O LEVEL BIOLOGY COMPLETE NOTES

DRUGS

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Plants are autotrophs, which means that they can make their own food. Their cells contain chlorophyll which helps in photosynthesis and thus, they make their own food (glucose). But humans cannot. Therefore we have to intake a balanced diet.
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Definition: A drug is any substance other than food, that is externally administered in the body and which affects the processes of metabolism.

Metabolism refers to all the chemical reactions that are taking place inside the body. It is of two types, catabolism and anabolism.
- catabolism is the breakdown of large, complex substances into smaller, simpler substances *remember it e.g: cutting an A4 size paper into smaller square parts
- anabolism is the making of larger complex substances from simpler and smaller ones.

There are:
• medicinal drugs
• drugs of abuse
• socially accepted drugs

*PAIN KILLERS*
Anaesthetics are drugs that numbs a part of the body therefore making it unable to feel pain.
e.g Novocain, nitrus oxide, morphine
Whereas analgesics releive pain without causing numbness.
e.g Aspirin, Paracetamol

ANTIBIOTICS are a group drugs that are used to fight against bacteria only and no other microorganism.
Penicillin was the first antibiotic discovered. Other examples include tetracycline, azitromacyn etc.

-Drugs of abuse are those that cause harm to the human body.

SMOKING

It's the act of burning tobacco and inhaling and exhaling the smoke that is produced.

Nicotine is a substance that is present in tobacco along with many other chemicals- which is addictive.

It stimulates secretion of the hormone, adrenaline in the body which is ultimately responsible for an increased chance and rate of the heart condition, atherosclerosis as it allows unwanted blood clots to occur in the lining of blood vessels easily. It may also cause narrowing of certain blood vessels.

Atherosclerosis is caused by the deposition of cholesterol (fatty substance) in blood vessels. The risk of this condition is higher for smokers as the adrenaline increases the heart rate and blood pressure (hypertension) which allows blood to clot easily thereby, blocking the vessel. Atherosclerosis of the coronary artery (artery supplying the heart) can lead to a heart attack.

** Atherosclerosis will be covered in detail in Transport in Mammals **

The drug is considered addictive as it temporarily stimulates brain activity making the person alert. But in the long run, it decreases brain activity.

*fact: nicotine is a natural insecticide.

Due to a limited amount of oxygen present during smoking, Carbon Monoxide (CO) is formed

It is considered a poisonous gas. Even if the concentration of Carbon Monoxide increases by 1%, it can cause as deadly effect on the people breathing that air. A person can die in about 10 minutes of breathing this high concentration of the gas.