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Picture Guide to Chapter 8 Photosynthesis. 8-1 Energy and Life.

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Presentation on theme: "Picture Guide to Chapter 8 Photosynthesis. 8-1 Energy and Life."— Presentation transcript:

1 Picture Guide to Chapter 8 Photosynthesis

2 8-1 Energy and Life

3 Objectives Explain where plants get the energy they need to produce food Describe the role of ATP in cellular activities

4 Q: Where does energy come from? A: Our food, but originally the energy in food comes from the sun

5 Autotrophs Make their own food

6 Heterotrophs Cannot make their own food

7 Chemical Energy and ATP The principal chemical compounds that cells use to store and release energy is called ATP adenosine triphosphate

8 Storing Energy ATP stores energy in the third phosphate ATP is like a fully charged battery

9 Releasing Energy Q: How is the energy in ATP released? A: Break bond between the second and 3 rd phosphates ADP 2

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11 Using Biomechanical Energy Active Transport Movement of organelles throughout cell Synthesis of proteins and nucleic acids Produce light –Blink of firefly caused by an enzyme powered by ATP

12 ATP Availability Most cells only have enough ATP for a few seconds of activity Why? –Not good at storing energy over the long term –Glucose stores 90 times the chemical energy of ATP –Cells generate ATP from ADP as needed by using the energy in foods like glucose

13 Biology in History 1643 – van Helmont: trees gain most of their mass from water 1771 – Priestly: discovered plants release oxygen 1779 – Ingenhousz: plants need sunlight to make oxygen 1845 – Mayer: proposed plants convert light energy into chemical energy

14 Bio in History pt – Calvin: traces chemical path that carbon follows to make glucose 1992 – Marcus: describes electron carrier molecules in electron transport chain 2004 – Iwata & Barber: identify the mechanism for splitting water in photosynthesis

15 8-2 Photosynthesis: An Overview

16 Photosynthesis The process in which plants use the energy of sunlight to convert water and carbon dioxide into high energy carbohydrates – sugars and starches – and oxygen as a waste product

17 Photosynthesis

18 The Photosynthesis Equation CO 2 +H2OH2O+C 6 H 12 O 6 O2O2 light (Carbon Dioxide)(Water)(Sun)(Glucose)(Oxygen)

19 Chlorophyll The plant’s principle pigment, absorbs light energy in the blue- violet and red spectrum of visible light

20 Absorption of Light by Chlorophyll a and Chlorophyll b Absorption of Light by Chlorophyll a and Chlorophyll b VBGYOR Chlorophyll b Chlorophyll a

21 Because light is a form of energy… Anything that absorbs light also absorbs the energy from that light When chlorophyll absorbs light, much of the energy is transferred to electrons in the chlorophyll molecule, raising the energy level of these electrons These high-energy electrons make photosynthesis work

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23 Thylakoids Sac-like photosynthetic membranes arranged in stacks

24 Grana Stacks of thylakoids

25 Stroma The fluid filled region outside the thylakoid

26 Scientists describe the reactions of photosynthesis in two parts 1.Light – dependent reactions (takes place in the thylakoid membranes) 2.Light – independent reactions (takes place in stroma)

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28 Carrier Molecule Compound that can accept a pair of high energy electrons and transfer them along with most of their energy to another molecule Ex.) NADP+

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30 Q: What does this do? NADP+ NADPH A: this traps sunlight in chemical form

31 Light Dependent Reactions Uses energy from light to produce 1.Oxygen gas 2.ATP 3.NADPH

32 8-3 The Reactions of Photosynthesis

33 Light-Dependent Rxns Function: use energy from sun to make oxygen and convert ADP & NADP+ into ATP and NADPH – Thylakoids have clusters of chlorophyll and proteins called photosystems

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35 Steps for L-D Rxns 1.Photosystem II – a. Light energy absorbed & excited electrons b. Water is split to replace electrons, releases Hydrogens (H+) and Oxygen

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37 Steps for L-D Rxns 2. Electron Transport Chain (ETC) – a. High energy electrons move to photosystem I b. Energy from electrons pumps H+ ions into thylakoid space

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39 Steps for L-D Rxns 3. Photosystem I – a. Electrons get reenergized by sunlight b. 2 nd ETC transfers electrons to NADP+, makes NADPH

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41 Steps for L-D Rxns 4. ATP Synthase – a. H+ ions build up creating + charge b. Each H+ crosses membrane rotating ATP synthase converting ADP to ATP

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43 The Calvin Cycle The ATP and NADPH formed by the light- dependent reactions contain an abundance of chemical energy Not stable enough to store that energy for more than a few minutes. The Calvin cycle uses ATP and NADPH from light – dependent reactions to produce high energy sugars

44 The Calvin Cycle These reactions don’t require light, therefore these reactions are called Light – independent reactions

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46 Light Indep. Rxns/The Calvin Cycle

47 Steps for L-ID Rxns 1.CO 2 Enters the Cycle – a. CO 2 enters the stroma & combines with 5-Carbon compounds b. Get twelve 3-Carbon compounds from 6 CO 2

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49 Steps for L-ID Rxns 2. Sugar Production – a. Midcycle, two of the 3-Carbon compounds removed. i. Used to make sugars, lipids, aminos & etc… b. Remaining ten 3-Carbon compounds go back to six 5-carbon compounds to cycle through again

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51 Steps for L-ID Rxns 3. Summary– a. Calvin Cycle used 6 CO 2 to make a single 6-Carbon sugar b. Energy needed to make this sugar comes from light-dependent rxns

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53 Photosynth – End Results Light-dependent rxns trap light & convert it to chemical energy Light-independent rxns use that chem energy to make high energy sugars END RESULT: Plenty of food and oxygen for animals

54 Factors Affecting Photosynthesis Not enough water Temperature Light intensity

55 1. Temperature High or low temps can slow or stop it - Enzymes for Photosynth work best between 0°C - 35°C

56 2. Light Intensity Light intensity - speed it up or slow it down –High intensity would naturally increase the rate (to a certain point)

57 3. Amount of Water Shortage could stop photosynth completely Can also damage plant tissues –Desert plants & conifers have waxy coating to protect from moisture loss

58 Extreme Conditions Photosynth C4 Photosynth CAM Plants

59 C4 Photosynth Special pathway to gather CO 2 in low light to pass to Calvin Cycle - 1 st molecule has 4 carbon (C4) Allows photosynth under harsh light and high temps Requires extra ATP to work Ex. Corn, sugar cane, and sorghum

60 C.A.M. Plant Crassulacean Acid Metabolism (C.A.M.) –Named after family of plants Bring in air only at night CO 2 combines with other molecules to make organic acids that trap Carbon - During the day, the plants squeeze leaves shut & use trapped Carbon for food. Ex. Pineapple trees & some cacti

61 Fun Fact C.A.M. plants are often planted along freeways to help “retard” brushfires

62 THE END


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