BioChem Flashcards
What amino acids are chiral/optically active/rotate plane polarized light?
All EXCEPT Glycine (Gly, G)
What amino acids are (S) configuration?
All EXCEPT Cysteine (Cys, C)
K38A means what?
Lysine (Lys, K) at position 38 is mutated to Alanine (Ala, A)
What is the average weight on an amino acid?
110 Da
Amino acids are ampho..?
Amphoteric: react as both acid and base, can gain protons under acidic conditions and lose protons under basic conditions
When pH < pKa…?
Protonated
When pH > pKa…?
Deprotonated
What is the pKa of carboxyl group?
~2
What is the pKa of amino group?
~9-10
What is a zwitterion?
A neutrally charged molecule by way of (+) and (-) charges offsetting each other
What is the pH and pKa relationship in a buffer?
pH approximately equals pKa +/- 1
What is a peptide bond and how is it formed/broken?
Peptide bond is an amide/covalent bond b/w a carboxyl and amino group that has partial double bond character through resonance (also means less rotation)
It is formed by dehydration/condensation (removing H2O) and broken by hydrolysis (adding H2O)
What is primary protein structure?
Amino acid sequence that runs from N-terminus to C-terminus
What is secondary protein structure?
The alpha-helices or beta-pleated-sheets that are formed by hydrogen bonding b/w amide protons and carbonyl oxygen
What is the role of Proline (Pro, P) in protein structure?
It destabilizes alpha-helices but is found in beta-pleated-sheet turns (which are rigid loops)
What is tertiary protein structure?
The 3D shape of a protein determined by hydrophobic groups sequestered inside and hydrophilic groups on the surface (that folding is b/c of increased entropy)
Formed by disulfide bonds b/w Cysteine (Cys, C) residues, formed by oxidation, broken by reduction
Also formed by salt bridges and hydrogen bonds
What is protein quaternary structure?
Found only in proteins w/ multiple subunits/chains like hemoglobin
Usually exhibit cooperative/allosteric effects
What is denaturation?
The unfolding of a protein’s 3D structure which results in inactivation of the protein
By: temperature, pH, and salinity (increase salt can disrupt bonds)
What are features of enzymes?
- lower Ea with no change in deltaG (increase rate without affecting equilibrium)
- specificity to substrate
- not consumed by reaction
Ligase function?
In synthesis reactions
Isomerase function?
In bond rearragement
Lyase function?
In single molecular cleavage into two products
Hydrolase function?
Cleavage by hydrolysis or addition of H2O
Protease function?
Protein cleavage by hydrolysis