Biology 9700 · AS & A Level · Carbohydrates and lipids

Carbohydrates and lipids — practice question

High fructose corn syrup, which is produced from maize, can replace sucrose as a sweetener in food and drink products. The industrial manufacture of high fructose corn syrup uses the enzyme glucose isomerase, taken from bacteria.
(a)[2]

Fructose and sucrose are both types of sugar. State two structural differences between fructose and sucrose.

(b)[3]

The glucose isomerase used in the production of high fructose corn syrup is taken from a strain of the bacterium, $\textit{Thermus thermophilus}$, which lives in hot springs. The enzyme has an optimum temperature of $95\,^{\circ}\text{C}$. Suggest and explain the advantages of using glucose isomerase from $T.\ thermophilus$ to produce high fructose corn syrup, rather than using glucose isomerase that has an optimum temperature of $37\,^{\circ}\text{C}$.

(c)[3]

The commercial production of high fructose corn syrup uses immobilised glucose isomerase. Fig. 3.1 shows how $pH$ affects the activity of immobilised glucose isomerase compared with glucose isomerase free in solution. With reference to Fig. 3.1, describe the differences shown between the immobilised enzyme and the free enzyme as $pH$ changes.

(d(i))[1]

Complete Table 3.1 using a $\checkmark$ or a $\times$ to show whether the student has used Table 3.2 correctly to identify the codons for each amino acid in the nucleotide sequence.

(d(ii))[3]

Discuss, with reasons, how an mRNA nucleotide sequence worked out to match the first five amino acids using Table 3.2 may not be the same as the mRNA nucleotide sequence for those amino acids found in the bacterial cell.

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: the sugar fructose

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