Proteins

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Proteins

Polymers composed of amino acids

Protein = Polypeptide (polymer) Monomer = Amino acids

Peptide bonds

Amino acid Amine Group (NH2)

Basic Carboxylic Acid Group (COOH)

Acidic

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Protein Functions

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4 Levels of Protein Structure

Primary level Sequence of amino acids Polar covalent bonds link the amino acids Only level that doesn’t use hydrogen bonds

Secondary Hydrogen bonding between amino acid side groups The sequence of amino acids converts into 1 of 2 forms

α-helix β-pleated sheets

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1’ and 2’ Levels Protein Structure

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1’ & 2’ Animations

05_21aPrimaryStructure.swf

05_21bSecondaryStructure.swf

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3’ & 4’ Structure

Tertiary 3D shape of a polypeptide Many types of bonds/interactions between side groups Disulfide bridges are most significant here

Quaternary 2 or more polypeptides (subunits) of a protein Not found in all proteins Same bonds/interactions as tertiary level

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Tertiary & Quaternary Levels

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3’ & 4’ Animations

05_21cTertiaryStructure.swf

05_21dQuaternaryStructure.swf

Animation-03-01.swf

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Protein Denaturation

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Protein Denaturation

Denaturation Protein unravels and loses its native conformation

Structure & Function Change in the protein’s structure = loss of function

Denaturation occurs: Organic solvent Any chemical that disrupts the tertiary structure Heat (excessive)

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Chaperonins

Proteins that assist the proper folding of other proteins

Provide stable, insulated environment for polypeptide to achieve the correct conformation

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Protein Questions

Name all of the bonds in primary protein structure?

What bonds hold together secondary structure?

What about tertiary level? Quaternary?

Which level of protein structure is NOT found in all proteins?

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Protein Questions (Page 2)

What is the name of a protein’s monomer?

What is the name of a protein’s polymeric form?

What are the 2 functional groups on an Amino Acid?