Chapter 3.2 - Proteins 

• Most structurally & functionally diverse group of biomolecules

• Involved in almost everything in biology

Functions:

• Enzymes

• structure (keratin, collagen)

• carriers & transport (membrane channels)

• receptors & binding (defense)

• contraction (actin & myosin)

• Signaling, communication/response (hormones)

• Monomer: amino acid (1 link in a chain)

• Polymers: polypeptide chain 

  • The bond that holds the acids together, is called a peptide bond

  • Forms large and complex molecules, 3-D shape, folded and twisted 

  • Human body: 400 amino acids

Amino

• Same structure

  • Central carbon

  • Amino group

  • Carboxyl group

    • All three stay the same ^

  • R group/Variable Group ( only thing that is different): gives amino acid its unique chemical properties

Nonpolar Amino Acids:

• Nonpolar & hydrophobic side chains, it’s consider if the side chains are nonpolar - causes them to be hydrophobic

  • ( Amino acids list on notes)

Polar Amino Acids

• Polar/Charged (positive or negative) & hydrophilic side chains

Building Proteins:

• All macromolecules are made through dehydration synthesis - creates peptide bonds

  • Linking NH2 of 1 amino acids to COOH of another (removes H2O)

  • C - N bond

• Polypeptide chain

  • N-terminal = NH2 and (beginning)

  • C-terminal = take OH and get rid of them as water molecules, COOH end (end)

    • Same repeated process for the entire backbone (growth in one direction)

Protein Structure & Function

• Function depends on structure

  • 3D shape: twisted, folded, coiled into unique shape

• All started w/ the order of amino acids (instructions in DNA to tell what to do)

• 4 levels with proteins folding

Primary (1) Structure

• Order of amino acids in chain

  • Amino acid sequences determined by DNA

  • Slight change in amino sequence, even 1,  can affect protein’s structure & function

SIckle Cell Anemia: 

Secondary Structure

• “Local folding”: folding along short sections of the polypeptide

• Interaction between adjacent amino acids

• Caused by hydrogen bonding along the backbone

  • Alpha (a) helix

  • Beta (b) Pleated sheet (has creased)

Tertiary Structure 

• Global (whole folding) Folding  

• Caused/determined by Interactions between the R groups 

  • Hydrophobic interactions

  • Disulfide bridge - help stabilize structure 

Quaternary Structure

• Not all proteins have this

• Joins together more than 1 polypeptide chain, then it’ll be functional

Chaperonin Proteins 

• Guides protein folding, gives isolated space to be folded properly 

  • Provide shelter for folding polypeptide

  • Keep the proteins segregated from cytoplasmic influences 

    • Will be released after so the protein can do what it needs

Protein Structure (On Notes 3.2 PowerPoint)

Denature a Protein (Unfold/Unravel)

• Disrupts 3 structure

  • pH

  • Temperature

  • Salt

• In conditions of the environment changes, denature/unravel protein

  • Can disrupt H bonds, ionic bonds, attraction, & disulfide bridges

  • Won’t work anymore

• Some proteins can return/refold to their shape, some cannot