Protein structures

[fpr85]

Advertisement - Members don't see this ad

I figured this would be the best forum to post this in even though it's not MCAT related.

I'm having a bit of difficulty understanding the four structures of proteins (primary, secondary, tertiary, and quaternary) and would appreciate some help.

Based on what I read in my book, at first I thought that each structure was unique to a particular type of protein, then after looking at some supplementary material I found out that they're actually phases that proteins go through before becoming "mature proteins" (read this in Princeton's Guide to AP Biology).

My instructor handed out a review sheet and one of the questions relating to this asked:
Distinguish between: primary, secondary, tertiary, structure of polypeptides; quaternary structure of proteins. Cite nature of bonds and interactions responsible for each

I suppose my first question would be, are the three structures (not 4 because the quaternary only happens if you have more than one polypeptide, I think) phases that proteins go through before becoming "mature proteins"?

Why did the instructor write "primary, secondary, tertiary structure of polypeptides and quaternary structure of proteins? Polypeptides (which are made of amino acids) make up proteins, I'm not seeing the difference here.

The book (Campbell Biology 6th Edition) used the bacteria-eating enzyme lysozyme as an example for the primary structure -- does lysozyme only stay in the primary structure?
1st structure - amino acid sequence
2nd structure - alpha helix / beta pleated sheet
3rd structure - the raveling of the protein into globular/fibular form
4th structure - wrapping of two or more polypeptides

I don't have my notes in front of me and am doing this from memory so please correct me if I'm wrong.

Final question is, from the bonds that hold these proteins together(disulfur bridge, hydrogen, and ionic bonds... I think), are these present in all of the 3/4 stages?

I appreciate any help, I've done a decent amount of reading on this and just want to clarify these things, I would've asked the professor but unfortunately his office hours don't coincide with when I don't have class.

Thanks

PS: This is BIO 101 if that helps any, so try and dummy it down for me 😉

 

[fahimaz7]

I figured this would be the best forum to post this in even though it's not MCAT related.

I'm having a bit of difficulty understanding the four structures of proteins (primary, secondary, tertiary, and quaternary) and would appreciate some help.

Based on what I read in my book, at first I thought that each structure was unique to a particular type of protein, then after looking at some supplementary material I found out that they're actually phases that proteins go through before becoming "mature proteins" (read this in Princeton's Guide to AP Biology).

My instructor handed out a review sheet and one of the questions relating to this asked:
Distinguish between: primary, secondary, tertiary, structure of polypeptides; quaternary structure of proteins. Cite nature of bonds and interactions responsible for each

I suppose my first question would be, are the three structures (not 4 because the quaternary only happens if you have more than one polypeptide, I think) phases that proteins go through before becoming "mature proteins"?

Why did the instructor write "primary, secondary, tertiary structure of polypeptides and quaternary structure of proteins? Polypeptides (which are made of amino acids) make up proteins, I'm not seeing the difference here.

The book (Campbell Biology 6th Edition) used the bacteria-eating enzyme lysozyme as an example for the primary structure -- does lysozyme only stay in the primary structure?
1st structure - amino acid sequence
2nd structure - alpha helix / beta pleated sheet
3rd structure - the raveling of the protein into globular/fibular form
4th structure - wrapping of two or more polypeptides

I don't have my notes in front of me and am doing this from memory so please correct me if I'm wrong.

Final question is, from the bonds that hold these proteins together(disulfur bridge, hydrogen, and ionic bonds... I think), are these present in all of the 3/4 stages?

I appreciate any help, I've done a decent amount of reading on this and just want to clarify these things, I would've asked the professor but unfortunately his office hours don't coincide with when I don't have class.

Thanks

PS: This is BIO 101 if that helps any, so try and dummy it down for me 😉

Alright, I'll take this one.

Primary structure is the linear sequence of codons before any extra bonding occurs (vanders, h-bonds, S-S bonds etc.)

Secondary: This is the structure of a length of cod in the folding sequence. Alpha helices and Beta sheets are the two types. Alpha is a helical shape and B-sheets are basically lines of H-phobic protiens attached together (They make B-barrels of integral membrane protiens) Bonding is mainly H-bonds, amide and carboxy bonds

Tert: An important part of 3 structure is that the parts of the code that are far away from each other have the opportunity to be brought together permitting side chain interaction. (tert structure is stabalized by noncovalent interactions-mainly phobic- between the side chains of amino acid residues. This is where you see S-S bonds)
-=----Closely packed w/ alpha and beta structures present

4th: Multiple subunits of protiens (i.e. more than one mRNA has been translated and these mult. protiens come together to make a protien (ribosomes, etc)
---Oligomer: mult subunit protiens. (>1 polypeptide chain)

Good luck with it.. YOu'll see a lot more in the future.

Scott
CBIO major at UGA.

 

[bonez318ti]

All proteins will have primary, secondary, and tertiary structures. If the protein has more than one polypeptide, it will have a quarternary structure.

Primary structure is simply the order of the amino acids that make up the polypeptide.. ie: Gly-Trp-Pro-Cys-Met

Secondary structure is any hydrogen bonding that may occur within this polypeptide.. since each amino acid in the polypeptide has atleast one O=H and one NH bond, there will be hydrogen bonding (this may be alittle more complex than you need to know for bio101 since it requires some understanding of orgo). This you will need to know: examples of secondary structures are Alpha Helixes and Beta Sheets..

Tertiary structure is the structure due to other interactions and forces. An example are disulfide bridges formed by Cysteine.

Quarternary structure is when multiple polypeptides interact with each other to form a larger aggregate.

 

[bgreet]

You have it right on the money. When you talk about structures, its just a description of the protein, and not a conformational system that it goes through. For example, the polypeptide doesnt go through primary structure, then secondary, etc. etc. However, every protein has 3 forms of structure, and if there are multi subunits, there is quaternary structure. Disulfide bonds, hydrogen bonds, and ionic bonds are only a factor in secondary, tertiary, and quaternary structure. They occur between R groups on each amino acid, and help determine 3 dimensional structure (secondary, tertiary, quaternary structure). In primary structure, only peptide bonds occur between each amino acid. Hope this helped!

 

[fpr85]

Thank you all, you guys really helped clarify things 👍

My professor has his own way of teaching things, he relies totally on his lecture notes when it comes time for the test and I feel what he is teaching us is the bare minimum of what there really is to learn about the subject (I read in the book too and there's way more info then what he's given us). A common phrase of his is "I try and teach (biology) at a major level but I test at a non-major level", which is nice of him to be considerate of the people who are just taking the course for the science credit but... hmmm... I feel like I should be learning more. He's a good teacher though and I guess I'll eventually learn it in time or will have to learn it on my own. I couldn't find "oligosaccharide" in the book, I know what it means though, wonder why the book doesn't have it in there.

What do you guys think of this matter?

 

[bgreet]

You'll learn more in later courses. Just take it as it comes 🙂

 

[fpr85]

You'll learn more in later courses. Just take it as it comes 🙂

Yeah, I spoke too soon. After I took a look at my notes I was overwhelmed by what seemed to be superfluous information! I have the test in fifteen minutes. Wish me luck! 😉

 

[fahimaz7]

Good luck. Maybe you'll make it to a 4k+ level cell class and have the joy of learning how they interact to form the 4th structure as well as all the individual subunits and then the actual binding point of a proton during ATP synthase on the C-subunit of the F0 structure. ATP synthase is a F0/F1 protien with like.. hmmm..26 subunits.

Scott