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Chromatography is often used for the analysis of the mixture of amino acids that is formed when proteins are broken down - VCE - SSCE Chemistry - Question 5 - 2003 - Paper 1
Question 5
Chromatography is often used for the analysis of the mixture of amino acids that is formed when proteins are broken down. The small protein enkephalin is known for i... show full transcript
Worked Solution & Example Answer:Chromatography is often used for the analysis of the mixture of amino acids that is formed when proteins are broken down - VCE - SSCE Chemistry - Question 5 - 2003 - Paper 1
Step 1
Explain how an Rf value is calculated.
Answer
The Rf value is calculated by taking the ratio of the distance moved by the substance from the origin (zero point/initial spot) to the distance moved by the solvent from the origin (zero point/initial spot). This is expressed mathematically as:
The significance of this calculation lies in the fact that it allows for the comparison of the movement of different amino acids relative to the solvent front.
Step 2
Calculate the Rf of the methionine spot.
Answer
To calculate the Rf value for methionine, we first need to determine the distances. According to the chromatogram:
- Distance moved by the methionine spot = 17.4 cm
- Distance moved by the solvent front = 28.8 cm
Using the formula mentioned earlier:
Therefore, the Rf value of the methionine spot is approximately 0.61.
Step 3
Describe how the sample containing the mixture of the four amino acids was added to the paper in order to begin the procedure.
Answer
The sample containing the amino acids was applied to the chromatography paper using a capillary tube or a small dropper. This was done at the zero point/initial spot on the paper. It is crucial to ensure that a small and concentrated spot is placed on the paper to allow for proper separation of the amino acids during the chromatography process.
Step 4
What factors determine the different Rf values of the different amino acids?
Answer
The different Rf values of amino acids can be attributed to several key factors:
- Polarity: Amino acids with different polarities will interact differently with the mobile phase (solvent) and the stationary phase (paper).
- Solubility: The solubility of the amino acids in the mobile phase influences how far they travel during the chromatography process.
- Molecular size: Larger molecules may move more slowly compared to smaller ones, affecting their Rf values.
- Interactions with the stationary phase: The ability of an amino acid to adhere to the stationary phase will also impact its distance traveled, hence its Rf value.