P.+Photosynthesis+(10)

Before you start studying in depth about photosynthesis, here is a short quiz covering the basics of what goes into and comes out of photosynthetic reactions:[]


 * __TARGET I__- MASTERY OF THE LIGHT REACTIONS **
 * //Chapter 10.1-10.2// **
 * 1) ** Describe how different wavelengths of light interact with pigments in the photosynthetic process. **
 * 2) ** Describe the structure of a chlorophyll molecule and how it initiates the photosynthetic process. **
 * 3) ** Differentiate between photosystem I and photosystem II (include the following terms: light, ATP, G3P/PGAL, NADPH, NADP, oxygen, electrons, electron transport chain, water, primary electron receptor, P680, P700). **
 * 4) ** Differentiate between linear electron flow and cyclic electron flow. **
 * 5) ** Differentiate between the structure of chloroplasts and mitochondria and differentiate chemiosmosis in each. **
 * 6) ** Describe the inputs and primary products of the light reactions. **
 * 7) ** Explain how paper chromatography can be used to separate pigments (use the terms: molecular mass, solubility). **

__**Target 1.1:**__ Photosystem I (P700) absorbs light photons with a wavelength of 700nm while Photosystem II (P680) absorbs light photons with a wavelength of 680nm. So, in comparison, Photosystem I needs a stronger photon than Photosystem II because Photosystem I powers the enzyme NADP+ Reductase on the thylakoid membrane.

__**Target 1.2:**__ Chlorophyll are arranged with proteins and organic molecules into photosystems of thylakoid membranes. A cluster of chlorophyll //a//, chlorophyll //b//, and carotenoid make an antenna complex that passes photons along to chlorophyll //a// in the reaction center (where first light-driven chemical reaction of photosynthesis occurs) has primary electron acceptor that takes the electron from chlorophyll //a// by a redox reaction when the photon excites the electron.



__**Target 1.3:**__ Photosystem I and Photosysem II are the light receptors in the light reactions. In non-cyclic photophosphorilation, Photosystem II absorbs photons with a wavelength of 680nm to split apart a H2O molecule (into an inorganic Oxygen and two H+ and electorns) to get the new electrons to replace the recently excited electrons from Photosystem II. These excited electrons have moved along the electron transport chain (ETC) of the thylakoid membrane. As they move along the ETC, they facilitate the active transport of H+ ions inside the thylakoid space from the stroma to create a high proton gradient. This proton gradient is necessary for the ATP synthase enzyme to synthesize ATP molecules. The previously excited electrons from the ETC move to Photosystem I (P700) and await a photon of wavelength 700nm to energize them. Once energized, the electrons move on to power the NADP+ Reductase to form NADPH.

__**Target 1.4:**__

Linear Electron Flow: Occurs during light reactions of photosynthesis as electrons flow through the photosystems and other components built into the thylakoid membrane.
 * Photosystem II, then PS I
 * Photosystem utilizes P680 as reaction center chlorophyll
 * PS II makes both ATP & NADPH
 * Occurs in ALL plans (mosses → pine → angiosperms)
 * P680 is a strong oxidizing agent and stimulates enzyme to split water to replace e- of oxidized pigment (P680) & make O2 (H20 > 2H+ + OH- + 2e-
 * Meanwhile, e- passed down electron transport chain of cytochrome complex; move H+ ions form stoma to inner thylakoid space (chemiosmosis)
 * H+ diffuse back into stroma through ATP synthase
 * Electrons then used to reduce P700 of Photosystem I
 * Photosystem I passes e- to reduce NADP+ with help of reductase enzyme to make NADPH



Cyclic Electron Flow: This uses photosystem I only. In this process, the excited electrons from photosystem I cycle back from ferredoxin to the P700 chlorophyll reaction center complex. No NADPH is produced and no oxygen is released in this process, but it does produce ATP (significantly less than the ATP produced in Linear Electron Flow).


 * Photosystem I: reaction center chlorophyll = P700: chlorophyll //a//
 * P700 absorbs light at λ=700nm
 * P700 found in algae; most primitive Photosystem
 * PS I makes **__ATP only__**, no NADPH (directly)
 * Fd (ferredoxin) passes e- from P700 through cytochome complex and then returns e- to oxidized P700
 * Cytochrome comples performs chemiosmosis
 * H+ ions move from stroma into inner thylakoid space to create a gradient of H+ inside thylaoid relative to stroma
 * H+ allowed to diffuse down concentration gradient (back into stroma) through **__ATP synthase__**



__**Target 1.5:**__


 * __Chemiosmosis in:__**
 * __**Chloroplasts**__ || __**Mitochondria**__ ||
 * -Electrons that power chemiosmosis come from water. || -Electrons that power the chemiosmosis come from organic molecules. ||
 * -Transforms light energy into chemical energy in ATP || -Transfers chemical energy from food molecules to ATP ||



__**Target 1.6:**__ LIGHT REACTIONS (Redox Process): Inputs...
 * SUNLIGHT (light photons)
 * Water

Outputs...
 * ATP
 * NADPH
 * O2 (by-product)

DARK REACTIONS: Inputs...
 * ATP
 * CO2
 * NADPH

Outputs...
 * sugars (which eventually bind to form glucose-->C6H12O6)
 * ADP
 * NADP+

__**Target 1.7:**__ Paper chromatography can be used to separate pigments by three primary characteristics: molecular size, polarity, and solubility. If the solvent is polar, then polar, small pigments will travel the farthest up the paper while non-polar, large pigments will travel the least. If the solvent is non-polar, then non-polar, small pigments will travel the farthest up the paper while polar, large pigments will travel the least.


 * __TARGET II__- MASTERY OF THE CALVIN CYCLE **
 * //Chapter 10.3// **
 * 1) ** Explain the step of carbon fixation (include RUBISCO in your explanation). **
 * 2) ** Explain the step of reduction. **
 * 3) ** Explain how RuBP is regenerated. **
 * 4) ** Identify the location in the chloroplast where the Calvin Cycle occurs. **
 * 5) ** Describe the inputs and primary products of the Calvin Cycle. **

__ **Target 2.1:** __ Carbon Fixation occurs in Phase 1 of the Calvin Cycle. Enzyme RuBisCO assists in joining together RuBP (a 5 carbon chain) and CO2 (1 carbon chain). The result is a 6 carbon chain that is very unstable and immediately splits into 2, 3 carbon chains of PGA. [] Watch this video and then take a quiz to see how much you know!

__ **Target 2.2** __

Reduction is Phase 2 of the Calvin Cycle. 6 ATP and 6 NADPH are used to reduce PGA into G3P (PGAL), a sugar usable by the plant for energy.

__ **Target 2.3** __

During Phase 3 of the Calvin Cycle, RuBP is regenerated by adding 3 ATP to G3P. It is important that RuBP is regenerated because each plant has a specific amount of RuBP, and can not produce or absorb more.

__**Target 2.4**__

The Calvin Cycle occurs in the stroma of the chloroplasts.



__**Target 2.5**__

Inputs: 3 CO2, 9 ATP, 6 NADPH.

Outputs: 9 ADP, 6 NADP+, 6 P, 1 PGAL (G3P)



//Quick Concept Check of Calvin(Dark) Cycle://

1. Name the molecules that start the Calvin Cycle.

__2. How many CO2 are fixed in one turn of the Calvin Cycle?__

3. How many C02 is used to make one PGAL(G3P)? _

4. How many turns of the Calvin Cycle is (are) required to make 1 molecule of GLUCOSE?

__5. How many PGAL(G3P) make one glucose?__ _

6. Where in the chloroplast does the Calvin Cycle Occur?

__7. How many ATP and NADPH are required to make 1 glucose molecule?__

__ANSWERS:__ __1. ATP, NADPH, CO2__ __2. 1 CO2 per turn__ __3. 3 CO2__ __4. Six turns__ __5. 2 PGAL(G3P)__ __6. The Stroma__ __7. 18 ATP, 12 NADPH__

**TARGET III__- MASTERY OF PHOTOSYNTHETIC ADAPTATIONS TO HOT CLIMATES**
 * //Chapter 10.4// **
 * 1) ** Explain how C3 plants respond to hot, dry weather (photorespiration, Calvin cycle, mesophyll cells). **
 * 2) ** Explain how C4 plants respond to hot, dry weather (include the following in your explanation: carbon fixation, bundle-sheath cells, OAA, mesophyll cells, PEP carboxylase, spatial separation, Calvin cycle). **
 * 3) ** Explain how CAM plants respond to hot, dry weather (include the following in your explanation: carbon fixation, mesophyll cells, temporal separation, Calvin cycle) **

Here is a great overview of CAM, C4, and C3 plants. []

Here is an overview of what happens in hot, dry weather:
 * __Target 3.1__ **

C3 plants partially close their stomata in hot, dry conditions and produce less sugar because the declining levels of CO2 in the leaf starves the calvin cycle. Water is lost from the stomata closing their stomata, known as transpiration. The plants can't fix carbon anymore because they have used all of it up and can't get anymore since the stomata are closed. O2 accumulates in the //mesophyll// because the light reactions still continue to occur because it is sunny outside. They undergo the process of //photorespiration// in which rubisco binds RuBP to O2 in place of CO2 and therefore adds O2 to the //Calvin Cycle//. A two carbon molecule is released by the process and converted back to CO2 by peroxisomes and mitochondria. Now, RUBP is lost from the Calvin cycle. Unlike normal cellular respiration, no ATP is generated by this process and in fact consumes ATP. Also, no sugar is produced by this process.

Some things to remember about photorespiration:
 * 1) Oxygen concentration > CO2 concentration
 * 2) Consumes oxygen and ATP
 * 3) Releases CO2


 * __Target 3.2__ **

C4 plants almost never saturate with light and under hot, dry conditions. They use a two-stage process were CO2is fixed, by carbon fixation, in thin-walled mesophyll cells to form a 4-carbon intermediate, malate (malic acid). The reaction involves phosphoenol pyruvate (PEP) which fixes CO2 in a reaction catalyzed by PEP carboxylase. It forms oxaloacetic acid (OAA) which is quickly converted to malic acid. The 4-carbon acid is actively pumped across the cell membrane into a thick-walled bundle sheath cell where it is split to CO2and a 3-carbon compound. This CO2 then enters the Calvin cyclein a chloroplast of the bundle sheath cell and produces G3P and subsequently sucrose, starch and other carbohydrates that enter the cells energy transport system.

//Test your understanding!//

//C4 Plants Quiz//

1. Bundle sheath cells, cells arranged in tight sheaths around the veins of the leaf, are important because the _ takes place in them. A) Carbon fixation B) Calvin Cycle C) ATP

Match the correct noun to its function or description. Each may be used more than once or not at all. A) Bundle Sheath Cells B) Malate C) CO2 D) Mesophyll Cells E) PEP carboxylase F) OAA

2. Export malate to bundle-sheath cells through plasmodesmata. 3. Here, malate releases CO2. 4. Breaks into Pyruvate and CO2. 5. Solid store of 4 carbon molecules. 6. Adds CO2 to PEP forming 4C product. 7. Where the CO2 enters. 8. ATP is used here to convert pyruvate to PEP. 9. Contain PS1 and carry out cyclic electric flow. 10. Converted to malate.

11. Cyclic electron flow is important for C4 plants because it ___.__ A) Regenerates PEP. B) Pumps CO2 into the mesophyll cells. C) Generates ATP. D) Releases CO2.

12. directly allows for rubisco to bind to CO2 rather than Oxygen. A) Malate. B) PEP carboxylase binding PEP to CO2. C) Regeneration of ATP. D) High CO2 concentration in the bundle sheath cells

ANSWERS! 1)B 2)D 3)A 4)B 5)F 6)E 7)D 8)D 9)A 10)F 11)C 12)D

< Big Picture: The Calvin Cycle happens in the stroma, which is in the chloroplasts, which are in the mesophyll cells, which are in the leaf.

media type="youtube" key="Ux1eted7nGE" height="315" width="420"


 * __Target 3.3__**

==== When exposed to heat and dry weather, the stomata close tightly to conserve water and the malic acid is decarboxylated to release the CO2for fixing by the Calvin cycle. PEP is used for the initial short-term carbon fixation as in the C4 plants, but the entire chain of reactions occurs in the same cell rather than handing off to a separate cell as with the C4 plants. ==== CAM plants fix carbon only at night into a 2 Carbon organic acid we call OAA.So they open their stomata only at night. They undergo the Calvin Cycle during the day so the CO2 builds up at night. CAM plants have temporal seperation which means they obtain CO2 when the temperature is cooler so less transpiration occurs.


 * Some pictures to help better understand the differences between the plants:**





__All Targets/ Big Idea Help__
This is an incredible site for various quizzes covering all aspects of photosynthesis. []

This is a great quiz to test your overall understanding of photosynthesis. Only questions 1-18 are really relevant to what we have learned. []



media type="youtube" key="m8v7prlscM0" height="315" width="560"media type="youtube" key="2IygaV0_-B0" height="315" width="560"

[] ^ This is a link to flash cards for photosynthesis that are really useful because the book the author used is the AP Biology Campbell. Under the flashcards, there are options for other useful methods of actively studying, like a test and some fun games.

[|Photosynthesis Rap] -- Here is a pretty informative video I found. The pictures during the video are slightly more helpful the the actual lyrics to the rap. Josh Gerber from Miss I 4B-5

Are all the molecules hard to keep track of? Use this website to practice! []

Target 3: Adaptations [|Photosynthesis adaptations quiz]