Proteins Flashcards
What are the monomers of proteins?
Amino acids
What is formed when two amino acids join?
A dipeptide
What is a polypeptide?
A polypeptide is formed when more than two amino acids join together
What is the structure of an amino acid?
A carboxyl group (-COOH), an amino group (NH2) and an R group (variable group)
How are amino acids joined together?
Amino acids are linked together by condensation reactions to form polypeptides. A molecule of water is released and a peptide bond is formed between the amino acids
What are the four levels in a proteins structure?
- Primary
- Secondary
- Tertiary
- Quaternary
What is the primary structure of a protein?
The sequence of amino acids in the polypeptide chain
What is the secondary structure of a protein?
Hydrogen bonds form between the amino acids in the polypeptide chain. This makes it coil into an alpha helix or fold into a beta pleated sheet
What is the tertiary structure of a protein?
More bonds form between different parts of the polypeptide chain including hydrogen bonds, ionic bonds and disulphide bridges (the sulfur atom in one cysteine bonds to the sulfur atom in another cysteine when they’re close together). For proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure
What is the quaternary structure of a protein?
Some proteins are made from several different polypeptide chains held together by bonds. The quaternary structure is the way these polypeptide chains are assembled together
Give four functions of proteins
- Enzymes
- Antibodies
- Transport proteins
- Structural proteins
How would you test for proteins?
Biuret test
Explain the biuret test for proteins
- The test solution needs to be alkaline to add a few drops of sodium hydroxide solution
- Then add copper(II) sulphate solution. If protein is present the solution turns purple. If there’s no protein it will stay blue
