L8: Proteins - Structure Flashcards
What makes up proteins?
- Amino acids
What does an amino acid consist of?
- Amino group
- Carboxyl group
- R-group (side chain)
Which groups do the peptide bond join?
- Carboxyl group (one molecule) and amino group (other molecule)
What are amino acyl residues in a peptide?
- Amino acids with either OH (from carboxyl group) or H (from amino group) removed in the formation of a peptide bond
- One H2O removed per peptide bond
What is the directionality of a protein?
- N-terminus to C-terminus
What is the backbone of a polypeptide chain?
- The covalent linkages from one amino acid to the next
What makes each amino acid different?
- R-group (side chain)
Describe HYDROPHOBIC amino acids.
- Non-polar side chains
Describe HYDROPHILIC amino acids.
- Charged and polar side chains
Describe ACIDIC amino acids.
- Negatively charged
Describe BASIC amino acids.
- Positively charged
When does a polypeptide become a protein?
- When it’s folded
What is the key concept in regards to protein structure?
- Sequence determines structure, structure determines function
What are the 4 levels of protein structure
- Primary
- Secondary
- Tertiary
- Quaternary
What can determine the structure of a protein?
- The makeup of R-groups in a polypeptide chain
Describe the primary structure.
- The sequence of amino acids
- The amino acid sequence determines the protein’s 3D structure (i.e. the order, sequence & makeup of different aa’s)
- Order is determined by the DNA genetic code
Describe the secondary structure.
- Results from the interaction of nearby amino acids.
What are the two types of secondary structure?
- Alpha-helixes
- Beta-pleated sheets
How does the secondary structure form?
- Carbonyl group in one peptide bond and an amide group in another form repetitive H-bonds
How is the secondary structure stabilized?
- H-bonds w/ backbone atoms stabilize/keeps atoms together.
Describe the tertiary structure.
- 3D shape of a protein
- 3D structure (fold) of the entire polypeptide
- Can be the final structure in some proteins
How is the tertiary structure stabilized?
- By side-chain interactions (non-covalent & disulfide bonds)
- Interactions between side chains and backbone atoms
Describe the quaternary structure.
- Results from interactions of protein subunits
How is the quaternary structure stabilized?
- Stabilized by non-covalent interactions between subunits.
