The Chemistry of Life Proteins Ms. Richardson - SBI4U

Proteins - Overview Involved in almost everything cells do Includes enzymes, immunoglobulins, hemoglobin, keratin, fibrin, etc. Proteins are made up of many amino acids (each is called a residue)

Amino Acids Proteins are made of one or more amino acids The 20 amino acids differ in the R groups they contain (8 amino acids are essential) These side chains can make the amino acid polar (hydrophilic), non-polar (hydrophobic), or charged (acidic/basic) ...when dissolved in water at a pH of 7, the ‘carboxyl’ donates an H+ ion to the ‘amino

Nonpolar Amino Acids

Polar Amino Acids

Acidic and Basic Amino Acids

Protein Structure Amino acids are the monomers that make up proteins Amino acids are held together by peptide bonds which are formed by a dehydration synthesis reaction

Protein Structure Also called the conformation There are four levels of structure/conformation Depends on the amino acids it contains, and the interaction between those amino acids

Primary Structure Polypeptide chain  many amino acids in a chain connected by peptide bonds The sequence of amino acids is determined by the nucleotide sequence of a particular gene In a protein with ‘X’ number of amino acids, number of possibilities is 20X

Secondary Structure Folding and coiling of amino acid chain Formed by hydrogen bonds between oxygen atoms of a carboxyl group and hydrogen atoms of an amino group Two types: α helix – tight coil produced by H-bonds every 4 peptide bonds repeated β pleated sheets – H-bonds formed between parallel stretches of a polypeptide

Tertiary Structure The polypeptide chain undergoes additional folding due to side chain (R-group) interactions.

Quaternary Structure Two or more polypeptide chains come together, such as in collagen and haemoglobin