Ch. 4 Flashcards
Are amino acids chiral?
Yes except for glycine
Which amino acid can form disulfide bonds?
Cysteine
- Stabilizes 3D structure of proteins
What are some common modifications of hydrophilic amino acids?
- Kinases are add a phosphate group to a protein.
- ATP is the phosphate donor.
- Commonly occur with Ser
and Thr
- Phosphatases remove the
phosphate group
TL;DR - add or remove a phosphate group
What are the important roles of some types of amino acids?
- Nonpolar
- Proline: α helix breaker, imino acid
- Methionine: first amino acid at N terminus of protein (AUG codon)
- Polar
- On surface of proteins in aquatic cell environment
- Ser/thr/tyr
- Can phosphorylate
- Regulation of a protein’s activity
- Basic
- Parts of histones
- Electrostatic interaction with DNA
- Hydrophobic (have more C than H)
- Can be part of membranes
- Assist with transport
- Acidic
- Can interact with salts or metal ions
- Aromatic (usually also hydrophobic and in membranes)
- Strong absorbance at 280 nm
What are the functions of amino acids?
- Proteins
- Source of energy
- Regulation
- Precursor to other biomolecules
What is a zwitterion?
An electrically neutral but dipolar molecule that contains both positive and negative charges
What is the isoelectric point (pI)?
pH at which amino acid is neutral (no net charge)
- Average the 2 pKa values that yield a neutral charge half the time
How are peptide bonds formed and broken?
- Formed by condensation between the amine and carboxylic acid groups
- Water is a product
- Catalyzed by RNA component of ribosomes
- Hydrolysis breaks peptide bonds
- Catalyzed by proteases
What is the primary structure of a protein?
Amino acid sequence
What is the secondary structure of a protein?
H bonds among backbone atoms
What is the tertiary structure of a protein?
All 4 types of interactions between R groups
What is the quaternary structure of a protein?
All 4 types of interactions between R groups to join more than one peptide
Which amino acid can’t be in alpha helices?
Proline
