building blocks of proteins
Amino acid
is attached to four different substituents
Alpha-carbon
Categories of amino acid
- Polar
- Electrically charged amino acids
- Nonpolar
What are the polar amino acids
STAG C
- Serine
- Threonine
- Asparigine
- Glutamine
- Tyrosine
- Cystein
Types of non-polar/hydrophobic amino acid
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- Glycine
- Alanine
- Valine
- Leucine
- Isoleucine
- Methionine
- Proline
- Phenylalanine
- Tryptophan
Negatively charged R groups
Aspartic acid, Glutamic Acid
Positively charged R groups
Lysine, Arginine, Histidine
• Formed by dehydration synthesis
• Allows free rotation of attached atoms
> various shapes of polypeptide
- Holds amino acids
Peptide Bond
Unbranched chain of amino acids
Polypeptide chain
May consists of one or more polypeptide chains
protein
the primary structure of a protein is a sequence of amino acids linked together by peptide bonds, forming a polypeptide
Primary structure
Local regions of the resulting polypeptide can then be coiled into a a-helix.
Secondary structure
Regions of secondary structure associate with each other in a specific manner to form this structure
The final folding of the polypeptide
Tertiary structure
For multimeric proteins, the quarternary structure describes the association of two or more polypeptides as they inetract to form the final structure.
a functional protein
Quarternary structure
What is the difference between peptides and proteins in terms of amino acid chain length?
Peptides: fewer than 50 amino acids
Proteins: more than 50 amino acids
a peptide that has 2 amino acids
Dipeptides
a peptide that have 3 amino acids
tripeptides
A peptide that have more than 10 amino acids
Polypeptides
Two folds of Secondary structure
- α-helix
- β pleated sheet
Spiral turn of α-helix
3.6 amino acids
α-helix is symbolized by ______ ______
Helical ribbon/coil
- Most commn 2° structure
- stabilized by almost linear hydrogen bonds between the NH and CO groups of residues
- with disulfide linkages (S–S)
alpha-helix
- the peptide planes are arranged like a regularly pleated sheet
- H-bonds can only form between neighboring chains within a sheet
β-pleated sheet
gives a specific three dimensional shape to the polypeptide chain
- tertiary structure
