[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.00,0:00:06.04,Default,,0000,0000,0000,,(MUSIC)
Dialogue: 0,0:00:06.46,0:00:11.13,Default,,0000,0000,0000,,When we were kids, growing up in West Texas, our winters would be cold, but rarely experienced
Dialogue: 0,0:00:11.13,0:00:12.13,Default,,0000,0000,0000,,snow.
Dialogue: 0,0:00:12.13,0:00:14.88,Default,,0000,0000,0000,,But we did have ice, which resulted in the roads being salted.
Dialogue: 0,0:00:14.88,0:00:19.66,Default,,0000,0000,0000,,As the salt mixes in and dissolves into water on the road, this can lead to a lower freezing
Dialogue: 0,0:00:19.66,0:00:22.76,Default,,0000,0000,0000,,point, which can help prevent the roads from icing over.
Dialogue: 0,0:00:22.76,0:00:26.78,Default,,0000,0000,0000,,And while this is great for making the roads more safe, it wasn’t so great for the plants
Dialogue: 0,0:00:26.78,0:00:28.74,Default,,0000,0000,0000,,that lived right along the roadside.
Dialogue: 0,0:00:28.74,0:00:30.58,Default,,0000,0000,0000,,It often caused them to die.
Dialogue: 0,0:00:30.58,0:00:35.55,Default,,0000,0000,0000,,Now winter can be hard for many plant species, but I’m talking about this salt affecting
Dialogue: 0,0:00:35.55,0:00:37.82,Default,,0000,0000,0000,,even some hardy plant life.
Dialogue: 0,0:00:37.82,0:00:41.44,Default,,0000,0000,0000,,This issue with salt and plants isn’t limited to winter.
Dialogue: 0,0:00:41.44,0:00:46.54,Default,,0000,0000,0000,,During hurricanes near the coast, salty ocean water can be dumped in large quantities into the
Dialogue: 0,0:00:46.54,0:00:47.54,Default,,0000,0000,0000,,soil.
Dialogue: 0,0:00:47.54,0:00:49.92,Default,,0000,0000,0000,,This can eventually kill plants- including
Dialogue: 0,0:00:49.92,0:00:53.20,Default,,0000,0000,0000,,trees- that had originally survived the hurricane.
Dialogue: 0,0:00:53.20,0:00:54.31,Default,,0000,0000,0000,,Why?
Dialogue: 0,0:00:54.31,0:00:57.02,Default,,0000,0000,0000,,Do plants just dislike salt that much?
Dialogue: 0,0:00:57.02,0:01:00.91,Default,,0000,0000,0000,,Well, it's actually related to a term called osmosis.
Dialogue: 0,0:01:00.91,0:01:05.17,Default,,0000,0000,0000,,When you are talking about osmosis, you are talking about the movement of water through a
Dialogue: 0,0:01:05.17,0:01:08.37,Default,,0000,0000,0000,,semi-permeable membrane, like a cell membrane.
Dialogue: 0,0:01:08.37,0:01:13.02,Default,,0000,0000,0000,,Water molecules are so small that they can travel through the cell membrane unassisted,
Dialogue: 0,0:01:13.02,0:01:18.00,Default,,0000,0000,0000,,or they can travel in larger quantities through protein channels like aquaporins.
Dialogue: 0,0:01:18.00,0:01:22.17,Default,,0000,0000,0000,,The movement of water molecules traveling across a cell membrane is passive transport,
Dialogue: 0,0:01:22.17,0:01:25.43,Default,,0000,0000,0000,,which means, it does not require energy.
Dialogue: 0,0:01:25.43,0:01:30.74,Default,,0000,0000,0000,,In osmosis, water molecules travel from areas of a high concentration (of water molecules)
Dialogue: 0,0:01:30.74,0:01:33.02,Default,,0000,0000,0000,,to a low concentration (of water molecules).
Dialogue: 0,0:01:33.02,0:01:36.86,Default,,0000,0000,0000,,But there’s another way to think about water movement in osmosis.
Dialogue: 0,0:01:36.86,0:01:42.82,Default,,0000,0000,0000,,A low water concentration likely means there is a greater solute concentration.
Dialogue: 0,0:01:42.82,0:01:48.56,Default,,0000,0000,0000,,Solutes are substances like salt or sugar that can be dissolved within a solvent like
Dialogue: 0,0:01:48.56,0:01:49.56,Default,,0000,0000,0000,,water.
Dialogue: 0,0:01:49.56,0:01:55.57,Default,,0000,0000,0000,,Water has the tendency to move to areas where there is a higher solute concentration, which
Dialogue: 0,0:01:55.57,0:01:58.59,Default,,0000,0000,0000,,would mean less water concentration.
Dialogue: 0,0:01:58.59,0:02:03.82,Default,,0000,0000,0000,,So, if you want to easily figure out where the water will travel in osmosis, look to the side
Dialogue: 0,0:02:03.82,0:02:07.26,Default,,0000,0000,0000,,where there is a greater solute concentration.
Dialogue: 0,0:02:07.26,0:02:11.55,Default,,0000,0000,0000,,Unless we bring in another variable, like pressure, water will generally have a net
Dialogue: 0,0:02:11.55,0:02:14.90,Default,,0000,0000,0000,,movement to the area of higher solute concentration.
Dialogue: 0,0:02:14.90,0:02:16.29,Default,,0000,0000,0000,,So, let’s bring out a U-tube!
Dialogue: 0,0:02:16.29,0:02:17.30,Default,,0000,0000,0000,,Ha, U-tube.
Dialogue: 0,0:02:17.30,0:02:18.32,Default,,0000,0000,0000,,That’s funny.
Dialogue: 0,0:02:18.32,0:02:21.15,Default,,0000,0000,0000,,There’s a semi-permeable membrane in the middle of it.
Dialogue: 0,0:02:21.15,0:02:26.08,Default,,0000,0000,0000,,Let’s assume that it is similar to a cell membrane and that water molecules can squeeze
Dialogue: 0,0:02:26.08,0:02:29.68,Default,,0000,0000,0000,,through it—the molecules are quite small—but salt can’t.
Dialogue: 0,0:02:29.68,0:02:33.01,Default,,0000,0000,0000,,Right now, there is just water in this U-tube.
Dialogue: 0,0:02:33.01,0:02:36.36,Default,,0000,0000,0000,,The water levels on side A and side B are equal.
Dialogue: 0,0:02:36.36,0:02:39.91,Default,,0000,0000,0000,,That doesn’t mean that the water molecules aren’t moving---water molecules like to
Dialogue: 0,0:02:39.91,0:02:43.21,Default,,0000,0000,0000,,move---but the net movement across the two\Nsides is zero.
Dialogue: 0,0:02:43.21,0:02:47.02,Default,,0000,0000,0000,,That means, the overall change in the direction of movement is zero.
Dialogue: 0,0:02:47.02,0:02:52.91,Default,,0000,0000,0000,,Now let’s imagine on side B, you dump a huge amount of salt there.
Dialogue: 0,0:02:52.91,0:02:59.40,Default,,0000,0000,0000,,So, which direction will the water initially move towards, A or B?
Dialogue: 0,0:02:59.40,0:03:01.87,Default,,0000,0000,0000,,Think about what we mentioned with osmosis.
Dialogue: 0,0:03:01.87,0:03:04.44,Default,,0000,0000,0000,,The answer is B!
Dialogue: 0,0:03:04.44,0:03:11.08,Default,,0000,0000,0000,,Side B has a higher solute concentration than side A. Water moves to areas of higher solute
Dialogue: 0,0:03:11.08,0:03:14.20,Default,,0000,0000,0000,,concentration, which is also the area of lower water concentration.
Dialogue: 0,0:03:14.20,0:03:20.34,Default,,0000,0000,0000,,You will also see the water level on side B rise as the water moves to that area.
Dialogue: 0,0:03:20.34,0:03:25.63,Default,,0000,0000,0000,,You can almost think of the water as trying to equalize the concentrations diluting
Dialogue: 0,0:03:25.63,0:03:30.54,Default,,0000,0000,0000,,side B. Once equilibrium is reached, the net movement of water across the two sides will
Dialogue: 0,0:03:30.54,0:03:35.08,Default,,0000,0000,0000,,be zero, but remember that water still likes to move and movement still occurs.
Dialogue: 0,0:03:35.08,0:03:40.84,Default,,0000,0000,0000,,Now here’s some vocabulary to add in here---we call side B hypertonic.
Dialogue: 0,0:03:40.84,0:03:44.79,Default,,0000,0000,0000,,That means higher solute concentration!
Dialogue: 0,0:03:44.79,0:03:49.24,Default,,0000,0000,0000,,But we can’t just say something is hypertonic without comparing it to something else.
Dialogue: 0,0:03:49.24,0:03:55.45,Default,,0000,0000,0000,,We say side B is hypertonic to side A because it has a higher solute concentration than
Dialogue: 0,0:03:55.45,0:04:00.56,Default,,0000,0000,0000,,side A. In osmosis, water moves to the hypertonic side.
Dialogue: 0,0:04:00.56,0:04:08.74,Default,,0000,0000,0000,,We say side A is hypotonic (hypo rhymes with low which helps me remember that it is the low solute concentration)
Dialogue: 0,0:04:08.74,0:04:12.55,Default,,0000,0000,0000,,when compared to side B. Let’s get a little more real life now instead
Dialogue: 0,0:04:12.55,0:04:13.55,Default,,0000,0000,0000,,of just the U-tube.
Dialogue: 0,0:04:13.55,0:04:18.47,Default,,0000,0000,0000,,As you know, water is important for your body and many processes that occur in the body.
Dialogue: 0,0:04:18.47,0:04:23.56,Default,,0000,0000,0000,,When someone gets an IV in a hospital, it may look like the fluid in the IV is just
Dialogue: 0,0:04:23.56,0:04:24.56,Default,,0000,0000,0000,,pure water.
Dialogue: 0,0:04:24.56,0:04:26.30,Default,,0000,0000,0000,,But it is certainly not pure water.
Dialogue: 0,0:04:26.30,0:04:29.04,Default,,0000,0000,0000,,That would be a disaster because of osmosis, let’s explain.
Dialogue: 0,0:04:29.04,0:04:32.68,Default,,0000,0000,0000,,Let’s say hypothetically pure water was in an IV.
Dialogue: 0,0:04:32.68,0:04:37.81,Default,,0000,0000,0000,,Now an IV tube typically runs through a vein, so that you have access to your blood stream,
Dialogue: 0,0:04:37.81,0:04:40.31,Default,,0000,0000,0000,,really useful for running medication through.
Dialogue: 0,0:04:40.31,0:04:44.12,Default,,0000,0000,0000,,Blood actually consists of many different types of components and red blood cells are
Dialogue: 0,0:04:44.12,0:04:45.73,Default,,0000,0000,0000,,a great example.
Dialogue: 0,0:04:45.73,0:04:49.21,Default,,0000,0000,0000,,So, what do you think has a higher solute concentration,
Dialogue: 0,0:04:49.21,0:04:52.85,Default,,0000,0000,0000,,the hypothetical pure water in this IV tube
Dialogue: 0,0:04:52.85,0:04:54.66,Default,,0000,0000,0000,,or the red blood cells?
Dialogue: 0,0:04:54.66,0:04:58.60,Default,,0000,0000,0000,,Well, cells are not empty vessels, they contain solutes.
Dialogue: 0,0:04:58.60,0:05:02.71,Default,,0000,0000,0000,,The pure water that hypothetically is running through this IV tube has no solutes.
Dialogue: 0,0:05:02.71,0:05:04.89,Default,,0000,0000,0000,,So, where does the water go?
Dialogue: 0,0:05:04.89,0:05:11.21,Default,,0000,0000,0000,,It goes to the area of higher solute concentration which in this case is inside the cells.
Dialogue: 0,0:05:11.21,0:05:16.26,Default,,0000,0000,0000,,The cells are hypertonic compared to the pure water in the IV tube because the cells have
Dialogue: 0,0:05:16.26,0:05:18.62,Default,,0000,0000,0000,,a greater solute concentration,
Dialogue: 0,0:05:18.62,0:05:21.38,Default,,0000,0000,0000,,the cells would swell and possibly burst!
Dialogue: 0,0:05:21.38,0:05:22.75,Default,,0000,0000,0000,,Exploding red blood cells are not good.
Dialogue: 0,0:05:22.75,0:05:27.14,Default,,0000,0000,0000,,If a person needs fluids, they typically will receive a solution that is isotonic to their
Dialogue: 0,0:05:27.14,0:05:29.06,Default,,0000,0000,0000,,blood plasma.
Dialogue: 0,0:05:29.06,0:05:33.85,Default,,0000,0000,0000,,Isotonic means equal concentration, so you won’t have any swelling or shrinking red
Dialogue: 0,0:05:33.85,0:05:34.85,Default,,0000,0000,0000,,blood cells.
Dialogue: 0,0:05:34.85,0:05:37.06,Default,,0000,0000,0000,,Another example, let’s talk about the aquarium.
Dialogue: 0,0:05:37.06,0:05:41.19,Default,,0000,0000,0000,,I have always wanted a saltwater fish tank, ever since I was a little kid.
Dialogue: 0,0:05:41.19,0:05:42.93,Default,,0000,0000,0000,,But I’ve only had freshwater tanks
Dialogue: 0,0:05:42.93,0:05:44.02,Default,,0000,0000,0000,,so far.
Dialogue: 0,0:05:44.02,0:05:48.30,Default,,0000,0000,0000,,I did often question when I was a kid, why is it that a saltwater fish can’t be in
Dialogue: 0,0:05:48.30,0:05:49.38,Default,,0000,0000,0000,,my freshwater tank?
Dialogue: 0,0:05:49.38,0:05:53.28,Default,,0000,0000,0000,,Well, let me explain one reason why this would be dangerous to a saltwater fish and how it
Dialogue: 0,0:05:53.28,0:05:55.49,Default,,0000,0000,0000,,relates to osmosis.
Dialogue: 0,0:05:55.49,0:05:59.08,Default,,0000,0000,0000,,First ask---where is there a higher solute concentration?
Dialogue: 0,0:05:59.08,0:06:00.93,Default,,0000,0000,0000,,In the saltwater fish cells
Dialogue: 0,0:06:00.93,0:06:05.46,Default,,0000,0000,0000,,or in the freshwater that the fish would be hypothetically placed in?
Dialogue: 0,0:06:05.46,0:06:07.41,Default,,0000,0000,0000,,Definitely in the saltwater fish cells.
Dialogue: 0,0:06:07.41,0:06:08.86,Default,,0000,0000,0000,,So, where would the water go?
Dialogue: 0,0:06:08.86,0:06:14.41,Default,,0000,0000,0000,,It goes to the area where there is a higher solute concentration----the hypertonic side----so
Dialogue: 0,0:06:14.41,0:06:17.22,Default,,0000,0000,0000,,it goes into the cells of that poor saltwater fish.
Dialogue: 0,0:06:17.22,0:06:19.09,Default,,0000,0000,0000,,If not rescued, it could die.
Dialogue: 0,0:06:19.09,0:06:24.71,Default,,0000,0000,0000,,Now one thing to clarify: saltwater fish and freshwater fish are not necessarily isotonic to
Dialogue: 0,0:06:24.71,0:06:25.71,Default,,0000,0000,0000,,their surroundings.
Dialogue: 0,0:06:25.71,0:06:30.55,Default,,0000,0000,0000,,But they have special adaptations that allow them to live in their environment and usually
Dialogue: 0,0:06:30.55,0:06:35.15,Default,,0000,0000,0000,,cannot make a major switch from a saltwater environment to a freshwater one.
Dialogue: 0,0:06:35.15,0:06:37.81,Default,,0000,0000,0000,,Now---not all fish have this problem.
Dialogue: 0,0:06:37.81,0:06:43.69,Default,,0000,0000,0000,,There are some fish that have this amazing adaptations to switch between fresh and salt water, and
Dialogue: 0,0:06:43.69,0:06:45.92,Default,,0000,0000,0000,,they have to deal with this osmosis problem.
Dialogue: 0,0:06:45.92,0:06:47.16,Default,,0000,0000,0000,,Salmon for example.
Dialogue: 0,0:06:47.16,0:06:50.88,Default,,0000,0000,0000,,I think if I could pick to be a fish, I’d be a salmon.
Dialogue: 0,0:06:50.88,0:06:51.88,Default,,0000,0000,0000,,Osmosis 
Dialogue: 0,0:06:51.88,0:06:54.51,Default,,0000,0000,0000,,explains how many kinds of plants get their water.
Dialogue: 0,0:06:54.51,0:06:56.23,Default,,0000,0000,0000,,Sure, many plants have roots.
Dialogue: 0,0:06:56.23,0:06:58.73,Default,,0000,0000,0000,,But how does the water get into the roots?
Dialogue: 0,0:06:58.73,0:07:01.69,Default,,0000,0000,0000,,When it rains, the soil becomes saturated with water.
Dialogue: 0,0:07:01.69,0:07:06.37,Default,,0000,0000,0000,,The root hair cells generally have a higher concentration of solutes within them than
Dialogue: 0,0:07:06.37,0:07:09.34,Default,,0000,0000,0000,,the solute concentration in the saturated soil.
Dialogue: 0,0:07:09.34,0:07:14.31,Default,,0000,0000,0000,,The water travels into the root hair cells as the root hair cells are hypertonic compared to
Dialogue: 0,0:07:14.31,0:07:15.56,Default,,0000,0000,0000,,the hypotonic soil.
Dialogue: 0,0:07:15.56,0:07:21.79,Default,,0000,0000,0000,,By the way, you may wonder---well, why don’t those root hair cells burst with all the
Dialogue: 0,0:07:21.79,0:07:23.41,Default,,0000,0000,0000,,water that is going in them.
Dialogue: 0,0:07:23.41,0:07:28.86,Default,,0000,0000,0000,,That brings us to our next osmosis topic and why plant cell walls are amazing!
Dialogue: 0,0:07:28.86,0:07:34.98,Default,,0000,0000,0000,,So, let’s bring in another variable that can influence osmosis: pressure potential.
Dialogue: 0,0:07:34.98,0:07:40.37,Default,,0000,0000,0000,,This is when it’s very useful to understand how one can calculate water potential.
Dialogue: 0,0:07:40.37,0:07:45.80,Default,,0000,0000,0000,,Water potential considers both solute potential AND pressure potential.
Dialogue: 0,0:07:45.80,0:07:50.08,Default,,0000,0000,0000,,In osmosis, water travels to areas of lower water potential.
Dialogue: 0,0:07:50.08,0:07:55.92,Default,,0000,0000,0000,,So, the formula is water potential is equal to the pressure potential plus the solute potential.
Dialogue: 0,0:07:55.92,0:08:00.62,Default,,0000,0000,0000,,Adding solute actually causes the solute potential to have a negative value and the overall water
Dialogue: 0,0:08:00.62,0:08:02.96,Default,,0000,0000,0000,,potential to lower.
Dialogue: 0,0:08:02.96,0:08:06.48,Default,,0000,0000,0000,,Water will travel to areas of lower water potential.
Dialogue: 0,0:08:06.48,0:08:12.60,Default,,0000,0000,0000,,But exerting pressure can raise the pressure potential, a positive value, therefore raising
Dialogue: 0,0:08:12.60,0:08:13.86,Default,,0000,0000,0000,,the total water potential.
Dialogue: 0,0:08:13.86,0:08:16.43,Default,,0000,0000,0000,,So, let’s give a quick example.
Dialogue: 0,0:08:16.43,0:08:20.98,Default,,0000,0000,0000,,In the popular water potential in potato cores lab---all kinds of neat variations of this
Dialogue: 0,0:08:20.98,0:08:26.90,Default,,0000,0000,0000,,lab procedure exist online---you can calculate the water potential in potato cores using
Dialogue: 0,0:08:26.90,0:08:28.89,Default,,0000,0000,0000,,the water potential formula.
Dialogue: 0,0:08:28.89,0:08:34.45,Default,,0000,0000,0000,,When a potato core is first put into distilled water—that’s pure water---the potato core
Dialogue: 0,0:08:34.45,0:08:36.34,Default,,0000,0000,0000,,cells start to gain water.
Dialogue: 0,0:08:36.34,0:08:37.77,Default,,0000,0000,0000,,You’d expect that.
Dialogue: 0,0:08:37.77,0:08:40.27,Default,,0000,0000,0000,,The water is moving towards the higher solute concentration.
Dialogue: 0,0:08:40.27,0:08:46.03,Default,,0000,0000,0000,,Thanks to their higher solute concentration, they have a lower solute potential.
Dialogue: 0,0:08:46.03,0:08:50.82,Default,,0000,0000,0000,,That means a lower total water potential than the surroundings and water travels to areas
Dialogue: 0,0:08:50.82,0:08:53.02,Default,,0000,0000,0000,,of lower water potential.
Dialogue: 0,0:08:53.02,0:08:58.34,Default,,0000,0000,0000,,But over time as the potato core cells gain water, the water that has entered exerts pressure
Dialogue: 0,0:08:58.34,0:09:02.71,Default,,0000,0000,0000,,against the plant cell walls from inside the plant cells,
Dialogue: 0,0:09:02.71,0:09:07.28,Default,,0000,0000,0000,,therefore raising the overall water potential in the potato core cells.
Dialogue: 0,0:09:07.28,0:09:12.17,Default,,0000,0000,0000,,We want to point out that this turgor pressure that results in plant cells, thanks to osmosis
Dialogue: 0,0:09:12.17,0:09:17.21,Default,,0000,0000,0000,,and plant cell walls, is critical for overall plant structure and the ability of plants
Dialogue: 0,0:09:17.21,0:09:19.88,Default,,0000,0000,0000,,to grow upright and not wilt.
Dialogue: 0,0:09:19.88,0:09:22.49,Default,,0000,0000,0000,,Turgor pressure is definitely something to explore.
Dialogue: 0,0:09:22.49,0:09:25.74,Default,,0000,0000,0000,,In summary, where would living organisms be without osmosis?
Dialogue: 0,0:09:25.74,0:09:32.23,Default,,0000,0000,0000,,After all, it involves movement of one of our very valuable resources: water.
Dialogue: 0,0:09:32.23,0:09:35.08,Default,,0000,0000,0000,,Well, that’s it for the Amoeba Sisters and we remind you to stay curious!