Chapter 2 Flashcards
Functions of proteins
They act like enzymes, hormones, receptors, antibodies and support structures inside/outside the cell
What are proteins composed of? What does their composition sequence determine?
Proteins are composed of 20 different amino acids. The composition and sequence determines the function.
Polar Hydrophilic amino acids
“Polar-Bears Sometimes Carry Tyny Things Around Glaciers” Serine, cysteine, tyrosine, threonine, asparagine, glutamine. Polar Bear: Water loving
Non-Polar Hydrophobic amino acids
Glycine, alanine, valine, leucine, isoleucine, phenylalanine, tryptophan, methionine, proline. “Giant Ants Vandalize Local Icecream Parlor To Meet Peppermint”
Hydrophobic Amino Acid Properties
aliphatic (alkyl) or aromatic side chains. Found in the inside of the protein. larger side groups have > repelling forces. aliphatic = organic compounds whose carbon atoms are linked in open chains rather than in a benzene ring
polar amino acids
amino acids that are polar enough to form hydrogen bonds, but not enough to act as an acid or base serine, threonine, tyrosine –> hydrophobic aromatic rings.
basic amino acids
Hydrophilic; lysine (pKa~10), arginine (pKa~12), histidine (pKa~6.5): can act as an acid or base sine pKa is close to 7, can be proton accept/donor
acidic amino acids
Hydrophilic [Glutamic acid & Aspartic acid] pKa~4, contain 3 groups that can act as acids or bases, the two backbone groups and the R-group.
Amino acids that contain sulfur
Cysteine and Methionine
Two bond types and location
peptide bonds: link amino acids together in a polypeptide chain disulfide bridge: formed between cysteine R-groups
Where the peptide bond links
carbonyl and alpha amino group between two amino acids with the loss of water
The disulfide bond forms where?
between the thiol of one cysteine and the thiol of another. can happen between two different chains or within one
What proteins structure does the disulfide bond stabilize?
stabilizes tertiary protein structure
protein folding is vital to
the function of the protein
Denaturation occur in what structures?
occurs in 2,3,4 structures
Denaturation is
disruption of a proteins shape without breaking peptide bonds. Usually by urea since it disrupts hydrogen bonding interactions
causes of denaturation
extremes of pH, extremes of temperatures, changes in salt concentration (Tonicity)
primary structure
amino acid sequence: order amino acids are bonded to each other in the polypeptide chain
secondary structure
hydrogen bonds between backbone groups. initial folding of the polypeptide chain into shapes stabilized by hydrogen bonds between backbone NH and CO groups
α- helix
2nd structure. always right handed. hormones receptors/ion channels are found within the α- helix membrane integrated into hydrophobic membranes proline residues are never found here because they kink the polypeptide chain
β- pleated sheets
2nd structure. bonding occurs between residues distant from each other in the chain/ separate polypeptide chains. back bone is extended not coiled. there are two kinds (1) parallel β- pleated sheet (2) β- antiparallel β- pleated sheet
Tertiary structure
hydrophobic/hydrophilic interactions. interactions between amino acid resides located more distantly from each other in the polypeptide chain disulfide bonds are considered this structure
quaternary structure
various bonds between separate chains. interactions between polypeptide subunits.
What kind of interactions are involved in a quaternary structure
interactions involved include hydrogen bond, hydrophobic interactions, van ser Waals and for this structure covalent bonding applies as well.
