photosynthesis

CO₂+ H₂O --> C₆H₁₂O₆ + O₂

_{Non-Cyclic Electron Flow}

• 1.       Light photon strikes PS II (P680), electron gets excited and goes to the reaction center.
  2.       Z protein splits H₂O into O₂ (leaves the cell) , H⁺ proton which goes into lumen, and releases 2 electrons (photolysis)
  3.       Electron passes to PQ, which passes to B₆F through redox reaction, and during this process, H⁺ ion gets pumped into the lumen from stroma ([H⁺] increases inside lumen, prepares for chemiosmosis)
  4.       The electron continues to pass to PC, then
  5.       At PS I (P700), when light photon strikes, the electron passes to Fd, then to FNR (or NADP reductase).
  6.       FNR uses the two electrons and H⁺ (from stroma) to reduce NADP⁺ to NADPH (which goes to Calvin Cycle).
  7.       At ATPase complex, because of the H⁺ ions that added up inside the lumen, this drives the chemiosmosis, in which the high [H⁺] would move from inside the lumen to outside (stroma).
  8.       As protons move through the ATPase to stroma, ATP is formed (photophosphorylation)
  
  
  Cyclic Electron Flow
  
  
  9.        When light is not sufficient, only PS I is involved in a cyclic electron flow: photons strike PSI, electron passed to Fd, then B₆F complex then to PC (an ATP is made in the process), then back to PSI
  
  
  Calvin Cycle 
  (C₃ Plants @ cool, moist environments) (e.g. soybean, wheat, rice)
  
  
  10.   Calvin cycle starts with 3 molecules of ribulose RuBP (1,5-biphosphate) in Phase 1: Carbon fixation where 3 CO₂ are added to the enzyme rubisco to make 6 molecules of PGA (3-phosphoglycerate), which is extremely polar and need an extra P
  11.   Phase 2: reduction reaction: Uses 6 ATP to add a phosphate to each of the PGA to make it into 1,3 BPG (1,3-biphosphoglycerate)
  12.   The first phosphate is attracted to NADPH’s H⁺, so 6 NADPH are used and becomes 6 NADP⁺ (6 P’s run away with 6 H⁺’s), resulting with 6 molecules of G3P (glyceraldehydes 3-phosphate)
  13.   1 molecule of G3P comes out of the cycle and combines with another G3P to form glucose/starch/sucrose {*need to run cycle twice to get a sugar since 2 G3P come to make a sugar}
  14.   Phase 3: regeneration of RuBP : RuBP is regenerated through a series of steps, and produces 3 molecules of RuBP again to continue the cycle
  
  
  C₄ Plants @ hot, dry environments (e.g. sugar cane, corn)
  (separate by location)
  
  
  15.   There are alternative mechanisms of carbon fixation evolved in hot, acid climates for C₄ plants (their stomata are clsed on hot, dry days, but there’s still light and O₂, so they need a carbon storage)
  16.   When stomata is open, they fix extra carbon, store extra carbon in mesophyll cells
  17.   They use an enzyme called PEP carboxylase and catalyzes the addition of a CO₂ molecule to a three-carbon molecule called PEP, which makes oxaloacetate (OAA) ßstore carbon
  
  
  
  
  CAM Plants @ hot, dry, desert environments
  (separate by time, same location) (e.g. pineapple)
  
  
  18. In dry environments, stomata has to be very carefully regulated
  19. Daytime: stomata shut tight, to preserve water, use the CO₂ stored in vacuoles from night time to use in Calvin cycle
  20. Night time: temperature is less hot, humidity is higher, stomata opens to get CO₂ 

enzyme lab (pH levels)

Purpose: To see the effects of varying pH on the enzyme activity and to find the optimal pH for catalase to work.

Procedure:

1. Dilute solutions of HCl and NaOH in different test tubes according to the table below, add 5 mL of H₂O_{2 to each test tube, swirl to mix}
2. _{Set up a water displacing station: fill a water trough and graduated cylinder with water (to the top), invert the graduated cylinder into the water trough carefully (do not let air in).  Place a beaker underneath the water trough to collect displaced water.}
3. Insert a rubber tube into the graduated cylinder that is connected to a rubber stopper (will be used to cover Erlenmeyer flask)
4. _{In an Erlenmeyer flask, add 5 pieces of filter paper (soaked in liver juice) to the bottom of the flask}
5. _{Add the first dilution into the flask, shake and cover the flask immediately, use a timer to record time needed for the reaction.}
6. _{Stop timer and record results when oxygen stops displacing water and when water stops overflowing from the water trough}
7. _{Repeat steps 2-6 for other dilutions}

Dilutions:

HCL	0ml	3ml	1ml
Water	0ml	2ml	4ml
time	39’	1:07’	1:45’
Amount water displaced	0 ml	0ml	5ml

NaOH		1ml	2ml	3ml	1ml *2nd trail
Water		4ml	3ml	2ml	4ml
time		2:10’	3:00’	2:40’	2:21’
Amount of displaced	gas	153ml	15ml	5ml	167ml
	water	115ml	11ml	2ml	220ml

lab partners: Ellen Zhou, Grace