Name two $\alpha$-amino acids which form a dipeptide which is 100 times more sweet than cane sugar ?
Aspartame is the most successful and widely used artificial sweetener. It is methyl ester of dipeptide formed from aspartic acid and phenylalanine. Its use is limited to cold foods and soft drinks because it is unstable at cooking temperature.
Structure of aspartame is
Aspartame is unstable at cooking temperature, where would you suggest aspartame to be used for sweetening?
Aspartame is used in cold foods and soft drinks. It is an artificial sweetening agent.
Sodium salts of some acids are very useful as food preservatives. Suggest a few such acids.
A preservative is naturally occuring or synthetically produced substance that is added to foods to prevent decomposition by microbial growth or by undesirable chemical changes. Sodium salts of same acids are very useful as food preservatives. Some examples of such acids are as follows
(i) Benzoic acid in the form of its sodium salt, constitutes one of the most common food preservative. Sodium benzoate is a common preservative in acid or acidified foods such as fruit, juices, pickles etc. Yeasts are inhibited by benzoate to a greater extent than are moulds and bacteria.
(ii) Sorbic acid and its salts (sodium, potassium and calcium) also have preservative activities but the applications of sodium sorbate $\mathrm{C}_6 \mathrm{H}_7 \mathrm{NaO}_2$ are limited compared to that for potassium salt.
(iii) Sodium erythorbate $\mathrm{C}_6 \mathrm{H}_7 \mathrm{NaO}_6$ is a food additive used predominate in meats, poultry and soft drinks.
(iv) Sodium propanoate $\mathrm{Na}\left(\mathrm{C}_2 \mathrm{H}_5 \mathrm{COO}\right)$ is used in bakery products as mold inhibitor.
Explain the role of allosteric site in enzyme inhibition?
Some drugs do not bind to the active site of enzymes to inhibit their activities. These bind to a different site of enzyme. This binding of inhibitor (drug) changes the shape of the active site in such a way that substrate cannot recognise it.
The site different from active site of an enzyme where a drug molecule can bind is called the allosteric site.
Non-competitive inhibitor changes the active site of enzyme after binding at allosteric site.
How are receptor proteins located in the cell membrane?
Receptor proteins are embedded in the cell membrane in such a way that their small part possessing active site projects out of the surface of the it membrane and opens on the outside region of the cell membrane.
