AP Bio Unit 1: Chp 3: Carbon and the Molecular Diversity of Life (Proteins)

Proteins

Examples of uses are enzymes, defense, store, and transport

Types of proteins

Enzymatic proteins, defensive, storage (of amino acids), transport, hormonal, receptor, contractile and motor, and structural

Polypeptides

Proteins consist of 1 or more of these, they are unbranched polymers built from the same set of 20 amino acids (peptide chain)

Amino Acids

monomer unit of proteins; organic molecules with carboxyl and amino groups, differ in properties due to different side chains (r groups)

Side chains of amino acids (r groups) can be...

hydrophobic (nonpolar), hydrophilic (polar), electrically charged (acidic [-] and basic [+])

Peptide bonds

Amino acids are linked by these

Polymers of amino acids

Polypeptides, they range in length from a. few to more than a thousand monomers, each are unique linear sequence of amino acids with a carboxyl end (C-terminus) and an amino end (N-terminus)

Functional protein

Consists of one or more polypeptides precisely twisted, folded and coiled into a unique shape

Shape of Proteins

3D shape is why the protein has it's function; Structure determines function

Sequence of amino acids

are determined genetically, leads to 3D structure

4 Levels of protein stucture

1. Primary Structure, 2. Secondary structure, 3. Tertiary Structure, 4. Quaternary Structure

Primary Structure

Unique sequence of amino acids (linked peptide bonds); beaded necklace

Secondary Structure

Consists of coils and folds in polypeptide chain; alpha helix or beta pleated sheet, result of hydrogen bond from polypeptide backbone

Tertiary Structure

Determined by R groups (side chains); Hydrophilic interactions, disulfide bridges -between cysteines- (covalent bonds) ionic and hydrogen bonds between polar side chains

Quaternary Structure

2 separate proteins that combine together

Slight changes in primary structure can

affect protein structure and ability to function

Sickle cell disease

results from a single amino acid substitution in the protein hemoglobin

Denaturation

Protein unravels; Caused by changes in pH, salt concentration, temperature, or other environmental factors

Renaturation

The reverse of denaturation; It involves the reconstruction of a protein into its original tertiary structure after denaturation