Organisms Capture & Store Free Energy for Use in Biological Processes

1. Organisms Capture & Store Free Energy for Use in Biological Processes Photosynthesis & Cellular Respiration Anabolic pathway Catabolic pathway

2. Heterotrophs -Capture free energy present in carbon compounds produced by other organisms.

3. Autotrophs -Capture free energy from physical sources in the environment.

4. Photosynthesis • Plants & other photosynthetic organisms produce foods that begin food chains. • The sun is a constant energy source. • Must be converted into a chemical energy in order to be useful to all non-photosynthetic organisms. • Most common chemical energy is glucose which is also the most common fuel organisms use for cellular respiration (more on that later)

6. How does the CO2 get to the chloroplast?

7. LET’S COUNT STOMATA!!!!

8. Post Lab Questions

9. Define transpiration • Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. • evaporation of water from plant leaves. • Transpiration also includes a process called guttation, which is the loss of water in liquid form from the uninjured leaf or stem of the plant, principally through water stomata.

10. How do guard cells open & close stomata?

11. Why does the density of stomata differ among plants? It depends on the environmental conditions, such as: • Amount of sunlight • Amount of atmospheric carbon dioxide concentrations • Amount of humidity in the environment

12. At what time of day might more stomata be closed & justify your answer. • Usually plants open most of their stomata during the day. • In drier regions, plants usually have more of their stomata open in order to reduce loss of water vapor.

13. Why does the lower epidermis usually have more stomata than the upper epidermis? • Many plants are adapted to an environment where the upper surface is exposed to strong sunlight and higher temperatures and/or where water is more limited compared to a watery environment. • =more stomata on the bottom than the top What about other plants? • Underwater plants are in 100 percent humidity; transpiration does not occur. So there is no need for water vapor. • = zero stomata • Plants adapted to an environment where only the upper side of the leaf is exposed to air; thus, only one surface can exchange water vapor with the environment. • = lots of stomata on the upper side of the leaves

14. What does a larger number of leaf stomata indicate about the growing climate of that plant? A large number of stoma indicate that there is an excess rate of transpiration from the leaves which is an indication that the plant is in excess water supply

15. Outer Membrane Inner Membrane Stroma Thylakoid

16. Where do plants get the resources they need to make their own food? The sun, air, and soil What does each resource offer the plant? Sun  is the energy source used to drive anabolic/endergonic synthesis of glucose. Air  provides the carbon necessary for glucose production. Soil  water and trace elements come from here. What are the by-products of photosynthesis? Oxygen and water

17. If plants, bacteria & other autotrophs did not make glucose from air & sunlight, , how would the earth’s heterotrophs be affected? They would all die once everything on earth had been eaten, since only autotrophs can make food.

18. What pigments do leaves have? chlorophyll a, chlorophyll b, carotene, an xanthophyll LET’S CHECK THEM OUT!!!

19. ACTION AND ABSORPTION SPECTRA OF PHOTOSYNTHESIS Various pigments in photosynthesis absorb photons of light from specific wavelengths of the visible spectrum.

21. Which leaves are able to absorb shorter wavelengths of light? Longer? short long SHORTER LONGER

22. Overall Process of Photosynthesis

23. There are two major stages The Light-Dependent Reaction The Light-Independent Reaction (Calvin Cycle) Write a one-sentence summary, describe what happens in each of these phases.

24. Light Dependent Reactions • The photon energy of sunlight is captured and converted to molecules that can be used to power the second phase; specifically NADPH & ATP. Light Independent Reactions (Calvin Cycle) • The molecules from the light dependent reactions are used to build carbon chains from carbon dioxide

25. Let’s start with the Light Reactions

26. How does a satellite dish bring more TV stations & better reception to your TV? The larger the parabola, the more signals it can gather & bounce on to a single focus point before it sends the signal to your TV.

27. How are the pigments like a satellite dish? Accessory pigments in the thylakoid membranes train the collected energy onto a focal point so that the sum total of its strength is used to excite the electrons on chlorophyll a. Which pigments are at the focal point? Chlorophyll a Which pigments are accessory pigments surrounding the chlorophyll a? Chlorophyll b & carotenoids What are these central chlorophyll a molecules called? Photosystems – PS I and PS II

29. Modern-day plants have 2 photosystems • Photosystem I • Most efficient at absorbing wavelengths at 700nm • Photosystem II • Most efficient at absorbing wavelengths at 680nm • These 2 photosytems work together to bring about a non-cyclic electron transfer.

30. Light Dependent Reaction • Occurs in the thylakoids or grana of chloroplast. • Light is absorbed in the pigments (chlorophylls and carotenoids) which are organized on the membranes of the thylakoids. • The regions of organization are called photosystems which include: • Chlorophyll a molecules • Accessory pigments • A protein matrix • The reaction centre is the portion of the photosystem that contains: • A pair of cholorophyll molecules • A matrix of protein • A primary electron acceptor

31. If an atom’s electrons are energized, then they can get so excited they will leave the orbital & jump off the atom/molecule in a state of high energy At what point does the electron have the greatest potential energy? When the electron is in its excited state

32. Photosystem II Collects photons from the surrounding pigments embedded in the thylakoid membranes & uses that gathered energy to excite two electrons on a chlorophyll a molecule in the reaction center (also embedded in the thylakoid membrane). Chlorophyll a now has two excited, high energy electrons in PS II & needs to capture their kinesthetic energy to convert it to ATP or NADPH (the 2 energy molecules needed to fuel the Calvin cycle). When would be the best time to capture the electron’s energy?

33. PHOTOSYSTEM II These electrons are captured by the primary acceptor of the reaction center. Chlorophyll a is a strong oxidizing agent when it has lost its electron. What will the chlorophyll a molecule do now that it is missing an electron from its orbital? Water is split by an enzyme to produce electrons, hydrogen ions, and an oxygen atom. This process is driven by light energy & is called photolysis. The electrons are supplied one by one to the chlorophyll a molecules of the reaction center. The leftover oxygen will find another broken water molecule & become O2 gas (a by-product of photosynthesis).

34. The excited electrons pass from the primary acceptor down an electron transport chain (ETC) losing energy at each exchange. The energy lost from the electrons moving down the ETC drives chemiosmosis to bring about phosphorylation of ADP to produce ATP Movement of ions down their electrochemical gradient through a selectively permeable membrane.

35. The Calvin cycle needs 18ATP molecules and 12 NADPH molecules for every molecule of glucose produced. NADPH is an energy storage/shuttle molecule. We have just discussed how ATP is generated. How do you think NADPH is generated?

36. PS I captures light energy (nearly the same manner PS II captured light to generate ATP) & generates an NADPH molecule. • Chlorophyll a molecule from PS I replaces its missing electrons with the electrons that came from the electron transport chain following PS II. • NADPH is not made from a chemiosmotic gradient in the thylakoids, but instead the electron pair is given to NADP+ directly to be used in the form of NADPH. Photophosphorylation High-energy electrons derived from light activation of chlorophyll molecules -no carbon fuel source necessary -Final electron acceptor is NADPH

37. What does the Light Dependent Reactions Do Overall? • The production of: • NADPH(Nicotinamide Adenine Dinucleotide Phosphate Hydrogen) • ATP(Adenosine Tri-Phosphate) • Oxygen is given off as a waste product (lucky for us  ). NADPH & ATP supply the chemical energy for the light independent reactions.

38. Now for the Light Independent Reactions AKA Calvin Cycle Occurs within the stroma of the chloroplast

39. Light Independent ReactionsAKA: Calvin Cycle • This reaction uses the ATP and NADPH produced by the light dependent reaction. • We are synthesizing sugar in this reaction.

40. What are the starting molecules and the ending molecules? The process begins with carbon dioxide binding to ribulose bisphosphate After three turns of the Calvin cycle, half a glucose molecule, called G3P, is produced.

41. How much energy is used to fuel this anabolic process? Sunlight, 9 ATP molecules and 6 NADPH molecules are used to make one molecule of G3P

42. What Happens in the Calvin Cycle? • Ribulosebisphosphate (RbBP), a 5 carbon compound, binds to an incoming CO2 molecule in a process called carbon fixation. • RuBPcarboxylase (rubisco) catalyzes this fixation. • An unstable 6 carbon compound is made & then breaks down to two 3 carbon compounds known as glycerate-3-phosphate. • These molecules are acted upon by ATP & NADPH (remember these guys?) to form 2 more compounds called glyceraldehyde 3 phosphate (triose phosphate). • These molecules may then go in one of two directions. • Leave the cycle to become sugars • Continue in the cycle to help reproduce the originating compound RuBP with the help of ATP

43. 2 of these are made

44. The overall equation of the Calvin cycle (black circles represent carbon atoms)

45. Products of one turn of the Calvin Cycle • 2 glyceraldehyde-3-phosphate (G3P) molecules, 3 ADP, and 2 NADP+. • (ADP and NADP+ are not really "products." They are regenerated and later used again in the light-dependent reactions). • Each G3P molecule is composed of 3 carbons. In order for the Calvin cycle to continue, RuBP (ribulose 1,5-bisphosphate) must be regenerated. • So, 5 out of 6 carbons from the 2 G3P molecules are used for this purpose. Therefore, there is only 1 net carbon produced to play with for each turn. • To create 1 surplus G3P requires 3 carbons, and therefore 3 turns of the Calvin cycle. • To make one glucose molecule (which can be created from 2 G3P molecules) would require 6 turns of the Calvin cycle.

46. Each reaction in this multi-step process is catalyzed by a reactant-specific enzyme. The 1st enzyme performs a critical step of capturing CO2 & “fixing” it so that it’s committed to entering the Calvin cycle. Name this 1st enzyme: Rubisco (aka RuBP carboxylase) is the enzyme that binds carbon to ribulosebiphosphate.

47. How does the Calvin cycle regenerate the starting molecule ribulose bisphosphate (RuBP)? The cycle uses a series of reactions and 3 molecules of ATP to regenerate RuBP.

49. CHLOROPLAST STRUCTURE & FUNCTIONS

50. It’s time for a simulation!!!!