protein structure + function Flashcards
how shape of protein is made
polypeptide chain folds in on itself to form specific shapes
difference between levels of structure in protein (general)
-levels 1-3 in protein structure =single polypeptide chain
-level 4 = 2+ polypeptide chains
primary structure definition
sequence of amino acids bonded by covalent peptide bonds
secondary structure definition
contains hydrogen bonds
where to h bonds occur
between h atoms and N/O atoms in polypeptide chains
how weak are h bonds
contains about 10% the energy of covalent bonds
when do h bonds form
when the h atoms come closer to larger atoms like n or o
when does polarity occur
H atoms elecrton becomes attracted to larger nucleus
what does polarity mean for the molecule
charge in molecule isnt evenly distributed
what does polarity lead to
weak electrostatic attraction between molecules - hydrogen bond
are hydrogen bonds evenly disrupted
yes- by higher temperatures or phs
how many types of secondary structures in proteins
1 - alpha helix
2 - beta pleated sheet
when is a alpha helix formed
when an H bond forms between every fourth peptide bond (between the oxygen of the carboxyl group and the hydrogen of the amine group)
when does a beta pleated sheet form
when the protein folds so that two parts of the polypeptide chain are parallel to each other enabling hydrogen bonds to form between parallel peptide bonds
when does a tertiary structure occur
interactions between the different R groups of the amino acids that form the primary sequence / polypeptide chain
types of things that occur in tertiary structure
- Some R groups are polar and so form H-bonds
- The R group of the amino acid cysteine contains Sulfur - so 2 cysteine R together can form a covalent S-S bond called a disulfide bridge.
- Some R groups are charged - they form ionic bonds
- Some non-polar R groups form very weak temporary interactions when close together (London forces)
when does quaternary structure occur
when 2 or more polypeptide chains attach together to form even more complex proteins.
what type of protein is catalase
globular protein
two typed of proteins
fibrous and globular
what bonds do sulphur form with polypeptide chains and between what
disulphide bonds between R group and sulphur
binding chains together
causing stability
where to peptide bonds form between
between carboxyl group and amino group
how many polypeptides does a functional protein contain
1+
what is the test for proteins
biuret test
add water
blue to lilac if present
