Protein structures

[soccerboi]

Hi, could someone explain the difference between the primary,secondary and tertiary structure of protein? I don't understand the difference and what each refer to.

Thanks in advance 

[abeybaby]

Proteins are a linear chain of amino acids. there are 20 naturally occuring amino acids. the order of the amino acids, read from N terminus to C terminus, is called the primary structure.
eg, alanine, valine, glutamin, threonine, etc etc. this list is the primary structure.

now when you have a linear chain of stuff, it doesnt just sit there and stay linear. it curls up, because the amino acids interact with each other. The majority will curl up into 1 of 2 shapes: the alpha helix, or the beta sheet, the difference just being the shape... the helix is.... helical, and the sheet is a bit like a 2d plane (but obviously its not 2d). this structure is called the secondary structure.

now these sheets and helices dont just sit there alone, they interact with each other. the way that they interact with each other is called the tertiary structure.

http://www.proprofs.com/flashcards/upload/a3985729.JPG

& pretty pictures to help

[soccerboi]

Are the primary,secondary and tertiary structure of DNA the exact same as for proteins? or is there a difference?

[Somye]

primary for DNA is your sequences of bases, secondary is the double helix, and tertiary is the chromosomes

[pi]

The way I like to think of it:

For Proteins

Primary - the sequence of amino acids; covalent bonding

Secondary - the aplha-helices, bet-pleated sheets (and random coils, but they are a special case); hydrogen bonding

Tertiary - a functional 3 dimensional structure; hydrogen bonding, covalent (disulfide linkages and such), dispersion forces, ion-dipole interactions, dipole-dipole interactions

Quaternary - many polypeptide chains bound together (the other three forms describe a single polypeptide chain btw)



For DNA

Primary - the raw sequence of bases (one strand only)

Secondary - The base pairing between strands to produce the double helix

Tertiary - The specific "shape" of the DNA as it binds to histone proteins to form a chromosome or to form DNA that is ready to be transcribed (this definition varies textbook t textbook)