Topic 1a- Biological molecules- Proteins Flashcards
What groups do all amino acid molecules have in common?
Amino acids have the same general structure- a carboxyl group, n amine or amino group and an R group.
Give three functions of proteins
Proteins acting as enzymes catalyse biological processes, greatly accelerating the rate of reactions.
In defence, antibodies (proteins) bind to specific foreign particles (antigens) helping to protect the body.
Proteins provide structural support in organisms.
Describe how you would test for the presence of protein in a sample.
Biuret test.
1) The test solution needs to be alkaline, so first you add a few drops of sodium hydroxide solution.
2) Then you add some copper sulfate solution.
If protein is present, the solution turns purple.
If there’s no protein, the solution will stay blue. The colours are pale, so you need to look carefully.
Leucyl-alanine is a dipeptide. Describe how a dipeptide is formed.
A dipeptide is formed when 2 amino acids join together.
Myoglobin is a protein formed from a single polypeptide chain. Describe the tertiary structure of a protein like myoglobin.
The secondary structure is coiled and folded further to form the protein’s final 3D structure. More bonds, including hydrogen bonds, ionic bonds and disulphide bridges, form between different parts of the polypeptide chain.
What term is used to describe the structure of a protein made of two or more polypeptides.
The quaternary structure.
Describe 2 ways in which all dipeptides are similar and one way in which they might differ.
Similarities- all dipeptides contain carbon, hydrogen, nitrogen, and oxygen.
All dipeptides formed from a condensation reaction.
Differences- two isomers of the dipeptide are possible, depending on the sequence.
The secondary structure of a polypeptide is produced by bonds between amino acids. Describe how.
Due to hydrogen bonds that form between the oxygen atom of one amino acid and the nitrogen atom of another.
Two proteins have the same number and type of amino acids but different tertiary structures. Explain why.
The order of the amino acids (primary structure) in the two proteins may be different. Can result in ionic, hydrogen, disulphide bonds to form in different locations in each protein. These differences cause variations in the three dimensional structures of the proteins. (tertiary structure)
Name the chemical element found in all amino acids that is not found in triglycerides.
Nitrogen
Explain how the shape of an enzyme molecule is related to it’s function.
The shape of an enzyme’s active site is complementary to the shape of it’s specific substrate or substrates.
Bacteria produce enzymes which cause food decay. Explain how vinegar, which is acidic, can prevent the action of bacterial enzymes in some preserved foods.
The low pH of vinegar (acidic) results in the deforming of the specific tertiary structure of the enzymes as it disrupts it’s ionic bonds + disulphide bridges.
