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PHOTOSYNTHESIS Autotrophs: Plants and plant-like organisms make their energy (glucose) from sunlight or chemical bonds Phototroph - use light as an energy.

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Presentation on theme: "PHOTOSYNTHESIS Autotrophs: Plants and plant-like organisms make their energy (glucose) from sunlight or chemical bonds Phototroph - use light as an energy."— Presentation transcript:

1 PHOTOSYNTHESIS Autotrophs: Plants and plant-like organisms make their energy (glucose) from sunlight or chemical bonds Phototroph - use light as an energy sourcePhototroph Chemotroph – obtain energy from chemicals (inorganic)Chemotroph VideoVideo - chemotroph means "putting together with light."

2 Heterotrophs Animals and other organisms that must get energy from food instead of sunlight or inorganic chemicals Depend on autotrophs to obtain energy

3 Why is Photosynthesis important? Makes organic molecules (glucose) out of inorganic materials (CO 2 and H 2 O) 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.

4 6CO 2 + 6H 2 O + sunlight  C 6 H 12 O 6 + 6O 2

5 Photosynthesis-starts to ecological food webs!

6 How do we know that plants make carbohydrates from just carbon dioxide water and light energy? 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. Experiments!

7 Photosynthesis Carbon dioxide + water glucose + oxygen sunlight absorbed by chlorophyll 6CO 2 + 6H 2 O + energy  C 6 H 12 O 6 + 6O 2 As 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 reaction Light-independent: uses ATP, NADPH, and CO 2 to make simple sugars.


11 PHOTOSYNTHESIS Light-dependent reaction (LIGHT Reaction) Requires light Occurs in chloroplast- which have 2 membranes Thylakoids –system of membranes inside the inner membrane; arranged as flattened sacs Grana – stacks of layered thylakoids Stroma – solution surrounding the grana membrane

12 Chloroplasts make the sugars!

13 Plant Cells

14 Elodea leaf x400

15 Chloroplasts make the oxygen too!

16 Plants Leaves are green because they contain the pigment: chlorophyll Leaves have a large surface area to absorb as much light as possible light

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 object Main pigment: Chlorophyll a –directly involved in light reactions - absorbs less blue light but more red light than chlorophyll b Accessory pigments: Chlorophyll b and Carotenoids – enable plants to capture more energy by absorbing colors that chlorophyll a cannot -These pigments absorb all wavelengths (light) BUT green! Why are plants green? - video


20 LIGHT behaves as if it were composed of "units" or "packets" of energy that travel in waves. These packets are photons. The wavelength of light determines its color.

21 Ted Talks – animation Photosynthesis - song

22 PHOTOSYSTEMS There 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 Photosynthesis - song


24 THE LIGHT REACTIONS STEP 1: Begins when pigments (PSI and PSII) absorb light Light 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: Primary Electron Acceptor – accepts the e- lost from chlorophyll a STEP 3: Primary Electron Acceptor donates the e- the first molecules of the ELECTRON TRANSPORT CHAIN As e- are passed along the chain, they lose most of the energy the acquired when they were excited This 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 PSII e- move from a pair of chlorophyll a molecules in PSI to another Primary Electron Acceptor The 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 Electrons A special water splitting enzyme exists at the base of PSII. The water splitting enzyme splits water into its parts. Water (H 2 O) H + : The hydrogen proton will accumulate inside the thylakoids in the lumen. O 2 : 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 CHEMIOSMOSIS the process of the movement of protons down their concentration gradient for the synthesis of ATP concentration 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. Plants, for example, excrete O 2, 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 CO 2 increases, rate of photosynthesis increases

39 PHOTOSYNTHESIS What affects photosynthesis? Temperature: Temperature Low = Rate of photosynthesis low Temperature Increases = Rate of photosynthesis increases If temperature too hot, rate drops

40 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?


42 Calvin Cycle

43 The Calvin Cycle –carbon fixing 1.6 CO 2 molecules enter the cycle. 2.Enzyme “RuBisCo” combines six 5-carbon (RuBp) molecules with the carbon from CO 2 and forms them into twelve 3-carbon molecules 3.12 ATP and 12 NADPH form the twelve 3-carbon molecules into twelve High-energy 3-carbon molecules (G3P) 4.2 (G3P)of the twelve 3-carbon molecules are combined to form a 6-carbon sugar 5.6 ATP molecules are used to convert the 10 remaining 3-carbon molecules back into the six 5- carbon molecules the cycle began with (RuBp)

44 Calvin Cycle

45 Types of Photosynthesis C3 Photosynthesis C4 Photosynthesis CAM Photosynthesis

46 C3 Photosynthesis : C3 plants Called C3 because the CO 2 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 CO 2. 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 C 4 Photosynthesis : C4 plants Called C 4 because the CO 2 is first incorporated into a 4-carbon compound. Stomata are partially closed during the hottest parts of the day. Have an enzyme that allows CO 2 to be taken into the plant very quickly when CO 2 levels are low and O 2 levels are high. Photosynthesizes faster than C3 plants. Has better water use efficiency because plants do not need to keep stomata open as much C 4 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 CO 2 is stored as an acid before use in photosynthesis. Stomata open at night (evaporation rates are lower) and are closed during day. CO 2 is converted to an acid and stored during the night. During the day, the acid is broken down and the CO 2 is released to RUBISCO for photosynthesis Better 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


52 Videos and other resources: Carbon Cycle Ted Talks - videoCarbon Cycle Ted Talks Bozeman Science – videoBozeman Science Crash Course –videoCrash Course Calvin Cycle game

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