protein structure

Question 1

primary structure

Answer 1

linear sequence of amino acids
determined by the covalent peptide bond linking each amino acid
not altered by denaturation by heating

Question 2

secondary structure

Answer 2

local structure stabilized by backbone interactions (mainly hydrogen bonds)
characterized by how the linear sequence folds on itself
a-helices
B-pleated sheets: antiparallel (more stable) vs parallel

Question 3

tertiary protein structure

Answer 3

3D structure stabilized by
distant interactions hydrophobic interactions, polar interactions, acid-base interactions (salt bridges), hydrogen bonding, and disulfide bonds
disulfide bonds occur on the exterior of the cell due to oxidizing environment

Question 4

quaternary structure of proteins

Answer 4

interactions between subunits
consist of multiple polypeptides
stabilized by internal hydrophobic interactions and external hydrophilic hydrogen bonds/ionic bonds between side chains

Question 5

solvation shell

Answer 5

layer of solvent surrounding a protein, ex: water solvent interaction with polar amino acids

Question 6

denaturation

Answer 6

when a protein loses active-state conformation and becomes inactive
occurs by changing pH, temperature, chemicals, or other enzymes

Question 7

hydrophobic interactions

Answer 7

hydrophobic regions of protein aggregate, and releases water
this increases the entropy of water, which is the major thermodynamically favorable component of protein folding

Question 8

protein separation techniques

Answer 8

isoelectric focusing - gel electrophoresis method that separates proteins on the basis of their relative contents of acidic and basic residues. gel used has a pH gradient
electrophoresis - separates proteins based on size/charge. there is one cathode and one anode. larger molecules have a harder time moving. DNA molecules are only separated by size in electrophoresis (same amount of charge/mass)

Question 9

isoelectric point

Answer 9

pI is determined by average the pKa values that refer to protonation and deprotonation of zwitterion

Question 10

Native page

Answer 10

electrophoresis where migration rate is dependent on both the mass and the structure (charge) of the protein

Question 11

SDS-page

Answer 11

electrophoresis where migration is dependent on size only, as proteins are denatured to have same charge