Presentation on theme: "PHOTOSYNTHESIS means "putting together with light.""— Presentation transcript:
1 PHOTOSYNTHESISmeans "putting together with light."Autotrophs: Plants and plant-like organisms make their energy (glucose) from sunlight or chemical bondsPhototroph - use light as an energy sourceChemotroph – obtain energy from chemicals (inorganic)Video - chemotroph
2 HeterotrophsAnimals and other organisms that must get energy from food instead of sunlight or inorganic chemicalsDepend on autotrophs to obtain energy
3 Why is Photosynthesis important? Makes organic molecules (glucose) out of inorganic materials (CO2 and H2O)It begins all food chains/webs. Thus all life is supported by this process.It also makes oxygen gas!!Plants use glucose as food for energy and as a building block for growing.
6 How do we know that plants make carbohydrates from just carbon dioxide water and light energy? Experiments!Ex: Jan Baptisa van Helmont (1648) planted a willow branch weighing 5 pounds into 200 pounds of soil and then after 4 years the tree weighed 169 lbs. and the soil was still nearly 200 lbs.
7 Photosynthesis 6CO2 + 6H2O + energy C6H12O6 + 6O2 Carbon dioxide + water glucose + oxygensunlightabsorbed by chlorophyll6CO2 + 6H2O + energy C6H12O6 + 6O2As can be seen from the equation for photosynthesis, the wood, bark, and root came from water and carbon dioxide.
9 PHOTOSYNTHESIS 2 Phases Light-dependent reaction (Light Reactions)Light-independent reaction (Calvin Cycle)Light-dependent: converts light energy into chemical energy; produces ATP molecules and NADPH to be used to fuel light-independent reactionLight-independent: uses ATP, NADPH, and CO2 to make simple sugars.
11 PHOTOSYNTHESIS Light-dependent reaction (LIGHT Reaction) Requires lightOccurs in chloroplast- which have 2 membranesThylakoids –system of membranes inside the inner membrane; arranged as flattened sacsGrana – stacks of layered thylakoidsStroma – solution surrounding the granamembrane
16 Leaves are green because they contain PlantsLeaves are green because they containthe pigment:chlorophyllLeaves have a large surface area to absorb as much light as possible
17 Pigments: compounds that absorb different colors of white light (ROY G BIV) – visible spectrum Visible light is only a small part of the electromagnetic spectrum (all forms of light).
18 When white light strikes an objet, its component colors can be reflected or absorbed by the pigments in the objectMain pigment:Chlorophyll a –directly involvedin light reactions absorbs less blue light butmore red light than chlorophyll bAccessory pigments:Chlorophyll b and Carotenoids –enable plants to capture moreenergy by absorbing colors thatchlorophyll a cannot -These pigments absorb allwavelengths (light) BUT green!Why are plants green? - video
22 PHOTOSYSTEMSPhotosynthesis - songThere are 2 photosystems, photosystem II and photosystem I.They contain chlorophyll a, chlorophyll b, and carotenoids.They are embedded in the thylakoid membrane.There is a pair of “chlorophyll a” molecules at the base of each photosystem that harnesses all the energy captured by the pigments.Their job (chlorophyll a molecules) is to absorb light energy and pass it on to the electrons.Photosystem I and Photosystem II – different roles in the light reactions
24 THE LIGHT REACTIONS STEP 1: Begins when pigments (PSI and PSII) absorb lightLight energy forces electrons (e-) to enter a higher energy level in a pair of chlorophyll a molecules of PSII“excited” e- leave chlorophyll a (oxidation reaction)Each oxidation reaction must be accompanied by a reduction reaction so something has to accept the e-
26 THE LIGHT REACTIONS STEP 2: STEP 3: Primary Electron Acceptor – accepts the e- lost from chlorophyll aSTEP 3:Primary Electron Acceptor donates the e- the first molecules of the ELECTRON TRANSPORT CHAINAs e- are passed along the chain, they lose most of the energy the acquired when they were excitedThis energy is used to move protons (H+) into thylakoid
28 THE LIGHT REACTIONS STEP 4: Light is absorbed into PSI – happens at same time that light is absorbed into PSIIe- move from a pair of chlorophyll a molecules in PSI to another Primary Electron AcceptorThe e- lost by these chlorophyll a molecules are replaced by the e- that have passed through the ETC from PSII
30 THE LIGHT REACTIONS STEP 5: At the end of the second ETC the electrons will be used to bond NADP+ and H+ to make NADPH an energy storing compound used in the Calvin Cycle.This happens in the stroma of the chloroplast.
31 Replacing ElectronsA special water splitting enzyme exists at the base of PSII.The water splitting enzyme splits water into its parts.Water (H2O)H+: The hydrogen proton will accumulate inside the thylakoids in the lumen.O2: The oxygen will be released by the thylakoids and it will end up in our atmosphere.The electrons from the hydrogen atom will enter at the base of PSII.
32 CHEMIOSMOSISthe process of the movement of protons down their concentration gradient for the synthesis of ATPconcentration of (H+) is great inside the thylakoid (from the splitting of water and the H+ that were pumped on by the ETC)concentration gradient causes the H+ to diffuse through ATP synthase (an enzyme that helps make ATP by using the energy from the moving H+)That energy bonds ADP with a phosphate to make ATP in the stroma.Some of the H+ flowing into the stroma can be used to make NADPH.Both ATP and NADPH will be used in the Calvin Cycle (The Dark Reactions)
35 In plants and simple animals, waste products are removed by diffusion In plants and simple animals, waste products are removed by diffusion. Plants, for example, excrete O2, a product of photosynthesis.
37 PHOTOSYNTHESIS What affects photosynthesis? Light intensity: as light increases, rate of photosynthesis increases
38 PHOTOSYNTHESIS What affects photosynthesis? Carbon Dioxide: As CO2 increases, rate of photosynthesis increases
39 PHOTOSYNTHESIS What affects photosynthesis? Temperature: Temperature Low = Rate of photosynthesis lowTemperature Increases = Rate of photosynthesis increasesIf temperature too hot, rate drops
40 Stoma This opening how plants exchange gases Stoma This opening how plants exchange gases! Can you name the two important gases that go in and out of the leaves?Why are the stomata located on the underside of leaves?
41 "Thanks for the Glucose!“ LET’S PRACTICE! - game
43 The Calvin Cycle –carbon fixing 6 CO2 molecules enter the cycle.Enzyme “RuBisCo” combines six 5-carbon (RuBp) molecules with the carbon from CO2 and forms them into twelve 3-carbon molecules12 ATP and 12 NADPH form the twelve 3-carbon molecules into twelve High-energy 3-carbon molecules (G3P)2 (G3P)of the twelve 3-carbon molecules are combined to form a 6-carbon sugar6 ATP molecules are used to convert the 10 remaining 3-carbon molecules back into the six 5-carbon molecules the cycle began with (RuBp)
45 Types of Photosynthesis C3 PhotosynthesisC4 PhotosynthesisCAM Photosynthesis
46 C3 Photosynthesis : C3 plants Called C3 because the CO2 is first incorporated into a 3-carbon compound.Stomata are open during the day.RUBISCO, the enzyme involved in photosynthesis, is also the enzyme involved in the uptake of CO2.Adaptive Value: more efficient than C4 and CAM plants under cool and moist conditions and under normal light because requires less machinery (fewer enzymes and no specialized anatomy).Most plants are C3.
48 C4 Photosynthesis : C4 plants Called C4 because the CO2 is first incorporated into a 4-carbon compound.Stomata are partially closed during the hottest parts of the day.Have an enzyme that allows CO2 to be taken into the plant very quickly when CO2 levels are low and O2 levels are high.Photosynthesizes faster than C3 plants.Has better water use efficiency because plants do not need to keep stomata open as muchC4 plants include corn, sugar cane, and many of our summer annual plants.
50 CAM Photosynthesis : Crassulacean Acid Metabolism Named after plant family in which it was first found (Crassulaceae) & because CO2 is stored as an acid before use in photosynthesis.Stomata open at night (evaporation rates are lower) and are closed during day.CO2 is converted to an acid and stored during the night.During the day, the acid is broken down and the CO2 is released to RUBISCO for photosynthesisBetter water use efficiency than C3 plants under arid conditions due to opening stomata at night (no sunlight, lower temperatures, lower wind speeds, etc.)include many succulents such as cactuses and agaves and also some orchids and pineapples