Lab Exam: Lab 6 Flashcards
What happens to the electrons when chlorophyll absorbs light?
Its electrons are excited to high energy levels
Where are the excited electrons transferred to?
They are transferred to other electron acceptors in the chloroplast membrane
Where does electron deficit chlorophyll receive its electron?
Electron removed from water
Is water oxidized or reduced in photosynthesis?
Oxidized because water loses an electron
What is the result of the oxidation of water?
Oxygen gas is produced, as well as electrons and protons
What is the independent variable?
Amount of chloroplast added to reaction mixture
What is the dependent variable?
The rate of water oxidation
How did we measure the rate of water oxidation?
We paired it with the reduction of DPIP which loses its blue color when reduced (water oxidation) which can then be measured using a spectrophotometer
Why was a buffer used for the isolation and function assessment of chloroplasts?
The buffer was most likely the ideal pH for chloroplast function, thus, it ensured that the chloroplasts were functioning at its highest ability to make results most favorable
Why was bisulfite added to the “blank” tubes in your experiments with chloroplast function?
Bisulfite reacts with DPIP to make the overall solution colorless; DPIP is reduced with bisulfite is added
In the experiment where the amount of chloroplasts was varied, what do your results show about chloroplast function?
The solutions with more concentrated chloroplast undergo photosynthesis more because more chloroplast is able to absorb light and oxidize water (reduce DPIP)
If DPIP spontaneously loses its blue color, what should have happened in the the “No light, no heat” control?
There would have been a significance difference in absorption from t=0 and t=10 because in reality, there was very little change in absorbance
If heat is necessary for the DPIP to change color, what should have happened in the “No light, heat” control?
There would have been a significant change in absorption from t=0 to t=10 because that means the chloroplast were able to undergo photosynthesis and oxidize water (and reduce DPIP)
If light and heat are required for DPIP to lose its color, how should the change in absorbance be different between the “Light and heat” control and the “Light, no heat” condition?
The “Light and heat” condition would have a greater difference in absorbance than the “Light, no heat” condition because both are needed to reduce DPIP
Does light alone appear to be needed to drive the DPIP reduction? How can you tell?
Light, while a major factor to reduce DPIP, is not all that is needed. This is because the “Light, no heat” control had a change in absorbance but not as significant as “Light and heat” condition
Where are the electrons that reduce the DPIP coming from?
They are coming form the oxidation of water which occurs when chloroplasts absorb light and then become electron-deficit
Where do these electrons (from chloroplast) normally end up when the full process of photosynthesis is occurring?
They normally end up getting transferred to other electron acceptors in the chloroplast membrane
How important electron transfer to the overall process of photosynthesis?
This electron transfer allows plants to generate its own energy and convert carbon dioxide and water to sugar into the fuel its cellular functions
What wavelengths would have been most effective for driving the reduction of DPIP?
Blue light because chloroplasts best absorb blue light for photosynthesis and thus will cause the reduction of DPIP faster
What wavelength would have been the least effective for driving the reduction of DPIP?
Green light because chloroplasts do not absorb green light very well and thus will not undergo photosynthesis which will limit the reduction of DPIP
