chapter 3 Flashcards
proteins
core structure of an amino acid consists of a
central carbon atom / alpha carbon
central carbon atom/alpha carbon is covalently bonded to
a hydrogen atom, amino functional group (NH2), carboxyl group (COOH), and a side chain/ r group
proteins are derived from
20 different amino acids
in our cells amino acids are
ionized
ionized form is when
The amino group acts as a base + accepts a hydrogen atom….
The carboxyl group acts as an acid bc of the 2 electronegative oxygen atoms
why are amino acids unique?
due to the different R groups and each of them affect chemical properties of an amino acid
what are the 3 r group types
- charged (basic or acidic)
- polar (partial charge)
- nonpolar (no charge)
polar and charged r groups…
are hydrophilic (interact w water) bc their charges allow them to interact w. waters partial charges
Charged Acidic amino acids
contains R group with negative charge
Charged Basic amino acids
has R-group with positive charge
Polar amino acids have
R group with partially negative oxygen atom
nonpolar r groups
hydrophobic (dont interact w water) bc they lack a charge so they cant interact with partial charges of water
nonpolar amino acids
lack r-group with any charge/ partially charged oxygen atom
how do amino acids link to one another?
thru formation of a peptide bond
how do peptide bonds form?
when a carboxyl functional group of one amino acid reacts (dehydration/condensation reaction) with the amino group of another amino acid
where can you find a stable covalent bond between C and N
peptide bond
stable bc the formation of intermittent C N double bond
peptide
when amino acids link tg in a chain of 50 amino acids
polypeptides
50 + amino acids linked
protein
any chain of amino acids
3 things to know about peptide
- r group of each amino acid is oriented away from amino acid backbone
- directionality where amino group is at one end of chain + carboxyl group at opposite end
- bonds neighboring peptide bonds can rotate giving it flexibility
four levels of structures of protein
primary, secondary, tertiary, quaternary
primary structure
represents the unique sequence of amino acids in a protein
what does the sequence of amino acids determine?
the shape and function of a protein due to the unique r group properties that affect size, reactivity and solubility
secondary structure
result of hydrogen bonding between oxygen atom of carbonyl functional group and hydrogen atom in amino group resulting in 2 possible secondary structures
2 types of secondary structures
alpha helix- coiled polypeptide backbone
beta sheet / pleated- polypeptide chain bends 180 and folds in the same plane
whether peptide/polypeptide chain will form into these depends on sequence of amino acids (primary structure)
why are some amino acids more/less likely to form alpha helix or b sheet pleated structures?
due to specific geomtry/properties of the R side chain
tertiary structure
protein 3D shape which forms from primart and secondary structures/interactions between r groups of different amino acids orr between r groups of amino acids AND peptide backbone
5 types of r group interactions
hydrogen bonding
hydrophobic interactions
van der waals interactions
covalent bonding
ionic bonding
hydrogen bonding
form between polar side chains and opposite partial charges
hydrophobic interactions
water forces hydrophobic side chains tg
van der waals interactions
weak electrical interactions between hydrophobic side chains
covalent bonding
covalent bonds between side chains of sulfhydryl groups (disulfide bonds)
ionic bonding
form between groups with full and opposing charges
quaternary structure
result of two or more individual polypeptides interacting w. one another to form a single functional protein
has subunits
includes polypeptides w. distinct primary, secondary, and or tertiary structures
what do the individual polypeptides that make up quaternary structure interact by?
Interact via same chemical bonds + interactions found in tertiary structures
dimers
proteins that consist of 2 individual polypeptides
trimers
proteins that consist of 3 individual polypeptides
tetramers
proteins that consist of 4 individual polypeptides
polypeptides subunit names
same - homo…. homodimer etc
different- hetero../heterotrimer etc
protein functions depends on what
correct folding
enzymes
effective catalysts bc they hold reactants (substrates) in precise orientation so that chemical reaction is more likely to occur
which structure of a protein contains all info required for the proper folding of the protein and in protein folding necessary for its function
primary
what does the lock and key model illustrate
how enzymes and substrates interact
enzymes orient substrates in a way to bring a reaction to act on specific substrates (active site)
active site
location where chemical reaction occurs
