Science Video - Biology

• Science Video
• Biology
• High Intermediate / Advanced Listening

Before you listen, check these words in a dictionary:

• nematode
• paralyzed
• molecular switch
• U-V Light
• charge
• electron

Part 1: Listen for Gist

The key point about the presentation is that

A) Nematodes can change color.
B) Light can stop a worm form moving.
C) Chemicals turn blue under UV light.

Part 2: Listen for Gist

1. The nematodes change color:

A) Quickly
B) Slowly.
C) Immediately.

2. The nematodes turn blue because:

A) They are paralyzed by UV light.
B) The molecules change shape.
C) The chemical inside them changes.

3. Branda says the worms are paralyzed because

A) The molecule take energy from the worm’s cells.
B) The changed molecule stops the worm from breathing.
C) The molecule’s new shape interferes with the worm’s nerves.

4.All the worms recover from the paralysis.
The molecule’s new shape interferes with the worm’s nerves

A) TRUE.
B) FALSE.

5. The research has been going on for a while.

A) TRUE.
B) FALSE.

6. The goal is to better control medicine in people.

A) TRUE.
B) FALSE.

Source: Science Friday

Script

I know it may not seem like fun reading material, but look at these key words. Let me give you a quick reenactment.

A couple of scientists took a worm. Not just any worm, specifically a nematode. C. Elegans. It’s about this size in relation to a flea and it’s used all the time for scientific experiments. And then the scientists feed the worm a chemical. No, not actually like that. They stick it in a bath with the chemical and the worm slurps it up – more like that. Next, they shine UV light on the worm. And here’s where it gets good. After the UV light, the worm turns blue and becomes paralyzed. If stun gun applications are coming to mind, halt.

“The goal was not to paralyze worms” - that’s chemist Neil Branda who headed up the study. “The goal was to show we can turn off and on a biological function.” – using a light-sensitive chemical – “called dithienylethene” – that’s hard to say so – “We just refer to them as molecular photo switches”.

These chemicals change in the presence of certain types of light. “The light is absorbed and that triggers a photochemical reaction” A reaction that can do things like change the chemical’s color – in this case the chemical turns blue under UV light and turns the worm blue with it. “The color change is almost instantaneous”

UV light also changes this chemical’s molecular shape. . . . And . . . “It changes the way the molecules can accept the charge” – which is bad for these guys.  Branda hypothesizes that the changed chemical hijacks electrons from the cell’s energy-generating pathways and the result is this . . . a paralyzed nematode. Until the nematade is shined with visible light. At which point the chemical changes back and the nematodes start squirming again – although results may vary. “Some of the worms woke up very quickly, other worms never did.” But just the fact that some woke up at all is noteworthy. Branda says that turning the biological function – in this case paralysis – on and then off, using light, is new. The idea is down the road, way down, “This is really early days research” You could use this in higher-level organisms and design drugs that could be turned on and off with a light switch.

For science Friday, I’m Flora Lichtman.

Part 1 Answers
1. B

Part 2 Answers

1. C
2. C
3. A

4. False

5. False

6. True