Photosynthesis

Non-cyclic Electron Flow (yield ATP & NADPH)

 

-Light is radiated to plants' leaves and reaches chloroplast where most of the photosynthetic reactions take place. The photons strike PSII (photosystem two) consisting antenna complex and a reaction centre.

-Antenna absorbs photons and transfer the energy from one to another, until it reach to reaction centre-chlorophyll a.

-The energy is used to excite an electron at chlorophyll P680. The electron is captured by electron acceptor, pheophytin.  Through redox reactions, the electron is transferred to plastoquinone (PQ).

- When the electron is missing at PS 680,  Z protein would splits 2H₂O à O₂ + 4H⁺+ 4e^-, the electrons produced will be use to replace the missing one; the oxygen get released as a byproduct; and the hydrogen ions are kept inside in the thylakoid lumen. The process of splitting water is called, photolysis.   

-The electron carrier PQ transfer the electron to b₆-f cytochrome complex while this is happening, hydrogen ions from the chloroplast stroma are being pumped into the thylakoid lumen.

-The electron gets carried away by plastocyanin (Pc) to PSI (photosystem one) replacing the missing electron excited by the last photon energy.

-The electron in PSI excited by photon energy and transferred to FNR (ferredoxin NADP reductase) by ferredoxin the electron carrier.

-The transferred 2e^- +H⁺ floating in the stroma to convert NADP⁺ into NADPH for use of Calvin Cycle.

-The hydrogen ions accumulated through the reaction increases the electrochemical gradient. To balance the pH level between the thylakoid lumen and stroma, H⁺ is pumped out though a complex called, ATP synthase.  By doing so, ADP can be converted into ATP by adding Pi in the process of photophosphorylation.

Cyclic Electron Flow (yield only ATP)                  

-Happens when not enough light or water is presented in the plant cell.

-Photon energy excites the electron at PSI, the electron is transferred through ferredoxin to b6-f cytochrome and back to PSI.

-H+ is being pumped into the lumen adding gradient for chemiosmosis which will produce ATP same as non-cyclic electron flow.    

pH level affecting the rate of enzyme activity Lab

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} 

Title: pH level affecting the rate of enzyme activity Lab 

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