1. Chapter 8: Photosynthesis

2. Section 8.1 : Energy and Life I.Chemical Energy and ATP 1. energy – the ability to do work 2. Without the ability to obtain and use energy life would cease to exist. 3. Forms of Energy a) light b) heat c) electricity d) chemical compounds

3. 4. Adenosine Triphosphate (ATP) – compound that stores and releases energy; composed of adenine, 5 carbon ribose sugar, and 3 phosphate groups.

4. A.Storing Energy 1. Adenosine Diphosphate (ADP) – looks like ATP, but only has 2 phosphates. *ADP is like a rechargeable battery; it can store small amounts of energy by picking up another phosphate: ADP + P  ATP

5. B. Releasing Energy – energy is released from ATP by the breaking of the chemical bonds between phosphates. ATP can easily release and store energy by breaking and re-forming the bonds between it’s phosphate groups. This characteristic of ATP makes it exceptionally useful as a basic energy source for all cells.

6. Storing and Releasing of ATP Energy

7. C. Using Biochemical Energy *Cells use energy for: 1. active transport – cells use energy to pump materials against their gradient, or in a direction they do not want to go; LOW  HIGH 2. synthesizing proteins *Cells only have a small amount of ATP at any given time b/c ATP is not a good molecule for storing large amounts of energy in the long term. *Glucose stores 90 times more energy than ATP

8. Why ATP cannot store a lot of Energy for long periods: Because of the Phosphate groups being POLAR, the carry many negative charges which repel the groups away from one another, thus the more phosphate groups there are, the more energy it takes to keep the molecule held together.

9. ATP, ADP, and AMP

10. II. Heterotrophs and Autotrophs *Cells are not “born” with ATP; they must produce it, but how? A. Heterotrophs 1. heterotrophs – obtain energy by consuming other living organisms. 2. examples – carnivores, herbivores, omnivores, scavengers, and decomposers.

11. B. Autotrophs 1. Autotrophs – organisms that can make their own food and energy. 2. Photosynthesis – autotrophs can convert the sun’s energy into chemical bonds of high energy carbohydrates such as sugars and starches.

12. Section 8.2 : Phototsynthesis: An Overview I.Chlorophyll and Chloroplasts A. Light 1. Energy from the sun travels to Earth in the form of light. 2. Sunlight is composed of “white light.” 3. White light – made up of many different wavelengths. ex) “ROY G BIV”

13. ROY G BIV; The Prism

14. B. Pigments 1. pigments – light absorbing molecules 2. chlorophyll – the principle pigment in plants a) chlorophyll a – absorbs light waves in the blue/ violet and red range b) chlorophyll b – absorbs light waves in the blue/ violet and red range as well. *chlorophyll does not absorb green wavelengths, thus we see green because it is reflected.

15. 3. Carotenoids – absorbs violet and blue wavelengths 4. The intense green color of chlorophyll is enough to overwhelm other accessory pigments, but as temperature drops the chlorophyll breaks down first and therefore the green color is lost but the orange, red, and yellow pigments remain stronger a little while longer.

16. C. Chloroplasts 1. chloroplasts – the organelles where photosynthesis occurs. 2. thylakoids – saclike photosynthetic membranes which contain chlorophyll. *each stack is referred to as a GRANUM or GRANA 3. stroma – the fluid portion of the chloroplasts, surrounds the grana.

17. Chloroplasts

18. D. Energy Collection 1. Any compound that absorbs light also absorbs the energy from the light; therefore chlorophyll absorbs light energy. 2. When chlorophyll absorbs light, the energy is transferred to electrons in the chlorophyll molecule; this knocks the electrons out of their levels and supplies the energy to make photosynthesis work.

19. The Chlorophyll Molecule

20. II. High Energy Electrons A. Energy Carriers 1. The high energy electrons need a special “vehicle” to carry them. 2. electron carrier – a compound that can accept a pair of high energy electrons and transfer them, along with their energy, to another molecule. 3. NADP + - (NicotinamideAdenine Dinucleotide Phosphate) accepts and carries 2 high energy electrons as well as an H + ion. NADP + + 2e + H +  NADPH

21. *NADP + is like a truck, once the electrons are in the flatbed it becomes NADPH *NADPH can deliver the energy to where it is needed to build glucose.

22. Overview of Photosynthesis

23. B. Overview of Photosynthesis *Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high energy sugars and oxygen.

24. 1. Light-dependent reactions – require the direct involvement of light and light-absorbing pigments; use energy to make ATP. a) light energy  chemical energy; ATP b) takes place in chlorophyll located in the thylakoids c) requires water (H 2 O); releases oxygen (O 2 ) d) at the end, electrons are picked up by NADP +

25. Light-Dependent versus Light-Independent

26. 2. Light – independent reactions – ATP & NADPH molecules that are produced during the dependent reactions are now used to produce sugar from carbon dioxide. a) NO light is required for this b) independent reactions occur in the STROMA

27. Section 8.3 : The Process of Photosynthesis I.The Light-Dependent reactions: Generating ATP & NADPH *The light-dependent reactions encompass the steps of photosynthesis that directly involve sunlight; they use energy from sunlight to produce oxygen and convert ADP  ATP and NADP+  NADPH 1. Location – light-dependent reactions occur in the thylakoid membranes of chloroplasts. 2. Photosystems – contain clusters of chlorophyll and accessory pigments that absorb sunlight.

28. A.Photosystem II 1. The electrons in the chlorophyll of PII absorb sunlight energy, which increases the energy of the electrons. The high energy electrons are passed to an electron transport chain. 2. electron transport chain – series of carrier proteins that accepts the high energy electrons and passes them along using their energy to make ATP.

29. Photosystems and the ETC

30. 3. How are electrons replaced? a) photolysis – sunlight also splits water, releasing oxygen and taking electrons from the hydrogen to replace those that left the chlorophyll. b) H 2 O  H and O 1) the O will combine with another O and form O 2, which is released out of the plant into the atmosphere. 2) The H will give its electrons to the chlorophyll and become H+ 3) H+ will be used to set up a “concentration gradient.”

31. PHOTOLYSIS

32. B. Electron Transport Chain 1. As electrons are passed down the chain energy from the electrons is used to pump H+ ions from the thylakoid space to the stroma. 2. This produces a concentration gradient that will be used to generate ATP. 3. At the end of the ETC the electrons are passed to photosystem I.

33. Photosystems and the ETC

34. C. Photosystem I *When the electrons arrive at photosystem I they do not contain as much energy because some of it was used to pump the H+ ions across the membrane. 1. Pigments – pigments in PI use sunlight to re-energize the electrons, which then go through another ETC. 2. NADP + - at the end of the second chain NADP + picks up the electrons as well as H+ creating NADPH. NADP + + e + H +  NADPH 3. NADPH will be used later to build sugar.

35. D. Hydrogen Ion Movement and ATP Formation 1. H + - has been accumulating in the thylakoid space in two ways: a) from water molecules that split b) from the ETC pumping them in 2. facilitated diffusion – the difference in H + across the membrane causes the H + to move from high  low; however b/c they are charged, they must pass through a channel protein. 3. ATP Synthase – the channel protein through which H + ions move to go from high  low.

36. 4. Chemiosmosis – as H + passes through the ATP Synthase, it rotates the ATP synthase like a rotor, which provides the energy to add a P onto ADP ADP + P  ATP *if the H + gradient is NOT maintained, meaning it evens out, then it will no longer continue to move through the ATP Synthase, thus no more ATP will be produced…. This is why plants need water!

39. E. Summary of the Light –Dependent Reactions 1. Produce O 2 from splitting of water (H 2 O) 2. Replace e from splitting of water (H 2 O) 3. Provide H + from splitting of water (H 2 O) 4. Produce ATP and NADPH, which will be used to build sugar.

40. II. The Light-Independent Reactions: Producing Sugars *The ATP and NADPH formed by the light-independent reactions contain an abundance of chemical energy, but they are not stable enough to store that energy for more than a few minutes. 1.Calvin Cycle – “light-independent reactions” ATP and NADPH are used to produce high-energy sugars; named after Melvin Calvin

41. 2. Location – occurs in the stroma

42. A.Carbon Dioxide (CO 2 ) Enters the Cycle 1. CO 2 enters the Calvin Cycle from the atmosphere. 2. An enzyme in the stroma adds CO 2 to a 5 carbon molecule creating a 6 carbon molecule. 3. The 6 carbon molecule then splits in half to make two 3 carbon molecules.

43. B. Sugar Production 1. Midway through the cycle some of the 3 carbon sugars leave the cycle. 2. The other 3 carbon molecules get recycled back to the starting molecule.

44. C. Summary of the Calvin Cycle 1. Uses 6 molecules of CO 2 to make 1 molecule of glucose, C 6 H 12 O 6 2. ATP and NADPH are used to add the CO 2 to build sugar. 3. Sugars produced by the Calvin Cycle are used by the plant to meet its’ needs for growth and development. 4. When animals eat the plant, they use the sugar for energy.

45. THE CALVIN CYCLE/ LIGHT-INDEPENDENT REACTIONS

46. D. The End Result 1. Light-Dependent + Light-Independent = SUGAR 2. This sugar is the basis for all food chains and webs. III. Factors Affecting Photosynthesis A. Temperature, Light, Water 1. Temperature a) enzymes in the plant work best at 0-35 O C b) at low temperatures photosynthesis slows down

47. c) at high temperatures the enzymes get denatured and won’t function 2. Light Intensity *The greater the light intensity, the greater the rate of photosynthesis. 3. Water a) not enough water, photosynthesis stops b) adaptations to prevent water loss: -waxy coating leaves -specialized leaves

48. B. Photosynthesis under extreme conditions 1. guard cells – cells on leaf that close to prevent transpiration *unfortunately this prevents CO 2 from getting in and thus the Calvin Cycle will not occur, therefore sugar will not get made

49. 2. Alternative types of Photosynthesis a) C4 Photosynthesis – makes a 4 Carbon compound that allows plants to do photosynthesis under extreme temperatures and intense light; requires more energy to do so. ex) corn, sugar cane

50. b) CAM Plants *Crassulacean Acid Metabolism Found in dry climates, these plants admit air into their leaves at night when it is cooler; CO 2 enters at night and is stored until daylight when the light-dependent reactions can occur. ex) pineapple cacti