How do you rank these molecules in order by relative size?

Question

From smallest to biggest: glucose molecules, water molecules, IKI molecules, membrane pores, starch molecules?

Answer 1

First, we're going to have to talk about what you mean by SIZE. There are two ways that we can consider size when it comes to molecules. One is mass, (molecular weight in daltons) and another is volume. This is actually interesting when it comes to some of the molecular species you've mentioned.

Taking these items in the order in which you stated them, let's think about what they are and what order of magnitude they are in size relative to eachother.

First, consider glucose. Glucose is a ring shaped molecule made from 6 carbons. It is a "carbohydrate" meaning that it has an equal proporation of carbon and water in its molecular accounting. Glucose is C6H12O6.

Water, next, is H2O, so clearly glucose is more than 6 times as large since there are the equivalent of 6 water molecules in one molecule of glucose and then there are even 6 more carbon atoms.

IKI is just iodine potassium iodide, if i remember correctly. The molecular formula is exactly that which you see, namely "IKI". Where does this fit in relation to glucose and water? Well, Iodine has a molecular weight of 53, and potassium has a molecular weight of 19 so that IKI weighs 125. H2O weighs 10 (2 hydrogens at 1 each, and oxygen at 8). Therefore IKI is heavier than water. Interestingly, the glucose, which is made of lighter atoms than IKI, weighs in at only 96. IKI is therefore a heavier molecule than glucose, too. However, glucose, which has more neuclei and more bonds is a significantly larger structure. If by "size" you mean mass, then IKI is bigger, if on the other hand you mean "diameter" then glucose is bigger. I will choose to go by mass.

Cellular membrane pores are large protein molecules, with complex 3D structure. These types of compounds are called macromolecules and weigh in in the 10's of thousands, so concluding that these are bigger than the above 3 molecular species is a no-brainer. The question is then reduced to which of the two, protein or starch macromolecules, tends to be larger.

Well, it turns out that although a membrane proteins may be in the molecular weight range of 20,000, starches are in the hundreds of thousands. These are really enormous. starches are long chains, often long feathery branched chains, of sugar upon sugar.

The final result then from smallest to largest (by molecular weight):

1) water
2) glucose
3) iodine potassium iodide
4) membrane pores
5) starch

However, if you go by volume, then you would need to switch the positions of numbers 2 and 3.

Hope that helps.

Please don't just cut and paste this into your homework! ;)

Answer 2

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RE:
How do you rank these molecules in order by relative size?
From smallest to biggest: glucose molecules, water molecules, IKI molecules, membrane pores, starch molecules?

Answer 3

This is from a typical osmosis experiment and you don't care about the molecular weight but for the actual 3D structure.

IKI is a solution of I2 and KI. Iodine is not very soluble in water, that's why you also have KI. I2 reacts with I(-) from KI forming the soluble complex I3(-). In solution K(+) has dissociated from the ion and you are interested in I3(-) because that is coloured and will give the blue colour with starch.

Though I is heavier than C and O the total number of atoms and bonds in glucose (C6H12O6) is greater than in I3(-) so the molecule of glucose is bigger.

Membrane pores are not molecules but anyway you want to see what can pass through them

Starch is a glucose polymer

the order is usually
water < IKI (I3(-)) < glucose < membrane pores < starch.

However depending on the membrane you have different pore size, so you could actually have
water < IKI (I3(-)) < membrane pores < glucose < starch

Answer 4

Molecular Weight Of Ki

Answer 5

How big is a iodine molecule?

Answer 6

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Answer 7

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Answer 8

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Answer 9

Was thinking to ask this question too

Answer 10

1. water molecules
2. IKI molecules (not sure what this is)
3. pores
4. glucose
5. starch