BSI Lecture 2 Protein Structure Flashcards
What are proteins made of ?
Amino acids
Primary protein structure
Amino acid sequence
Secondary protein structure
Formation of alpha helix and beta sheets
Tertiary protein structure
Overall 3-dimensional shape of protein
Quaternary protein structure
More than one polypeptide (dimers, oligomers)
How many amino acids are there?
20 (8 essential and 12 nonessential)
What is the basic structure of an amino acid?
Central carbon (alpha carbon) with a single hydrogen atom, amino group, a carboxyl group, and a side chain (R group).
Asp
Aspartic acid, negative (acidic side chain)
Glu
Glutamic acid, negative (acidic side chain)
Arg
Arginine, positive (basic side chain)
Lys
Lysine, positive (basic side chain)
His
Histidine, positive (basic side chain)
Asn
Asparagine, uncharged polar
Gln
Glutamine, uncharged polar
Ser
Serine, uncharged polar
Thr
Threonine, uncharged polar
Tyr
Tyrosine, uncharged polar
Ala
Alanine, nonpolar
Gly
Glycine, nonpolar
Val
Valine, nonpolar
Leu
Leucine, nonpolar
Ile
Isoleucine, nonpolar
Pro
Proline, nonpolar
Phe
Phenylalanine, nonpolar
Met
Methionine, nonpolar
Trp
Tryptophan, nonpolar
Cys
Cysteine, nonpolar
Which amino acids can be phosphorylated? Why?
Serine, Threonine, and Tyrosine because they have a hydroxyl group (OH).
Which amino acid can form disulfide bonds? Why?
Cysteine because it contains SH functional group
What are the 8 essential amino acids that can’t be produced by the body?
Threonine, Methionine, Lysine, Valine, Leucine, Isoleucine, Phenylalanine, Tryptophan
3 Facts about Primary Structures
- Stabilized by peptide bond
- Peptide bond is covalent
- Bond forms between amino group and and carboxyl group, resulting in the loss of a water molecule
What is the end of the protein?
Carboxyl Group
What is the beginning of the protein?
Amino Group
4 Facts about Secondary Structures
- Alpha helix and beta sheets are most common
- Hydrogen bonds stabilize
- Hydrogen bonds are non-covalent
- Hydrogen bond between back
- Very stable and rigid structures
- These structures do not involve unique side chains, therefore they do not require a unique amino acid sequence to form
4 Facts about Tertiary Structures
- Folded polypeptide strand into three dimensional shape (no two proteins will have the same tertiary structure)
- Determined by unique amino acid sequence
- Domains
- Types of bonds that will stabilize tertiary structures are Hydrogen bonds, Ionic bonds, hydrophobic interactions, Van der Waals attractions, and Disulfide bonds
Facts about Quaternary structures
More than one polypeptide chain (dimers and oligomers)
Hydrogen bond
weak interactions that form between a hydrogen with a partial positive charge and a more electronegative atom
Hydrophobic interaction
The tendency of nonpolar molecules in a polar solvent (usually water) to interact with one another.
Ionic bond
The complete transfer of valence electron(s) between atoms that form a cation and anion.
Van der Waals attraction
The attraction of intermolecular forces between molecules.
Disulfide bridge
A covalent bond derived from two thiol groups.
Homodimer
Formed by two identical molecules (a process called homodimerisation)
Heterodimer
A heterodimer is formed by two different macromolecules (called heterodimerisation).
Oligomer
a molecular complex that consists of a few monomer units.
