Chapter Note: Drugs | Biology for GCSE/IGCSE - Year 11 PDF Download

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Drugs
? Any substance taken into the body that modifies or affects chemical reactions in the body is known as a
drug
? Medicinal drugs
? It's a type of drug which prevents or treats the symptoms of various diseases etc.
? Antibiotics
? Antibiotics are substances which kill bacteria, but do not harm other living cells.
? The first antibiotic to be discovered was penicillin. It killed bacteria by stopping them making
their cell walls
? Many antibiotics kill bacteria by damaging their cell walls, viruses don't have cell walls so they
are unharmed by antibiotics
Misuse of drugs
? Heroin
? Opium which contains a number of different chemicals such as morphine and codeine(used for
pain relief). Opium is also a raw material used to make heroin
? Heroin is a powerful depressant, it means that it slows down the functions of the brain. It
reduces pain and slows down breathing. It also slows down the functions of the hypothalamus.
? When a person takes heroin it produces an intense feeling of happiness, this causes people to
become rapidly addicted
? Some people take heroin by injecting it into their veins. THis can be dangerous as the needles
used for injection are often not sterile and pathogens such as hepatitis virus can be introduced
to the body. Sharing of needles by heroin addicted have been a major cause for HIV
? Endorphins help to reduce the sensations of pain, affect mood and reduce sensations of hunger
and thirst. When it enters the brain, heroin is metabolised to morphine. Morphine molecules fit
into endorphin receptors, that's why heroin can make people feel so good.’
? Alcohol
? Alcohol is a depressant, that means even a small amount of alcohol can slow down the actions
of the brain and it slows down reaction time.
? Alcohol can increase aggression in some people.
? Large alcohol intakes can cause death. It’s a poison
? Alcoholism
? Excessive alcohol drinking damages the brain, it can cause memory loss and confusion
? One form of liver disease resulting from alcohol damage is cirrhosis where fibres grow in the
liver. It can be very fatal
? Alcohol in the body fluids draws water out of cells by osmosis. When this happens to brain cells,
they shrink and may be irreversibly damaged.
? Drinking alcohol causes a lot of dilute urine to be produced resulting in low levels of water in the
blood
Page 2


Drugs
? Any substance taken into the body that modifies or affects chemical reactions in the body is known as a
drug
? Medicinal drugs
? It's a type of drug which prevents or treats the symptoms of various diseases etc.
? Antibiotics
? Antibiotics are substances which kill bacteria, but do not harm other living cells.
? The first antibiotic to be discovered was penicillin. It killed bacteria by stopping them making
their cell walls
? Many antibiotics kill bacteria by damaging their cell walls, viruses don't have cell walls so they
are unharmed by antibiotics
Misuse of drugs
? Heroin
? Opium which contains a number of different chemicals such as morphine and codeine(used for
pain relief). Opium is also a raw material used to make heroin
? Heroin is a powerful depressant, it means that it slows down the functions of the brain. It
reduces pain and slows down breathing. It also slows down the functions of the hypothalamus.
? When a person takes heroin it produces an intense feeling of happiness, this causes people to
become rapidly addicted
? Some people take heroin by injecting it into their veins. THis can be dangerous as the needles
used for injection are often not sterile and pathogens such as hepatitis virus can be introduced
to the body. Sharing of needles by heroin addicted have been a major cause for HIV
? Endorphins help to reduce the sensations of pain, affect mood and reduce sensations of hunger
and thirst. When it enters the brain, heroin is metabolised to morphine. Morphine molecules fit
into endorphin receptors, that's why heroin can make people feel so good.’
? Alcohol
? Alcohol is a depressant, that means even a small amount of alcohol can slow down the actions
of the brain and it slows down reaction time.
? Alcohol can increase aggression in some people.
? Large alcohol intakes can cause death. It’s a poison
? Alcoholism
? Excessive alcohol drinking damages the brain, it can cause memory loss and confusion
? One form of liver disease resulting from alcohol damage is cirrhosis where fibres grow in the
liver. It can be very fatal
? Alcohol in the body fluids draws water out of cells by osmosis. When this happens to brain cells,
they shrink and may be irreversibly damaged.
? Drinking alcohol causes a lot of dilute urine to be produced resulting in low levels of water in the
blood
? Anabolic steroids
? Many steroid hormones stimulate metabolic reactions in body cells that build up large molecules
from small ones. These reactions are called anabolic reactions
? Steroid hormones that stimulate these reactions are known as anabolic steroids
? One type of reaction that is stimulated by anabolic reactions is the synthesis of proteins to be
made in muscles, this increases muscle mass by a lot which potentially helps in sports.
? Tobacco smoking
? Nicotine affects the brain, it is a stimulant which means it makes a person feel more alert. It is
an addictive drug which smokers find hard to give up.
? Nicotine damages the circulatory system making blood vessels narrower, this can increase
blood pressure leading to hypertension.
? Tar contains many different chemicals, some of which are carcinogens, this can cause cancer.
? The chemicals can affect behaviour of some cells in the respiratory passages and lungs causing
them to divide uncontrollably, the cells divide over and over again, forming a lump or tumor. If
the tumor is malignant, it is cancer. Cells will break and spread to the body causing more
tumors.
? Carbon monoxide is poisonous gas which affects the blood, and combines with haemoglobin
inside the red blood cells. This means that less oxygen can be carried. The body cells are
therefore deprived of oxygen.
? The delicate walls of the alveoli tend to break down, therefore there is less surface area across
which gas exchange can take place, the person is said to have emphysema. They find it difficult
to get enough oxygen into their blood.