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Concept 8.1 PHOTOSYNTHESIS USES LIGHT ENERGY TO MAKE FOOD.

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Presentation on theme: "Concept 8.1 PHOTOSYNTHESIS USES LIGHT ENERGY TO MAKE FOOD."— Presentation transcript:

1 Concept 8.1 PHOTOSYNTHESIS USES LIGHT ENERGY TO MAKE FOOD

2 PHOTOSYNTHESIS Process that converts light energy to chemical energy Occurs in chloroplasts of green plants

3 CHLOROPLASTS Most are located in leaves— major site of photosynthesis Contain pigment called chlorophyll Gives chloroplasts their green color

4 CHLOROPLAST STRUCTURE Enclosed by two membranes Inner membrane encloses a thick fluid called stroma Disk-shaped sacs called thylakoids are suspended in stroma Granum: stack of thylakoids

5 CHLOROPLAST STRUCTURE

6 PHOTOSYNTHESIS EQUATION sunlight 6 CO H 2 O  C 6 H 12 O O 2 sunlight 6 carbon dioxide + 6 water  glucose + 6 oxygen Occurs in two main stages: 1. light reactions 2. Calvin cycle

7 CHLOROPLAST STRUCTURE ORGANIZES PHOTOSYNTHESIS Reactions take place in different areas of chloroplast: Light reactions occur in thylakoid membranes Calvin cycle occurs in the stroma

8 PHOTOSYNTHESIS OVERVIEW

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10 PHOTOSYNTHESIS and CELLULAR RESPIRATION The two processes are linked: photosynthesis: process by which plants use the sun’s energy to convert water and carbon dioxide into sugars cellular respiration: chemical process that uses oxygen to convert chemical energy stored in food molecules to produce ATP

11 PHOTOSYNTHESIS and CELLULAR RESPIRATION Both processes recycle common set of chemicals: Water, carbon dioxide, oxygen, glucose Products of photosynthesis are the ingredients for cellular respiration Products of cellular respiration are the ingredients for photosynthesis

12 PHOTOSYNTHESIS and CELLULAR RESPIRATION Photosynthesis Equation: sunlight 6CO H 2 O  C 6 H 12 O O 2 sunlight 6 Carbon Dioxide + 6 Water  Glucose + 6 Oxygen Cellular Respiration Equation: C 6 H 12 O O 2  6 CO H 2 O + ATP Glucose + 6 Oxygen  6 Carbon Dioxide + 6 Water

13 PHOTOSYNTHESIS and CELLULAR RESPIRATION

14 LIGHT REACTIONS Convert energy in sunlight to chemical energy in steps Chlorophyll molecules capture light energy ( units called photons ) Captured energy is used to split water molecules  photolysis H 2 O  O 2 and H + ions produced

15 LIGHT REACTIONS O 2 escapes from leaf as waste product H + bonds to NADP + (electron carrier molecule) forming NADPH NADPH moves to stroma ATP is produced by light energy

16 THE CALVIN CYCLE Glucose made from atoms of CO 2, hydrogen, ATP, and electrons carried by NADPH Enzymes for Calvin cycle reactions are located outside thylakoids  dissolved in stroma ATP from light reactions provides energy to make glucose

17 THE CALVIN CYCLE Calvin cycle reactions are also called the light-independent or dark reactions ( can occur without direct light ) Cannot continue indefinitely without two inputs supplied by light reactions: 1. ATP 2. NADPH

18 Concept 8.2 THE LIGHT REACTIONS CONVERT LIGHT ENERGY TO CHEMICAL ENERGY

19 LIGHT ENERGY & PIGMENTS Visible light: part of the electromagnetic spectrum our eyes detect as different colors  ROY G BIV Pigments: chemicals that absorb, transmit, or reflect different wavelengths of light

20 CHLOROPLAST PIGMENTS Absorb blue-violet & red-orange light Convert absorbed light energy to chemical energy Do not absorb green light well: reflect or transmit it back makes leaves look green

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22 LIGHT REACTIONS & PHOTOSYSTEMS Photosystems: clusters of chlorophyll and other molecules in thylakoid membranes of the chloroplast Two photosystems involved in light reactions Each photosystem uses a different chlorophyll molecule and performs a different task Electron transport chain connects the two photosystems and produces ATP

23 PHOTOSYSTEM 2 “Water-splitting” photosystem Produces hydrogen ions (H + ) and releases oxygen (O 2 ) as a waste product Electrons released in splitting H 2 O are used to make ATP

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25 PHOTOSYSTEM 1 “NADPH producing photosystem” Light striking another chlorophyll molecule causes electrons to gain energy and leave the molecule These electrons along with H + ions from water are added to NADP + to produce NADPH

26 PHOTOSYSTEMS

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28 LIGHT REACTIONS - SUMMARY

29 What you need to know about the light reactions Occur on thylakoid membranes Get energy from photons of light Reactants: H 2 O, light End products: O 2, NADPH, ATP

30 What you need to know about the light reactions Destination of end products: ATP and NADPH go to stroma (Calvin cycle) O 2 leaves as waste product

31 Concept 8.3 THE CALVIN CYCLE MAKES SUGAR FROM CARBON DIOXIDE

32 CALVIN CYCLE Uses carbon dioxide and a 5- carbon sugar (RuBP) along with molecules from the light reactions (ATP & NADPH) to produce glucose—the main cellular fuel Occurs in the stroma of chloroplast

33 What you need to know about the Calvin cycle What are the reactants? 1. RuBP 2. NADPH 3. ATP 4. CO 2

34 CALVIN CYCLE Where do the reactants come from? - RuBP  present in stroma - CO 2  from atmosphere - NADPH, ATP  from light reactions

35 CALVIN CYCLE What are the end products? - 3-carbon sugar G3P  used by plant cells to produce more complex carbohydrates - glucose - starch - cellulose

36 CALVIN CYCLE Where does energy for Calvin cycle come from? - ATP produced in light reactions Where does the Calvin cycle occur? - stroma of chloroplast

37 CALVIN CYCLE

38 SUMMARY OF PHOTOSYNTHESIS

39 6 CO H 2 O  C 6 H 12 O O 2 LIGHT REACTIONS: Occur on thylakoid membranes Convert light energy to chemical energy of ATP Use reactant H 2 O from the equation and releases product O 2

40 SUMMARY OF PHOTOSYNTHESIS CALVIN CYCLE: Occurs in stroma of chloroplast Uses ATP and NADPH from light reactions Uses the reactant CO 2 from the equation and produces sugar

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42 Concept 8.4 PHOTOSYNTHESIS HAS A GLOBAL IMPACT

43 THE CARBON CYCLE Process by which carbon moves from inorganic to organic compounds and back Photosynthesis converts inorganic carbon dioxide to organic compounds Consumers eat producers and return carbon dioxide to the atmosphere via cellular respiration

44 CARBON CYCLE

45 PHOTOSYNTHESIS & GLOBAL CLIMATE Photosynthesis uses CO 2 to make sugars Most organisms give off CO 2 in cellular respiration Total effect of all the organisms on Earth has a large effect on the amount of CO 2 in the atmosphere

46 GREENHOUSE EFFECT Amount of CO 2 in atmosphere has been increasing rapidly greenhouse effect: CO 2 traps heat from the sun that would otherwise escape into space Increased CO 2 —mainly from fossil fuels—traps more heat leading to global warming

47 GREENHOUSE EFFECT

48 THE END

49 THE CALVIN CYCLE

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55 PHOTOSYSTEMS 1 & 2

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57 PHOTOSYSTEM SUMMARY Light energy used to break down H 2 O, releasing O 2, electrons (carried as NADPH), H+ ions, and producing ATP Calvin cycle produces glucose using the ATP and hydrogen ions, and NADPH from light reactions

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59 PHOTOSYTEMS & ATP PRODUCTION

60 PHOTOSYSTEM 2 “Water-splitting” photosystem Light strikes chlorophyll  electrons pass down electron transport chain Energy used to make ATP Electrons released by chlorophyll are replaced by electrons released when a H 2 O is split into H + ions and oxygen

61 PHOTOSYSTEM 1 Produces the carrier molecule NADPH * e - + H + + NADP +  NADPH + H + Electrons (carried by NADPH) and H + ions are carried to Calvin cycle where sugars are produced

62 LIGHT REACTIONS

63 PHOTOSYSTEMS

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