Required Practical 8 Flashcards

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1
Q

What is the function of dehydrogenase in chloroplasts?

A

It catalyses the acceptance of electrons by NADP in the light dependant reactions

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2
Q

What is the purpose of DCPIP?

A
  • It is a redox indicator dye and acts as an alternate electron acceptor instead of NADP
  • It turns from blue to colourless when reduced
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3
Q

Why is the plant extract chilled in an ice-water bath?

A

To lower the activity of enzymes to prevent them from breaking down the chloroplasts

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4
Q

How is the control set up

A

Fill a cuvette with chloroplast extract and distilled water

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5
Q

How is light intensity controlled?

A
  • Adjust the distance of the lamp from the set up
  • Perform the practical in a dark room so that the only light source is the lamp
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6
Q

What is the function of the muslin cloth?

A

To filter out any debris in the ground leaf mixture but allowing chloroplasts to pass through

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7
Q

Why are the stalks of leaves removed before grinding?

A

The stalks do not contain any chloroplasts

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8
Q

What was the purpose of using a blender?

A

to break open cells and release chloroplasts

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9
Q

Explain why it was important that the isolation medium was isotonic with the spinach tissue

A
  • Prevents osmosis
  • So organelles don’t burst or shrivel
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10
Q

There are large pieces of tissue and other organelles in your chloroplast suspension. Describe hoe you could isolate the chloroplasts from the other components in the suspension

A
  • Filter
  • At low speed, then high speed
  • Collect pellet
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11
Q

DCPIP is decolourised more slowly when ammonium hydroxide is added. Use your knowledge of the light-dependant reaction to suggest a reason why

A

Ammonium hydroxide stops transfer of electrons along ETC

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12
Q

Some weed killers are substances that accept electrons during photosynthesis. Suggest how these substances kills weeds.

A
  • Slows light dependant reaction
  • Less ATP/ NADPH made
  • Light independent reaction slowed
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13
Q

Suggest one disadvantage of using these weed killers on weeds growing in a crop

A
  • Reduced grow
  • Slows respiration
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