1.4.1 proteins

Draw the general structure of an amino acid

Describe the general properties of proteins

• COOH= carboxyl group

• R= variable side chain

• H2N= amine group

How many amino acids are common in all organisms, how do they differ

20. Differ in their side chain (R)

Describe how amino acids join together

• by condensation reaction

• Removing a water molecule

• Between carboxyl and amine group

• Forming a peptide bond

Draw amino acids joined together

.

What is a dipeptide

2 amino acids joined together

What are polypeptides

Many amino acids joined together

What is a functional protein

A protein that may contain one or more polypeptides

Describe the primary structure of a protein

• Sequence of amino acids in a polypeptide chain

• Joined by peptide bonds

Describe the secondary structure of a protein

• folding polypeptide chain. Alpha helix/ beta pleated sheets

• Due to hydrogen bonding between amino acids

• Between NH and C=O

Describe the tertiary structure of a protein

• 3D folding of polypeptide chain

• Due to interactions between amino acid R groups

• Forming hydrogen bonds, ionic bonds and disulfide bridges

Describe the quaternary structure of a protein

• more than one polypeptide chain

• Formed by interactions between polypeptides (hydrogen bonds, ionic bonds and disulfide bridges)

Describe the test for proteins

1. Add biuret reagent

2. Positive= purple/ lilac. Negative= blue