3.1.4.1 General Properties of Proteins Flashcards
Q: What are the monomers from which proteins are made?
A: Amino acids.
Q: Describe the general structure of an amino acid.
A: An amino acid consists of an amine group (NH₂), a carboxyl group (COOH), a hydrogen atom, and a variable side chain (R group) attached to a central carbon atom.
Q: How do the twenty common amino acids differ from each other?
A: They differ only in their side chain (R group).
Q: What type of reaction forms a peptide bond between two amino acids?
A: A condensation reaction.
Q: What is a dipeptide, and how is it formed?
A: A dipeptide is a molecule formed by the condensation of two amino acids.
Q: What is a polypeptide, and how is it formed?
A: A polypeptide is a molecule formed by the condensation of many amino acids.
Q: Can a functional protein contain more than one polypeptide?
A: Yes, a functional protein may contain one or more polypeptides.
Q: What types of bonds and bridges play a role in the structure of proteins?
A: Hydrogen bonds, ionic bonds, and disulfide bridges.
Q: What relationship should students understand regarding protein structure?
A: The relationship between primary, secondary, tertiary, and quaternary structures, and protein function.
Q: What test can be used to detect the presence of proteins?
A: The Biuret test.
Q: Describe the initial steps of the Biuret test for detecting proteins in a sample.
A: To begin the Biuret test, a liquid solution of the sample is treated with sodium or potassium hydroxide to make it alkaline. Then, a few drops of copper (II) sulfate solution, which is blue, are added to the sample
Q: What indicates the presence of protein in the Biuret test, and what precautions should be taken during observation?
A: A colour change from blue to lilac/purple indicates the presence of protein. The colour change can be subtle, so it’s advisable to hold the test tubes against a white tile for better observation. If no colour change occurs, no protein is present.
