B1.2 Proteins Flashcards
amino acids, structure, denaturation, R-groups, insulin vs collagen
what is the word equation for the formation of a dipeptide?
amino acid + amino acid = dipeptide + water
what is an essential amino acid?
9 amino acids that are not able to be synthesized by body and have to be consumed in diet
why are animal products known as complete proteins?
they contain all 9 essential amino acids
what is a non-essential amino acid?
11 amino acids that are able to be synthesized by body
how is there so much variety in polypeptide chains?
they can have any number of amino acids (eg 51 in insulin vs 34,000 in titin) in any order, and some amino acids are modified after synthesis
define denaturation
when a protein temporarily loses structure due to changes in temperature putting stress on or changes in pH preventing hydrogen bonds; if too extreme, peptide bonds are broken and becomes irreversible
what properties of R-groups determine their interactions?
they can be either non-polar, polar because of polar-bonding atoms, polar because of a positive charge (basic), or polar because of a negative charge (acidic)
what is the order of structure in proteins?
- primary
- secondary
- tertiary
- quaternary
what is the primary structure of a protein?
number and order of amino acids; held together by peptide bonds
what is the secondary structure of a protein?
folding of polypeptide chains into beta-pleated sheets or alpha helices held together by hydrogen bonds between residues; polypeptides with only secondary structure have only non-polar R-groups and are fibrous
what are residues?
carboxyl and amine groups that form peptide bonds
are amino acids charged, even if their R-groups are not?
yes; COOH acts as acid and donates hydrogen ion, becoming negative; NH2 acts as base and accepts, becoming positive
what is the tertiary structure of a protein?
3D folding of polypeptide chain due to R-group interactions
what bonds/interactions are responsible for tertiary structure?
ionic, hydrogen, and covalent bonds and hydrophobic/philic interactions
what covalent bonds are used to hold together a protein’s tertiary structure?
disulfide bonds between sulphur atoms of cysteine amino acids; strongest bonding force
how do hydrophobic/philic interactions influence the structure of a protein?
hydrophobic amino acids cluster into inner globular protein, while hydrophilic amino acids make up outer surface
what are examples of hydrophobic/philic interactions in proteins?
integral proteins (embedded in membrane) and lipase (hydrolysing enzyme)
what is the quaternary structure of a protein?
folding of multiple polypeptide chains by ionic, hydrogen, and covalent bonds and hydrophobic/philic interactions
what is a conjugated protein?
protein with polypeptide chains attached to 1 or more prosthetic group
what is a non-conjugated protein?
protein with only polypeptide chains
what is a prosthetic group?
non-polypeptide group in protein
how many non-polar R-groups are there, and what makes an R-group non-polar?
9; has only hydrocarbons
how many polar R-groups are there, and what makes an R-group polar?
11; 6 have elements making polar covalent bonds (O, N, S), 3 act as bases (positive charge), 2 act as acids (negative charge)
where does insulin come from and what is its purpose?
hormone secreted from pancreas that controls glucose levels; bonds to receptors, setting off chain of reactions (signal pathway) that opens channels allowing glucose through membrane
