Module 4 Flashcards
what are peptide bonds
covalent linkages between carboxyl + amino group of 2 separate amino acids
what is the repeating pattern of polypeptide main chains?
NCCNCC
what is primary structure?
linear sequence of amino acids
N-> C terminus
what is the primary structure pattern?
YGGFL
what is ramachadran plots?
illustrate possible configurations of phi + psi
what is the secondary structure?
localized folding within polypeptide
how is secondary structure maintained?
H+ bonds between main chain amide + carbonyl groups
what are the 2 key rules of secondary structure?
- optimize potential
- represent a favoured configuration
why are hydrogen acceptors/donors important in secondary structure?
for optimization
how are PHI bonds attached to alpha carbons?
on the N terminus
how are PSI bonds attached to alpha carbons?
on the C terminus
think “C for Psi”
what are the 2 characteristics of Alpha Helices?
- right handed
- have 3.6 residues per turn
what 4 amino acids are not found in alpha helices?
- proline
- glycine
- amino acids with side branches
- amino acids with H+ groups near main chain
why is proline not found in alpha helices?
its too rigid
why is glycine not found in alpha helices?
too flexible
what charge does the N terminus carry?
partial positive charge with negative residues (asp, glu)
what charge does the C terminus carry?
partial negative charge with positive residues
what are beta sheets made of?
4 or 5 B strands arranged side by side
configuration of B sheets?
fully extended polypeptide chain
true or false: antiparallel beta sheets are more stable than parallel sheets
true, they have better alignment of H+ donors + acceptors
what are mixed beta sheets?
both parallel + antiparallel strands
what is the pattern of side chains in amphipathic B sheets?
alternating pattern above & below polypeptide chain, they attach polar face to the non-polar face
what is denaturation?
adding heat to a protein to disrupt structure (is reversible)
what is tertiary structure?
the final folding pattern of a single polypeptide
what is native confirmation of tertiary structure?
biological active folding pattern
true or false: primary structure dictates tertiary structure
true
what is stability?
tendency to maintain native conformation
what does stability reflect?
the difference in free energy of folded/unfolded states
what amount of free energy is most stable?
lowest free energy
2 characteristics of folded proteins?
- low energy state
- greatest stability
is protein folding a slow or rapid process?
rapid
what are chaperones?
heat shock proteins that help the protein perform complex functions
why are chaperones often called heat shock proteins?
b/c they are induced by shock
what are quaternary structures?
subset of proteins
how are quaternary structures formed?
when 4 subunits non-covalently join together and create a binding site
what are 3 advantages of quaternary structure?
- stability
- produce active sites
- produce complex combinations
how big are proteins?
100-1000 amino acids in length
at 51 amino acids ( ) is used as a threshold of when a polypeptide becomes a protein
insulin
what is the smallest protein?
insulin
what is the largest protein?
Titin
how to calculate the number of amino acids a protein has?
molecular weight / 110
what is the most important force & why?
non-covalent b/c they stabilize structure
what are fibrous proteins?
simple proteins that hold your body together
what are the 3 fibrous proteins?
- keratin
- collagen
- Silk
what are Globular Proteins?
proteins that perform highly complex functions & structures
role of hemoglobin
transporting O2 in bloodstream
role of myglobin
storage of O2 in the lungs
what is keratin?
primary component in hair, nails & horns
what does a pseudo trend mean in keratin?
positions a & d are hydrophobic residues
where is the hydrophobic strip located in keratin?
along the length of the helix
what are keratin coiled coils?
when 2 amphipathic keratin helices put their hydrophobic faces together
when are coiled coils formed?
when 2 or more helices entwine to form a stable structure
what are the 2 reasons for coiled coils?
- greater strength
- greater durability
what kind of helices are involved in keratin coiled coils?
2 right handed wrapped to the left
what is post translational stabilization?
covalently modified structures through the use of disulphide bonds
how much protein does collagen make up in the body?
25%
where is collagen found?
skin, tendons & vascular system
primary structure of collagen
GLY-X-Y pattern (X is often proline)
1/3 of residues in collagen is ( ) and the other 1/3 is ( )
glycine and proline
how many residues per turn does collagen have?
3
how are collagen coiled coils formed?
when 3 left handed helices join together & wrap to the right
where are proline side chains located on collagen coiled coils?
on the outside
what is post-translational modification in collagen?
occur from hydroxyproline & hydroxylysine
what vitamin is required for collagen post-translational modifcation?
vitamin C, is needed for stable crosslinks
What is silk’s primary structure?
has a 6 residue repeat (GSGAGA)
what is silk’s secondary structure?
beta sheets
what is the strongest silk material?
cross sectional
what do fully extended polypeptide chains give?
strength
what does association of strands by hydrogen bonding allow for?
flexibility
what 2 amino acids come together & form a zipper?
alanine & glycine
is silk non-immuniogenetic or immunogenetic?
non-immuniogenetic
what does non-immuniogenetic mean?
when the body can recognize the molecule has not itself and provokes an immune response
what is a steric interference
2 groups cannot occupy the same space at the same time
