Primary Structure

Primary Structure - Primary Structure Polypeptide chain of...

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Primary Structure Polypeptide – chain of approximately 200-500 amino acids long Peptide bonds – formed between amino and carboxyl groups in amino acids Type of amide bond – bond between an amide and organic acid o Peptide bond forces protein “backbone” to exhibit directionality o End of the protein with unlinked amino group = N-terminus o End of the protein with unlinked carboxyl group = C-terminus Since N and O are more electronegative: o O gains partial negative charge from the bond o H gains partial positive charge as it loses electrons to N Secondary Structure Principle secondary structures include: o Alpha (α) helix H-bonds from O and H of peptide bond create spiral shape of α helix N-terminus located upwards and C-terminus located downwards due to H- bond orientation Complete turn of spiral approximately every 3.6 residues (amino acids) R-groups directed outward will determine hydrophobicity of protein o Beta (β) sheet Composed of laterally packed β strands, each about 5-8 residues long, that form pleated sheet Hydrogen bonding occurs between separate β strands (rather than nearly adjacent AAs as in α-helix) Β strands can be within the same polypeptide chain (with looping between
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Primary Structure - Primary Structure Polypeptide chain of...

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