Chemistry- Chapter 19 - Amino Acids and Proteins

Amino Acids

Proteins are composed of building blocks called

Primary structure

the sequence of amino acids in a polypeptide, polymers of amino acids held together by peptide bonds

secondary structure

peptide bonds can H- bond with each other

a-helices: backbone forms a tight coil with side chains projecting outward

B-sheets: sections of backbone lined up in parallel rows

tertiary structure

shape of protein that results from all interactions involving side chains

quaternary structure

some proteins contain two of more polypeptide chains that are attracted to one another, the way in which two or more polypeptides join to form active proteins

protein denaturation

any disruption of interactions in the protein that renders it inactive is known as denaturation, may unfold completely or shift into a different, non-active fold

changing the solvents

organic solvents will shift the positions of hydrophobic and hydrophilic side chains

hydrophobic: side chains will move to the exterior

hydrophilic: side chains will cluster in interior

changing the PH

the ionization of the acidic and basic side chains will change, and ion-ion attraction is disrupted

lowering the PH will protonate carboxylic acid side, increasing the pH will deprotonate the amine side chain

raising temp and violent agitation

As temperature increases, molecules have increasingly rapid

molecular motion

This motion will denature most proteins between 50°C and

70°C.

adding ionic substances

addition of high concentrations of ionic compounds will interrupt ion-ion attractions, soaps will interrupt ion-ion attractions and hydrophilic and hydrophobic interactions, heavy metal ions such as ions of lead, mercury are strongly attracted to sulfur and will disrupt disulfide bridges