practical 8 Flashcards
Investigation into the effect of a named factor on the rate of dehydrogenase activity in extracts of chloroplasts.
The effect of ammonium hydroxide on the time taken for chloroplasts to decolourise DCPIP.
In this investigation you will use a chloroplast suspension and a blue dye called DCPIP to monitor the rate of dehydrogenase activity. DCPIP goes from blue to colourless when it accepts electrons released by the chlorophyll.
1(a) You were told not to put the leaf midrib or leaf stalk in the blender (Step 2). Suggest why.
few/no chloroplasts present/ tough material so will no be cut by blender
Investigation into the effect of a named factor on the rate of dehydrogenase activity in extracts of chloroplasts.
The effect of ammonium hydroxide on the time taken for chloroplasts to decolourise DCPIP.
In this investigation you will use a chloroplast suspension and a blue dye called DCPIP to monitor the rate of dehydrogenase activity. DCPIP goes from blue to colourless when it accepts electrons released by the chlorophyll.What was the purpose of using a blender?
break open cells/break cell wall/allow release of chloroplast
Investigation into the effect of a named factor on the rate of dehydrogenase activity in extracts of chloroplasts.
The effect of ammonium hydroxide on the time taken for chloroplasts to decolourise DCPIP.
In this investigation you will use a chloroplast suspension and a blue dye called DCPIP to monitor the rate of dehydrogenase activity. DCPIP goes from blue to colourless when it accepts electrons released by the chlorophyll. The isolation medium was cold and was also isotonic with the spinach tissue.
(a) Explain why it was important that the isolation medium was cold. (3)
1.slows/stops enzyme activity
2.enzymes released during blending
3.chloroplast not damaged/photosynthesis/fucntion continues
Explain why it was important that the isolation medium was isotonic with the spinach
tissue.
same water potential/ no osmosis/ no water movement out
chloroplast organelles do not burst/ shrivel chloroplast not damaged
. There are large pieces of tissue and other organelles in your chloroplast suspension.
Describe how you could isolate the chloroplasts from the other components in the
suspension. 3
filter/centrifugate
at high speed then higher speed
collect pellet
Investigation into the effect of a named factor on the rate of dehydrogenase activity in extracts of chloroplasts.
The effect of ammonium hydroxide on the time taken for chloroplasts to decolourise DCPIP.
In this investigation you will use a chloroplast suspension and a blue dye called DCPIP to monitor the rate of dehydrogenase activity. DCPIP goes from blue to colourless when it accepts electrons released by the chlorophyll.
. You were told to wrap tube A in aluminium foil (step 8). Explain why.
prevent entry of light/keep in the dark/ slow release of electrons from chlorophyll/photosynthesis only occurs in the light/ stop photosynthesis
Investigation into the effect of a named factor on the rate of dehydrogenase activity in extracts of chloroplasts.
The effect of ammonium hydroxide on the time taken for chloroplasts to decolourise DCPIP.
In this investigation you will use a chloroplast suspension and a blue dye called DCPIP to monitor the rate of dehydrogenase activity. DCPIP goes from blue to colourless when it accepts electrons released by the chlorophyll.
Tube B was a control experiment (step 8). Explain how the results in this tube acted
as a control experiment 3
colour does not change in B
colour change not due to isolation medium
colour change is due to chloroplast/chlorophyll
In your investigation, the colour change in DCPIP was caused by the transfer of
electrons from chlorophyll. Name the part of a chloroplast where this transfer of
electrons takes place.
chloroplast membrane/thylakoid membrane.
DCPIP is decolourised more slowly when ammonium hydroxide is added. Use your
knowledge of the light-dependent reaction to suggest a reason why. 2
1ammonium hydroxide has stopped/slowed transfer of electrons
2along electron transfer chain
or
ammonium hydroxide affects pH
pH affects proteins in ETC
Some weed killers are substances that accept electrons during photosynthesis.
(a) Suggest how these substances kill weeds.
3
1stops/slows LDR
2stops/less production of reduced NADP/ATP
3LIR slowed/photosynthesis slows
Suggest one disadvantage of using these weed killers on weeds growing in a crop.
Explain your answer.
1(substance in weed killer) absorbed by crop
2 reduced growth/yield of crop
3 toxic affects on wild life
4 slows/stops respiration
