greatly reduced revealing the other pigments • Carotenoids are pigments that are either red, orange, or yellow
Light Reactions 1.Light Reaction or Light Dependent Reaction - • Occurs within the thylakoid membranes • Reactant: H2O • Product: O2 (and ATP)
Remember Ingenhousz? Plant + Light = OXYGEN!
Dark Reactions 2. Calvin Cycle or Light Independent Reaction • Also called Carbon Fixation or C3 Fixation • Reactant: CO2 (ATP is used) • Product: Glucose and other high-energy carbohydrates
Remember Calvin? • The 6 Carbons in Glucose comes from 6 molecules of CO2 • How do plants get CO2?STOMATA = SITE OF GAS EXCHANGE IN PLANTS