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.
What happens when the bond formed between an enzyme and an inhibitor is a strong covalent bond?
Generally, a weak bond such as H-bonding, van der Waals' interactions, etc., is formed between the enzyme and inhibitor. If a strong covalent bond is formed between the enzyme and the inhibitor which cannot be broken easily, then the enzyme is blocked permanently. The body then degrades the enzyme-inhibitor complex and synthesises the new enzyme.
Match the medicines given in Column I with their uses given in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Ranitidine | 1. | Tranquilizer |
| B. | Furacine | 2. | Antibiotic |
| C. | Phenelzine | 3. | Antihistamine |
| D. | Chloramphenicol | 4. | Antiseptic |
| 5. | Antifertility drug |
A. $\rightarrow(3)$ B. $\rightarrow$ (4) C. $\rightarrow$ (1) D. $\rightarrow(2)$
A. Ranitidine It prevents the interaction of histamine with the receptors present in the stomach wall. Thus, it controls the secretion of HCl and pepsin in stomach.
B. Furacine Furacine is an antiseptic. It can be applied to the living tissues to kill or to prevent the growth of microorganisms.
C. Phenelzine It is also known as Nardil. Its structure is
It is used to treat depression.
D. Chloramphenicol It is a broad spectrum antibiotic. It can be given orally in case of typhoid, acute fever, dysentary, certain urinary infections, meningitis and pneumonia.