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Discuss The Structure Of Proteins And The Roles Different Forms Of Bonding Play In Protein Folding Notes

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Discuss the structure of proteins and the roles different forms of bonding play in protein folding? How do we study structure?
Proteins act as the variable biological molecules of all life, acting as the direct phenotypic consequence of DNA sequences. They are the physical result of DNA mutations, determining the phenotype of every living organism through their ability to catalyse chemical reactions. This catalysis is itself dependent on protein structure and therefore it is crucial to understand how enzymes fold and form the structures they do, in order to understand how life works. Fundamentally proteins are composed of 20 different amino acid monomers, all of which are coded for by unique triplet codes along DNA molecules. Their structure (see Fig. 1) is made up of a carboxyl group and an amine group bonded to a central α-carbon, with a proton and variable R group also attached to it. The R group varies between the amino acids, providing them with unique chemical properties, giving proteins the potential to have a huge range of structures themselves. As a result, this chemical diversity on the monomer level gives rise to almost limitless functional diversity of proteins, allowing the complexity of life we see to evolve.

T α-carbon is asymmetric, making amino acids chiral. They are all L enantiomers, necessary The R-group may contain hydrophobic or hydrophilic groups, crucial in protein folding.

Fig. 1 - Amino Acid Structure


These amino acid monomers are polymerised by peptide bonds to form a polypeptide structure. These amide bonds are formed between the amine and carboxyl groups in a condensation reaction and significantly are planar, leading to the polypeptide being restricted in the thermodynamically stable shapes it may form. It is planar due to a degree of delocalisation about the bond, leading to rotation requiring an activation energy, causing the equilibrium planar shape to be most stable. T structures that may form to be limited, with only 2 bond angles being variable structure, with only a small range of ϕ (psi) and Ψ
(phi) angles forming stable structures. This limitation is crucial to permitting unique protein folding given a certain primary structure (much like universal chirality), therefore allowing a one-to-one function between a DNA sequence and eventual protein structure. Without this property life could not evolve, since a far greater proportion of mutations would be deleterious. T
. These are universal among proteins no matter what their primary structure, since hydrogen bonds are formed between the backbone carboxyl and amine groups, common to all amino acids. They are the stable building blocks which can be manipulated through R group interactions to form Daniel Day


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