Michaelmas week 7 Flashcards
What does an oxygen electrode do?
Allows you to measure rate of photosynthesis by measuring rate of oxygen consumption
Draw the oxygen electrode
(See notes for diagram)
What is a teflon membrane?
A membrane only permeable to oxygen
Why must all electron donors and acceptors be present?
In order for oxygen to be generated there must be a flow of electrons
What artificial electron acceptors did we use in our experiment?
Fericyanide (Fe(CN)6)3-) –> general electron acceptor, accepts electrons from PS1 and PS11
Phenyl quinone –> only accepts electrons when bound at plastoquinone (QB) site of PS11 and doesn’t aaccept electrons from PS1
What can we use these artificial acceptors to do?
Separate action of PS1 and 11 to work out where a herbicide targets within an ETC
Where do you keep chloroplast preparation and why?
Sucrose medium, ensures they are in an isotonic medium and remain intact
When placed in acetone what happens to chloroplasts?
They rupture and chrorophyll is dissolved
Draw signal in mV vs. time when light is shone and when herbicide is added
(See notes for diagram)
Photosynthetic rate=?
Rate in light- rate in dark
How do you convert mV to oxygen conc at 25 degrees?
1000mV = air saturated water = 0.255 micromol 02 per ml
How do we calibrate the electrode to 0 and 1000 mV
0 mV –> use sodium dithionite which reacts with oxygen
1000mV –> use air-saturated water
What did we see from our experiment?
PS11 definitely targeted because even when PhQ is present rate of oxygen evolution is inhibited
PS1 targeted
What herbicide did we use and what does it do?
DCMO
Blocks quinone binding site at PS11 and therefore electrons cannot pass either from natural plastaquinone or artificial phenylquinone and ETC stops
Draw graph of O2 electrode reading vs time with PhQ added, in the dark and in the light and then with a PS11 inhibitor
(See notes for diagram)
