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Proteins: Structure, Function, Folding

– Structure and properties of the peptide bond – Structural hierarchy in proteins – Structure and function of fibrous proteins – Protein folding and denaturation – Structure analysis of globular proteins

Key topics:

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What are they made of? •  What is in Protein powder? •  Why?

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Amino Acids Continued…

•  It is the properties of the R group that determine the property of the AA and ultimately the protein

•  Hydrophobicity, polarity and charge are common measures

Primary Structure

Proteins •  Contain C, H, O, plus

nitrogen

•  Formed from amino acids joined together

•  More than 20 amino acids can be joined in any order or number to make countless proteins (think of how many words can be made from 26 letters!)

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http://www.youtube.com/watch?v=yZ2aY5lxEGE

Protein folding

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Secondary Structure

Secondary Structure of a Protein

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Secondary Structure

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Proteins •  Chains are folded

and twisted giving each protein a unique shape

•  All of the bonds help maintain protein’s shape

•  Shape of protein is important to its function!

Amylase Lipase

•  Tertiary structure refers to the overall spatial arrangement of atoms in a polypeptide chain or in a protein

Protein Tertiary Structure

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Quaternary Structure

•  Quaternary structure is formed by spontaneous assembly of individual polypeptides into a larger functional cluster

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Protein Structures

•  Levels of Organization – Primary

•  (the AA sequence of its polypeptide chain) – Secondary

•  (H bonding between peptide bonds) – Tertiary

•  (covalent, ionic, H bonding, hydrophobic)

– Quaternary •  (involves more than one subunit)

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Stabilizing the Protein •  pH: extremes will denature the protein •  Temperature: thermal stability varies among

proteins –  Typically high temp more damaging –  A lot of protein purification happens at 0C or refrigerated

conditions

•  Proteases and nucleases: degradative enzymes •  Adsorption surfaces: many proteins denatured by

contact w/air, water, glass, or plastic

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Proteins •  Provide structure

– Ex: Collagen- makes up your skin, muscles & bones

•  Aid chemical activities in your body – Enzymes- work to speed up

reactions in your body

•  Transport substances into or out of cells

•  Help fight diseases