CIE IGCSE Biology Unit 15: Drugs

Drug

any substance taken into the body that modifies or affects chemical reactions in the body

Use of antibiotics

the treatment of bacterial infection, some bacteria are resistant to antibiotics which reduces the effectiveness of antibiotics

How development of resistant bacteria such as MRSA can be minimised

use antibiotics only when essential and

ensuring treatment is completed

Why antibiotics kill bacteria, but do not affect viruses

Antibiotics dissolve the cell wall of the bacteria and contents of bacteria leak out, as virus is not a cell, it does not affect viruses

The effects of excessive alcohol consumption

* - powerful depressant drugs

- effect on reaction times and self-control

- addiction and withdrawal symptoms

- negative social implications, e.g. crime

- can cause liver damage

Alcohol affects nervous system as it is absorbed into the blood rapidly,as it is a small molecule it is not broken down, long term alcohol consumption causes stomach ulcers, heart disease and brain damage, the alcohol impedes metabolism in liver so fat is build up, condition is known as fatty liver, if continued damage will cause liver tissue to be replaced with scar tissue.

The effects of heroin abuse

* - powerful depressant drugs

- effect on reaction times and self-control

- addiction and withdrawal symptoms

- negative social implications, e.g. crime

- can cause infections such as HIV

Heroin becomes part of the metabolism of the body so body builds resistance to drug, as body does not produce own painkillers, the addict must rely on more heroin to reduce the pain

The effects of tobacco smoking

- can cause chronic obstructive pulmonary disease (COPD), lung cancer and coronary heart disease

- * the effects on the gas exchange system of tobacco smoke and its major toxic components, limited to carbon monoxide, nicotine and tar

-nicotine is absorbed quickly through alveoli into the bloodstream, causes heart rate to increase, it is not a depressant nor a stimulant. Nicotine increases stickiness of blood

-carbon monoxide is absorbed by haemoglobin in red blood cells and binds permanently with haemoglobin, reduces volume of oxygen that blood can carry

Evidence for the link between smoking and lung cancer

As cigarette smoke contains many carcinogens, causes the cells DNA structure to change and divide out of control thus leading to cancer

Use of hormones to improve sporting performance

* limited to testosterone and anabolic steroids

Liver

site of break down of alcohol and other toxins