iGCSE Biology Notes Drugs

[q] What is a Drug?

[a] 

○ A drug is any substance taken into the body that modifies or affects chemical reactions in the body
○ Some drug are medicinal drugs that are used to treat the symptoms or causes of disease (antibiotics, etc)

[q] Antibiotics

[a] 

○ Antibiotics are chemical substance made by certain fungi or bacteria that affect the working of bacterial cells, either by disrupting their structure or function or by preventing them from reproducing
○ Antibiotics kill bacteria but do not affect viruses
○ Antibiotics when in contact with a bacterial cell can rupture the cells and then the bacterial cell will die when it tries to grow
○ Some bacteria are resistant to antibiotics which reduces the effectiveness of antibiotics

[q] Why antibiotics don’t affect viruses?

[a] 

○ Viruses cannot be treated with antibiotics
○ Disrupting cell functions such as respiration, or breaking down the structure
○ Since viruses do not carry out any cell functions and do not have cell walls, they cannot be affected

[q] Antibiotic resistance

[a] 

Antibiotic resistance
○ Antibiotics are widely overused
○ Commonly prescribed antibiotics are becoming less effective due to these reasons:
■ Overuse and being prescribed when not necessary
■ Patients failing to complete the fully described course by the doctor
■ Large scale use of antibiotics in farming to prevent diseases
○ If a bacteria becomes resistant to all known antibiotics we call that bacteria a superbug and the most common bacteria is MRSA
○ Prevention methods
■ Only taking antibiotics when essential
■ Ensure the entire course is completed

[q] Misused Drugs

Alcohol

[a] 

○ Wine, beer and spirits contain an alcohol called ethanol
○ It is a depressant drug – it slows down signals in the nerves and brain
○ Alcohol increases reaction times (slowing the body)
○ Effects of alcohol
■ Vomiting (alcohol toxicity)
■ Impaired judgement and violent behaviour
■ Impaired balance and muscle control
■ Sleepiness and in excess can cause unconsciousness
■ Damages the brain causing memory loss and confusion (long term)
■ Heavy alcohol abuse over a long period of time damages the liver, causing cirrhosis
■ The liver is the site of breakdown of alcohol and other toxins
○ It is an addictive drug

[a] 

○ Depressant drug
○ Slows down reaction time
○ Require higher dosage over time
■ Overdose can cause death
○ May result in committing crimes to get the drug
○ Withdrawal symptoms
■ Nause
■ Muscle cramps
■ Sweating
■ Anxiety
■ Difficulty sleeping
○ Syringes are required to inject drug needles could be affected by HIV

Heroin effect on the nervous system

[a] 

○ The heroine is metabolised to morphine in the body
○ Morphine molecules fit into some fo the endorphin receptors (reduce sensation) and this is why taking heroin makes users feel so good
○ Taking heroin can reduce the production of natural endorphins thus requiring more of the substance to get the same feeling

Tobacco & Gas exchange system

[a] 

○ Smoking causes various lung cancers and coronary heart disease
○ Cigarettes contain:
○ Tar – a carcinogen (a substance that causes cancer)
■ Tar increases the chance of cancerous cells developing in the lungs
■ Also Contributes to COPD
■ Chronic bronchitis is caused by tar which stimulates goblet cells and mucus glands to enlarge, producing more mucus
■ It destroys cilia, inhibiting the cleaning of the airways and mucus builds up blocking the smallest bronchioles
■ Emphysema develops as a result of frequent infection, meaning phagocytes are attracted to the lungs where they release elastase – an enzyme that breaks down the elastin in the alveoli walls to enable them to reach the surface where the bacteria are.
● Without elastin, the alveoli will burst, making it harder for the smoker to breathe

Tobacco & Gas exchange system

[a] 

○ Nicotine – an addictive substance which also narrows blood vessels
■ Nicotine narrows blood vessels so i’ll put more strain on the circulatory system and increase blood pressure
■ Narrow blood vessels get clogged up easier, this causes coronary heart disease
■ The heart muscles are not receiving enough oxygen and so less aerobic respiration takes place
■ To compensate, the cells respire anaerobically, producing lactic acid which cannot be removed
■ This creates a low pH environment in the cells causing enzymes to denature and eventually heart muscle cells will die
● If enough die this can cause a heart attack

Tobacco & Gas exchange system

[a] 

○ Carbon monoxide – reduces the oxygen-carrying capacity of the blood
■ Carbon monoxide binds irreversibly to haemoglobin, reducing the capacity of
blood to carry oxygen
■ Puts strain on the breathing system
■ Increases risk of Coronary heart disease

[q] Drugs in sport

[a] 

○ Hormones produced in the body help to control the way it develops and responds to changes
■ Drugs are used to increase these effects

[a] 

■ Testosterone
● Hormone produce in testes affects the development of male secondary sexual characteristics
● More proteins to be made in muscles so that muscles become larger and stronger
■ Steroid
● Group of hormones which stimulate anabolic reactions to occur in the body (synthesis of large molecules from smaller ones), so it is known as an anabolic steroid
● increases muscle mass, helps athletes train harder and for longer periods of time, and can increase aggression which can give an edge when competing

[a] 

Side effects
■ Increase the risk of heart disease
■ Increases risk of liver damage
■ Increases risk of kidney damage
■ Affect the menstrual cycle in women
■ Increase immunity of the body