Properties Flashcards
Which amino acids are hydrophobic and aliphatic?
Glycine (G), Alanine (A), Leucine (L), Valine (V), Isoleucine (I), Methionine (M), Proline (P)
Which amino acids are hydrophobic and charged?
Phenylalanine (F) and Tryptophan (W)
Which amino acids are hydrophilic and charged?
Aspartate (D), Glutamate (E), Lysine (K), Histidine (H), Arginine (R)
Which amino acids are hydrophilic and neutral?
Asparagine (N), Glutamine (Q), Serine (S), Threonine (T), Cysteine (C)
What is the first amino acid in a protein sequence?
Methionine
Which amino acid with a sulfide R group creates peptide bonds?
Cysteine
What do tryptophan, tyrosine, and phenylalanine have in common?
Absorb light at 280 nm, are aromatic
How are serine and threonine modified?
OH glycosylation and phosphorylation
How is asparagine modified?
N-liked glycolsylation
How is proline modified and how does it affect the structure of DNA?
Can be hydroxylated, ring causes bend in DNA structure
What is unique about a dipeptide bond?
Stronger than a normal bond but with double bond characteristics (Such as rotational freedom)
After how many amino acids is a polypeptide considered a protein?
50
What is common to all peptide chains?
N terminal, C terminal, moves from N to C terminal
What is the range of amino acids in a naturally occurring protein?
50-2,000
What type of interaction is present in a primary protein structure?
Peptide bonds
Which interactions are present in a secondary protein structure?
Peptide bonds and hydrogen bonds
Name the types of secondary protein structure and the characteristics for each type.
Alpha helix: Rod-like structure, coiled peptide chain, R groups stick out of helix, bonding is parallel to the chain (In line with the helix), 3.6 AAs per turn, naturally occur in right handed helices
Beta sheet: Extended polypeptide chain, H bonding between different polypeptides, strands can run in parallel or anti-parallel (With beta turns), often contain proline because it is bulky
How is a protein stabilized in the tertiary structure?
Weak, non-covalent bonds between R-groups
What types of interactions can be found in a tertiary protein structure?
Hydrogen bonding, electrostatic interactions, hydrophobic interactions, Van der Waals forces, disulphide bonding between cysteine residues
What is characteristic of a quaternary protein structure?
Several polypeptide units interacting, covalent and non-covalent interactions, bonds are able to break and reform repeatedly, allosteric proteins have quaternary structure
How can proteins be denatured?
Heat (Breaks weak bonding), pH (Disrupts H bonding), detergents/organic solvents (Disrupts hydrophobic bonding), chaotropic agents (Form H bonds with AAs and disrupts existing H bonds)
Name three agents that can denature primary and tertiary protein structure.
Urea, guanine HCl, mercaptoethanol (Reduces disulphide bonds)
What is unique about denaturing a tertiary protein structure?
It can be reformed if all information is retained and denaturing agents are removed
Which protein stage determines the entire protein structure?
Primary
