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CHAPTER 8 PHOTOSYNTHESIS
SECTION 8-1 ENERGY and LIFE
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AUTOTROPHS AND HETEROTROPHS
What is the key source of energy for most things? THE SUN Plants and other organisms such as blue-green algae use light energy from the sun to produce food. These organisms are called AUTOTROPHS. Use simple inorganic molecules to do this.
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AUTOTROPHS and HETEROTROPHS
Heterotrophs are organisms that obtain energy from the food they consume. Unable to use sunlight directly. ALL organisms must release energy in sugars and other compounds.
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CHEMICAL ENERGY and ATP
What are three forms of energy? Light, heat, and electricity Energy can be stored in compounds. Electrons release energy when a piece of wood is set on fire. When chemical bonds are broken and electrons shift from higher energy levels to lower energy levels, the extra energy is released as light and heat.
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CHEMICAL ENERGY and ATP
How do organisms such as humans store and release energy? Chemical compounds are used to do this. What is ATP? Adenosine Triphosphate (ENERGY storing molecule) ATP consists of ADENOSINE, a 5-CARBON SUGAR, and 3 PHOSPHATE GROUPS
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What is ATP?
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RELEASING ENERGY How is stored energy released from ATP to be used by the cell? Energy stored in chemical bond between the second and third phosphate groups. Breaking this bond releases the energy stored in it.
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RELEASING ENERGY ATP is the basic energy source for all cells.
What are different cellular functions that ATP can power within the cell? ACTIVE TRANSPORT PROTEIN SYNTHESIS MUSCLE CONTRACTION
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USING BIOCHEMICAL ENERGY
What is a SODIUM – POTASSIUM Pump? Used during Active Transport Pumps Na- ions out of the cell and K+ ions in Assists in transport of glucose into cell Maintains muscle movement and control Controls cell volume Why do most cells only have a small amount of ATP? Not a good molecule for storing large amounts of energy over a long period of time. Cells regenerate ATP How do cells store energy for long periods of time? Glucose stores 90 times more energy than ATP
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Question of the Day Oct 29 Which early scientist discovered that oxygen was the mystery substance produced by plants? A. Joseph Priestley B. Jan Ingenhousz C. Jan van Helmont D. Melvin Calvin
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AGENDA Oct 29 Objective: Debate the importance of early experiments and the discovery of photosynthesis. 1. QoD – Early Experiments – Light spectrum and Chlorophyll 4. Review and Homework QUIZ – Tomorrow Chapter 8-1 and 8-2 What we have covered in class including today!
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8-2 Photosynthesis: An Overview
What is PHOTOSYNTHESIS? Plants use the energy of sunlight to convert water and carbon dioxide into high energy carbohydrates Sugars and starches And Oxygen, a waste product.
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Investigating Photosynthesis
As a tree grows bigger and bigger in size, where does the tree’s increase in mass come from? SOIL, WATER, AIR? This simple question asked hundreds of years ago began the research into photosynthesis. Let’s take a closer look at some of the experiments that led to the discovery of photosynthesis…
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Van HELMONT’S Experiment
1643, Belgian physician Jan van Helmont. What did he do? Experiment to investigate if plants grew by taking materials out of the soil. His experiment? 1. Determined mass of a pot of dry soil and a seedling.
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Van HELMONT Experiment
2. Planted the seedling in the pot of soil. Watered regularly. 3. At the end of 5 years, the seedling had grown into a small tree. Mass gain of 75 grams. 4. Mass of soil remained almost unchanged. His Conclusion Mass of the tree came from the water – only thing he added. Accounted for the “HYDRATE” portion of a CARBOHYDRATE Where does the “CARBO” portion come from? Carbon Dioxide
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Priestley’s Experiment
1771, English minister Joseph Priestley What did he do? Lit a candle, placed a jar over it, and watched the flame gradually die out. What did he reason about the candle flame? Something in the air was necessary to keep the candle burning.
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Priestley’s Experiment
What was his next step? He placed a spring of mint underneath the jar with the candle. After a few days, candle could be relit. Burned for a longer period of time. His conclusion? The mint sprig released something needed to keep the candle flame burning. What was this mystery substance? OXYGEN
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The Ingenhousz Experiment
1779, Dutch scientist Jan Ingenhousz What did he do? Showed the effect observed by Priestley only occurred when plant exposed to light. What did these experiments show? When a plant is exposed to light, it transforms carbon dioxide and water into carbohydrates and releases oxygen.
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PHOTOSYNTHESIS EQUATION
What is the balanced equation of photosynthesis? Compare the equation of photosynthesis with another cellular process.
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Light and Pigments White light - mixture of different wavelengths of light visible spectrum Different wavelengths = different colors.
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Light and Pigments What are colored substances that absorb or reflect light? PIGMENTS Why are plants green? chlorophyll: principle pigment in green plants Absorbs red and blue-violet light Chlorophyll a and Chlorophyll b Reflect green light which is why plants look green.
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Absorption of Light B – carotene
Red and orange pigments that absorb light in other regions of the spectrum.
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SECTION 8-3: The Reactions
Where do they occur? The Chloroplast Contains Thylakoids Photosynthetic membranes. Arranged in stacks called GRANA (GRANUM) Photosystems: chlorophyll and pigments in the thylakoid LIGHT-Collecting Units of the Chloroplast
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8-3: Reactions of Photosynthesis
1. Light-Dependent Reactions In the thylakoid membranes 2. Light-Independent Reactions or The Calvin Cycle Take place in the stroma
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NADP+ AN ELECTRON CARRIER
Carries 2 High-energy electrons (e-) and a hydrogen ion (H+). Converts NADP+ into NADPH Sunlight energy is trapped in chemical form. NADPH carries HE e- produced in chlorophyll to chemical reactions in the cell.
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LIGHT DEPENDENT REACTIONS
PRODUCE Oxygen gas CONVERT ADP and NADP+ into energy carriers ATP and NADPH STEP A: Pigments in Photosystem II absorb light. Electrons absorb light energy making them HIGH-Energy electrons HIGH-Energy electrons passed to Electron Transport Chain (ETC)
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LIGHT DEPENDENT REACTIONS
STEP A CONTINUED: Does chlorophyll run out of electrons? No Where do the new electrons come from? WATER is broken down by enzymes. 1 WATER molecule 2 H+ ions and 1 O atom 2 H+ ions replace the HE electrons passed to the ETC Oxygen is released into the atmosphere
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LIGHT DEPENDENT REACTIONS
STEP B: HE e- move through ETC from Photosystem II to Photosystem I Energy used in ETC to transport H+ ions from Stroma to Thylakoid. STEP C: Pigments in Photosystem I use light energy to recharge electrons. NADP+ picks up HE e- and H+ ions NADP+ becomes NADPH
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LIGHT DEPENDENT REACTIONS
STEP D: H+ ions are pumped across the thylakoid membrane. Inside of membrane fills up with H+ ions Outside of membrane becomes negatively charged. This difference in charges provides the energy to make ATP. What is the importance of H+ ions?
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LIGHT DEPENDENT REACTIONS
STEP E: ENERGY MAKING STEP ATP SYNTHASE found in cell membrane. Allows H+ ions to pass through. ATP Synthase rotates and binds ADP with a Phosphate making ATP. LDR ETC produces HIGH-Energy electrons and ATP
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LIGHT DEPENDENT REACTIONS
Why are they called LIGHT DEPENDENT REACTIONS? They require light energy to take place. Let’s look at the bigger picture. What would happen if plants do not get sunlight? Plants could not perform photosynthesis. They would not produce sugars. Or release Oxygen Gas into the atmosphere. Other organisms like you and me(heterotrophs) would not be able to survive.
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Bozeman Science Video http://www.youtube.com/watch?v=g78utcLQrJ4
Stop at 8:35 of video clip
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