architecture of proteins
TRANSCRIPT
What are proteins? What are proteins made of ? Classification of amino acids: selected properties. Peptide bonds. Protein Structures. Classification of Structures. Primary Structure. Secondary Structure. Tertiary Structure. Quaternary Structure.
Index
Proteins are large biological molecules, or macromolecules, consisting of one or more long chains of amino acid residues.
Proteins perform a vast array of functions within living organisms ∼
Catalysing metabolic reactions Replicating DNA Responding to stimuli Transporting molecules from one location to another.
What are proteins?
Proteins are made up of smaller building blocks called amino acids, joined together in chains.
Some proteins are just a few amino acids long, while others are made up of several thousands.
These chains of amino acids fold up in complex ways, giving each protein a unique 3D shape.
There are 20 different amino acids.
What are proteins made of ?
Classification of Amino acids: Selected properties
The amide group is planar with N-H trans to C=O (trans-peptide bond).
C-N of the peptide bond has partial double bond -character.
Peptide bonds
Protein structure is the bio molecular structure of a protein molecule.
Proteins are polymers – specifically polypeptides -sequences formed from various L-α-amino acids. Each unit of a protein is called an amino acid residue because it is the residue of every amino acid that forms the protein by losing a water molecule.
proteins fold into one or more specific spatial conformations, driven by a number of non-covalent interactions such as hydrogen bonding, ionic interactions, Van der Waals forces, and hydrophobic packing.
Protein structures
Depending on the complexity of the structure, it can be classified as –
1) Primary structure 2) secondary structure 3) tertiary structure 4) quaternary structure
Classification of Structures
The primary structure of a peptide or protein is the linear sequence of its amino acid structural units, and partly comprises its overall bimolecular structure. By convention, the primary structure of a protein is reported starting from the amino-terminal (N) end to the carboxyl-terminal (C) end.
The amino acids differ in structure by the substituent on their side chains. These side chains confer different chemical, physical and structural properties to the final peptide or protein.
Each amino acid has both a one-letter and three-letter abbreviation. These abbreviations are commonly used to simplify the written sequence of a peptide or protein.
Primary Structure
The term secondary structure refers to the interaction of the hydrogen bond donor and acceptor residues of the repeating peptide unit.
The two most important secondary structures of proteins, the alpha helix and the beta sheet, were predicted by the American chemist Linus Pauling in the early 1950s.
Both the alpha helix and the beta sheet represent a way of saturating all the hydrogen bond donors and acceptors in the peptide backbone.
Secondary structures
The tertiary structure of a protein is a description of the way the whole chain (including the secondary structures) folds itself into its final 3-dimensional shape.
Shape is stabilized by various interactions, among the R groups of polypeptide chain.
Tertiary structure
The quaternary protein structure involves the clustering of several individual peptide or protein chains into a final specific shape.
There are two major categories of proteins with quaternary structure - fibrous and globular.
Quaternary Structures
