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Drugs and drug interactions play a major role in our life. Every human being takes drugs in some form at least once in their lifetime. All the vaccines, medications we consume are some forms of drugs. Drugs aid in several biological processes but they don't always give the desired effect. That is why it is important to study drugs and drug interactions so that we can understand how drugs interact with different components in our body and what their effects are.
Also Read: Adolescence and Drug Abuse
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Key Takeaways: Drugs, Medicines, Molecular Targets, Enzymes, Receptors, Enzyme Inhibitors, Neurons
What are Drugs?
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Drugs are synthetically prepared chemicals that physiologically affect all living beings when taken. Different drugs have different actions. Each drug interacts with a specific part of the body. Not all drugs are good for living beings, some are quite toxic. That is why it is important to know the effect of any drug before taking it.
Drugs are often used in the healthcare industry. They are used to diagnose, prevent, control, and treat diseases. Drugs that are used for these purposes are called medicines.
Drugs interact with the body. There are macromolecules present in living bodies that interact with these drugs. It is called drug interaction. Different drugs deliver different biological responses. Their effects depend on their target.
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Drug Targets
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Drugs are classified based on molecular targets. Molecular targets are defined as the macromolecules present in a living body with which drugs interact to give a biological response.
Enzymes and receptors are two excellent drug targets. Enzymes are defined as biomolecules that act as catalysts of biological systems. They are mostly proteins. Receptors are defined as proteins that can receive and transmit signals in biological systems. Interactions of drugs with enzymes and receptors deliver desired and undesired responses from the living body.
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Enzymes as Drug Targets
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Enzymes are proteins with active sites. These active sites provide binding sites to substrates. The substrates are then locked in a sole position so that the attack of reagents on substrates becomes easy. Enzymes have functional groups that interact with substrates to perform the necessary chemical reactions. This explains the catalytic behaviour of enzymes.
Enzyme Inhibitors
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Enzyme inhibitors are defined as drugs that disturb the catalytic action of enzymes. They bind with the active sites of enzymes and leave no room for substrates. This causes the catalytic action to inhibit. There are two types of enzyme inhibitors: competitive inhibitors and non-competitive inhibitors.
Competitive Inhibitors
Certain substrates bind only to certain active sites on the enzyme. These substrates are unable to bind to any other type of active site. Competitive inhibitors compete with the substrates to bind with the same active sites. When competitive inhibitors are successful in binding with these active sites, the catalytic function of enzymes inhibits. These inhibitors should be administered in definite amounts because if the number of substrates is greater than the number of competitive inhibitors then the therapy will be unsuccessful.
Non-Competitive Inhibitors
Non-competitive inhibitors do not compete with the substrates. They simply bind to other available active sites, also known as allosteric sites. This binding changes the shape of the enzyme and also of the binding sites. So, the active sites for substrates get deformed and they are no longer able to bind. This eventually inhibits the catalytic function of enzymes.
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Receptors as Drug Targets
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Receptors are present on the cell membrane. They are a connection of the outside environment to the inside of the cell. Receptors receive chemical signals through neurons with the help of chemical messengers. These chemical messengers bind with the receptors to transmit the signal. Drugs interact with these messengers and bind to them so that they cannot bind with the receptors. Thus, the signal carried by them is not transmitted. The drugs that inhibit the activity of receptors are called antagonists.
Things to Remember
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- Drugs are synthetically prepared chemicals that physiologically affect all living beings when taken.
- There are macromolecules present in living bodies that interact with drugs. It is called drug interactions.
- Molecular targets are defined as the macromolecules present in a living body with which drugs interact to give a biological response.
- Enzymes and receptors are two excellent drug targets.
- There are two types of enzyme inhibitors viz. competitive inhibitors and non-competitive inhibitors.
Sample Questions
Ques. Drugs can inhibit the catalytic activity of enzymes by binding at: (2 Marks)
- Active Site
- Allosteric Site
- Both of the above
- None of the above
Ans. c. Both of the above. There are various drugs that can bind to the active sites and others to the allosteric sites. By doing so, in both instances, the catalytic activity of enzymes is inhibited.
Ques. What are drug interactions? (3 Marks)
Ans. The interaction between drugs and macromolecules in living organisms is called drug interaction. Because of drug interactions, the normal functions of those macromolecules get altered in some way. This alteration in their function generates a different biological response that is usually absent.
Ques. What are the types of enzyme inhibitors? (3 Marks)
Ans. There are two known types of enzyme inhibitors. They are:
- Competitive inhibitors
- Non-competitive inhibitors
Competitive inhibitors are inhibitors of enzymes that compete with the substrates to occupy active sites, whereas, non-competitive inhibitors are inhibitors of enzymes that do not compete with the substrates but rather occupy the allosteric sites which change the shape of the active site.
Ques. Explain non-competitive inhibitors of enzymes in detail. (3 Marks)
Ans. Non-competitive inhibitors do not compete with the substrates to occupy the active sites. They simply bind to allosteric sites. This binding changes the shape of the enzyme and also of the active sites. So, the active sites for substrates get deformed and substrates are no longer able to bind. This inhibits the catalytic function of enzymes.
Ques. How do receptors act as drug targets? (3 Marks)
Ans. Receptors receive chemical signals via neurons with the help of chemical messengers. These chemical messengers bind with the active sites on receptors. This transmits the signal from outside of the cell to inside the cell. Drugs interact with these messengers and bind to them so that they cannot bind with the receptors. Thus, the signal carried by them is not transmitted.
Ques. What are different drug targets? (2 Marks)
Ans. Different drug targets in living bodies can be biomolecules such as proteins, receptors, hormones, nucleic acids, enzymes, ion channels, etc.
Ques. Give some uses of drugs. (3 Marks)
Ans. Uses of drugs:
- They are used in the diagnosis of diseases.
- They are used to cure diseases.
- They are used to strengthen the immune system.
- They are used to prevent certain biological outcomes such as pain.
Ques. What are antagonists? Give some examples. (2 Marks)
Ans. Drugs that bind to the receptor and inhibit their activity are called antagonists. Examples of antagonists are naltrexone, methadone, buprenorphine, haloperidol, chlorpromazine, fluphenazine, and naloxone.
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