Proteins Flashcards
Draw and describe the structure of an amino acid.
There is a central carbon atom bonded to an amino group, a carboxyl group, an H group and a variable R group.
. Describe how a peptide bond is formed between two amino acids.
A condensation reaction occurs between the amino group of one amino acid and the carboxyl group of another amino acid, producing a molecule of water .
Draw a dipeptide.
Describe the primary structure of a protein (polypeptide).
The sequence of amino acids that have been joined by the condensation reaction to form a polypeptide chain.
. Describe how the secondary structure of a protein is produced.
There are hydrogen bonds between the amino group of one amino acid and the C=O group of another, forming α-helix or β-pleated sheet.
Describe how the tertiary structure of a protein is produced.
The specific sequence of amino acids in the polypeptide chain will fold into the complex 3-D tertiary structure due to different bonds between the different R-groups. These bonds are disulphide bridges, ionic bonds and hydrogen bonds.
Describe how the quaternary structure of a protein is produced.
Different polypeptide chains combine in various ways, and may also be associated with a non-protein group.
Two proteins have the same number and type of amino acids, but different tertiary structures. Explain how.
They could have a different primary structure (sequence of amino acids) and therefore the bonds between the R-groups, such as disulphide bridges, ionic bonds and hydrogen bonds would be in different places.
A protein can change shape due to the pH of the solution it is in. Explain how.
The ionic and hydrogen bonds that hold the 3-D tertiary structure in place are affected by the pH. Disruption of these bonds will therefore change the structure of the protein
Describe the biochemical test for proteins (and enzymes!)
Add Biurets reagent to the test solution. A positive result is from blue to purple.
