생물학에서 확산과 삼투의 이해

### AP 생물학 실험실의 확산과 삼투 1
* 📚 확산은 고농도 영역에서 저농도 영역으로 분자가 이동하는 것을 말하며, **삼투는 반투과성 막을 통해 물만 이동하는 특정 유형의 확산**입니다.
* 💧 확산 실험에서는 물, 포도당, 전분으로 채워진 투석 튜브를 물과 IKI가 들어있는 비커에 넣습니다. 약 **40분 동안 그대로 두면 튜브 안팎의 포도당과 전분의 존재**를 IKI로 인한 색상 변화를 통해 유추할 수 있습니다.
* 🥔 감자 실험에서는 감자를 캐서 당 농도(0.0, 0.2, 0.4, 0.6, 0.8, 1.0 몰)가 다른 비커에 넣는 과정을 거칩니다. 감자는 **증류수와 저농도 용액에서는 삼투를 통해 물이 이동하여 질량이 증가**하는 반면, **고농도 용액에서는 물이 빠져나가면서 질량이 감소**합니다.
* 📈 감자의 질량 변화와 당 농도를 비교하여 그래프로 표시하면 **질량의 순 변화가 없는 감자의 몰도**를 확인할 수 있습니다.
* ❓ 확산 실험에서 논의되지 않은 한 가지는 물의 움직임이었는데, 이는 **시스템의 전후 질량을 측정**하여 확인할 수 있었습니다.
* "다시 말해, 투석 튜브 내부의 구멍이 **IKI보다 더 큰가요?** 물론, IKI는 바깥쪽에서 안으로 움직일 수 있었기 때문입니다. **전분보다 더 큰가요?** 아니요, 전분은 빠져나갈 수 없기 때문입니다."
* 📏 투석 튜브가 있는 확산 실험실과 감자 실험실은 **확산과 삼투의 개념을 실제로 시연**하는 데 도움이 되는 실용적인 실험입니다.

확산과 삼투는 AP 생물학 실험실 1에서 분자와 물의 움직임을 통해 시연됩니다.

Hi, it's Mr. Andersen. And welcome
to the AP Biology Lab 1 walkthrough. This lab is on two things. It's on diffusion and
osmosis. And the diffusion portion of this lab we're actually just going to do a demonstration.
And the osmosis lab we'll do the potato lab. So we're going to put potatoes in different
concentrations of sugar water. But let me quickly define what diffusion and osmosis
are. Diffusion is going to be movement of molecules from an area of high concentration
to low concentration. So if I were to remove this lid on the top of the perfume, the perfume
molecules are going to move from an area of high concentration inside the bottle to low
concentration, in the air. And so pretty soon you'd be able to smell that perfume just due
to diffusion. Now osmosis is a specific type of diffusion. It's movement of water. And
so we're going to study that in this lab using

potatoes and sugar water. And so let me go
into a little more depth on those two processes. First one is diffusion. Diffusion is, best
example would be right here. Let's say we have this jar. And this jar is separated in
the middle using a membrane. And that membrane is porous. In other words, it allows material
to move back and forth. Well, if I were to let it sit here at time 0 and come back at
time 15 minutes, what we're going to find is that on this side we have sugar water. On
this side, we could have less sugar water. Or almost distilled water on this side. If
we let it sit for 15 minutes, however, those sugar molecules are going to start to migrate
over here on to this side. So when we come back, it's going to be in equal concentration
of sugar on either side. Now the water would have also been flowing. But the water and
the sugar are going to move back and forth.

and it's essentially going to be isotonic
on either side of that membrane. That's diffusion. It's simply movement of molecules from an
area of high to an area of low concentration. Now osmosis is a specific type of diffusion.
It's the movement of only water across a semi-permeable membrane. So how does that work? Well let's
say we have the same set up. Different container. But it's got semi-permeable membrane down
the middle. This only allows the movement of water, but it doesn't allow the movement
of those solute molecules. Well, you can see right here that this side over here is going
to be hypertonic. In other words, it has more solute on that side, and less water. This
side over here is going to be hypotonic. And so if we let it sit now for another 15 minutes,
it's going to magically raise on this side. And the reason why is that water is going
to flow from an area of high water concentration

to low water concentration. Now what aren't
the sugar molecules moving? It's because they can't move through that membrane. And so this
would be osmosis. It would be the flow of water across a semi-permeable membrane. And
so we'll see how that plays out in just a second. And so the first part of this lab
is the diffusion lab. In this diffusion lab, we're going to do essentially a quick demonstration.
And so to do this, you're going to use dialysis tubing. So we're going to have dialysis tubing
on this side. Dialysis tubing is a little bit of tubing that's used in kidney dialysis.
It's essentially, it looks just like plastic but it's going to have tiny little holes in
it. Tiny little pores in it that you can't see. And then we're going to have a beaker.
Now in the beaker, we're going to put water or H2O. And then we're going to put a chemical
called IKI. IKI essentially has iodine inside

of it. So in the beaker, all we've got is water and IKI. Inside the dialysis tubing, we're going to have water. We're going to have glucose. Glucose, remember, is a simple sugar. It's a monosaccharide. So it's going to just have one sugar. We could test for the presence of glucose using something called testate. We put it into the solution. We're going to find that there's going to be glucose inside there. And then we're going to have starch. Now, starch is a polysaccharide. So instead of just one sugar molecule, it's going to be sometimes hundreds if not thousands of sugar molecules that are attached together. Starch is going to be that sugar that you find in stuff like pasta. And so inside here, we've got water, starch, and glucose. Outside, no glucose. Now we're going to let it sit for, I do this during class. So we let it sit for about 40 minutes. Before I show you what happens.

I should also remind you of this. We can test for the presence of glucose using test tape, which is simply a little bit. It almost looks like litmus paper. But to test for the presence of starch, if IKI and starch are ever in the same place at the same time, it's going to turn this bluish color. So let's see what happens. An hour later, it's going to look like this. And so in class, I ask students to figure out, you know, what's going on? Why do we get this blue color on the inside? What has moved back and forth? And so basically when we test it when it's done, we'll find that there's glucose again inside the dialysis tubing. Makes sense because it was there before. There's starch, there's water. But we can infer that IKI has moved inside. And how do we know that? Well, starch and IKI, if they're

ever in the same place at the same time, we're
going to get this blue color. On the outside, we could test, and we'll find that there's
a presence of glucose inside here. There's IKI like there was before. There's water.
But there's no starch on the outside. How do we know there's no starch? Well, there's
no blue color on the outside. And so we could figure out the size of all these molecules
in relation to the sizes in the holes in the dialysis tubing. In other words, are the holes
inside the dialysis tubing bigger than the IKI? For sure, because the IKI was able to
move on the outside in. Are they bigger than the starch? No, because the starch is not
able to make its way out. And so what we're showing here is diffusion. What's the one
thing that we didn't talk about the movement of? That would be water. In order to figure
out if water is moving or not, we'd have to

mass it before and mass it after, and see if
there's a change in mass. Alright. Let's get to the actual potato lab. In the potato lab,
what you're going to do is you're going to core potatoes. So you're going to basically
cut out a little core of a potato like that. We usually use about 3 of those inside there.
And then you're going to put them into a beaker that's containing different amounts of sugar
concentration. And so we're going to put it in distilled water: 0 molar, 0.2, 0.4, 0.6,
0.8, and 1.0 molar. So this is a ton of sugar inside it. We're going to get the mass of
them on day 1. And then we're going to get the mass of them on day 2. So this would be
like the mass on day 1. This is the mass on

day 2. And so if we think about osmosis, and what's going on, well in the distilled water, you can see here that on day 1, the mass of those two potato cores was 4.74 grams. And then on day two, it's 6.14 grams. And so what's happening? Well, if you put the potatoes inside distilled water, they're gaining mass. Why are they gaining mass? It's due to osmosis. In other words, water is flowing into the potatoes because it's moving from an area of high water concentration outside the potato to low water concentration on the inside. Or from hypotonic to hypertonic. If we look at the 0.2, the 0.2 is also increasing mass. If we graph this out. But as we look at the 0.4, 0.6, 0.8, and 1.0, we find that it's actually losing mass.

In other words, it's shriveling out. Why is
that? Well, if we put it in real sugary water, high molarity water, what we're finding is
that now the water, instead of moving into the potato, is actually moving from the potato
out. And so you can see here that there's like a best fit line. If I were to draw it,
I'd put the best first line somewhere like that. And so basically what you can figure
out is that point at which this line crosses the axis, that would be 0% change in mass.
And so we can really figure out the molarity of the potato. Because if you took a potato with
the molarity of, I don't know what this is, like right around 0.3 molar, and we were to
put in 0.3 molar, it's going to have movement of water back and forth, but it's not going
to relatively change its mass. And so that's

the potato lab. That's diffusion. And I hope
that's helpful.

AP Biology Lab 1: Diffusion and Osmosis

Bozeman Science

AP 생물학 실험실에서 확산과 삼투의 이해

이 워크스루에서는 삼투를 연구하기 위해 확산을 시연하고 감자 실험을 수행하는 데 중점을 둡니다.

확산은 분자가 고농도에서 저농도로 이동하는 것으로, 설탕물을 이용한 병 실험을 통해 설명합니다.

특정 유형의 확산인 삼투는 반투과성 막을 가로지르는 물의 이동을 포함하며, 막이 있는 용기를 사용하여 다양한 농도 사이의 물의 흐름을 보여줍니다.

투석 튜브를 이용한 삼투 및 확산의 이해

당 분자는 투석관 막을 통과할 수 없기 때문에 삼투 과정을 거치게 됩니다.

확산 실험에서는 투석 튜브 내부에 물, IKI, 포도당, 전분을 넣고 외부에는 물과 IKI만 넣습니다.

40분 동안 그대로 두면 실험 결과를 통해 삼투와 확산의 원리를 확인할 수 있습니다.

포도당 및 전분 테스트: 실험실 실험

포도당의 존재는 테스트 테이프를 사용하여 테스트할 수 있으며, 전분의 존재는 IKI와 전분의 반응으로 푸르스름한 색으로 변하는 것으로 확인할 수 있습니다.

실험실 실험에서 투석 튜브를 통한 분자의 이동은 확산 과정을 보여 주며, 물도 이동에 관여한다는 것을 보여줍니다.

감자 심을 깍아 다양한 당 농도의 비커에 넣은 다음 1일째와 2일째에 무게를 측정합니다.

2 몰 농도에서 감자 코어는 높은 농도에서 낮은 농도로 삼투압으로 인해 질량이 증가합니다.

0 몰 농도의 비커에서는 감자 코어의 질량이 감소합니다.

몰수가 감자 질량 변화에 미치는 영향

몰수가 높은 물은 물이 감자 안으로 들어가지 않고 밖으로 이동하여 수축을 일으킵니다.

가장 잘 맞는 선이 축을 가로지르는 지점은 질량 변화가 0%를 나타내며, 이를 통해 감자의 몰수를 결정할 수 있습니다.

질량의 큰 변화 없이 물의 균형 잡힌 이동을 위해서는 약 0.