2.2.9 proteins 2: protein structure & bonding Flashcards
primary structure
sequence of amino acids found in molecule
secondary structure
coiling/folding of amino acid chain (often due to h bond formation between diff. parts of chain)
–> main forms of secondary structure = alpha helix or beta pleated sheet
tertiary structure
overall 3-dimensional shape of a protein molecule
–> arises due to interactions incl. h bonding, disulphide bridges, ionic bonds & hydrophobic interactions
quaternary structure
protein structure where protein consists of 1+ polypeptide chain
what does the order of amino acids in the primary structure determine
shape of protein molecule (through 2nd, 3rd, 4th structure)
what’s the alpha helix held by in the secondary structure (& between what)
hydrogen bonds between -NH group of 1 amino acid & -CO group of another 4 places ahead of it in the chain
what holds the beta pleated sheet together
hydrogen bonds between the -NH group of 1 amino acids & the -CO group of another further down the strand
how are the alpha helix/beta pleated sheet made stable structures at optimal temp. & pH
due to the amount of hydrogen bonds formed
how is the precise shape of the tertiary structure held together
bonds between amino acids (which lie close to each other)
what may the tertiary structure adopt
- supercoiled shape (eg. in fibrous proteins)
OR - more spherical shape (in globular proteins)
what bond primarily holds the secondary structure
hydrogen bonds
what do hydrogen bonds form between
hydrogen atoms with slight positive charge & other atoms with slight negative charge
in amino acids, where do the h bonds form
form in hydroxyl, carboxyl & amino groups
where can ionic bonds form
- what do these ionise into?
between the carboxyl & amino groups that are part of R groups
- ionise into NH3+ & COO- = strongly attracted to each other
what does the R group of the amino acids cysteine contain
sulfur
