What is the diagnostic test for CF? What is a normal value?
Sweat test Normal = < 40
How do uncharged polar amino acids behave?
Zero net charge at physiologic pH (7.4) R groups form hydrogen bonds with water
How do proteins fold?
Naturally, to reach lowest energy state With the help of chaperone proteins
When is an amino acid a zwitterion?
At pH 7 charge is balanced between + and - forms
Which amino acids tend to cluster stabilizing proteins through hydrophobic interactions?
Alanine Valine Leucine Isoleucine (last 3 are branched chain AAs)
How is pI calculated for nonionizable R groups?
= (pka1 + pka2) / 2
What is a "motif"? Does it have function?
Classified as (recognizable) folding patterns which may include multiple secondary structures e.g. helix-turn-helix Motifs do not have inherent function
Which AAs can act as attachment sites for oligosaccharides and glycoproteins? What group do they attach to?
Asn - amide group
Ser - hydroxyl group
Thr - hydroxyl group
What is an example of a "disordered" protein? What does this mean?
p53 tumor suppressor Is disorganized and flexible, usually means it can bind to multiple things
What are stabilizing influences to protein structure?
Most important: sequence! Chemical properties Covalent and disulfide bonds Hydrophobic interactions Van der Waals forces Electrostatic forces
What indicates a strong acid?
Do proteins play a major role in the buffering system of cells and plasma?
Which AAs have ionizable side chains?
What AAs promote the alpha helix? Which ones do not?
Promote: Met, Ala, Leu Destabilize: Asp, His, Lys (charged) Pro Glu
Describe the beta sheet:
Composed of 2 or more regions of one OR MORE polypeptide chains R groups can be above or below plane of sheet
What is the isoelectric point (pI)?
The point at which proteins and some amino acids are electrically neutral
What is the quaternary structure of proteins?
Arrangement of 2 or more polypeptide chains/subunits
What are three new CF drugs?
Ivacaftor Dornase alfa Orkambi (helps deltaF508 patients!)
What is the bond between amino acids?
What is the basic structure of an amino acid?
Carbon with 1 H, a Carboxyl group, an amino group + VARIABLE R group
What is the secondary structure of amino acids?
Alpha helix Beta sheet Loops Coils
Which AAs cause MSUD when they fail to be broken down? What do they have in common with one another?
Branched chain AAs! Valine Leucine Isoleucine
What are two general categories of proteins?
What do globular proteins do?
Enzymes, regulatory proteins, immunoglobulins, transport proteins, motor proteins, etc.
Which amino acid forms disulfide (S-S) bonds? Are these especially strong bonds?
Cysteine YES! Can be formed between 1 or 2 polypeptides
What elevated protein is indicative (but not diagnostic) of cystic fibrosis? Where is it produced?
Immunoreactive Trypsinogen (IRT) Produced by the pancreas
Which AA is barely charged and what is it good for?
Histidine is weakly basic and thus makes a good buffer
Which AAs have polar hydroxyl groups that can be attachment sites for groups (e.g. phosphate)?
Serine Threonine Tyrosine
What is a protein domain? Does it have function?
Regions of polypeptide chains that can fold stably and independently with respect to the protein. Has function even outside of the protein as a whole!
Describe the structure of globular proteins
Polypeptide strands folded into globular shape, tend to have complex tertiary structures e.g. myoglobin and hemoglobin