Photosynthesis (Ch. 8) 1

ATP (for energy!) ATP = adenosine triphosphate ATP is the molecule that DIRECTLY provides energy to do cellular work Chemical energy from organic molecules is transferred to ATP 2

ATP Structure 3 P P P AdenineRibose Phosphates

How does ATP transfer energy? When ATP loses the 3rd phosphate – energy stored between those phosphate groups is released – this energy is used by the cell – ADP is left 4 P P P ATP P P P ADP Energy

Obtaining Energy Photosynthesis – converts light energy from the sun into chemical energy found in glucose 5

Overview of Photosynthesis The oxygen (O 2 ) and some of the organic compounds produced by photosynthesis are used by cells in a process called cellular respiration. 6

Overview of Photosynthesis Equation of Photosynthesis: 6CO 2 + 6H 2 O light energy C 6 H 12 O 6 + 6O 2 7 Carbon Dioxide + Water light energy Glucose + Oxygen

Capturing Light Energy The light reactions begin with the absorption of light in chloroplasts 8

Capturing Light Energy Light and Pigments – White light from the sun is composed of an array of colors called the visible spectrum. 9

Capturing Light Energy Pigment – absorb certain colors of light and reflect or transmit the other colors 10

Capturing Light Energy Chloroplast Pigments – Located in the membrane of the thylakoids of chloroplasts are several pigments, including chlorophylls (such as chlorophyll a and chlorophyll b) Carotenoids (accessory pigments) 11

Chloroplasts Chloroplasts have a double membrane – thylakoids inner membranes numerous – grana stacks of thylakoids – stroma fluid-like 12

Overview of Photosynthesis Photosynthesis can be divided into two stages: Light Reactions and Calvin Cycle – light reactions Creates two energy storing molecules (ATP & NADPH) – Calvin Cycle Sugars are formed using CO 2 and the chemical energy stored in ATP and NADPH 13

Overview of Photosynthesis Equation of Photosynthesis: 6CO 2 + 6H 2 O light energy C 6 H 12 O 6 + 6O 2 14

Capturing Light Energy The light reactions begin with the absorption of light in chloroplasts 15

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Converting Light Energy To Chemical Energy Replacing Electrons in Light Reactions – The electrons used are created by splitting water molecules. 17

– Oxygen produced when water molecules are split diffuses out of the chloroplast and then leaves the plant. The plants could also use the oxygen during cellular respiration. 18

Converting Light Energy To Chemical Energy Making ATP in Light Reactions – ATP is created by an enzyme in the thylakoid membrane. – The concentration of H + is used to make the ATP 19

Light Dependent Reaction Inputs Light H 2 O ADP NADP+ Outputs O2 ATP NADPH 20 Thylakoid membrane

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Light Independent Reactions Calvin cycle – the ATP and NADPH produced in the light reactions drive this stage to create glucose carbon fixation – CO 2 is incorporated into organic compounds, a process called carbon fixation 22

Carbon Fixation The Calvin cycle – occurs in the stroma of the chloroplast – a series of enzyme-assisted chemical reactions that produces a three-carbon sugar. 23

Calvin Cycle Inputs CO 2 ATP NADPH Outputs Sugar ADP NADP+ 24

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Factors Affecting the Rate of Photosynthesis Light Temperature Carbon Dioxide 26

Light 27

Temperature 28

Carbon Dioxide 29

Photosynthesis and Global Warming 30