Unformatted text preview: s expensive to dehydrate with all the water that’s around)
Proteins are also formed by condensation
and broken down by hydrolysis.
This makes it expensive to make a protein (maybe 300 amino acids).
But proteins are much more expensive to make than
you’d think, if hydration were the only problem
---- wonder why? Protein = a speciﬁc polymer of amino acids
end And popping out of that “backbone” is also a simple repea5ng structure of H’ s and O’ s
(we’ re ignoring the R
groups)… NH3+ end HO HO HO HO + H NCCNCCNCCNCCNCCNCCNCCNCCO- H HO HO HO HO This backbone structure by itself helps the protein fold into “ secondary
forming ﬂat planes, or rigid cylinders. These planes and
cylinders are stabilized by hydrogen bonds between the repea5ng N
C=O groups in the backbone. The “backbone” is a very simple repea5ng structure… NCCNCCNCC
Protein sequences are always wri[en star5ng with the N terminus. The R groups inﬂuence whether the protein will fold into a cylinder or
sheet (or “random” loop), but the hydrogen bonds within the backbone
itself hold these secondary structures together. What’s a hydrogen bond?
• A hydrogen bond is sort of a baby polar bond, and
sort of a way for two atoms to share a single H.
For example: View Youtube v ideo, if we’re lucky Hydrogen bonds are weak interac5ons
not at all like covalent bonds. But
they can really add up… The N
H and carbonyl (C=O) groups in a protein can H bond to each other
to produce either ﬂat sheets or rigid rods.
Although any one H bond is quite weak, many bonds can collaborate to
form a stable structure. HO HO HO Figure 3.6 The Four Levels of
Protein Structure HO + H NCCNCCNCCNCCNCCNCCNCCNCC H HO
Alpha helix The serpen5ne winding shown here will...
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