Question

are small proteins polar or non-polar? are they soluble in water?
are large proteins polar or non-polar? are they soluble in water?

Answer 1

can you come up with some examples of each?

Answer 2

I found out that smaller ones are very polar and dissolve, I'm assuming the opposite is true for large. My book is not very specific with examples!

Answer 3

yup, large ones (e.g. keratin) wont be soluble in water (i.e. will be non-polar).

Answer 4

Do you know out of lipids (fats), carbohydrates (sugars), small proteins and large proteins which should dissolve in methylene chloride?

Answer 5

hmm lipids

Answer 6

maybe large proteins too if non-polar

Answer 7

Okay, that's what I was thinking, but the chart in my book doesn't really explain it, so could you explain that process a little better?

Answer 8

well we know that "like-dissolves-like", and since methylene chloride (dichloromethane) is no soluble in water, we know it will be soluble in other non-polar solvents (and likewise will dissolve non-polar compounds).

Answer 9

So if a solvent is non-polar, it will dissolve other non-polar things.

Answer 10

Okay thank you so much! And...large proteins are the only ones out of the four that denature, correct? Which means the attractions in large proteins get interrupted, causing them to change shape and become less soluble?

Answer 11

yup! that sounds right. smaller proteins ( a few amino acids) will often be able to regain their conformation.


alot of other larger proteins are water soluble though because they form a globular shape exposing only polar amino acids to the outer, water environment