Scottish Highers Chemistry proteins: Uncooked egg white is mainly com

Question

Uncooked egg white is mainly composed of dissolved proteins. During cooking processes, the proteins become denatured as the protein chains unwind, and the egg white solidifies.

(a) Explain why the protein chains unwind.

(b) The temperature at which the protein becomes denatured is called the melting temperature. The melting temperature of a protein can be determined using fluorescence. In this technique, the protein is mixed with a dye that gives out visible light when it attaches to hydrophobic parts of the protein molecule. The hydrophobic parts of the structure are on the inside of the protein and the dye has no access to them unless the protein unwinds.

(i) Ovalbumin is a protein found in egg white. Part of the structure of unwound ovalbumin is shown below.

Circle the part of the structure to which the hydrophobic dye is most likely to attach.

(ii) Another protein in egg white is conalbumin. The temperature of a conalbumin/dye mixture is gradually increased. The fluorescence is measured and a graph is produced.

The melting temperature is the temperature at which the fluorescence is halfway between the highest and lowest fluorescence values.

Determine the melting temperature, in °C, for this protein.

(c) Once cooked and eaten, the digestive system breaks the protein chains into amino acids with the help of enzymes.

(i) State the name of the digestion process where enzymes break down proteins into amino acids.

(ii) A) State how many amino acid molecules joined to form this section of protein.

B) Draw the structure of one amino acid that would be produced when this section of the protein chain is broken down.

Uncooked egg white is mainly composed of dissolved proteins - Scottish Highers Chemistry - Question 6 - 2015

Worked Solution & Example Answer:Uncooked egg white is mainly composed of dissolved proteins - Scottish Highers Chemistry - Question 6 - 2015

Explain why the protein chains unwind.

Determine the melting temperature, in °C, for this protein.

State the name of the digestion process where enzymes break down proteins into amino acids.

State how many amino acid molecules joined to form this section of protein.

Draw the structure of one amino acid that would be produced when this section of the protein chain is broken down.

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