How do the following noncovalent interactions help to stabiliz...

Question

How do the following noncovalent interactions help to stabilize the tertiary and quaternary structure of a protein? Give an example of a pair of amino acids that could give rise to each interaction.

a. Hydrophobic interactions

Accepted Answer

Welcome back everyone. Our next problem says identify the non covalent interaction that results in proteins folding into a globe like shape, forming a water loving exterior give two examples of amino acids that will have this interaction. A hydrophobic interaction. Examples of amino acids that can form this interaction are vain and pyla amine b hydrophilic interaction. Examples of amino acids that can form this interaction are thine and glutamine. See ionic interaction. Examples of amino acids that can form this interaction are aspartic acid and Argen or D hydrogen bonding. Examples of amino acids that can form this interaction are asparagine and searing. So let's pick through the information we're given and see, think about what we're being asked for. So we know we're looking for a non covalent interaction. So we're not going to be talking about for instance, um disulfide bonds which are covalent bonds and this interaction results in a globe like shape. So we're talking about tertiary structure of the protein and tertiary structure is determined by our group interactions. So the secondary structure is formed by interactions between the atoms on the backbone of the protein. But the tertiary is determined by what kinds of R groups there are and we have this globular shape. Now, this question is a little bit tricky because it causes us to focus by saying there's a water loving exterior, it kind of points us to this hydrophilic exterior of our globe. And those amino acids on the exterior, there are groups will be polar or ionic and they will have hydrogen bonding with the water if it's in an aqueous solution. But although those things occur, the hydrogen bonds are not what determines the structure itself. What determines the structure is the hydrophobic interactions in the interior. And these occur between nonpolar our groups. And this can make sense if we think about the fact, if you think about a solution with oil and water, the oil will begin to gather together in droplets away from the water. And just like that, these nonpolar r groups cluster together away from the water in the solution forming this in these interior water free pockets. So these are water free pockets in the interior. So you can see how in that sense, the formation of those pockets leads to the globe like shape. Even though there are hydrogen bonding hydrophilic interactions going on on the outside. The shape itself is determined by the hydrophobic interactions. So our answer is going to be choice a hydrophobic interaction. Then just to double check it says examples of amino acids that can form this interaction are valine and phenylalanine. Well, these are indeed nonpolar amino acids, vine has a sort of isopropyl r group ch two with two methyl groups on it. So on hydrocarbons only not completely nonpolar and phelan phenylalanine or phe consists of ch two and then a benzene ring. So again, only carbon and hydrogen not completely nonpolar. So let's look at choice b hydrophilic interaction. So again, we will see hydrophilic interaction taking place hydrophilic interaction between polar uh our groups and water in the form of hydrogen bonding or even just polar interactions between partially positive, partially negatively charged uh atoms. But it is not what determines the shape. So we'll say it doesn't determine shape, even though they are present on the exterior and three ending and glutamine are polar R groups, they would participate in hydrophilic interaction. But again, since that's not what determines our shape. Choice B is not our answer toy says ionic interaction, this would occur when you have charged R groups as aspartic acid and arginine are spar acid having a carboxylic acid group that can carry a negative cocharge arginine having an NH two group that can pick up a proton and carry a positive charge. So these will have, you know, these interactions because they have, they're oppositely charged these salt bridges. But again, not what forms the shape. That's the nonpolar R groups. So choice C not our correct answer. And finally, choice, the hydrogen bonding, we know hydrogen bonding occurs when we have electron atoms bonded to hydrogen atoms, which is the case in aero gene that has an NH two group and sine that has an alcohol group on alcohol functional group on its R chain. So they are capable of hydrogen bonding. Those the strong difference in electronegativity makes extra strong polar interactions with water, which also is capable of hydrogen bonding that are non covalent interactions. But again, that would only occur on the exterior of the shape, not be the determiner of the shape itself. So choice d incorrect. So once again, the non covalent interaction that results in proteins folding into a globe like shape with a water loving exterior. And two examples of amino acids with this interaction are choice a hydrophobic interaction. With the examples being veiling and phenylalanine. See you in the next video.

How do the following noncovalent interactions help to stabilize the tertiary and quaternary structure of a protein? Give an example of a pair of amino acids that could give rise to each interaction.
a. Hydrophobic interactions

Key Concepts

Hydrophobic Interactions

Tertiary Structure

Quaternary Structure

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