Class 12 - Chemistry - Chemistry In Everyday Life
Why do we need to classify drugs in different ways?
The classification of drugs and the reasons for classification are as follows:
(i) On the basis of pharmacological effect:
This classification provides doctors the whole range of drugs available for the treatment of a particular type of problem.
Hence, such a classification is very useful to doctors.
(ii) On the basis of drug action:
This classification is based on the action of a drug on a particular biochemical process.
Thus, this classification is important.
(iii) On the basis of chemical structure:
This classification provides the range of drugs sharing common structural features and often having similar pharmacological activity.
(iv) On the basis of molecular targets:
This classification provides medicinal chemists the drugs having the same mechanism of action on targets.
Hence, it is the most useful to medicinal chemists.
Explain the term, target molecules or drug targets as used in medicinal chemistry?
In medicinal chemistry, drug targets are those important molecules which are involved in certain metabolic pathways,
whose alterations in levels can lead to disease conditions. Carbohydrates, proteins, lipids are examples of drug targets.
Drugs targets are those molecules which are targeted for action by specific drugs to achieve a predetermined result.
Drugs bind to specific receptors on cells and carry out the effect on target molecules through signalling pathways.
Name the macromolecules that are chosen as drug targets.
The macromolecules chosen as drug targets are carbohydrates, lipids, proteins, and nucleic acids.
Why should not medicines be taken without consulting doctors?
A medicine can bind to more than one receptor site. Thus, a medicine may be toxic for some receptor sites.
Further, in most cases, medicines cause harmful effects when taken in higher doses than recommended.
As a result, medicines may be poisonous in such cases. Hence, medicines should not be taken without consulting doctors.
Define the term chemotherapy.
Chemotherapy is the clinical use of chemical substances to treat cancer. It prevents the growth of or kills malignant cancer cells.
This form of treatment is administered by injecting the cancer-fighting medication into the veins.
In many cases, it involves multiple types of medications to treat the cancer, and when this happens, the patient receives a group of drugs that work like a team to kill more cancer cells.
Chemotherapy is frequently a preferred choice for cancer treatment since it travels throughout the body, unlike treatment with radiation and surgery.
Which forces are involved in holding the drugs to the active site of enzymes?
Either of the following forces can be involved in holding drugs to the active sites of enzymes.
(i) Ionic bonding
(ii) Hydrogen bonding
(iii) Dipole − dipole interaction
(iv) van der Waals force
While antacids and antiallegric drugs interfere with the function of histamines, why do these not interfere with the function of each other?
Drugs designed to cure some ailment in one organ in the body do not affect the other because they work on different receptors.
For example, secretion of histamine causes allergy. It also causes acidity due to release of hydrochloric acid in the stomach.
Since anti-allergic and antacids drugs work on different receptors, therefore, antihistamines remove allergy while antacids remove acidity.
Low level of noradrenaline is the cause of depression. What type of drugs is needed to cure this problem? Name two drugs?
Anti-depressant drugs are needed to counteract the effect of depression.
These drugs inhibit enzymes catalysing the degradation of the neurotransmitter, noradrenaline.
As a result, the important neurotransmitter is slowly metabolised and then it can activate its receptor for longer periods of time.
Two anti-depressant drugs are:
What is meant by the term ‘broad spectrum antibiotics’? Explain?
Broad spectrum antibiotics are effective against several different types of harmful bacteria.
For example: - tetracycline, chloramphenicol and ofloxacin.
Chloramphenicol can be used in case of typhoid, dysentery, acute fever, urinary infections, meningitis and pneumonia.
How do antiseptics differ from disinfectants? Give one example of each.
Antiseptics and disinfectants are effective against micro-organisms.
However, antiseptics are applied to the living tissues such as wounds, cuts, ulcers, and diseased skin surfaces, while disinfectants are applied to inanimate objects such as floors, drainage system, instruments, etc.
Disinfectants are harmful to the living tissues. Iodine is an example of a strong antiseptic.
Tincture of iodine (2 − 3 percent of solution of iodine in alcohol − water mixture) is applied to wounds.
1 percent solution of phenol is used as a disinfectant.
Why are cimetidine and ranitidine better antacids than sodium hydrogen carbonate or magnesium or aluminium hydroxide?
Antiseptics are chemical substances which prevent the growth of microorganisms and may even kill them but not harmful to human or animal tissue.
For example: - Dettol and Savlon. They are generally applied on wounds, cuts, ulcers and diseased skin surfaces.
Furacin and soframycin are well known antiseptic creams.
Disinfectants are chemical substances which kill microorganisms but are not safe to be applied to the living tissues.
These are generally used to kill microorganisms present in the drains toilets, floors, etc.
Some common examples of disinfectants are phenol (1% solution) and chlorine (0.2 to 0.4 ppm).
Name a substance which can be used as an antiseptic as well as disinfectant.
Phenol can be used as an antiseptic as well as a disinfectant. 0.2 percent solution of phenol is used as an antiseptic,
while 1 per cent of its solution is used as a disinfectant.
What are the main constituents of dettol?
Chloroxylenol and α-terpineol in a suitable solvent
What is tincture of iodine? What is its use?
Tincture of iodine is a 2 − 3 percent solution of iodine in alcohol − water mixture. It is applied to wounds as an antiseptic.
What are food preservatives?
Food preservatives are chemicals that prevent food from spoilage due to microbial growth.
Table salt, sugar, vegetable oil, sodium benzoate (C6H3COONa), and salts of propanoic acid are some examples of food preservatives.
Why is use of aspartame limited to cold foods and drinks?
Aspartame is non-saccharide sweetener which is used as sugar substitute.
Its use is limited to cold drinks and food to keep its consumption on the lower side and within range to avoid its harmful effect.
Aspartame breaks down to give one of its products as phenylalanine which is harmful. Aspartame becomes unstable at cooking temperature.
This is the reason why its use is limited to cold foods and drinks.
What are artificial sweetening agents? Give two examples.
Artificial sweetening agents are chemicals that sweeten food.
However, unlike natural sweeteners, they do not add calories to our body.
They do not harm the human body. Some artificial sweeteners are aspartame, saccharin, sucrolose, and alitame.
Name the sweetening agent used in the preparation of sweets for a diabetic patient.
Artificial sweetening agents such as saccharin, alitame, and aspartame can be used in preparing sweets for diabetic patients.
What problem arises in using alitame as artificial sweetener?
Alitame is a high potency artificial sweetener.
Therefore, it is difficult to control the sweetness of the food to which it is added.
How are synthetic detergents better than soaps?
They can be used in hard water as well as in acidic solution.
The reason being that sulphonic acids and their calcium and magnesium salts are soluble in water
but soaps of fatty acids and their calcium and magnesium salts are insoluble
Explain the following terms with suitable examples
(i) Cationic detergents
(ii) Anionic detergents and
(iii) Non-ionic detergents.
Cationic detergents are quaternary ammonium salts of acetates, chlorides, or bromides.
These are called cationic detergents because the cationic part of these detergents
contains a long hydrocarbon chain and a positive charge on the N atom. For example:
Anionic detergents are of two types:
These detergents are sodium salts of long chain alkylbenzenesulphonic acids.
They are prepared by Friedel-Crafts alkylation of benzene with long chain alkyl halides or alkenes.
The obtained product is first treated with concentrated sulphuric acid and then with sodium hydroxide.
Sodium 4-(1-dodecy) benzenesulphonate (SDS) is an example of anionic detergents.
Polyethylene glycol stearate.
What are biodegradable and non-biodegradable detergents? Give one example of each?
Detergents that can be degraded by bacteria are called biodegradable detergents.
Such detergents have straight hydrocarbon chains. For example: sodium lauryl sulphate
Detergents that cannot be degraded by bacteria are called non-biodegradable detergents.
Such detergents have highly-branched hydrocarbon chains.
For example: sodium -4- (1, 3, 5, 7- tetra methyl octyl) benzene sulphonate
Why do soaps not work in hard water?
Soaps are sodium or potassium salts of long-chain fatty acids. Hard water contains calcium and magnesium ions.
When soaps are dissolved in hard water,
these ions displace sodium or potassium from their salts and form insoluble calcium or magnesium salts of fatty acids.
These insoluble salts separate as scum.
This is the reason why soaps do not work in hard water.
Can you use soaps and synthetic detergents to check the hardness of water?
Soaps get precipitated in hard water, but not in soft water.
Therefore, soaps can be used for checking the hardness of water.
However, synthetic detergents do not get precipitated either in hard water or in soft water.
Therefore, synthetic detergents cannot be used for checking the hardness of water.
Explain the cleansing action of soaps.
Soap molecules form micelles around an oil droplet (dirt) in such a way that the hydrophobic parts of the stearate ions
attach themselves to the oil droplet and the hydrophilic parts project outside the oil droplet.
Due to the polar nature of the hydrophilic parts, the stearate ions (along with the dirt) are pulled into water,
thereby removing the dirt from the cloth.
If water contains dissolved calcium hydrogencarbonate, out of soaps and synthetic detergents which one will you use for cleaning clothes?
Calcium bicarbonate makes water hard. Therefore, soap cannot be used because it gets precipitated in hard water.
On the other hand, a synthetic detergent does not precipitate in hard water because its calcium salt is also soluble in water.
Therefore, synthetic detergents can be used for cleaning clothes in hard water.
3RCOONa + Ca (HCO3)2 --> (RCOO) 2 Ca + 2NaHCO3
Label the hydrophilic and hydrophobic parts in the following compounds:
(a) CH2 (CH2)10CH2OSO3 -Na+
(b) CH3 (CH2)15 – N+ (CH3)3Br–
(c) CH3 (CH2)16COO (CH2CH2O) nCH2CH2OH.
Hydrophobic part Hydrophilic Part
Hydrophobic part Hydrophilic Part
Hydrophobic part Hydrophilic Part