Chapter 4: Protein Structure Flashcards
What is the isoelectric point of an amino acid? What is a zwitterion?
- When the pH of the amino acid carries no net charge it is known as a zwitterion
How can approximate pI values be calculated?
pI = [pK1 + pK2]/2
What is an enantiomer
A mirror reflection of a molecule
Do all amino acids have chiral centers?
19/20 excluding glycine
How are amino acids joined together or split?
Formation of peptide bonds via condensation (hydrolysis for splitting)
How is energy obtained to react the unfavorable ( ΔG > 0) peptide bond formation/splitting?
use of ATP and GTP
What is used to make the stable peptide bond degrade?
Proteases are used to catalyze peptide bond hydrolysis
What does the Ramachandran plot show?
The allowable combinations of psi and phi angles
Describe the primary protein structure?
Describe the secondary protein structure?
Describe the tertiary protein structure?
Describe the quaternary protein structure
Primary:
- an amino acid sequence that can form energetically stable 3D structure
Secondary:
- Polypeptide backbone in repetitive rearrangements
- β strands, α helices, and β turns
Tertiary:
- polypeptide with side chains and atoms
Quaternary:
- More than one polypeptide chain with a multi-subunit protein complex
Describe the structure of the α-helix
- Secondary structure stabilized by intrastrand H bonds
- Right handed
- Function groups point out from the center of the spiral
Where do H bonds form in amino acids
the carbonyl oxygen
How do hydrophilic and hydrophobic amino acids align along the helix?
The hydrophobic face is on one side while the hydrophilic face is on another
Describe the structure of a β strand
- side chains positioned above and below the polypeptide backbone
- a large distance from adjacent amino acids
- unstable
Describe the structure of a β sheet
- energetically stable
- parallel and antiparallel to accomidate H bonding
Describe the structure of β turns and loops
Type 1 has carbonyl oxygen pointed inward while Type 2 has carbonyl oxygen pointed outward
What is the TIM barrel and what does it look like
alternating alpha helix and beta strands
