Lesson 8: Proteins

Proteins

• diverse functions (part of the cell membrane, enzymes, muscles, cell repair)

• 50% of the dry mass of cells

• monomer: amino acids

  • 20 aa

    • 8 essential aa (must be consumed)

    • 12 the body creates

• 4 levels of structure

  • not a functional group without all 4 levels of structure

Amino acid

check notes for diagram

Primary Structure

: order of amino acids that are bonded together

• forms a peptide bond (condensation reaction)

• check notes for diagram

• not a functional protein, it is a polypeptide chain

Secondary Structure

: the first shaping of the molecule chain caused by H creating H bonds

• 2 choices of shape

  • alpha-helix (right handed coil)

  • beta-pleated sheet (folded up like paper)

Tertiary Structure

: final shaping of the molecule, dependant on the R group interactions

• hydrophobic, nonpolar R group

  • moves to the inside

• hydrophilic, polar R group

  • moves to the outside

• contains H

  • H bonds form between R groups

• contains S

  • strong disulfide bridges can form

    • S - S

Quaternary Structure

: # of polypeptide chains that interact with each other to form a protein (e.g. hemoglobin has 4 chains, collagen has 3 chains, etc.)

Denatured

: when a protein is outside its optimal range (temperature, pH, etc.) it will lose its structure and shape, therefore, it cannot function.

• if the Primary Structure is not broken and its optimal range is returned, the protein can reform