AP Biology Day 22. Monday, October 10, PDF Free Download

AP Biology Day 22 Monday, October 10, 2016

Discuss: Do-Now Group Discussion What is the equation for photosynthesis, and why is it a redox reaction? What are the steps of photosynthesis, and where does each occur? Briefly explain what happens at each step. Turn in lab notebooks

Essen+al knowledge standards 2.A.1: All living systems require constant input of free energy 2.A.2: Organisms capture and store free energy for use in biological processes

FLT I will be able to: describe the structure of a chloroplast describe the the role of ATP and NADPH in the Calvin Cycle compare and contrast oxidative phosphorylation and photophosphorylation in chloroplasts By completing Ch. 10 Lecture Notes

Ch. 10: Photosynthesis

Now Let s add a li9le detail about photosynthesis J 6

7 Light Dependent Reac+ons

REVIEW 1. The light dependent reactions Occur in the within and across the thylakoid membrane Chloroplasts split H 2 O into hydrogen and oxygen (photolysis) The electrons hold the free energy from the light Through an ETC, light energy is transformed into ATP and NADPH Generate ATP by photophosphorylation 8

Photosystems Photosystem = reac5on-center complex made up of many pigments that can collect light-energy 9

How a photosyste m harvests light Photon Light-harvesting complexes Photosystem Reaction-center complex STROMA Primary electron acceptor Thylakoid membrane e Transfer of energy Special pair of chlorophyll a molecules Pigment molecules THYLAKOID SPACE (INTERIOR OF THYLAKOID)

Photosystems Chlorophylls in photosystems absorb free energy from light, and boost e - s to a higher energy level Heat 11

Photosystems Energy from the sun powers the transfer of an electron from chlorophyll a to an electron acceptor 13

AP Biology Day 23 Wednesday, October 12, 2016

Do-Now: Group Discussion Put the following terms together in a coherent explana+on: Photosynthesis Cellular Respiration Plants Animals Oxidized Reduced Thylakoid Stroma Calvin Cycle Light Dependent Reactions NADPH ATP Excited electrons Proton Motive Force ATP Synthase

Announcements Clear missing assignments! Study for Ch. 10 quiz & Ch. 9-10 test J Quarter 1 ends 10/14 Ch. 10 Quiz?

9. Ch. 10 VCN CW/HW Assignments 10. Photosynthesis Pre-Lab PLANNER 1. Pre-labs due by Friday 2. Get stamps 3. Study!! Test Wednesday J

Essen+al knowledge standards 2.A.1: All living systems require constant input of free energy 2.A.2: Organisms capture and store free energy for use in biological processes

Recall The thylakoid membranes allow for an increased surface area for reac+ons of the ETC to take place There are two types of photosystems embedded in the thylakoid membranes (ETC): Photosystem II (PS II) Photosystem I (PS I) 20

Light-Dependent Reac+ons Overview Photosystem II Ø Goal: Produce ATP Ø Light energizes e - s and powers them through the ETC Ø Photolysis: Light E helps split water Ø H 2 O à ½ O 2 + 2H + + 2e - (provides H + + e -!!!!!) Ø e - s are energized and create a H + gradient within the thylakoid membrane Ø Chemiosmosis occurs (the PMF is used to synthesize ATP via ATP synthase) 22

Light-Dependent Reac+ons Overview Photosystem II Ø Chemiosmosis occurs (the PMF is used to synthesize ATP via ATP synthase) 24 Note: this is different than cellular respiration because Energy was originally harvested from solar energy (thus its called photophosphorylation) The proton gradient forms INSIDE the membrane instead of outside Oxygen is not required

Light-Dependent Reac+ons Overview Photosystem I Ø Goal: Make NADPH (e - carrier) Ø e - s are reenergized & used to form NADPH 26

Light-Dependent Reac+ons Overview Overall: We broke down water Water provides electrons and protons O 2 is released as waste The ETC and PMF help create ATP and NADPH NADPH and ATP carry the captured energy and will be used in the Calvin cycle to create sugars J 28

Electron Flow in the LDR Linear (non-cyclic) flow = normal Photosystem II & I work together to make ATP and NADPH Cyclic electron flow uses only PS II ATP is made but not NADPH So why does cyclic electron flow occur??? If there is a shortage of ATP, we can produce more 29

Cyclic Electron Flow makes only ATP Primary acceptor Fd Primary acceptor Fd Pq Cytochrome complex NADP + reductase NADP + + H + NADPH Pc Photosystem II ATP Photosystem I

Photochemical = Light Reactions STROMA (low H + concentration) Light Photosystem II 4 H + Cytochrome complex Light Photosystem I Fd NADP + reductase 3 NADP + + H + Pq NADPH H 2 O THYLAKOID SPACE (high H + concentration) e e 1 1 / 2 O 2 +2 H + 2 4 H + Pc To Calvin Cycle STROMA (low H + concentration) Thylakoid membrane ATP synthase ADP + P i H + ATP

Pair-Share-Respond 1. Where can you find photosystems? 2. Iden5fy three products produced in the light dependent reac5ons 3. What provides the electrons for PS II? 4. Explain how ATP is produced in PS II. Be very specific J 5. Iden5fy the role of Photosystem I

33 Stage 2: The Calvin Cycle

REVIEW 2. The light independent reactions (Calvin Cycle) Takes place in the stroma Forms C 6 H 12 O 6 from CO 2 using ATP and NADPH The Calvin Cycle begins with carbon fixation, which incorporates CO 2 into organic molecules and then reduction produces sugar 34

Details The Calvin Cycle uses ATP and NADPH to convert CO 2 to sugar The Calvin cycle regenerates its star5ng material ayer molecules enter and leave the cycle The Calvin Cycle builds sugar from smaller molecules using CO 2, ATP, and NADPH 35

Calvin Cycle The Calvin Cycle has three phases: 1. Carbon fixation (CO 2 attaches to the 5-carbon RuBP catalyzed by Rubisco) 2. Reduction (sugar making) 3. Regeneration of RuBP (cycle) 36

Calvin Cycle Carbon enters the cycle as CO 2 and leaves as a sugar named glyceraldehyde-3-phosphate (G3P), which will be used to create the C 6 H 12 O 6 Note: G3P is sometimes also called PGAL Most G3Ps are used to regenerate RuBP 3 turns of the cycle fixes 3 CO 2 molecules and creates 1 extra G3P Glucose requires 6 turns of the cycle (2 extra G3Ps) 37

Pair-Share-Respond 1. What is the purpose of the Calvin cycle? 2. What are the three stages of the Calvin cycle? 3. Compare and contrast the Calvin cycle with the Krebs cycle J

What happens in hot, arid climates? On hot, dry days, plants close stomata, which conserves H2O but also limits photosynthesis Recall - stomata 40

What happens in hot, arid climates? The closing of stomata reduces access to CO 2 and causes O 2 to build up These condi+ons favor a seemingly wasteful process called photorespira+on 41

Photorespira+on Most plants (~85%) are C 3 plants - stomata are open during the day, and closed at night When stomata close, there is no gas exchange à low CO 2 causes the wasteful process of photorespira+on to occur O 2 is used without producing energy molecules In photorespira+on, rubisco bonds with and adds O 2 instead of CO 2 in the Calvin cycle Photorespira+on consumes O 2 and organic fuel and releases CO 2 without producing ATP or sugar. Wasteful L 42

Photorespira+on Photorespira+on may be an evolu+onary relic because rubisco first evolved at a +me when the atomosphere had far less O 2 and more CO 2 Photorespira+on limits damaging products of light reac+ons that build up in the absence of the Calvin cycle 43

Solu+ons? C4 & CAM Plants Photorespira+on 44

C 4 Plants C 4 plants = most efficient at carbon fixa+on Have thinner leaves Chloroplasts may be larger Found in high light intensity environments 45

C 4 Plants C 4 plants minimize the cost of photorespira+on by incorpora+ng CO 2 into four-carbon compounds in mesophyll cells This step requires the enzyme PEP carboxylase PEP carboxylase has a higher affinity for CO 2 than rubisco does; it can fix CO 2 even when CO 2 concentra+ons are low These four-carbon compounds are exported to bundlesheath cells, where they release CO 2 that is then used in the Calvin Cycle 46

Carbon fixation occurs in Bundle Sheath, a region with low O 2 Photosynthetic cells of C 4 plant leaf Mesophyll cell Bundlesheath cell Vein (vascular tissue) C 4 leaf anatomy The C 4 pathway Mesophyll cell CO 2 PEP carboxylase Oxaloacetate (4C) Malate (4C) PEP (3C) ADP ATP Stoma Bundlesheath cell CO 2 Pyruvate (3C) Calvin Cycle Sugar Vascular tissue

CAM Plants CAM plants are typically succulents (not always) that live in desert or arid environments They have an inverted stomatal cycle: stomates open at night, and close during the day 48

CAM Plants Some plants, including succulents, use crassulacean acid metabolism (CAM) for carbon fixa+on CAM plants open their stomata at night, incorpora+ng CO 2 into organic acids Stomata close during the day, and CO 2 is released from organic acids and used in the Calvin Cycle 49

Sugarcane C 4 CO 2 Pineapple CAM CO 2 Mesophyll cell Organic acid 1 CO 2 incorporated into four-carbon organic acids (carbon fixation) Organic acid Night Bundlesheath cell CO 2 CO 2 Calvin Cycle 2 Organic acids release CO 2 to Calvin cycle Calvin Cycle Day Sugar (a) Spatial separation of steps Sugar (b) Temporal separation of steps

Review The energy entering chloroplasts as sunlight gets stored as chemical energy in organic compounds Sugar made in the chloroplasts supplies chemical energy and carbon skeletons to synthesize the organic molecules of cells Plants store excess sugar as starch in structures such as roots, tubers, seeds, and fruits In addi+on to food produc+on, photosynthesis produces the O 2 in our atmosphere 51

CW/HW Photosynthesis Pre-Lab J Ch. 10 Quiz??? 52

AP Biology Day 22. Monday, October 10, 2016